Research ArticleBending Properties of Short-Cut Basalt Fiber Shotcrete in DeepSoft Rock Roadway

Shaoyang Yan12 Huazhe Jiao 12 Xiaolin Yang12 Jinxing Wang12 and Fengbin Chen12

1School of Civil Engineering Henan Polytechnic University Jiaozuo 454000 China2Henan Key Laboratory Underground Engineering and Disaster Prevention School of Civil EngineeringHenan Polytechnic University Jiaozuo 454000 China

Correspondence should be addressed to Huazhe Jiao jiaohuazhe126com

Received 15 October 2019 Revised 8 June 2020 Accepted 16 June 2020 Published 14 July 2020

Academic Editor Valeria Vignali

Copyright copy 2020 Shaoyang Yan et alis is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

To study the effect of short-cut basalt fiber (BF) on the bending and toughening properties of shotcrete bending toughness tests of short-cutBF shotcrete slabs with different volume fractions were carried out A transparent soil model and Scanning Electron Microscopy (SEM)were used to observe the distribution of BF with different volume fractions and analyze the toughness enhancement mechanism of basaltfiber shotcrete e supporting effect of basalt fiber shotcrete with different volume fractions was verified by an underground engineeringtest e test results show the following (1) when the fiber content is within 3sim45kgm3 the distribution of BF in transparent soil isuniform and it does not easily agglomerate which is beneficial to improving the bending toughness of shotcrete (2)e shotcreteslab with 45 kgm3 fiber content had the best reinforcing effect Compared with the control group the peak load and absorptioncapacity increased by 5667 and 63696 respectively and the maximum crack width decreased by 3210 (3)e SEM analysisindicated that the basalt fibers distributed randomly and evenly in the concrete which can form a three-dimensional spatialskeleton with a stable structure Excessive fiber incorporation can increase fiber agglomeration during stirring and spraying (4)e support results of an underground engineering test show that in 35 days short-cut basalt fiber shotcrete with 45 kgm3 fibercontent is better at restraining the surrounding rock than shotcrete with other fiber contents BF has the properties of crackresistance bridging and toughening for shotcrete and can significantly improve the ability of shotcrete to restrain surroundingrock deformation As a new type of fiber BF has great significance in deep soft rock underground engineering

1 Introduction

Surrounding rock stability control is one of the importantresearch areas in the field of deep soft rock undergroundengineering especially for practical problems such as dif-ficult control of the surrounding rock stability and largedeformation in the deep 800sim2000 m high-stress condition[1 2] Traditional shotcrete has some shortcomings such assmall elongation poor crack resistance and high brittlenesswhich reduce the support effect and seriously endanger thestability of the surrounding rock structure and personalsafety [3 4] Basalt fiber (BF) is a new fiber material with ahigh inorganic environmentally friendly green performanceCompared with other fibers (glass fiber and steel fiber)basalt fiber has better corrosion resistance a higher elastic

modulus better chemical stability impact resistance andfire resistance [5 6] Basalt fiber was originally used inmilitary and aerospace research programs [7 8] and is nowwidely used as a structural reinforcement material inbuildings [9ndash11] bridges [12 13] highways [14 15] tunnels[16 17] and other fields Basalt fibers have the functions ofcrack resistance bridging and toughening in concretewhich can significantly improve the fatigue resistance post-cracking toughness and durability of the concrete [18ndash20]

In recent years domestic and foreign scholars havecarried out a large number of experimental studies on fiberreinforced concrete Sim et al [21] found that the toughnessof basalt fiber reinforced concrete is 3sim5 times higher thanthat of ordinary concrete Zhang et al [22] suggested thatbasalt fibers could improve the toughness and crack resistance

HindawiAdvances in Civil EngineeringVolume 2020 Article ID 5749685 9 pageshttpsdoiorg10115520205749685

of concrete through experiments Pickel et al [23] tested themechanical properties of basalt fiber reinforced concretewith different content e basalt fibers were found togenerally increase the tensile and flexural strength (modulusof rupture) and it was found on inspection that the fibershad ruptured upon macrocracking Ayub et al [24] sug-gested that the addition of basalt fibers significantly in-creased the tensile splitting strength and the flexural strengthof HPFRC and slightly improved the compressive strengthAttia K et al [25] found that basalt fiber can improve thebending resistance of the concrete sheet strips Abed andAlhafiz [26] researched the effects of adding different typesof fibers to the concrete mixtures on the flexural behaviourof concrete beams which were reinforced longitudinallywith BFRP bars eir results showed that basalt fibers canimprove the bending resistance of these beams Wang et al[27] found that the bonding between the fibers and concretematrix is the main factor that improves the effect of thestrengthening and toughening of fiber reinforced concreteIyer [28] conducted mechanical property tests on concretewith different lengths and quantities of basalt fiber andfound that clumping of fibers at a high fiber content willcause mixing and casting problems Li et al [29] studied theeffect of hybrid fibers on the flexural toughness of concretesquare slabs and beams and used European and Americancodes to evaluate the flexural toughness characteristics Liet al [30] studied the early strength of steel fiber shotcreteslabs with different content according to the EuropeanEFNARC standard and found that steel fiber can signifi-cantly improve the impact resistance of early concreteHowever the research on the bending characteristics andstrengthening and toughening of BF shotcrete is not perfectso it is necessary to study the application of BF shotcrete indeep soft rock underground engineering

At present the research on the bending characteristicsand strengthening and toughening effect of BF shotcrete islimited to the laboratory only and the research resultscannot be used in underground engineering erefore thispaper studies the influence of short-cut BF shotcrete slabswith different volume fractions on the bending character-istics and toughness by using a test of underground shotcreteslabs e distribution of fiber in the shotcrete and thestrengthening and toughening mechanism are investigatedand analyzed by means of a transparent soil model and SEMtechnology Finally a field test is used to systematicallymonitor the convergence deformation of different volumesof BF sprayed concrete to verify the support effect

2 Experimental Materials and Methods

21 Experimental Materials and Mix Proportion e ex-perimental materials are as follows PO 425R Portlandcement produced by Qianye Cement Plant the coarse ag-gregate is calcareous macadam with a mud content of 02and maximum particle size of 10mm fine aggregate ismanufactured sand with fineness modulus of 3 and particlesize of 0sim3mm short-cut BF with 18mm fiber with pa-rameters as shown in Table 1 e accelerator is XingdeBrand accelerator Wuan City Hebei Province and the

water is tap water from Jiaozuo City e specimen mix isshown in Table 2

22 Experimental Methods

221 Fiber-Transparent Soil Model Experiment To preparethe fiber-transparent soil model different sizes of quartzsand were mixed in the mixer for 30 seconds adding dif-ferent amounts of short-cut basalt fiber stirring for 40seconds pouring the stirred mixture into a plexiglass box(100times100times100mm) and then adding the refractive index14585 calcium bromide solution prepared by using an abberefractometer e distribution of different fiber content intransparent soil was observed e fiber-transparent soilmodel was binarized by Image J software and the fiberdistribution was counted

222 Bending Toughness Experiment of Shotcrete SlabAccording to the European EFNARC standard for making600times 600times100mm shotcrete slab [31] specimens with fibervolume fractions of 0 kgm3 3 kgm3 45 kgm3 and 6 kgm3

were made in the bottom drainage roadway of Zhaogu No2coal mine respectively while square slabs with fiber volumefractions of 0 kgm3 were used as the control group reeparallel specimens were made for each groupe specimenswere demoulded 24 hours later and kept underground for 28days before being transported to the laboratory for testing

e flexural toughness test of the shotcrete slabs is di-vided into three steps Step one place the square slab on therigid frame and place a 100times100times100mm loading rigidblock at the centre of the specimen Step two apply load witha TAW-3000G electrohydraulic servo high rigid pressuretesting machine with a loading speed of 15mmmin Stepthree the CY050-2A deformmeter (range 50mm) and crackwidth gauge were used to monitor and record the load anddeflection of the centre slab the deformation of the centrebottom slab and the crack width and extension crack widthof the loading specimen e flow of the square slab test isshown in Figure 1

223 SEM Experiment For choosing failure specimens toconduct SEM in order to ensure focused scanning the testpieces were sliced and selected to be placed in a sample bagfor keeping e enclosed sample was taken out during thetest and fixed on the sample stage with a conductive pastee sample stage to which the sample is fixed is placed in anion sputtering equipment for gold coating en the SEMinstrument switch is turned on the appropriate beam spotvalue is selected and a SEM test is performed

3 Experimental Results and Analysis

31 Distribution of BF in Transparent Soil Model withDifferent Contents e fiber-transparent soil model was di-vided into 9 cells binary analysis was conducted by Image Jsoftware and the visible fiber distribution in different cells wascounted e distribution morphology of fiber with eachcontent in the transparent soil model is shown in Figure 2 and

2 Advances in Civil Engineering

the binarization image of the fiber distribution in the trans-parent soil is shown in Figure 3

In order to quantitatively evaluate the dispersion offiber in the transparent soil the dispersion coefficient offiber is proposed and its expression is shown in the fol-lowing formula

β exp minus 1113944XiXi)( 1113857

2

T1113888 1113891

(12)

⎡⎢⎢⎣ (1)

In the formula T is the number of cells in the field ofview Xi (i 1sim9) is the number of fibrous roots in dif-ferent cells Xa is the average number of fibrous roots in allcells in the entire image and β is the dispersion coefficientof the fiber

Define the dispersion coefficient of the weighted averagevalue of the content of BF contribution value αj(α0 1) andthe contribution growth coefficient cj(j 1sim5) where jcorresponds to (15 3 45 6 and 75 kgm3) five kinds ofcontents respectively Its expression is shown in the fol-lowing formulas

αj Vf middot βj (2)

cj αj minus αjminus1

αjminus1 (3)

Vf is the BF content and βj is the BF dispersion coefficiente dispersion of different content of BF in the transparentsoil is shown in Table 3

According to Table 3 the BF content has a great influenceon the fiber distribution When the content is 15 kgm3 thefiber dispersion coefficient is 07 and the fiber contribution rateis 005 In the transparent soil model the fiber distribution israndom with large gaps and a uniform network structurecannot be formed When the content is 3 kgm3 the fiberdispersion coefficient is 076 and the fiber contribution rate is1171e gaps between fibers are small andmultiple fibers areconnected to form a stable spatial network structure A fewbubbles appear in the transparent soil model When the fibercontent is 45 kgm3 the fiber dispersion coefficient is 052 andthe fiber contribution rate is 0026 which indicates fiber ag-glomeration When the fiber content is 60 kgm3 the fiber

Table2 Shotcrete mix of experimental specimens (kgm3)

Cement Coarse aggregate Fine aggregate Water Accelerator Early strength agent440 880 880 260 176 22

(a) (b) (c) (d)

Figure 1 Production of shotcrete specimen (a) On-site fabrication of square boards (b) Site maintenance (c) Demoulding andmaintenance (d) Slab pressing

(a) (b) (c) (d) (e) (f )

Figure 2 Fiber-transparent soil model with different content (a) 0 kgm3 (b) 15 kgm3 (c) 3 kgm3 (d) 45 kgm3 (e) 6 kgm3 (f) 75 kgm3

Table 1 Physical and mechanical properties of basalt fiber

Material Diameter(μm) Length (mm) Density

(gcm3)Tensile strength

(MPa)Modulus of elasticity

(GPa)Elongation at fracture

()Basalt fibers 13 18 265 4100sim4800 80sim100 27sim34

Advances in Civil Engineering 3

dispersion coefficient is 046 and the fiber contribution rate is0179e fiber distribution is uneven and bubbles in themodelincrease greatly

It can be seen that the proper amount of fiber can exert again effect and the excess fiber is entangled and overlappedWhen the fiber dispersion amount is 3sim45 kgm3 the BFdistribution uniformly forms a dense network structurewhich is less prone to clumping and has a small overlap ratiois is beneficial to improving the bending toughness of thesprayed concrete

32 Effect of BF on Bidirectional Reinforcement Mechanismand Toughness of Shotcrete Square Slab

321 Effect of BF on Bidirectional Reinforcement Mechanismof Shotcrete Square Slab e load-deflection curves ofsimply supported BF shotcrete square slabs under con-centrated loads can be divided into the elastic stage stressredistribution stage and unloading stage e load-deflec-tion curve of a square slab with 45 kgm3 content is shown inFigure 4

Elastic stage (OA segment) [32] with the increase ofload the two-way bending moment of the slab increasescontinuously When the bending moment is less than theultimate bending moment (M1) of the square slab there isno cracking in the square slab and it is approximatelyelastic When the unidirectional bending moment rea-ches the maximum bending moment (the load reachespoint A) a unidirectional microcrack appears at thebottom of the square slab

Stress redistribution stage (ABCDE segment) [33] thisstage can be divided into an internal microstructure effect(AB) stage and a BF effect (BE) stage AB segment under thecondition of external force the defects such as microcrackand pore expansion within the square slab leads to a decreaseof the bearing capacity BE segment with the increase of

load the bonding effect between the fiber and matrix delaysthe development of cracks and increases the bearing capacity

Unloading stage (EFGH segment) [30] after reachingthe peak load of 5411 kN the crack develops into a maincrack penetrating the matrix of the shotcrete square slabebridging fibers under the effect of tension are pulled out ofthe matrix of the shotcrete square slab and the bearingcapacity of the slab decreases to 4627 kN (EF segment)Before the fiber reaches its ultimate tensile strength its ownstrength enhances the bearing capacity of the concretematrix and the bearing capacity increases to 4906 kN (FGsegment) e fracture of the bridging fibers leads to a sharpdecline in the bearing capacity of the square slab until it isdestroyed (GH segment)

322 Comparative Analysis of Bending Properties of SquareSlab with BF Content e results of the mechanicalproperties of the basalt fiber shotcrete square slabs are shown

Table 3 e dispersion of different content of BF in transparent soil

Specimen Fiber content(kgm3) Visible fiber number Distribution situation Dispersion coefficient Fiber contribution

growth coefficientP0 0 0 0 mdash mdashP1 15 67 Large fiber spacing 07 005P2 3 126 Moderate fiber spacing 076 1171P3 45 158 Uniform distribution of fiber spacing 052 0026P4 6 196 Uneven distribution of fibers 046 0179P5 75 237 Poor fiber distribution 037 0005

F

H

GE

C

DB

Load

(kN

)

A

S3-3

z

y

xM1

M2 Crack 1

Crack 2

5 10 15 20 250Deflection (mm)

0

10

20

30

40

50

60

Figure 4 e load-deflection curve of a square slab with 45 kgm3

content

(a) (b) (c) (d) (e) (f )

Figure 3 Binarization model of fiber-transparent soil with different content (a) 0 kgm3(b) 15 kgm3(c) 3 kgm3 (d) 45 kgm3(e) 6 kgm3(f) 75 kgm3

4 Advances in Civil Engineering

in Table 4 and Figure 5 which indicate that the peak loads ofshotcrete square slabs with fiber content of 0 kgm3 3 kgm345 kgm3 and 6 kgm3 are 3467 kN 4351 kN 5322 kN and4519 kN respectively e variance of the peak loads is05110 08091 07562 and 06970 respectively It can beseen from the variance of the different fiber content that thefluctuation of the test data is small indicating that thedispersion of the test data is good Compared with thecontrol group the peak loads with fiber contents of 3 kgm345 kgm3 and 6 kgm3 increased by 1111 5667 and3221 respectivelye control group shotcrete square slabhas high brittleness and low toughness With the addition ofBF to the shotcrete concrete the ultimate load and toughnessof the concrete can be improved appropriately

In order to study the effect of different contents of basaltfibers on the toughness of the square slabs the energy ab-sorption value in the EFNARC standard is used to char-acterize the fracture toughness of the slabs e calculationmethod is as follows

W 1113946δ

0F(x)dx (4)

In the formula W is the square slab energy absorptionvalue (unit J) δ is the central deflection of the square slaband F(x) is the load corresponding to the central deflectionof the square slab X

According to the load-displacement curves of shotcretesquare slabs with different contents of basalt fiber in Fig-ure 5 the energy absorption values corresponding to dif-ferent deflections are obtained by the integral method asshown in Table 5 e energy absorption curve is shown inFigure 6

Figure 6 shows that the energy absorption capacity of squareslabs with fibers of 3 kgm3 45 kgm3 and 6kgm3 is 32208 J56510 J and 37323 J respectively Compared with the controlgroup (7668 J) the energy absorption capacity increased by32003 63696 and 38674 respectivelyerefore BF cansignificantly improve the toughness and energy absorptioncapacity of BF shotcrete

rough the analysis of the load-deflection curve andenergy absorption curve it can be seen that the square slab

with the 45 kgm3 volume fraction of fiber shows the highesttoughness and energy absorption capacity

323 Analysis of Failure Form of Shotcrete Square Slabe crack development law and failure pattern of basalt fibershotcrete square slab are shown in Table 6 and Figure 7

e conclusions drawn from Table 6 and Figure 7 are asfollows

e BF shotcrete square slabs have four cracks for eachamount and the fiber contents are 0 kgm3 3 kgm3 45 kgm3 and 6 kgm3 where the mean values of the corre-sponding crack width are 028mm 025mm 019mm and023mm respectively compared with the control groupecrack width reduced by 107 321 and 179 respec-tively With the increase of fiber content the crack width ofthe square slab first increases and then decreases ebridging effect of the fiber creates a bond between the fiberand the concrete matrix which causes the stress redistri-bution and limits the generation and expansion of the crackerefore increase of the fiber content is beneficial tolimiting the development of the crack in the square slab andappropriately raises its bearing capacity and ductilityHowever excessive fiber content increases the porosity

Table 4 Test results of mechanical properties of BF reinforced concrete square slabs

Content of BF(kgm3) Specimen Initial cracking

deflection (mm)Initial

crack loadAveragevalue

Peakdeflection(mm)

Peakload(kN)

Averagevalue

Residualload (kN)

Averagevalue

0S1-1 074 3386

3467074 3386

346700

000S1-2 067 3456 082 3456 00S1-3 081 3560 110 3560 00

3S2-1 130 4066

3955175 4335

4351298

337S2-2 128 3942 188 4462 352S2-3 113 3856 168 4257 362

45S3-1 094 4682

4680180 5351

5322862

848S3-2 087 4536 174 5204 850S3-3 118 4823 189 5411 833

6S4-1 074 3862

4001152 4551

4519545

511S4-2 082 4087 149 4602 502S4-3 081 4053 160 4405 486

Load

(kN

)

S3-3S4-1

S2-1S1-1

5 10 15 20 250Deflection (mm)

0

10

20

30

40

50

60

Figure 5 Load-deflection curve of BF shotcrete square slab

Advances in Civil Engineering 5

inside the concrete matrix resulting in a decrease in thetoughness of the matrix

e failure mode of the control group was brittlefailure with a flat fracture surface When the flexuralspecimens of plain sprayed concrete were destroyed thecracks developed rapidly With the addition of BF thetoughness of the basalt fiber shotcrete square slab wasimproved the crack interface of the square slab was notintersected at the centre point and the fracture interfaceappeared as an irregular fracture shape When the fibercontent is 45 kgm3 the average crack width is thesmallest and the irregularity of cracks is poor Combinedwith the analysis of the load and energy absorption of theslabs the peak load value and energy absorption value aremaximum of the slabs e bridging connection providedby the basalt fiber across the crack can effectively improvethe toughness and maximum elongation of the shotcretesquare slab avoiding sudden brittle fracture after thepeak load of the slab and making the slab graduallytransition from brittle failure to ductile failure

33 SEM Analysis Electron microscopic scanning is aneffective method to study the internal distribution andmicrostructure of cement-based hydration products [34 35]allowing the observation of the distribution of fibers and thebonding mode between fibers and matrix and analyzing theeffect of hydration products such as ettringite and C-S-H onthe microstructure of the fiber matrix e bonding mode ofthe fiber matrix is shown in Figure 8

Figure 8 shows that the basalt fibers are covered with densecement hydration matrix so there is a good chemical ce-mentation between the fibers and the matrix (Figure 8(a)) ebasalt fibers are distributed randomly and evenly in the con-crete which can form a three-dimensional spatial skeleton witha stable structure (Figure 8(b)) Excessive fiber incorporationcan increase fiber agglomeration during stirring and sprayingwhich may reduce the bonding property between BF andshotcrete matrix (Figure 8(c)) Once a new crack appears in thespecimen under external loads the fiber spanning the crackconsumes energy to restrain the crack development through thedebonding and slipping of the fiber thus delaying the drivingforce of crack propagation in the concrete (Figure 8(d))

When the existing crack driving force is restrained andenergy accumulates in the concrete the anisotropic distributionof the BFwill seek new cracks in theweak points of thematrix torelease energy again e toughness and strength of concrete isenhanced by the fiber skeleton distributed inside the concretee effect of single BFs dispersed in basalt fiber shotcrete issimilar to reinforcing barse secondary micro-reinforcement

effect of BF combined with shotcrete matrix can effectivelyimprove the mechanical properties of basalt fiber shotcrete

4 Field Application of BF Shotcrete

41 Engineering Background e short-cut basalt fibershotcrete is applied to the bottom extraction roadway of ZhaoguNo2 coal mine (the roadway elevation is minus848simminus850m) etest section of roadway is located in the fractured shatter zoneBecause of the action of the fault zone the marl fracture zone inthe test section of the roadway is well developed e sur-rounding rock of the roadway has a weak layer and a strongwater-rich layer e lithology soft easy to produce large de-formation (the maximum deformation of the support is300mm) Concrete cracking and detachment deformation ofsteel support and other phenomena occur very often resultingin the failure of supports a great threat to mine safetyerefore the short-cut basalt fiber shotcrete was used for thefield test and 200m of the bottom extraction roadway wasselected for the underground support test Every 40m a dif-ferent fiber content was selected for the bolt-shotcrete supportAfter the shotcrete was completed two sets of monitoringpoints were used to monitor the convergence deformation ofthe roadwaye layout of the convergence survey points in thebottom drainage roadway is shown in Figure 9

42 Analysis of Convergence Deformation of RoadwayAfter the basalt fiber shotcrete has set and hardened con-vergence deformation monitoring is carried out for 35 dayson the bottom drainage roadway e monitoring results areshown in Figure 10 e addition of BF increases the de-formation resistance of the supporting structure e

Table 5 Effect of BF on energy absorption of shotcrete square slabs

SpecimenEnergy absorption value (J)

δ 25 δ 50 δ 75 δ 100 δ 125 δ 150 δ 175 δ 200 δ 225 δ 250S2-1 8709 15857 20931 24337 26482 27701 28552 29410 30427 32208S3-3 10872 21185 29673 36326 41823 46253 49725 52255 54526 56510S4-1 9310 17045 22734 26763 29401 31308 32714 33892 35330 37323δ is the centre deflection of shotcrete square slab (mm)

Ener

gy (J

)

S1-3

S4-1

S3-3

S2-1

5 10 15 20 250Deflection (mm)

0

100

200

300

400

500

600

Figure 6 Energy absorption curve

6 Advances in Civil Engineering

ITZ

Crack

BF

Aggregate

(a)

BF SkeletonAggregate

(b)

BF

Aggregate

Ballingeffect

(c)

BF Aggregate

(d)

Figure 8 Bonding mode of fiber substrate (a) Matrix around fibers (b) Fiber random dispersion (c) Fiber dense distribution (d) Fiberbreakage under stress

Table 6 Crack development law of BF shotcrete square slabs

Contentof BF(kgm3)

Specimen

Maximumwidth of

initial crack(mm)

Averagevalue

Crackreductionrate ()

Limitcrackwidth(mm)

Averagevalue

Crackreductionrate ()

Maximumcrack width

(mm)

Averagevalue

Crackreductionrate ()

0S1-1 018

019 mdash028

028 mdash028

028 mdashS1-2 019 026 026S1-3 020 030 030

3S2-1 018

018 53025

025 107028

027 36S2-2 019 023 025S2-3 018 026 028

45S3-1 013

014 263018

019 321022

022 214S3-2 014 020 023S3-3 014 018 020

6S4-1 016

015 211021

023 179024

026 71S4-2 014 023 026S4-3 015 024 028

(a) (b) (c) (d)

Figure 7 Failure modes of shotcrete slabs with different BF contents (a) 0 kgm3(b) 3 kgm3 (c) 45 kgm3(d) 6 kgm3

0 15 3 45 6 75

1710 1910200

Botto

m p

late

six tr

ansv

erse

75deg

75deg90deg

1275deg

105deg

63deg

75deg

90deg

Figure 9 e layout of convergence survey points in the bottom drainage roadway

Advances in Civil Engineering 7

maximum deformation (7 days) of the plain sprayed con-crete retaining structure is 144mm When the BF content is3 kgm3 and 45 kgm3 the deformation of the roadway isonly 012mm in the first 7 days e total convergencedisplacement of the plain sprayed concrete at 35 days is247mmWhen the BF content is 45 kgm3 the convergencedisplacement of the bottom drainage roadway is 021mm Inthe stirring and spraying process the uniformly distributedBF will form a stable bearing structure inside the basalt fibershotcrete matrix thereby improving the resistance of theroadway to deformation

5 Conclusions

In this paper the effect of BF on the flexural toughness ofshotcrete square slab is studied e fiber-reinforcedmechanism is analyzed by means of a synthetic fiber-transparent soil model and SEM technology combined witha field test and the following conclusions are drawn

(1) rough the fiber-transparent soil model it is foundthat when the fiber content is within 3sim45 kgm3 thedistribution of BF is uniform and it forms a densenetwork structure in which agglomeration appearsand has a small ratio of pores which is beneficial toimproving the bending toughness of the shotcreteconcrete

(2) According to the comparison test of the bendingtoughness of the square slab it is found that when thefiber content is 45 kgm3 it had the best reinforcingeffect Compared with the control group the peakload and absorption capacity increased by 5667and 63696 respectively and the maximum crackwidth decreased by 3210

(3) e SEM analysis indicated that the three-dimen-sional random distribution of BF forms a stable load-bearing skeleton in the shotcrete improves the stressdistribution in the shotcrete matrix reduces thecrack driving force and restrains the generation anddevelopment of microcracks Excessive fiber

incorporation can increase fiber agglomerationduring stirring and spraying which may make BFand shotcrete matrix not fully bonded and affect thetoughness of basalt fiber shotcrete

(4) BF shotcrete has achieved a good support effect in adeep soft rock underground engineering test thebasalt fiber shotcrete support effect is improvedcompared with plain shotcrete and the ability ofrestraining the deformation of surrounding rock isenhanced e convergence displacement of theplain shotcrete support section is 247mm in 35 dayswhile the convergence displacement of the roadwayin the basalt fiber shotcrete support section with afiber dissolution of 45 kgm3 is only 021mm

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

is study was supported by the National Natural ScienceFoundation of China (51874123 and 51834001) the Scientificand Technological Research Projects of Henan ProvinceChina (182102310012) and Support Plan for Scientific andTechnological Innovation Talents in Colleges and Univer-sities of Henan Province China (19HASTIT047)

References

[1] J C Wang F Liu and L Wang ldquoSustainable coal mining andmining sciencesrdquo Journal of China Coal Society vol 41 no 11pp 2651ndash2660 2016 in Chinese

[2] E S Bernard ldquoAge-dependent changes in post-crack per-formance of fibre reinforced shotcrete liningsrdquo Tunnellingand Underground Space Technology vol 49 pp 241ndash248 2015

[3] M Khooshechin and J Tanzadeh ldquoExperimental and me-chanical performance of shotcrete made with nanomaterialsand fiber reinforcementrdquo Construction and Building Mate-rials vol 165 pp 199ndash205 2018

[4] J M Guo and Y S Zhang ldquoApplication research on mine-used high performance polymer modified concreterdquo Journalof Mining amp Safety Engineering vol 28 no 4 pp 660ndash6652011 in Chinese

[5] C High H M Seliem A EL-Safty and S H Rizkalla ldquoUse ofbasalt fibers for concrete structuresrdquo Construction andBuilding Materials vol 96 pp 37ndash46 2015

[6] F Akhlaghi R Eslami-Farsani and S Sabet ldquoSynthesis andcharacteristics of continuous basalt fiber reinforced alumi-num matrix compositesrdquo Journal of Composite Materialsvol 47 no 27 pp 3379ndash3388 2012

[7] V I Kostikov Soviet Advanced Composites Technology SeriesFibre Science and Technology Basalt Fibres and Articles Basedon ltem pp 581ndash605 Springer Moscow Russia 1995

[8] S M R Khalili M Najafi and R Eslami-Farsani ldquoEffect ofthermal cycling on the tensile behavior of polymer composites

021039

088099

107

247

The a

mou

nt o

f con

verg

ence

(mm

)

5 10 15 20 25 30 35 400Time (d)

00

05

10

15

20

25

30

0kgm3

3kgm3

6kgm3

15kgm3

45kgm3

75kgm3

Figure 10 Convergence deformation curve of bottom drainageroadway

8 Advances in Civil Engineering

reinforced by basalt and carbon fibersrdquo Mechanics of Com-posite Materials vol 52 no 6 pp 807ndash816 2017

[9] W W Hu H W Liu D F Zhao and Z B Yang ldquoAppli-cations and advantages of basalt assembly in constructionindustryrdquo Advanced Materials Research vol 332ndash334pp 1937ndash1940 2011

[10] R N Turukmane S S Culhane and A M Daberao ldquoBasalt-technical fiber for civil applicationsrdquo Technische Textilienvol 61 no 2 pp 69ndash71 2018

[11] R H Wu ldquoe application of basalt fiber in building ma-terialsrdquo Advanced Materials Research vol 450-451 pp 499ndash502 2012

[12] T I Kovalrsquo ldquoInvestigation of the reliability of bridge elementsreinforced with basalt plastic fibersrdquo Mechanics of CompositeMaterials vol 53 no 4 pp 479ndash486 2017

[13] X Wang Z Wu G Wu H Zhu and F Zen ldquoEnhancementof basalt FRP by hybridization for long-span cable-stayedbridgerdquo Composites Part B Engineering vol 44 no 1pp 184ndash192 2013

[14] K Krayushkina O Prentkovskis A Bieliatynskyi et alldquoPerspectives on using basalt fiber filaments in the con-struction and rehabilitation of highway pavements and air-port runwaysrdquo lte Baltic Journal of Road and BridgeEngineering vol 11 no 1 pp 77ndash83 2016

[15] S L Ma B Peng and Z Huang ldquoTest and analysis of basaltfiber reinforced concretersquos mechanical properties and pave-ment performancerdquo Advanced Materials Research vol 671-674 pp 1291ndash1296 2013

[16] M Wlodarczyk and I Jedrzejewski ldquoConcrete slabsstrengthened with basalt fibres - experimental tests resultsrdquoProcedia Engineering vol 153 pp 866ndash873 2016

[17] G Y Cui D Y Wang S Z Ni et al ldquoModel tests bearingcharacteristics of basalt fiber reinforced concrete tunnel lin-ingsrdquo Chinese Journal of Geotechnical Engineering vol 39no 2 pp 311ndash318 2017 in Chinese

[18] S K Sateshkumar P O Awoyera and T KandasamyldquoImpact resistance of high strength chopped basalt fibre-reinforced concreterdquo Revista De La Construccion vol 17no 2 pp 240ndash248 2018

[19] A Bentur and S Mindess Fiber Reinforced CementitiousComposites Taylor amp Francis Group Abingdon UK 2007

[20] D P Dias and C aumaturgo ldquoFracture toughness ofgeopolymeric concretes reinforced with basalt fibersrdquo Cementand Concrete Composites vol 27 no 1 pp 49ndash54 2005

[21] J Sim C Park and D Y Moon ldquoCharacteristics of basaltfiber as a strengthening material for concrete structuresrdquoComposites Part B Engineering vol 36 no 6-7 pp 504ndash5122005

[22] L F Zhang Y L Yin J W Liu et al ldquoMecha-nical proportiesstudy on basalt fiber reinforced concreterdquo Bulletin of theChinese Ceramic Society vol 33 no 11 pp 2834ndash2837 2014in Chinese

[23] D J Pickel J S West and A Alaskar ldquoUse of basalt fibers infiber-reinforced concreterdquo ACI Materials Journal vol 115no 6 pp 867ndash876 2018

[24] T Ayub N Shafiq and M F Nuruddin ldquoMechanicalproperties of high-performance concrete reinforced withbasalt fibersrdquo Procedia Engineering vol 77 pp 131ndash139 2014

[25] K Attia W Alnahhal A Elrefai and Y Rihan ldquoFlexuralbehavior of basalt fiber-reinforced concrete slab strips rein-forced with BFRP and GFRP barsrdquo Composite Structuresvol 211 pp 1ndash12 2019

[26] F Abed and A R Alhafiz ldquoEffect of basalt fibers on theflexural behavior of concrete beams reinforced with BFRPbarsrdquo Composite Structures vol 215 pp 23ndash34 2019

[27] Q SWang and H Yao ldquoApplication of reinforced concrete insoft rock tunnel at great depthrdquo Journal of Mining amp SafetyEngineering vol 25 no 2 pp 184ndash187 2008 in Chinese

[28] P Iyer S Y Kenno and S Das ldquoMechanical properties offiber-reinforced concrete made with basalt filament fibersrdquoJournal of Materials in Civil Engineering vol 27 no 11Article ID 04015015 2015

[29] H G Li W Z Sun Q L Qiu et al ldquoStudy on flexuraltoughness property of basalt fiber concrete mixed with steelfiberrdquo Journal of Highway and Transportation Research andDevelopment vol 33 no 9 pp 78ndash83 2016 in Chinese

[30] D Li and Y N Ding ldquoEffect of steel fiber on biaxial flexuralproperty of TRC with basalt fiber mesh in slab testrdquo ActaMateriae Compositae Sinica vol 20 no 1 pp 78ndash82 2017 inChinese

[31] EFNARC European Specification for Sprayed concreteLoughborough University Louthborough UK 1996

[32] X D Wang W Z Zhen and Y Wang ldquoInternal force re-distribution of umbonded prestressed concrete edge-sup-ported sl-absrdquo Journal of Harbin Institute of Technologyvol 47 no 2 pp 1ndash8 2015 in Chinese

[33] Z C Deng ldquoFlexural toughness and characterization methodof hybrid fibers reinforced ultra-high performance concret-erdquoActa Materiae Compositae Sinica vol 33 no 6 pp 1274ndash1280 2016 in Chinese

[34] S Cao E Yilmaz and W D Song ldquoEvaluation of viscositystrength and microstructural properties of cemented tailingsbackfillrdquo Minerals vol 8 no 8 p 352 2018

[35] S M Song J H Liu and X Q Zhang ldquoPerformance of thecement matrix composite material with rubber powderrdquoJournal of Wuhan University of Technology vol 19 no 1pp 77ndash80 2014

Advances in Civil Engineering 9

the binarization image of the fiber distribution in the trans-parent soil is shown in Figure 3

In order to quantitatively evaluate the dispersion offiber in the transparent soil the dispersion coefficient offiber is proposed and its expression is shown in the fol-lowing formula

β exp minus 1113944XiXi)( 1113857

2

T1113888 1113891

(12)

⎡⎢⎢⎣ (1)

In the formula T is the number of cells in the field ofview Xi (i 1sim9) is the number of fibrous roots in dif-ferent cells Xa is the average number of fibrous roots in allcells in the entire image and β is the dispersion coefficientof the fiber

Define the dispersion coefficient of the weighted averagevalue of the content of BF contribution value αj(α0 1) andthe contribution growth coefficient cj(j 1sim5) where jcorresponds to (15 3 45 6 and 75 kgm3) five kinds ofcontents respectively Its expression is shown in the fol-lowing formulas

αj Vf middot βj (2)

cj αj minus αjminus1

αjminus1 (3)

Vf is the BF content and βj is the BF dispersion coefficiente dispersion of different content of BF in the transparentsoil is shown in Table 3

According to Table 3 the BF content has a great influenceon the fiber distribution When the content is 15 kgm3 thefiber dispersion coefficient is 07 and the fiber contribution rateis 005 In the transparent soil model the fiber distribution israndom with large gaps and a uniform network structurecannot be formed When the content is 3 kgm3 the fiberdispersion coefficient is 076 and the fiber contribution rate is1171e gaps between fibers are small andmultiple fibers areconnected to form a stable spatial network structure A fewbubbles appear in the transparent soil model When the fibercontent is 45 kgm3 the fiber dispersion coefficient is 052 andthe fiber contribution rate is 0026 which indicates fiber ag-glomeration When the fiber content is 60 kgm3 the fiber

Table2 Shotcrete mix of experimental specimens (kgm3)

Cement Coarse aggregate Fine aggregate Water Accelerator Early strength agent440 880 880 260 176 22

(a) (b) (c) (d)

Figure 1 Production of shotcrete specimen (a) On-site fabrication of square boards (b) Site maintenance (c) Demoulding andmaintenance (d) Slab pressing

(a) (b) (c) (d) (e) (f )

Figure 2 Fiber-transparent soil model with different content (a) 0 kgm3 (b) 15 kgm3 (c) 3 kgm3 (d) 45 kgm3 (e) 6 kgm3 (f) 75 kgm3

Table 1 Physical and mechanical properties of basalt fiber

Material Diameter(μm) Length (mm) Density

(gcm3)Tensile strength

(MPa)Modulus of elasticity

(GPa)Elongation at fracture

()Basalt fibers 13 18 265 4100sim4800 80sim100 27sim34

Advances in Civil Engineering 3

dispersion coefficient is 046 and the fiber contribution rate is0179e fiber distribution is uneven and bubbles in themodelincrease greatly

It can be seen that the proper amount of fiber can exert again effect and the excess fiber is entangled and overlappedWhen the fiber dispersion amount is 3sim45 kgm3 the BFdistribution uniformly forms a dense network structurewhich is less prone to clumping and has a small overlap ratiois is beneficial to improving the bending toughness of thesprayed concrete

32 Effect of BF on Bidirectional Reinforcement Mechanismand Toughness of Shotcrete Square Slab

321 Effect of BF on Bidirectional Reinforcement Mechanismof Shotcrete Square Slab e load-deflection curves ofsimply supported BF shotcrete square slabs under con-centrated loads can be divided into the elastic stage stressredistribution stage and unloading stage e load-deflec-tion curve of a square slab with 45 kgm3 content is shown inFigure 4

Elastic stage (OA segment) [32] with the increase ofload the two-way bending moment of the slab increasescontinuously When the bending moment is less than theultimate bending moment (M1) of the square slab there isno cracking in the square slab and it is approximatelyelastic When the unidirectional bending moment rea-ches the maximum bending moment (the load reachespoint A) a unidirectional microcrack appears at thebottom of the square slab

Stress redistribution stage (ABCDE segment) [33] thisstage can be divided into an internal microstructure effect(AB) stage and a BF effect (BE) stage AB segment under thecondition of external force the defects such as microcrackand pore expansion within the square slab leads to a decreaseof the bearing capacity BE segment with the increase of

load the bonding effect between the fiber and matrix delaysthe development of cracks and increases the bearing capacity

Unloading stage (EFGH segment) [30] after reachingthe peak load of 5411 kN the crack develops into a maincrack penetrating the matrix of the shotcrete square slabebridging fibers under the effect of tension are pulled out ofthe matrix of the shotcrete square slab and the bearingcapacity of the slab decreases to 4627 kN (EF segment)Before the fiber reaches its ultimate tensile strength its ownstrength enhances the bearing capacity of the concretematrix and the bearing capacity increases to 4906 kN (FGsegment) e fracture of the bridging fibers leads to a sharpdecline in the bearing capacity of the square slab until it isdestroyed (GH segment)

322 Comparative Analysis of Bending Properties of SquareSlab with BF Content e results of the mechanicalproperties of the basalt fiber shotcrete square slabs are shown

Table 3 e dispersion of different content of BF in transparent soil

Specimen Fiber content(kgm3) Visible fiber number Distribution situation Dispersion coefficient Fiber contribution

growth coefficientP0 0 0 0 mdash mdashP1 15 67 Large fiber spacing 07 005P2 3 126 Moderate fiber spacing 076 1171P3 45 158 Uniform distribution of fiber spacing 052 0026P4 6 196 Uneven distribution of fibers 046 0179P5 75 237 Poor fiber distribution 037 0005

F

H

GE

C

DB

Load

(kN

)

A

S3-3

z

y

xM1

M2 Crack 1

Crack 2

5 10 15 20 250Deflection (mm)

0

10

20

30

40

50

60

Figure 4 e load-deflection curve of a square slab with 45 kgm3

content

(a) (b) (c) (d) (e) (f )

Figure 3 Binarization model of fiber-transparent soil with different content (a) 0 kgm3(b) 15 kgm3(c) 3 kgm3 (d) 45 kgm3(e) 6 kgm3(f) 75 kgm3

4 Advances in Civil Engineering

in Table 4 and Figure 5 which indicate that the peak loads ofshotcrete square slabs with fiber content of 0 kgm3 3 kgm345 kgm3 and 6 kgm3 are 3467 kN 4351 kN 5322 kN and4519 kN respectively e variance of the peak loads is05110 08091 07562 and 06970 respectively It can beseen from the variance of the different fiber content that thefluctuation of the test data is small indicating that thedispersion of the test data is good Compared with thecontrol group the peak loads with fiber contents of 3 kgm345 kgm3 and 6 kgm3 increased by 1111 5667 and3221 respectivelye control group shotcrete square slabhas high brittleness and low toughness With the addition ofBF to the shotcrete concrete the ultimate load and toughnessof the concrete can be improved appropriately

In order to study the effect of different contents of basaltfibers on the toughness of the square slabs the energy ab-sorption value in the EFNARC standard is used to char-acterize the fracture toughness of the slabs e calculationmethod is as follows

W 1113946δ

0F(x)dx (4)

In the formula W is the square slab energy absorptionvalue (unit J) δ is the central deflection of the square slaband F(x) is the load corresponding to the central deflectionof the square slab X

According to the load-displacement curves of shotcretesquare slabs with different contents of basalt fiber in Fig-ure 5 the energy absorption values corresponding to dif-ferent deflections are obtained by the integral method asshown in Table 5 e energy absorption curve is shown inFigure 6

Figure 6 shows that the energy absorption capacity of squareslabs with fibers of 3 kgm3 45 kgm3 and 6kgm3 is 32208 J56510 J and 37323 J respectively Compared with the controlgroup (7668 J) the energy absorption capacity increased by32003 63696 and 38674 respectivelyerefore BF cansignificantly improve the toughness and energy absorptioncapacity of BF shotcrete

rough the analysis of the load-deflection curve andenergy absorption curve it can be seen that the square slab

with the 45 kgm3 volume fraction of fiber shows the highesttoughness and energy absorption capacity

323 Analysis of Failure Form of Shotcrete Square Slabe crack development law and failure pattern of basalt fibershotcrete square slab are shown in Table 6 and Figure 7

e conclusions drawn from Table 6 and Figure 7 are asfollows

e BF shotcrete square slabs have four cracks for eachamount and the fiber contents are 0 kgm3 3 kgm3 45 kgm3 and 6 kgm3 where the mean values of the corre-sponding crack width are 028mm 025mm 019mm and023mm respectively compared with the control groupecrack width reduced by 107 321 and 179 respec-tively With the increase of fiber content the crack width ofthe square slab first increases and then decreases ebridging effect of the fiber creates a bond between the fiberand the concrete matrix which causes the stress redistri-bution and limits the generation and expansion of the crackerefore increase of the fiber content is beneficial tolimiting the development of the crack in the square slab andappropriately raises its bearing capacity and ductilityHowever excessive fiber content increases the porosity

Table 4 Test results of mechanical properties of BF reinforced concrete square slabs

Content of BF(kgm3) Specimen Initial cracking

deflection (mm)Initial

crack loadAveragevalue

Peakdeflection(mm)

Peakload(kN)

Averagevalue

Residualload (kN)

Averagevalue

0S1-1 074 3386

3467074 3386

346700

000S1-2 067 3456 082 3456 00S1-3 081 3560 110 3560 00

3S2-1 130 4066

3955175 4335

4351298

337S2-2 128 3942 188 4462 352S2-3 113 3856 168 4257 362

45S3-1 094 4682

4680180 5351

5322862

848S3-2 087 4536 174 5204 850S3-3 118 4823 189 5411 833

6S4-1 074 3862

4001152 4551

4519545

511S4-2 082 4087 149 4602 502S4-3 081 4053 160 4405 486

Load

(kN

)

S3-3S4-1

S2-1S1-1

5 10 15 20 250Deflection (mm)

0

10

20

30

40

50

60

Figure 5 Load-deflection curve of BF shotcrete square slab

Advances in Civil Engineering 5

inside the concrete matrix resulting in a decrease in thetoughness of the matrix

e failure mode of the control group was brittlefailure with a flat fracture surface When the flexuralspecimens of plain sprayed concrete were destroyed thecracks developed rapidly With the addition of BF thetoughness of the basalt fiber shotcrete square slab wasimproved the crack interface of the square slab was notintersected at the centre point and the fracture interfaceappeared as an irregular fracture shape When the fibercontent is 45 kgm3 the average crack width is thesmallest and the irregularity of cracks is poor Combinedwith the analysis of the load and energy absorption of theslabs the peak load value and energy absorption value aremaximum of the slabs e bridging connection providedby the basalt fiber across the crack can effectively improvethe toughness and maximum elongation of the shotcretesquare slab avoiding sudden brittle fracture after thepeak load of the slab and making the slab graduallytransition from brittle failure to ductile failure

33 SEM Analysis Electron microscopic scanning is aneffective method to study the internal distribution andmicrostructure of cement-based hydration products [34 35]allowing the observation of the distribution of fibers and thebonding mode between fibers and matrix and analyzing theeffect of hydration products such as ettringite and C-S-H onthe microstructure of the fiber matrix e bonding mode ofthe fiber matrix is shown in Figure 8

Figure 8 shows that the basalt fibers are covered with densecement hydration matrix so there is a good chemical ce-mentation between the fibers and the matrix (Figure 8(a)) ebasalt fibers are distributed randomly and evenly in the con-crete which can form a three-dimensional spatial skeleton witha stable structure (Figure 8(b)) Excessive fiber incorporationcan increase fiber agglomeration during stirring and sprayingwhich may reduce the bonding property between BF andshotcrete matrix (Figure 8(c)) Once a new crack appears in thespecimen under external loads the fiber spanning the crackconsumes energy to restrain the crack development through thedebonding and slipping of the fiber thus delaying the drivingforce of crack propagation in the concrete (Figure 8(d))

When the existing crack driving force is restrained andenergy accumulates in the concrete the anisotropic distributionof the BFwill seek new cracks in theweak points of thematrix torelease energy again e toughness and strength of concrete isenhanced by the fiber skeleton distributed inside the concretee effect of single BFs dispersed in basalt fiber shotcrete issimilar to reinforcing barse secondary micro-reinforcement

effect of BF combined with shotcrete matrix can effectivelyimprove the mechanical properties of basalt fiber shotcrete

4 Field Application of BF Shotcrete

41 Engineering Background e short-cut basalt fibershotcrete is applied to the bottom extraction roadway of ZhaoguNo2 coal mine (the roadway elevation is minus848simminus850m) etest section of roadway is located in the fractured shatter zoneBecause of the action of the fault zone the marl fracture zone inthe test section of the roadway is well developed e sur-rounding rock of the roadway has a weak layer and a strongwater-rich layer e lithology soft easy to produce large de-formation (the maximum deformation of the support is300mm) Concrete cracking and detachment deformation ofsteel support and other phenomena occur very often resultingin the failure of supports a great threat to mine safetyerefore the short-cut basalt fiber shotcrete was used for thefield test and 200m of the bottom extraction roadway wasselected for the underground support test Every 40m a dif-ferent fiber content was selected for the bolt-shotcrete supportAfter the shotcrete was completed two sets of monitoringpoints were used to monitor the convergence deformation ofthe roadwaye layout of the convergence survey points in thebottom drainage roadway is shown in Figure 9

42 Analysis of Convergence Deformation of RoadwayAfter the basalt fiber shotcrete has set and hardened con-vergence deformation monitoring is carried out for 35 dayson the bottom drainage roadway e monitoring results areshown in Figure 10 e addition of BF increases the de-formation resistance of the supporting structure e

Table 5 Effect of BF on energy absorption of shotcrete square slabs

SpecimenEnergy absorption value (J)

δ 25 δ 50 δ 75 δ 100 δ 125 δ 150 δ 175 δ 200 δ 225 δ 250S2-1 8709 15857 20931 24337 26482 27701 28552 29410 30427 32208S3-3 10872 21185 29673 36326 41823 46253 49725 52255 54526 56510S4-1 9310 17045 22734 26763 29401 31308 32714 33892 35330 37323δ is the centre deflection of shotcrete square slab (mm)

Ener

gy (J

)

S1-3

S4-1

S3-3

S2-1

5 10 15 20 250Deflection (mm)

0

100

200

300

400

500

600

Figure 6 Energy absorption curve

6 Advances in Civil Engineering

ITZ

Crack

BF

Aggregate

(a)

BF SkeletonAggregate

(b)

BF

Aggregate

Ballingeffect

(c)

BF Aggregate

(d)

Figure 8 Bonding mode of fiber substrate (a) Matrix around fibers (b) Fiber random dispersion (c) Fiber dense distribution (d) Fiberbreakage under stress

Table 6 Crack development law of BF shotcrete square slabs

Contentof BF(kgm3)

Specimen

Maximumwidth of

initial crack(mm)

Averagevalue

Crackreductionrate ()

Limitcrackwidth(mm)

Averagevalue

Crackreductionrate ()

Maximumcrack width

(mm)

Averagevalue

Crackreductionrate ()

0S1-1 018

019 mdash028

028 mdash028

028 mdashS1-2 019 026 026S1-3 020 030 030

3S2-1 018

018 53025

025 107028

027 36S2-2 019 023 025S2-3 018 026 028

45S3-1 013

014 263018

019 321022

022 214S3-2 014 020 023S3-3 014 018 020

6S4-1 016

015 211021

023 179024

026 71S4-2 014 023 026S4-3 015 024 028

(a) (b) (c) (d)

Figure 7 Failure modes of shotcrete slabs with different BF contents (a) 0 kgm3(b) 3 kgm3 (c) 45 kgm3(d) 6 kgm3

0 15 3 45 6 75

1710 1910200

Botto

m p

late

six tr

ansv

erse

75deg

75deg90deg

1275deg

105deg

63deg

75deg

90deg

Figure 9 e layout of convergence survey points in the bottom drainage roadway

Advances in Civil Engineering 7

maximum deformation (7 days) of the plain sprayed con-crete retaining structure is 144mm When the BF content is3 kgm3 and 45 kgm3 the deformation of the roadway isonly 012mm in the first 7 days e total convergencedisplacement of the plain sprayed concrete at 35 days is247mmWhen the BF content is 45 kgm3 the convergencedisplacement of the bottom drainage roadway is 021mm Inthe stirring and spraying process the uniformly distributedBF will form a stable bearing structure inside the basalt fibershotcrete matrix thereby improving the resistance of theroadway to deformation

5 Conclusions

In this paper the effect of BF on the flexural toughness ofshotcrete square slab is studied e fiber-reinforcedmechanism is analyzed by means of a synthetic fiber-transparent soil model and SEM technology combined witha field test and the following conclusions are drawn

(1) rough the fiber-transparent soil model it is foundthat when the fiber content is within 3sim45 kgm3 thedistribution of BF is uniform and it forms a densenetwork structure in which agglomeration appearsand has a small ratio of pores which is beneficial toimproving the bending toughness of the shotcreteconcrete

(2) According to the comparison test of the bendingtoughness of the square slab it is found that when thefiber content is 45 kgm3 it had the best reinforcingeffect Compared with the control group the peakload and absorption capacity increased by 5667and 63696 respectively and the maximum crackwidth decreased by 3210

(3) e SEM analysis indicated that the three-dimen-sional random distribution of BF forms a stable load-bearing skeleton in the shotcrete improves the stressdistribution in the shotcrete matrix reduces thecrack driving force and restrains the generation anddevelopment of microcracks Excessive fiber

incorporation can increase fiber agglomerationduring stirring and spraying which may make BFand shotcrete matrix not fully bonded and affect thetoughness of basalt fiber shotcrete

(4) BF shotcrete has achieved a good support effect in adeep soft rock underground engineering test thebasalt fiber shotcrete support effect is improvedcompared with plain shotcrete and the ability ofrestraining the deformation of surrounding rock isenhanced e convergence displacement of theplain shotcrete support section is 247mm in 35 dayswhile the convergence displacement of the roadwayin the basalt fiber shotcrete support section with afiber dissolution of 45 kgm3 is only 021mm

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

is study was supported by the National Natural ScienceFoundation of China (51874123 and 51834001) the Scientificand Technological Research Projects of Henan ProvinceChina (182102310012) and Support Plan for Scientific andTechnological Innovation Talents in Colleges and Univer-sities of Henan Province China (19HASTIT047)

References

[1] J C Wang F Liu and L Wang ldquoSustainable coal mining andmining sciencesrdquo Journal of China Coal Society vol 41 no 11pp 2651ndash2660 2016 in Chinese

[2] E S Bernard ldquoAge-dependent changes in post-crack per-formance of fibre reinforced shotcrete liningsrdquo Tunnellingand Underground Space Technology vol 49 pp 241ndash248 2015

[3] M Khooshechin and J Tanzadeh ldquoExperimental and me-chanical performance of shotcrete made with nanomaterialsand fiber reinforcementrdquo Construction and Building Mate-rials vol 165 pp 199ndash205 2018

[4] J M Guo and Y S Zhang ldquoApplication research on mine-used high performance polymer modified concreterdquo Journalof Mining amp Safety Engineering vol 28 no 4 pp 660ndash6652011 in Chinese

[5] C High H M Seliem A EL-Safty and S H Rizkalla ldquoUse ofbasalt fibers for concrete structuresrdquo Construction andBuilding Materials vol 96 pp 37ndash46 2015

[6] F Akhlaghi R Eslami-Farsani and S Sabet ldquoSynthesis andcharacteristics of continuous basalt fiber reinforced alumi-num matrix compositesrdquo Journal of Composite Materialsvol 47 no 27 pp 3379ndash3388 2012

[7] V I Kostikov Soviet Advanced Composites Technology SeriesFibre Science and Technology Basalt Fibres and Articles Basedon ltem pp 581ndash605 Springer Moscow Russia 1995

[8] S M R Khalili M Najafi and R Eslami-Farsani ldquoEffect ofthermal cycling on the tensile behavior of polymer composites

021039

088099

107

247

The a

mou

nt o

f con

verg

ence

(mm

)

5 10 15 20 25 30 35 400Time (d)

00

05

10

15

20

25

30

0kgm3

3kgm3

6kgm3

15kgm3

45kgm3

75kgm3

Figure 10 Convergence deformation curve of bottom drainageroadway

8 Advances in Civil Engineering

reinforced by basalt and carbon fibersrdquo Mechanics of Com-posite Materials vol 52 no 6 pp 807ndash816 2017

[9] W W Hu H W Liu D F Zhao and Z B Yang ldquoAppli-cations and advantages of basalt assembly in constructionindustryrdquo Advanced Materials Research vol 332ndash334pp 1937ndash1940 2011

[10] R N Turukmane S S Culhane and A M Daberao ldquoBasalt-technical fiber for civil applicationsrdquo Technische Textilienvol 61 no 2 pp 69ndash71 2018

[11] R H Wu ldquoe application of basalt fiber in building ma-terialsrdquo Advanced Materials Research vol 450-451 pp 499ndash502 2012

[12] T I Kovalrsquo ldquoInvestigation of the reliability of bridge elementsreinforced with basalt plastic fibersrdquo Mechanics of CompositeMaterials vol 53 no 4 pp 479ndash486 2017

[13] X Wang Z Wu G Wu H Zhu and F Zen ldquoEnhancementof basalt FRP by hybridization for long-span cable-stayedbridgerdquo Composites Part B Engineering vol 44 no 1pp 184ndash192 2013

[14] K Krayushkina O Prentkovskis A Bieliatynskyi et alldquoPerspectives on using basalt fiber filaments in the con-struction and rehabilitation of highway pavements and air-port runwaysrdquo lte Baltic Journal of Road and BridgeEngineering vol 11 no 1 pp 77ndash83 2016

[15] S L Ma B Peng and Z Huang ldquoTest and analysis of basaltfiber reinforced concretersquos mechanical properties and pave-ment performancerdquo Advanced Materials Research vol 671-674 pp 1291ndash1296 2013

[16] M Wlodarczyk and I Jedrzejewski ldquoConcrete slabsstrengthened with basalt fibres - experimental tests resultsrdquoProcedia Engineering vol 153 pp 866ndash873 2016

[17] G Y Cui D Y Wang S Z Ni et al ldquoModel tests bearingcharacteristics of basalt fiber reinforced concrete tunnel lin-ingsrdquo Chinese Journal of Geotechnical Engineering vol 39no 2 pp 311ndash318 2017 in Chinese

[18] S K Sateshkumar P O Awoyera and T KandasamyldquoImpact resistance of high strength chopped basalt fibre-reinforced concreterdquo Revista De La Construccion vol 17no 2 pp 240ndash248 2018

[19] A Bentur and S Mindess Fiber Reinforced CementitiousComposites Taylor amp Francis Group Abingdon UK 2007

[20] D P Dias and C aumaturgo ldquoFracture toughness ofgeopolymeric concretes reinforced with basalt fibersrdquo Cementand Concrete Composites vol 27 no 1 pp 49ndash54 2005

[21] J Sim C Park and D Y Moon ldquoCharacteristics of basaltfiber as a strengthening material for concrete structuresrdquoComposites Part B Engineering vol 36 no 6-7 pp 504ndash5122005

[22] L F Zhang Y L Yin J W Liu et al ldquoMecha-nical proportiesstudy on basalt fiber reinforced concreterdquo Bulletin of theChinese Ceramic Society vol 33 no 11 pp 2834ndash2837 2014in Chinese

[23] D J Pickel J S West and A Alaskar ldquoUse of basalt fibers infiber-reinforced concreterdquo ACI Materials Journal vol 115no 6 pp 867ndash876 2018

[24] T Ayub N Shafiq and M F Nuruddin ldquoMechanicalproperties of high-performance concrete reinforced withbasalt fibersrdquo Procedia Engineering vol 77 pp 131ndash139 2014

[25] K Attia W Alnahhal A Elrefai and Y Rihan ldquoFlexuralbehavior of basalt fiber-reinforced concrete slab strips rein-forced with BFRP and GFRP barsrdquo Composite Structuresvol 211 pp 1ndash12 2019

[26] F Abed and A R Alhafiz ldquoEffect of basalt fibers on theflexural behavior of concrete beams reinforced with BFRPbarsrdquo Composite Structures vol 215 pp 23ndash34 2019

[27] Q SWang and H Yao ldquoApplication of reinforced concrete insoft rock tunnel at great depthrdquo Journal of Mining amp SafetyEngineering vol 25 no 2 pp 184ndash187 2008 in Chinese

[28] P Iyer S Y Kenno and S Das ldquoMechanical properties offiber-reinforced concrete made with basalt filament fibersrdquoJournal of Materials in Civil Engineering vol 27 no 11Article ID 04015015 2015

[29] H G Li W Z Sun Q L Qiu et al ldquoStudy on flexuraltoughness property of basalt fiber concrete mixed with steelfiberrdquo Journal of Highway and Transportation Research andDevelopment vol 33 no 9 pp 78ndash83 2016 in Chinese

[30] D Li and Y N Ding ldquoEffect of steel fiber on biaxial flexuralproperty of TRC with basalt fiber mesh in slab testrdquo ActaMateriae Compositae Sinica vol 20 no 1 pp 78ndash82 2017 inChinese

[31] EFNARC European Specification for Sprayed concreteLoughborough University Louthborough UK 1996

[32] X D Wang W Z Zhen and Y Wang ldquoInternal force re-distribution of umbonded prestressed concrete edge-sup-ported sl-absrdquo Journal of Harbin Institute of Technologyvol 47 no 2 pp 1ndash8 2015 in Chinese

[33] Z C Deng ldquoFlexural toughness and characterization methodof hybrid fibers reinforced ultra-high performance concret-erdquoActa Materiae Compositae Sinica vol 33 no 6 pp 1274ndash1280 2016 in Chinese

[34] S Cao E Yilmaz and W D Song ldquoEvaluation of viscositystrength and microstructural properties of cemented tailingsbackfillrdquo Minerals vol 8 no 8 p 352 2018

[35] S M Song J H Liu and X Q Zhang ldquoPerformance of thecement matrix composite material with rubber powderrdquoJournal of Wuhan University of Technology vol 19 no 1pp 77ndash80 2014

Advances in Civil Engineering 9

dispersion coefficient is 046 and the fiber contribution rate is0179e fiber distribution is uneven and bubbles in themodelincrease greatly

It can be seen that the proper amount of fiber can exert again effect and the excess fiber is entangled and overlappedWhen the fiber dispersion amount is 3sim45 kgm3 the BFdistribution uniformly forms a dense network structurewhich is less prone to clumping and has a small overlap ratiois is beneficial to improving the bending toughness of thesprayed concrete

32 Effect of BF on Bidirectional Reinforcement Mechanismand Toughness of Shotcrete Square Slab

321 Effect of BF on Bidirectional Reinforcement Mechanismof Shotcrete Square Slab e load-deflection curves ofsimply supported BF shotcrete square slabs under con-centrated loads can be divided into the elastic stage stressredistribution stage and unloading stage e load-deflec-tion curve of a square slab with 45 kgm3 content is shown inFigure 4

Elastic stage (OA segment) [32] with the increase ofload the two-way bending moment of the slab increasescontinuously When the bending moment is less than theultimate bending moment (M1) of the square slab there isno cracking in the square slab and it is approximatelyelastic When the unidirectional bending moment rea-ches the maximum bending moment (the load reachespoint A) a unidirectional microcrack appears at thebottom of the square slab

Stress redistribution stage (ABCDE segment) [33] thisstage can be divided into an internal microstructure effect(AB) stage and a BF effect (BE) stage AB segment under thecondition of external force the defects such as microcrackand pore expansion within the square slab leads to a decreaseof the bearing capacity BE segment with the increase of

load the bonding effect between the fiber and matrix delaysthe development of cracks and increases the bearing capacity

Unloading stage (EFGH segment) [30] after reachingthe peak load of 5411 kN the crack develops into a maincrack penetrating the matrix of the shotcrete square slabebridging fibers under the effect of tension are pulled out ofthe matrix of the shotcrete square slab and the bearingcapacity of the slab decreases to 4627 kN (EF segment)Before the fiber reaches its ultimate tensile strength its ownstrength enhances the bearing capacity of the concretematrix and the bearing capacity increases to 4906 kN (FGsegment) e fracture of the bridging fibers leads to a sharpdecline in the bearing capacity of the square slab until it isdestroyed (GH segment)

322 Comparative Analysis of Bending Properties of SquareSlab with BF Content e results of the mechanicalproperties of the basalt fiber shotcrete square slabs are shown

Table 3 e dispersion of different content of BF in transparent soil

Specimen Fiber content(kgm3) Visible fiber number Distribution situation Dispersion coefficient Fiber contribution

growth coefficientP0 0 0 0 mdash mdashP1 15 67 Large fiber spacing 07 005P2 3 126 Moderate fiber spacing 076 1171P3 45 158 Uniform distribution of fiber spacing 052 0026P4 6 196 Uneven distribution of fibers 046 0179P5 75 237 Poor fiber distribution 037 0005

F

H

GE

C

DB

Load

(kN

)

A

S3-3

z

y

xM1

M2 Crack 1

Crack 2

5 10 15 20 250Deflection (mm)

0

10

20

30

40

50

60

Figure 4 e load-deflection curve of a square slab with 45 kgm3

content

(a) (b) (c) (d) (e) (f )

Figure 3 Binarization model of fiber-transparent soil with different content (a) 0 kgm3(b) 15 kgm3(c) 3 kgm3 (d) 45 kgm3(e) 6 kgm3(f) 75 kgm3

4 Advances in Civil Engineering

in Table 4 and Figure 5 which indicate that the peak loads ofshotcrete square slabs with fiber content of 0 kgm3 3 kgm345 kgm3 and 6 kgm3 are 3467 kN 4351 kN 5322 kN and4519 kN respectively e variance of the peak loads is05110 08091 07562 and 06970 respectively It can beseen from the variance of the different fiber content that thefluctuation of the test data is small indicating that thedispersion of the test data is good Compared with thecontrol group the peak loads with fiber contents of 3 kgm345 kgm3 and 6 kgm3 increased by 1111 5667 and3221 respectivelye control group shotcrete square slabhas high brittleness and low toughness With the addition ofBF to the shotcrete concrete the ultimate load and toughnessof the concrete can be improved appropriately

In order to study the effect of different contents of basaltfibers on the toughness of the square slabs the energy ab-sorption value in the EFNARC standard is used to char-acterize the fracture toughness of the slabs e calculationmethod is as follows

W 1113946δ

0F(x)dx (4)

In the formula W is the square slab energy absorptionvalue (unit J) δ is the central deflection of the square slaband F(x) is the load corresponding to the central deflectionof the square slab X

According to the load-displacement curves of shotcretesquare slabs with different contents of basalt fiber in Fig-ure 5 the energy absorption values corresponding to dif-ferent deflections are obtained by the integral method asshown in Table 5 e energy absorption curve is shown inFigure 6

Figure 6 shows that the energy absorption capacity of squareslabs with fibers of 3 kgm3 45 kgm3 and 6kgm3 is 32208 J56510 J and 37323 J respectively Compared with the controlgroup (7668 J) the energy absorption capacity increased by32003 63696 and 38674 respectivelyerefore BF cansignificantly improve the toughness and energy absorptioncapacity of BF shotcrete

rough the analysis of the load-deflection curve andenergy absorption curve it can be seen that the square slab

with the 45 kgm3 volume fraction of fiber shows the highesttoughness and energy absorption capacity

323 Analysis of Failure Form of Shotcrete Square Slabe crack development law and failure pattern of basalt fibershotcrete square slab are shown in Table 6 and Figure 7

e conclusions drawn from Table 6 and Figure 7 are asfollows

e BF shotcrete square slabs have four cracks for eachamount and the fiber contents are 0 kgm3 3 kgm3 45 kgm3 and 6 kgm3 where the mean values of the corre-sponding crack width are 028mm 025mm 019mm and023mm respectively compared with the control groupecrack width reduced by 107 321 and 179 respec-tively With the increase of fiber content the crack width ofthe square slab first increases and then decreases ebridging effect of the fiber creates a bond between the fiberand the concrete matrix which causes the stress redistri-bution and limits the generation and expansion of the crackerefore increase of the fiber content is beneficial tolimiting the development of the crack in the square slab andappropriately raises its bearing capacity and ductilityHowever excessive fiber content increases the porosity

Table 4 Test results of mechanical properties of BF reinforced concrete square slabs

Content of BF(kgm3) Specimen Initial cracking

deflection (mm)Initial

crack loadAveragevalue

Peakdeflection(mm)

Peakload(kN)

Averagevalue

Residualload (kN)

Averagevalue

0S1-1 074 3386

3467074 3386

346700

000S1-2 067 3456 082 3456 00S1-3 081 3560 110 3560 00

3S2-1 130 4066

3955175 4335

4351298

337S2-2 128 3942 188 4462 352S2-3 113 3856 168 4257 362

45S3-1 094 4682

4680180 5351

5322862

848S3-2 087 4536 174 5204 850S3-3 118 4823 189 5411 833

6S4-1 074 3862

4001152 4551

4519545

511S4-2 082 4087 149 4602 502S4-3 081 4053 160 4405 486

Load

(kN

)

S3-3S4-1

S2-1S1-1

5 10 15 20 250Deflection (mm)

0

10

20

30

40

50

60

Figure 5 Load-deflection curve of BF shotcrete square slab

Advances in Civil Engineering 5

inside the concrete matrix resulting in a decrease in thetoughness of the matrix

e failure mode of the control group was brittlefailure with a flat fracture surface When the flexuralspecimens of plain sprayed concrete were destroyed thecracks developed rapidly With the addition of BF thetoughness of the basalt fiber shotcrete square slab wasimproved the crack interface of the square slab was notintersected at the centre point and the fracture interfaceappeared as an irregular fracture shape When the fibercontent is 45 kgm3 the average crack width is thesmallest and the irregularity of cracks is poor Combinedwith the analysis of the load and energy absorption of theslabs the peak load value and energy absorption value aremaximum of the slabs e bridging connection providedby the basalt fiber across the crack can effectively improvethe toughness and maximum elongation of the shotcretesquare slab avoiding sudden brittle fracture after thepeak load of the slab and making the slab graduallytransition from brittle failure to ductile failure

33 SEM Analysis Electron microscopic scanning is aneffective method to study the internal distribution andmicrostructure of cement-based hydration products [34 35]allowing the observation of the distribution of fibers and thebonding mode between fibers and matrix and analyzing theeffect of hydration products such as ettringite and C-S-H onthe microstructure of the fiber matrix e bonding mode ofthe fiber matrix is shown in Figure 8

Figure 8 shows that the basalt fibers are covered with densecement hydration matrix so there is a good chemical ce-mentation between the fibers and the matrix (Figure 8(a)) ebasalt fibers are distributed randomly and evenly in the con-crete which can form a three-dimensional spatial skeleton witha stable structure (Figure 8(b)) Excessive fiber incorporationcan increase fiber agglomeration during stirring and sprayingwhich may reduce the bonding property between BF andshotcrete matrix (Figure 8(c)) Once a new crack appears in thespecimen under external loads the fiber spanning the crackconsumes energy to restrain the crack development through thedebonding and slipping of the fiber thus delaying the drivingforce of crack propagation in the concrete (Figure 8(d))

When the existing crack driving force is restrained andenergy accumulates in the concrete the anisotropic distributionof the BFwill seek new cracks in theweak points of thematrix torelease energy again e toughness and strength of concrete isenhanced by the fiber skeleton distributed inside the concretee effect of single BFs dispersed in basalt fiber shotcrete issimilar to reinforcing barse secondary micro-reinforcement

effect of BF combined with shotcrete matrix can effectivelyimprove the mechanical properties of basalt fiber shotcrete

4 Field Application of BF Shotcrete

41 Engineering Background e short-cut basalt fibershotcrete is applied to the bottom extraction roadway of ZhaoguNo2 coal mine (the roadway elevation is minus848simminus850m) etest section of roadway is located in the fractured shatter zoneBecause of the action of the fault zone the marl fracture zone inthe test section of the roadway is well developed e sur-rounding rock of the roadway has a weak layer and a strongwater-rich layer e lithology soft easy to produce large de-formation (the maximum deformation of the support is300mm) Concrete cracking and detachment deformation ofsteel support and other phenomena occur very often resultingin the failure of supports a great threat to mine safetyerefore the short-cut basalt fiber shotcrete was used for thefield test and 200m of the bottom extraction roadway wasselected for the underground support test Every 40m a dif-ferent fiber content was selected for the bolt-shotcrete supportAfter the shotcrete was completed two sets of monitoringpoints were used to monitor the convergence deformation ofthe roadwaye layout of the convergence survey points in thebottom drainage roadway is shown in Figure 9

42 Analysis of Convergence Deformation of RoadwayAfter the basalt fiber shotcrete has set and hardened con-vergence deformation monitoring is carried out for 35 dayson the bottom drainage roadway e monitoring results areshown in Figure 10 e addition of BF increases the de-formation resistance of the supporting structure e

Table 5 Effect of BF on energy absorption of shotcrete square slabs

SpecimenEnergy absorption value (J)

δ 25 δ 50 δ 75 δ 100 δ 125 δ 150 δ 175 δ 200 δ 225 δ 250S2-1 8709 15857 20931 24337 26482 27701 28552 29410 30427 32208S3-3 10872 21185 29673 36326 41823 46253 49725 52255 54526 56510S4-1 9310 17045 22734 26763 29401 31308 32714 33892 35330 37323δ is the centre deflection of shotcrete square slab (mm)

Ener

gy (J

)

S1-3

S4-1

S3-3

S2-1

5 10 15 20 250Deflection (mm)

0

100

200

300

400

500

600

Figure 6 Energy absorption curve

6 Advances in Civil Engineering

ITZ

Crack

BF

Aggregate

(a)

BF SkeletonAggregate

(b)

BF

Aggregate

Ballingeffect

(c)

BF Aggregate

(d)

Figure 8 Bonding mode of fiber substrate (a) Matrix around fibers (b) Fiber random dispersion (c) Fiber dense distribution (d) Fiberbreakage under stress

Table 6 Crack development law of BF shotcrete square slabs

Contentof BF(kgm3)

Specimen

Maximumwidth of

initial crack(mm)

Averagevalue

Crackreductionrate ()

Limitcrackwidth(mm)

Averagevalue

Crackreductionrate ()

Maximumcrack width

(mm)

Averagevalue

Crackreductionrate ()

0S1-1 018

019 mdash028

028 mdash028

028 mdashS1-2 019 026 026S1-3 020 030 030

3S2-1 018

018 53025

025 107028

027 36S2-2 019 023 025S2-3 018 026 028

45S3-1 013

014 263018

019 321022

022 214S3-2 014 020 023S3-3 014 018 020

6S4-1 016

015 211021

023 179024

026 71S4-2 014 023 026S4-3 015 024 028

(a) (b) (c) (d)

Figure 7 Failure modes of shotcrete slabs with different BF contents (a) 0 kgm3(b) 3 kgm3 (c) 45 kgm3(d) 6 kgm3

0 15 3 45 6 75

1710 1910200

Botto

m p

late

six tr

ansv

erse

75deg

75deg90deg

1275deg

105deg

63deg

75deg

90deg

Figure 9 e layout of convergence survey points in the bottom drainage roadway

Advances in Civil Engineering 7

maximum deformation (7 days) of the plain sprayed con-crete retaining structure is 144mm When the BF content is3 kgm3 and 45 kgm3 the deformation of the roadway isonly 012mm in the first 7 days e total convergencedisplacement of the plain sprayed concrete at 35 days is247mmWhen the BF content is 45 kgm3 the convergencedisplacement of the bottom drainage roadway is 021mm Inthe stirring and spraying process the uniformly distributedBF will form a stable bearing structure inside the basalt fibershotcrete matrix thereby improving the resistance of theroadway to deformation

5 Conclusions

In this paper the effect of BF on the flexural toughness ofshotcrete square slab is studied e fiber-reinforcedmechanism is analyzed by means of a synthetic fiber-transparent soil model and SEM technology combined witha field test and the following conclusions are drawn

(1) rough the fiber-transparent soil model it is foundthat when the fiber content is within 3sim45 kgm3 thedistribution of BF is uniform and it forms a densenetwork structure in which agglomeration appearsand has a small ratio of pores which is beneficial toimproving the bending toughness of the shotcreteconcrete

(2) According to the comparison test of the bendingtoughness of the square slab it is found that when thefiber content is 45 kgm3 it had the best reinforcingeffect Compared with the control group the peakload and absorption capacity increased by 5667and 63696 respectively and the maximum crackwidth decreased by 3210

(3) e SEM analysis indicated that the three-dimen-sional random distribution of BF forms a stable load-bearing skeleton in the shotcrete improves the stressdistribution in the shotcrete matrix reduces thecrack driving force and restrains the generation anddevelopment of microcracks Excessive fiber

incorporation can increase fiber agglomerationduring stirring and spraying which may make BFand shotcrete matrix not fully bonded and affect thetoughness of basalt fiber shotcrete

(4) BF shotcrete has achieved a good support effect in adeep soft rock underground engineering test thebasalt fiber shotcrete support effect is improvedcompared with plain shotcrete and the ability ofrestraining the deformation of surrounding rock isenhanced e convergence displacement of theplain shotcrete support section is 247mm in 35 dayswhile the convergence displacement of the roadwayin the basalt fiber shotcrete support section with afiber dissolution of 45 kgm3 is only 021mm

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

is study was supported by the National Natural ScienceFoundation of China (51874123 and 51834001) the Scientificand Technological Research Projects of Henan ProvinceChina (182102310012) and Support Plan for Scientific andTechnological Innovation Talents in Colleges and Univer-sities of Henan Province China (19HASTIT047)

References

[1] J C Wang F Liu and L Wang ldquoSustainable coal mining andmining sciencesrdquo Journal of China Coal Society vol 41 no 11pp 2651ndash2660 2016 in Chinese

[2] E S Bernard ldquoAge-dependent changes in post-crack per-formance of fibre reinforced shotcrete liningsrdquo Tunnellingand Underground Space Technology vol 49 pp 241ndash248 2015

[3] M Khooshechin and J Tanzadeh ldquoExperimental and me-chanical performance of shotcrete made with nanomaterialsand fiber reinforcementrdquo Construction and Building Mate-rials vol 165 pp 199ndash205 2018

[4] J M Guo and Y S Zhang ldquoApplication research on mine-used high performance polymer modified concreterdquo Journalof Mining amp Safety Engineering vol 28 no 4 pp 660ndash6652011 in Chinese

[5] C High H M Seliem A EL-Safty and S H Rizkalla ldquoUse ofbasalt fibers for concrete structuresrdquo Construction andBuilding Materials vol 96 pp 37ndash46 2015

[6] F Akhlaghi R Eslami-Farsani and S Sabet ldquoSynthesis andcharacteristics of continuous basalt fiber reinforced alumi-num matrix compositesrdquo Journal of Composite Materialsvol 47 no 27 pp 3379ndash3388 2012

[7] V I Kostikov Soviet Advanced Composites Technology SeriesFibre Science and Technology Basalt Fibres and Articles Basedon ltem pp 581ndash605 Springer Moscow Russia 1995

[8] S M R Khalili M Najafi and R Eslami-Farsani ldquoEffect ofthermal cycling on the tensile behavior of polymer composites

021039

088099

107

247

The a

mou

nt o

f con

verg

ence

(mm

)

5 10 15 20 25 30 35 400Time (d)

00

05

10

15

20

25

30

0kgm3

3kgm3

6kgm3

15kgm3

45kgm3

75kgm3

Figure 10 Convergence deformation curve of bottom drainageroadway

8 Advances in Civil Engineering

reinforced by basalt and carbon fibersrdquo Mechanics of Com-posite Materials vol 52 no 6 pp 807ndash816 2017

[9] W W Hu H W Liu D F Zhao and Z B Yang ldquoAppli-cations and advantages of basalt assembly in constructionindustryrdquo Advanced Materials Research vol 332ndash334pp 1937ndash1940 2011

[10] R N Turukmane S S Culhane and A M Daberao ldquoBasalt-technical fiber for civil applicationsrdquo Technische Textilienvol 61 no 2 pp 69ndash71 2018

[11] R H Wu ldquoe application of basalt fiber in building ma-terialsrdquo Advanced Materials Research vol 450-451 pp 499ndash502 2012

[12] T I Kovalrsquo ldquoInvestigation of the reliability of bridge elementsreinforced with basalt plastic fibersrdquo Mechanics of CompositeMaterials vol 53 no 4 pp 479ndash486 2017

[13] X Wang Z Wu G Wu H Zhu and F Zen ldquoEnhancementof basalt FRP by hybridization for long-span cable-stayedbridgerdquo Composites Part B Engineering vol 44 no 1pp 184ndash192 2013

[14] K Krayushkina O Prentkovskis A Bieliatynskyi et alldquoPerspectives on using basalt fiber filaments in the con-struction and rehabilitation of highway pavements and air-port runwaysrdquo lte Baltic Journal of Road and BridgeEngineering vol 11 no 1 pp 77ndash83 2016

[15] S L Ma B Peng and Z Huang ldquoTest and analysis of basaltfiber reinforced concretersquos mechanical properties and pave-ment performancerdquo Advanced Materials Research vol 671-674 pp 1291ndash1296 2013

[16] M Wlodarczyk and I Jedrzejewski ldquoConcrete slabsstrengthened with basalt fibres - experimental tests resultsrdquoProcedia Engineering vol 153 pp 866ndash873 2016

[17] G Y Cui D Y Wang S Z Ni et al ldquoModel tests bearingcharacteristics of basalt fiber reinforced concrete tunnel lin-ingsrdquo Chinese Journal of Geotechnical Engineering vol 39no 2 pp 311ndash318 2017 in Chinese

[18] S K Sateshkumar P O Awoyera and T KandasamyldquoImpact resistance of high strength chopped basalt fibre-reinforced concreterdquo Revista De La Construccion vol 17no 2 pp 240ndash248 2018

[19] A Bentur and S Mindess Fiber Reinforced CementitiousComposites Taylor amp Francis Group Abingdon UK 2007

[20] D P Dias and C aumaturgo ldquoFracture toughness ofgeopolymeric concretes reinforced with basalt fibersrdquo Cementand Concrete Composites vol 27 no 1 pp 49ndash54 2005

[21] J Sim C Park and D Y Moon ldquoCharacteristics of basaltfiber as a strengthening material for concrete structuresrdquoComposites Part B Engineering vol 36 no 6-7 pp 504ndash5122005

[22] L F Zhang Y L Yin J W Liu et al ldquoMecha-nical proportiesstudy on basalt fiber reinforced concreterdquo Bulletin of theChinese Ceramic Society vol 33 no 11 pp 2834ndash2837 2014in Chinese

[23] D J Pickel J S West and A Alaskar ldquoUse of basalt fibers infiber-reinforced concreterdquo ACI Materials Journal vol 115no 6 pp 867ndash876 2018

[24] T Ayub N Shafiq and M F Nuruddin ldquoMechanicalproperties of high-performance concrete reinforced withbasalt fibersrdquo Procedia Engineering vol 77 pp 131ndash139 2014

[25] K Attia W Alnahhal A Elrefai and Y Rihan ldquoFlexuralbehavior of basalt fiber-reinforced concrete slab strips rein-forced with BFRP and GFRP barsrdquo Composite Structuresvol 211 pp 1ndash12 2019

[26] F Abed and A R Alhafiz ldquoEffect of basalt fibers on theflexural behavior of concrete beams reinforced with BFRPbarsrdquo Composite Structures vol 215 pp 23ndash34 2019

[27] Q SWang and H Yao ldquoApplication of reinforced concrete insoft rock tunnel at great depthrdquo Journal of Mining amp SafetyEngineering vol 25 no 2 pp 184ndash187 2008 in Chinese

[28] P Iyer S Y Kenno and S Das ldquoMechanical properties offiber-reinforced concrete made with basalt filament fibersrdquoJournal of Materials in Civil Engineering vol 27 no 11Article ID 04015015 2015

[29] H G Li W Z Sun Q L Qiu et al ldquoStudy on flexuraltoughness property of basalt fiber concrete mixed with steelfiberrdquo Journal of Highway and Transportation Research andDevelopment vol 33 no 9 pp 78ndash83 2016 in Chinese

[30] D Li and Y N Ding ldquoEffect of steel fiber on biaxial flexuralproperty of TRC with basalt fiber mesh in slab testrdquo ActaMateriae Compositae Sinica vol 20 no 1 pp 78ndash82 2017 inChinese

[31] EFNARC European Specification for Sprayed concreteLoughborough University Louthborough UK 1996

[32] X D Wang W Z Zhen and Y Wang ldquoInternal force re-distribution of umbonded prestressed concrete edge-sup-ported sl-absrdquo Journal of Harbin Institute of Technologyvol 47 no 2 pp 1ndash8 2015 in Chinese

[33] Z C Deng ldquoFlexural toughness and characterization methodof hybrid fibers reinforced ultra-high performance concret-erdquoActa Materiae Compositae Sinica vol 33 no 6 pp 1274ndash1280 2016 in Chinese

[34] S Cao E Yilmaz and W D Song ldquoEvaluation of viscositystrength and microstructural properties of cemented tailingsbackfillrdquo Minerals vol 8 no 8 p 352 2018

[35] S M Song J H Liu and X Q Zhang ldquoPerformance of thecement matrix composite material with rubber powderrdquoJournal of Wuhan University of Technology vol 19 no 1pp 77ndash80 2014

Advances in Civil Engineering 9

in Table 4 and Figure 5 which indicate that the peak loads ofshotcrete square slabs with fiber content of 0 kgm3 3 kgm345 kgm3 and 6 kgm3 are 3467 kN 4351 kN 5322 kN and4519 kN respectively e variance of the peak loads is05110 08091 07562 and 06970 respectively It can beseen from the variance of the different fiber content that thefluctuation of the test data is small indicating that thedispersion of the test data is good Compared with thecontrol group the peak loads with fiber contents of 3 kgm345 kgm3 and 6 kgm3 increased by 1111 5667 and3221 respectivelye control group shotcrete square slabhas high brittleness and low toughness With the addition ofBF to the shotcrete concrete the ultimate load and toughnessof the concrete can be improved appropriately

In order to study the effect of different contents of basaltfibers on the toughness of the square slabs the energy ab-sorption value in the EFNARC standard is used to char-acterize the fracture toughness of the slabs e calculationmethod is as follows

W 1113946δ

0F(x)dx (4)

In the formula W is the square slab energy absorptionvalue (unit J) δ is the central deflection of the square slaband F(x) is the load corresponding to the central deflectionof the square slab X

According to the load-displacement curves of shotcretesquare slabs with different contents of basalt fiber in Fig-ure 5 the energy absorption values corresponding to dif-ferent deflections are obtained by the integral method asshown in Table 5 e energy absorption curve is shown inFigure 6

Figure 6 shows that the energy absorption capacity of squareslabs with fibers of 3 kgm3 45 kgm3 and 6kgm3 is 32208 J56510 J and 37323 J respectively Compared with the controlgroup (7668 J) the energy absorption capacity increased by32003 63696 and 38674 respectivelyerefore BF cansignificantly improve the toughness and energy absorptioncapacity of BF shotcrete

rough the analysis of the load-deflection curve andenergy absorption curve it can be seen that the square slab

with the 45 kgm3 volume fraction of fiber shows the highesttoughness and energy absorption capacity

323 Analysis of Failure Form of Shotcrete Square Slabe crack development law and failure pattern of basalt fibershotcrete square slab are shown in Table 6 and Figure 7

e conclusions drawn from Table 6 and Figure 7 are asfollows

e BF shotcrete square slabs have four cracks for eachamount and the fiber contents are 0 kgm3 3 kgm3 45 kgm3 and 6 kgm3 where the mean values of the corre-sponding crack width are 028mm 025mm 019mm and023mm respectively compared with the control groupecrack width reduced by 107 321 and 179 respec-tively With the increase of fiber content the crack width ofthe square slab first increases and then decreases ebridging effect of the fiber creates a bond between the fiberand the concrete matrix which causes the stress redistri-bution and limits the generation and expansion of the crackerefore increase of the fiber content is beneficial tolimiting the development of the crack in the square slab andappropriately raises its bearing capacity and ductilityHowever excessive fiber content increases the porosity

Table 4 Test results of mechanical properties of BF reinforced concrete square slabs

Content of BF(kgm3) Specimen Initial cracking

deflection (mm)Initial

crack loadAveragevalue

Peakdeflection(mm)

Peakload(kN)

Averagevalue

Residualload (kN)

Averagevalue

0S1-1 074 3386

3467074 3386

346700

000S1-2 067 3456 082 3456 00S1-3 081 3560 110 3560 00

3S2-1 130 4066

3955175 4335

4351298

337S2-2 128 3942 188 4462 352S2-3 113 3856 168 4257 362

45S3-1 094 4682

4680180 5351

5322862

848S3-2 087 4536 174 5204 850S3-3 118 4823 189 5411 833

6S4-1 074 3862

4001152 4551

4519545

511S4-2 082 4087 149 4602 502S4-3 081 4053 160 4405 486

Load

(kN

)

S3-3S4-1

S2-1S1-1

5 10 15 20 250Deflection (mm)

0

10

20

30

40

50

60

Figure 5 Load-deflection curve of BF shotcrete square slab

Advances in Civil Engineering 5

inside the concrete matrix resulting in a decrease in thetoughness of the matrix

e failure mode of the control group was brittlefailure with a flat fracture surface When the flexuralspecimens of plain sprayed concrete were destroyed thecracks developed rapidly With the addition of BF thetoughness of the basalt fiber shotcrete square slab wasimproved the crack interface of the square slab was notintersected at the centre point and the fracture interfaceappeared as an irregular fracture shape When the fibercontent is 45 kgm3 the average crack width is thesmallest and the irregularity of cracks is poor Combinedwith the analysis of the load and energy absorption of theslabs the peak load value and energy absorption value aremaximum of the slabs e bridging connection providedby the basalt fiber across the crack can effectively improvethe toughness and maximum elongation of the shotcretesquare slab avoiding sudden brittle fracture after thepeak load of the slab and making the slab graduallytransition from brittle failure to ductile failure

33 SEM Analysis Electron microscopic scanning is aneffective method to study the internal distribution andmicrostructure of cement-based hydration products [34 35]allowing the observation of the distribution of fibers and thebonding mode between fibers and matrix and analyzing theeffect of hydration products such as ettringite and C-S-H onthe microstructure of the fiber matrix e bonding mode ofthe fiber matrix is shown in Figure 8

Figure 8 shows that the basalt fibers are covered with densecement hydration matrix so there is a good chemical ce-mentation between the fibers and the matrix (Figure 8(a)) ebasalt fibers are distributed randomly and evenly in the con-crete which can form a three-dimensional spatial skeleton witha stable structure (Figure 8(b)) Excessive fiber incorporationcan increase fiber agglomeration during stirring and sprayingwhich may reduce the bonding property between BF andshotcrete matrix (Figure 8(c)) Once a new crack appears in thespecimen under external loads the fiber spanning the crackconsumes energy to restrain the crack development through thedebonding and slipping of the fiber thus delaying the drivingforce of crack propagation in the concrete (Figure 8(d))

When the existing crack driving force is restrained andenergy accumulates in the concrete the anisotropic distributionof the BFwill seek new cracks in theweak points of thematrix torelease energy again e toughness and strength of concrete isenhanced by the fiber skeleton distributed inside the concretee effect of single BFs dispersed in basalt fiber shotcrete issimilar to reinforcing barse secondary micro-reinforcement

effect of BF combined with shotcrete matrix can effectivelyimprove the mechanical properties of basalt fiber shotcrete

4 Field Application of BF Shotcrete

41 Engineering Background e short-cut basalt fibershotcrete is applied to the bottom extraction roadway of ZhaoguNo2 coal mine (the roadway elevation is minus848simminus850m) etest section of roadway is located in the fractured shatter zoneBecause of the action of the fault zone the marl fracture zone inthe test section of the roadway is well developed e sur-rounding rock of the roadway has a weak layer and a strongwater-rich layer e lithology soft easy to produce large de-formation (the maximum deformation of the support is300mm) Concrete cracking and detachment deformation ofsteel support and other phenomena occur very often resultingin the failure of supports a great threat to mine safetyerefore the short-cut basalt fiber shotcrete was used for thefield test and 200m of the bottom extraction roadway wasselected for the underground support test Every 40m a dif-ferent fiber content was selected for the bolt-shotcrete supportAfter the shotcrete was completed two sets of monitoringpoints were used to monitor the convergence deformation ofthe roadwaye layout of the convergence survey points in thebottom drainage roadway is shown in Figure 9

42 Analysis of Convergence Deformation of RoadwayAfter the basalt fiber shotcrete has set and hardened con-vergence deformation monitoring is carried out for 35 dayson the bottom drainage roadway e monitoring results areshown in Figure 10 e addition of BF increases the de-formation resistance of the supporting structure e

Table 5 Effect of BF on energy absorption of shotcrete square slabs

SpecimenEnergy absorption value (J)

δ 25 δ 50 δ 75 δ 100 δ 125 δ 150 δ 175 δ 200 δ 225 δ 250S2-1 8709 15857 20931 24337 26482 27701 28552 29410 30427 32208S3-3 10872 21185 29673 36326 41823 46253 49725 52255 54526 56510S4-1 9310 17045 22734 26763 29401 31308 32714 33892 35330 37323δ is the centre deflection of shotcrete square slab (mm)

Ener

gy (J

)

S1-3

S4-1

S3-3

S2-1

5 10 15 20 250Deflection (mm)

0

100

200

300

400

500

600

Figure 6 Energy absorption curve

6 Advances in Civil Engineering

ITZ

Crack

BF

Aggregate

(a)

BF SkeletonAggregate

(b)

BF

Aggregate

Ballingeffect

(c)

BF Aggregate

(d)

Figure 8 Bonding mode of fiber substrate (a) Matrix around fibers (b) Fiber random dispersion (c) Fiber dense distribution (d) Fiberbreakage under stress

Table 6 Crack development law of BF shotcrete square slabs

Contentof BF(kgm3)

Specimen

Maximumwidth of

initial crack(mm)

Averagevalue

Crackreductionrate ()

Limitcrackwidth(mm)

Averagevalue

Crackreductionrate ()

Maximumcrack width

(mm)

Averagevalue

Crackreductionrate ()

0S1-1 018

019 mdash028

028 mdash028

028 mdashS1-2 019 026 026S1-3 020 030 030

3S2-1 018

018 53025

025 107028

027 36S2-2 019 023 025S2-3 018 026 028

45S3-1 013

014 263018

019 321022

022 214S3-2 014 020 023S3-3 014 018 020

6S4-1 016

015 211021

023 179024

026 71S4-2 014 023 026S4-3 015 024 028

(a) (b) (c) (d)

Figure 7 Failure modes of shotcrete slabs with different BF contents (a) 0 kgm3(b) 3 kgm3 (c) 45 kgm3(d) 6 kgm3

0 15 3 45 6 75

1710 1910200

Botto

m p

late

six tr

ansv

erse

75deg

75deg90deg

1275deg

105deg

63deg

75deg

90deg

Figure 9 e layout of convergence survey points in the bottom drainage roadway

Advances in Civil Engineering 7

maximum deformation (7 days) of the plain sprayed con-crete retaining structure is 144mm When the BF content is3 kgm3 and 45 kgm3 the deformation of the roadway isonly 012mm in the first 7 days e total convergencedisplacement of the plain sprayed concrete at 35 days is247mmWhen the BF content is 45 kgm3 the convergencedisplacement of the bottom drainage roadway is 021mm Inthe stirring and spraying process the uniformly distributedBF will form a stable bearing structure inside the basalt fibershotcrete matrix thereby improving the resistance of theroadway to deformation

5 Conclusions

In this paper the effect of BF on the flexural toughness ofshotcrete square slab is studied e fiber-reinforcedmechanism is analyzed by means of a synthetic fiber-transparent soil model and SEM technology combined witha field test and the following conclusions are drawn

(1) rough the fiber-transparent soil model it is foundthat when the fiber content is within 3sim45 kgm3 thedistribution of BF is uniform and it forms a densenetwork structure in which agglomeration appearsand has a small ratio of pores which is beneficial toimproving the bending toughness of the shotcreteconcrete

(2) According to the comparison test of the bendingtoughness of the square slab it is found that when thefiber content is 45 kgm3 it had the best reinforcingeffect Compared with the control group the peakload and absorption capacity increased by 5667and 63696 respectively and the maximum crackwidth decreased by 3210

(3) e SEM analysis indicated that the three-dimen-sional random distribution of BF forms a stable load-bearing skeleton in the shotcrete improves the stressdistribution in the shotcrete matrix reduces thecrack driving force and restrains the generation anddevelopment of microcracks Excessive fiber

incorporation can increase fiber agglomerationduring stirring and spraying which may make BFand shotcrete matrix not fully bonded and affect thetoughness of basalt fiber shotcrete

(4) BF shotcrete has achieved a good support effect in adeep soft rock underground engineering test thebasalt fiber shotcrete support effect is improvedcompared with plain shotcrete and the ability ofrestraining the deformation of surrounding rock isenhanced e convergence displacement of theplain shotcrete support section is 247mm in 35 dayswhile the convergence displacement of the roadwayin the basalt fiber shotcrete support section with afiber dissolution of 45 kgm3 is only 021mm

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

is study was supported by the National Natural ScienceFoundation of China (51874123 and 51834001) the Scientificand Technological Research Projects of Henan ProvinceChina (182102310012) and Support Plan for Scientific andTechnological Innovation Talents in Colleges and Univer-sities of Henan Province China (19HASTIT047)

References

[1] J C Wang F Liu and L Wang ldquoSustainable coal mining andmining sciencesrdquo Journal of China Coal Society vol 41 no 11pp 2651ndash2660 2016 in Chinese

[2] E S Bernard ldquoAge-dependent changes in post-crack per-formance of fibre reinforced shotcrete liningsrdquo Tunnellingand Underground Space Technology vol 49 pp 241ndash248 2015

[3] M Khooshechin and J Tanzadeh ldquoExperimental and me-chanical performance of shotcrete made with nanomaterialsand fiber reinforcementrdquo Construction and Building Mate-rials vol 165 pp 199ndash205 2018

[4] J M Guo and Y S Zhang ldquoApplication research on mine-used high performance polymer modified concreterdquo Journalof Mining amp Safety Engineering vol 28 no 4 pp 660ndash6652011 in Chinese

[5] C High H M Seliem A EL-Safty and S H Rizkalla ldquoUse ofbasalt fibers for concrete structuresrdquo Construction andBuilding Materials vol 96 pp 37ndash46 2015

[6] F Akhlaghi R Eslami-Farsani and S Sabet ldquoSynthesis andcharacteristics of continuous basalt fiber reinforced alumi-num matrix compositesrdquo Journal of Composite Materialsvol 47 no 27 pp 3379ndash3388 2012

[7] V I Kostikov Soviet Advanced Composites Technology SeriesFibre Science and Technology Basalt Fibres and Articles Basedon ltem pp 581ndash605 Springer Moscow Russia 1995

[8] S M R Khalili M Najafi and R Eslami-Farsani ldquoEffect ofthermal cycling on the tensile behavior of polymer composites

021039

088099

107

247

The a

mou

nt o

f con

verg

ence

(mm

)

5 10 15 20 25 30 35 400Time (d)

00

05

10

15

20

25

30

0kgm3

3kgm3

6kgm3

15kgm3

45kgm3

75kgm3

Figure 10 Convergence deformation curve of bottom drainageroadway

8 Advances in Civil Engineering

reinforced by basalt and carbon fibersrdquo Mechanics of Com-posite Materials vol 52 no 6 pp 807ndash816 2017

[9] W W Hu H W Liu D F Zhao and Z B Yang ldquoAppli-cations and advantages of basalt assembly in constructionindustryrdquo Advanced Materials Research vol 332ndash334pp 1937ndash1940 2011

[10] R N Turukmane S S Culhane and A M Daberao ldquoBasalt-technical fiber for civil applicationsrdquo Technische Textilienvol 61 no 2 pp 69ndash71 2018

[11] R H Wu ldquoe application of basalt fiber in building ma-terialsrdquo Advanced Materials Research vol 450-451 pp 499ndash502 2012

[12] T I Kovalrsquo ldquoInvestigation of the reliability of bridge elementsreinforced with basalt plastic fibersrdquo Mechanics of CompositeMaterials vol 53 no 4 pp 479ndash486 2017

[13] X Wang Z Wu G Wu H Zhu and F Zen ldquoEnhancementof basalt FRP by hybridization for long-span cable-stayedbridgerdquo Composites Part B Engineering vol 44 no 1pp 184ndash192 2013

[14] K Krayushkina O Prentkovskis A Bieliatynskyi et alldquoPerspectives on using basalt fiber filaments in the con-struction and rehabilitation of highway pavements and air-port runwaysrdquo lte Baltic Journal of Road and BridgeEngineering vol 11 no 1 pp 77ndash83 2016

[15] S L Ma B Peng and Z Huang ldquoTest and analysis of basaltfiber reinforced concretersquos mechanical properties and pave-ment performancerdquo Advanced Materials Research vol 671-674 pp 1291ndash1296 2013

[16] M Wlodarczyk and I Jedrzejewski ldquoConcrete slabsstrengthened with basalt fibres - experimental tests resultsrdquoProcedia Engineering vol 153 pp 866ndash873 2016

[17] G Y Cui D Y Wang S Z Ni et al ldquoModel tests bearingcharacteristics of basalt fiber reinforced concrete tunnel lin-ingsrdquo Chinese Journal of Geotechnical Engineering vol 39no 2 pp 311ndash318 2017 in Chinese

[18] S K Sateshkumar P O Awoyera and T KandasamyldquoImpact resistance of high strength chopped basalt fibre-reinforced concreterdquo Revista De La Construccion vol 17no 2 pp 240ndash248 2018

[19] A Bentur and S Mindess Fiber Reinforced CementitiousComposites Taylor amp Francis Group Abingdon UK 2007

[20] D P Dias and C aumaturgo ldquoFracture toughness ofgeopolymeric concretes reinforced with basalt fibersrdquo Cementand Concrete Composites vol 27 no 1 pp 49ndash54 2005

[21] J Sim C Park and D Y Moon ldquoCharacteristics of basaltfiber as a strengthening material for concrete structuresrdquoComposites Part B Engineering vol 36 no 6-7 pp 504ndash5122005

[22] L F Zhang Y L Yin J W Liu et al ldquoMecha-nical proportiesstudy on basalt fiber reinforced concreterdquo Bulletin of theChinese Ceramic Society vol 33 no 11 pp 2834ndash2837 2014in Chinese

[23] D J Pickel J S West and A Alaskar ldquoUse of basalt fibers infiber-reinforced concreterdquo ACI Materials Journal vol 115no 6 pp 867ndash876 2018

[24] T Ayub N Shafiq and M F Nuruddin ldquoMechanicalproperties of high-performance concrete reinforced withbasalt fibersrdquo Procedia Engineering vol 77 pp 131ndash139 2014

[25] K Attia W Alnahhal A Elrefai and Y Rihan ldquoFlexuralbehavior of basalt fiber-reinforced concrete slab strips rein-forced with BFRP and GFRP barsrdquo Composite Structuresvol 211 pp 1ndash12 2019

[26] F Abed and A R Alhafiz ldquoEffect of basalt fibers on theflexural behavior of concrete beams reinforced with BFRPbarsrdquo Composite Structures vol 215 pp 23ndash34 2019

[27] Q SWang and H Yao ldquoApplication of reinforced concrete insoft rock tunnel at great depthrdquo Journal of Mining amp SafetyEngineering vol 25 no 2 pp 184ndash187 2008 in Chinese

[28] P Iyer S Y Kenno and S Das ldquoMechanical properties offiber-reinforced concrete made with basalt filament fibersrdquoJournal of Materials in Civil Engineering vol 27 no 11Article ID 04015015 2015

[29] H G Li W Z Sun Q L Qiu et al ldquoStudy on flexuraltoughness property of basalt fiber concrete mixed with steelfiberrdquo Journal of Highway and Transportation Research andDevelopment vol 33 no 9 pp 78ndash83 2016 in Chinese

[30] D Li and Y N Ding ldquoEffect of steel fiber on biaxial flexuralproperty of TRC with basalt fiber mesh in slab testrdquo ActaMateriae Compositae Sinica vol 20 no 1 pp 78ndash82 2017 inChinese

[31] EFNARC European Specification for Sprayed concreteLoughborough University Louthborough UK 1996

[32] X D Wang W Z Zhen and Y Wang ldquoInternal force re-distribution of umbonded prestressed concrete edge-sup-ported sl-absrdquo Journal of Harbin Institute of Technologyvol 47 no 2 pp 1ndash8 2015 in Chinese

[33] Z C Deng ldquoFlexural toughness and characterization methodof hybrid fibers reinforced ultra-high performance concret-erdquoActa Materiae Compositae Sinica vol 33 no 6 pp 1274ndash1280 2016 in Chinese

[34] S Cao E Yilmaz and W D Song ldquoEvaluation of viscositystrength and microstructural properties of cemented tailingsbackfillrdquo Minerals vol 8 no 8 p 352 2018

[35] S M Song J H Liu and X Q Zhang ldquoPerformance of thecement matrix composite material with rubber powderrdquoJournal of Wuhan University of Technology vol 19 no 1pp 77ndash80 2014

Advances in Civil Engineering 9

inside the concrete matrix resulting in a decrease in thetoughness of the matrix

e failure mode of the control group was brittlefailure with a flat fracture surface When the flexuralspecimens of plain sprayed concrete were destroyed thecracks developed rapidly With the addition of BF thetoughness of the basalt fiber shotcrete square slab wasimproved the crack interface of the square slab was notintersected at the centre point and the fracture interfaceappeared as an irregular fracture shape When the fibercontent is 45 kgm3 the average crack width is thesmallest and the irregularity of cracks is poor Combinedwith the analysis of the load and energy absorption of theslabs the peak load value and energy absorption value aremaximum of the slabs e bridging connection providedby the basalt fiber across the crack can effectively improvethe toughness and maximum elongation of the shotcretesquare slab avoiding sudden brittle fracture after thepeak load of the slab and making the slab graduallytransition from brittle failure to ductile failure

33 SEM Analysis Electron microscopic scanning is aneffective method to study the internal distribution andmicrostructure of cement-based hydration products [34 35]allowing the observation of the distribution of fibers and thebonding mode between fibers and matrix and analyzing theeffect of hydration products such as ettringite and C-S-H onthe microstructure of the fiber matrix e bonding mode ofthe fiber matrix is shown in Figure 8

Figure 8 shows that the basalt fibers are covered with densecement hydration matrix so there is a good chemical ce-mentation between the fibers and the matrix (Figure 8(a)) ebasalt fibers are distributed randomly and evenly in the con-crete which can form a three-dimensional spatial skeleton witha stable structure (Figure 8(b)) Excessive fiber incorporationcan increase fiber agglomeration during stirring and sprayingwhich may reduce the bonding property between BF andshotcrete matrix (Figure 8(c)) Once a new crack appears in thespecimen under external loads the fiber spanning the crackconsumes energy to restrain the crack development through thedebonding and slipping of the fiber thus delaying the drivingforce of crack propagation in the concrete (Figure 8(d))

When the existing crack driving force is restrained andenergy accumulates in the concrete the anisotropic distributionof the BFwill seek new cracks in theweak points of thematrix torelease energy again e toughness and strength of concrete isenhanced by the fiber skeleton distributed inside the concretee effect of single BFs dispersed in basalt fiber shotcrete issimilar to reinforcing barse secondary micro-reinforcement

effect of BF combined with shotcrete matrix can effectivelyimprove the mechanical properties of basalt fiber shotcrete

4 Field Application of BF Shotcrete

41 Engineering Background e short-cut basalt fibershotcrete is applied to the bottom extraction roadway of ZhaoguNo2 coal mine (the roadway elevation is minus848simminus850m) etest section of roadway is located in the fractured shatter zoneBecause of the action of the fault zone the marl fracture zone inthe test section of the roadway is well developed e sur-rounding rock of the roadway has a weak layer and a strongwater-rich layer e lithology soft easy to produce large de-formation (the maximum deformation of the support is300mm) Concrete cracking and detachment deformation ofsteel support and other phenomena occur very often resultingin the failure of supports a great threat to mine safetyerefore the short-cut basalt fiber shotcrete was used for thefield test and 200m of the bottom extraction roadway wasselected for the underground support test Every 40m a dif-ferent fiber content was selected for the bolt-shotcrete supportAfter the shotcrete was completed two sets of monitoringpoints were used to monitor the convergence deformation ofthe roadwaye layout of the convergence survey points in thebottom drainage roadway is shown in Figure 9

42 Analysis of Convergence Deformation of RoadwayAfter the basalt fiber shotcrete has set and hardened con-vergence deformation monitoring is carried out for 35 dayson the bottom drainage roadway e monitoring results areshown in Figure 10 e addition of BF increases the de-formation resistance of the supporting structure e

Table 5 Effect of BF on energy absorption of shotcrete square slabs

SpecimenEnergy absorption value (J)

δ 25 δ 50 δ 75 δ 100 δ 125 δ 150 δ 175 δ 200 δ 225 δ 250S2-1 8709 15857 20931 24337 26482 27701 28552 29410 30427 32208S3-3 10872 21185 29673 36326 41823 46253 49725 52255 54526 56510S4-1 9310 17045 22734 26763 29401 31308 32714 33892 35330 37323δ is the centre deflection of shotcrete square slab (mm)

Ener

gy (J

)

S1-3

S4-1

S3-3

S2-1

5 10 15 20 250Deflection (mm)

0

100

200

300

400

500

600

Figure 6 Energy absorption curve

6 Advances in Civil Engineering

ITZ

Crack

BF

Aggregate

(a)

BF SkeletonAggregate

(b)

BF

Aggregate

Ballingeffect

(c)

BF Aggregate

(d)

Figure 8 Bonding mode of fiber substrate (a) Matrix around fibers (b) Fiber random dispersion (c) Fiber dense distribution (d) Fiberbreakage under stress

Table 6 Crack development law of BF shotcrete square slabs

Contentof BF(kgm3)

Specimen

Maximumwidth of

initial crack(mm)

Averagevalue

Crackreductionrate ()

Limitcrackwidth(mm)

Averagevalue

Crackreductionrate ()

Maximumcrack width

(mm)

Averagevalue

Crackreductionrate ()

0S1-1 018

019 mdash028

028 mdash028

028 mdashS1-2 019 026 026S1-3 020 030 030

3S2-1 018

018 53025

025 107028

027 36S2-2 019 023 025S2-3 018 026 028

45S3-1 013

014 263018

019 321022

022 214S3-2 014 020 023S3-3 014 018 020

6S4-1 016

015 211021

023 179024

026 71S4-2 014 023 026S4-3 015 024 028

(a) (b) (c) (d)

Figure 7 Failure modes of shotcrete slabs with different BF contents (a) 0 kgm3(b) 3 kgm3 (c) 45 kgm3(d) 6 kgm3

0 15 3 45 6 75

1710 1910200

Botto

m p

late

six tr

ansv

erse

75deg

75deg90deg

1275deg

105deg

63deg

75deg

90deg

Figure 9 e layout of convergence survey points in the bottom drainage roadway

Advances in Civil Engineering 7

maximum deformation (7 days) of the plain sprayed con-crete retaining structure is 144mm When the BF content is3 kgm3 and 45 kgm3 the deformation of the roadway isonly 012mm in the first 7 days e total convergencedisplacement of the plain sprayed concrete at 35 days is247mmWhen the BF content is 45 kgm3 the convergencedisplacement of the bottom drainage roadway is 021mm Inthe stirring and spraying process the uniformly distributedBF will form a stable bearing structure inside the basalt fibershotcrete matrix thereby improving the resistance of theroadway to deformation

5 Conclusions

In this paper the effect of BF on the flexural toughness ofshotcrete square slab is studied e fiber-reinforcedmechanism is analyzed by means of a synthetic fiber-transparent soil model and SEM technology combined witha field test and the following conclusions are drawn

(1) rough the fiber-transparent soil model it is foundthat when the fiber content is within 3sim45 kgm3 thedistribution of BF is uniform and it forms a densenetwork structure in which agglomeration appearsand has a small ratio of pores which is beneficial toimproving the bending toughness of the shotcreteconcrete

(2) According to the comparison test of the bendingtoughness of the square slab it is found that when thefiber content is 45 kgm3 it had the best reinforcingeffect Compared with the control group the peakload and absorption capacity increased by 5667and 63696 respectively and the maximum crackwidth decreased by 3210

(3) e SEM analysis indicated that the three-dimen-sional random distribution of BF forms a stable load-bearing skeleton in the shotcrete improves the stressdistribution in the shotcrete matrix reduces thecrack driving force and restrains the generation anddevelopment of microcracks Excessive fiber

incorporation can increase fiber agglomerationduring stirring and spraying which may make BFand shotcrete matrix not fully bonded and affect thetoughness of basalt fiber shotcrete

(4) BF shotcrete has achieved a good support effect in adeep soft rock underground engineering test thebasalt fiber shotcrete support effect is improvedcompared with plain shotcrete and the ability ofrestraining the deformation of surrounding rock isenhanced e convergence displacement of theplain shotcrete support section is 247mm in 35 dayswhile the convergence displacement of the roadwayin the basalt fiber shotcrete support section with afiber dissolution of 45 kgm3 is only 021mm

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

is study was supported by the National Natural ScienceFoundation of China (51874123 and 51834001) the Scientificand Technological Research Projects of Henan ProvinceChina (182102310012) and Support Plan for Scientific andTechnological Innovation Talents in Colleges and Univer-sities of Henan Province China (19HASTIT047)

References

[1] J C Wang F Liu and L Wang ldquoSustainable coal mining andmining sciencesrdquo Journal of China Coal Society vol 41 no 11pp 2651ndash2660 2016 in Chinese

[2] E S Bernard ldquoAge-dependent changes in post-crack per-formance of fibre reinforced shotcrete liningsrdquo Tunnellingand Underground Space Technology vol 49 pp 241ndash248 2015

[3] M Khooshechin and J Tanzadeh ldquoExperimental and me-chanical performance of shotcrete made with nanomaterialsand fiber reinforcementrdquo Construction and Building Mate-rials vol 165 pp 199ndash205 2018

[4] J M Guo and Y S Zhang ldquoApplication research on mine-used high performance polymer modified concreterdquo Journalof Mining amp Safety Engineering vol 28 no 4 pp 660ndash6652011 in Chinese

[5] C High H M Seliem A EL-Safty and S H Rizkalla ldquoUse ofbasalt fibers for concrete structuresrdquo Construction andBuilding Materials vol 96 pp 37ndash46 2015

[6] F Akhlaghi R Eslami-Farsani and S Sabet ldquoSynthesis andcharacteristics of continuous basalt fiber reinforced alumi-num matrix compositesrdquo Journal of Composite Materialsvol 47 no 27 pp 3379ndash3388 2012

[7] V I Kostikov Soviet Advanced Composites Technology SeriesFibre Science and Technology Basalt Fibres and Articles Basedon ltem pp 581ndash605 Springer Moscow Russia 1995

[8] S M R Khalili M Najafi and R Eslami-Farsani ldquoEffect ofthermal cycling on the tensile behavior of polymer composites

021039

088099

107

247

The a

mou

nt o

f con

verg

ence

(mm

)

5 10 15 20 25 30 35 400Time (d)

00

05

10

15

20

25

30

0kgm3

3kgm3

6kgm3

15kgm3

45kgm3

75kgm3

Figure 10 Convergence deformation curve of bottom drainageroadway

8 Advances in Civil Engineering

reinforced by basalt and carbon fibersrdquo Mechanics of Com-posite Materials vol 52 no 6 pp 807ndash816 2017

[9] W W Hu H W Liu D F Zhao and Z B Yang ldquoAppli-cations and advantages of basalt assembly in constructionindustryrdquo Advanced Materials Research vol 332ndash334pp 1937ndash1940 2011

[10] R N Turukmane S S Culhane and A M Daberao ldquoBasalt-technical fiber for civil applicationsrdquo Technische Textilienvol 61 no 2 pp 69ndash71 2018

[11] R H Wu ldquoe application of basalt fiber in building ma-terialsrdquo Advanced Materials Research vol 450-451 pp 499ndash502 2012

[12] T I Kovalrsquo ldquoInvestigation of the reliability of bridge elementsreinforced with basalt plastic fibersrdquo Mechanics of CompositeMaterials vol 53 no 4 pp 479ndash486 2017

[13] X Wang Z Wu G Wu H Zhu and F Zen ldquoEnhancementof basalt FRP by hybridization for long-span cable-stayedbridgerdquo Composites Part B Engineering vol 44 no 1pp 184ndash192 2013

[14] K Krayushkina O Prentkovskis A Bieliatynskyi et alldquoPerspectives on using basalt fiber filaments in the con-struction and rehabilitation of highway pavements and air-port runwaysrdquo lte Baltic Journal of Road and BridgeEngineering vol 11 no 1 pp 77ndash83 2016

[15] S L Ma B Peng and Z Huang ldquoTest and analysis of basaltfiber reinforced concretersquos mechanical properties and pave-ment performancerdquo Advanced Materials Research vol 671-674 pp 1291ndash1296 2013

[16] M Wlodarczyk and I Jedrzejewski ldquoConcrete slabsstrengthened with basalt fibres - experimental tests resultsrdquoProcedia Engineering vol 153 pp 866ndash873 2016

[17] G Y Cui D Y Wang S Z Ni et al ldquoModel tests bearingcharacteristics of basalt fiber reinforced concrete tunnel lin-ingsrdquo Chinese Journal of Geotechnical Engineering vol 39no 2 pp 311ndash318 2017 in Chinese

[18] S K Sateshkumar P O Awoyera and T KandasamyldquoImpact resistance of high strength chopped basalt fibre-reinforced concreterdquo Revista De La Construccion vol 17no 2 pp 240ndash248 2018

[19] A Bentur and S Mindess Fiber Reinforced CementitiousComposites Taylor amp Francis Group Abingdon UK 2007

[20] D P Dias and C aumaturgo ldquoFracture toughness ofgeopolymeric concretes reinforced with basalt fibersrdquo Cementand Concrete Composites vol 27 no 1 pp 49ndash54 2005

[21] J Sim C Park and D Y Moon ldquoCharacteristics of basaltfiber as a strengthening material for concrete structuresrdquoComposites Part B Engineering vol 36 no 6-7 pp 504ndash5122005

[22] L F Zhang Y L Yin J W Liu et al ldquoMecha-nical proportiesstudy on basalt fiber reinforced concreterdquo Bulletin of theChinese Ceramic Society vol 33 no 11 pp 2834ndash2837 2014in Chinese

[23] D J Pickel J S West and A Alaskar ldquoUse of basalt fibers infiber-reinforced concreterdquo ACI Materials Journal vol 115no 6 pp 867ndash876 2018

[24] T Ayub N Shafiq and M F Nuruddin ldquoMechanicalproperties of high-performance concrete reinforced withbasalt fibersrdquo Procedia Engineering vol 77 pp 131ndash139 2014

[25] K Attia W Alnahhal A Elrefai and Y Rihan ldquoFlexuralbehavior of basalt fiber-reinforced concrete slab strips rein-forced with BFRP and GFRP barsrdquo Composite Structuresvol 211 pp 1ndash12 2019

[26] F Abed and A R Alhafiz ldquoEffect of basalt fibers on theflexural behavior of concrete beams reinforced with BFRPbarsrdquo Composite Structures vol 215 pp 23ndash34 2019

[27] Q SWang and H Yao ldquoApplication of reinforced concrete insoft rock tunnel at great depthrdquo Journal of Mining amp SafetyEngineering vol 25 no 2 pp 184ndash187 2008 in Chinese

[28] P Iyer S Y Kenno and S Das ldquoMechanical properties offiber-reinforced concrete made with basalt filament fibersrdquoJournal of Materials in Civil Engineering vol 27 no 11Article ID 04015015 2015

[29] H G Li W Z Sun Q L Qiu et al ldquoStudy on flexuraltoughness property of basalt fiber concrete mixed with steelfiberrdquo Journal of Highway and Transportation Research andDevelopment vol 33 no 9 pp 78ndash83 2016 in Chinese

[30] D Li and Y N Ding ldquoEffect of steel fiber on biaxial flexuralproperty of TRC with basalt fiber mesh in slab testrdquo ActaMateriae Compositae Sinica vol 20 no 1 pp 78ndash82 2017 inChinese

[31] EFNARC European Specification for Sprayed concreteLoughborough University Louthborough UK 1996

[32] X D Wang W Z Zhen and Y Wang ldquoInternal force re-distribution of umbonded prestressed concrete edge-sup-ported sl-absrdquo Journal of Harbin Institute of Technologyvol 47 no 2 pp 1ndash8 2015 in Chinese

[33] Z C Deng ldquoFlexural toughness and characterization methodof hybrid fibers reinforced ultra-high performance concret-erdquoActa Materiae Compositae Sinica vol 33 no 6 pp 1274ndash1280 2016 in Chinese

[34] S Cao E Yilmaz and W D Song ldquoEvaluation of viscositystrength and microstructural properties of cemented tailingsbackfillrdquo Minerals vol 8 no 8 p 352 2018

[35] S M Song J H Liu and X Q Zhang ldquoPerformance of thecement matrix composite material with rubber powderrdquoJournal of Wuhan University of Technology vol 19 no 1pp 77ndash80 2014

Advances in Civil Engineering 9

ITZ

Crack

BF

Aggregate

(a)

BF SkeletonAggregate

(b)

BF

Aggregate

Ballingeffect

(c)

BF Aggregate

(d)

Figure 8 Bonding mode of fiber substrate (a) Matrix around fibers (b) Fiber random dispersion (c) Fiber dense distribution (d) Fiberbreakage under stress

Table 6 Crack development law of BF shotcrete square slabs

Contentof BF(kgm3)

Specimen

Maximumwidth of

initial crack(mm)

Averagevalue

Crackreductionrate ()

Limitcrackwidth(mm)

Averagevalue

Crackreductionrate ()

Maximumcrack width

(mm)

Averagevalue

Crackreductionrate ()

0S1-1 018

019 mdash028

028 mdash028

028 mdashS1-2 019 026 026S1-3 020 030 030

3S2-1 018

018 53025

025 107028

027 36S2-2 019 023 025S2-3 018 026 028

45S3-1 013

014 263018

019 321022

022 214S3-2 014 020 023S3-3 014 018 020

6S4-1 016

015 211021

023 179024

026 71S4-2 014 023 026S4-3 015 024 028

(a) (b) (c) (d)

Figure 7 Failure modes of shotcrete slabs with different BF contents (a) 0 kgm3(b) 3 kgm3 (c) 45 kgm3(d) 6 kgm3

0 15 3 45 6 75

1710 1910200

Botto

m p

late

six tr

ansv

erse

75deg

75deg90deg

1275deg

105deg

63deg

75deg

90deg

Figure 9 e layout of convergence survey points in the bottom drainage roadway

Advances in Civil Engineering 7

maximum deformation (7 days) of the plain sprayed con-crete retaining structure is 144mm When the BF content is3 kgm3 and 45 kgm3 the deformation of the roadway isonly 012mm in the first 7 days e total convergencedisplacement of the plain sprayed concrete at 35 days is247mmWhen the BF content is 45 kgm3 the convergencedisplacement of the bottom drainage roadway is 021mm Inthe stirring and spraying process the uniformly distributedBF will form a stable bearing structure inside the basalt fibershotcrete matrix thereby improving the resistance of theroadway to deformation

5 Conclusions

In this paper the effect of BF on the flexural toughness ofshotcrete square slab is studied e fiber-reinforcedmechanism is analyzed by means of a synthetic fiber-transparent soil model and SEM technology combined witha field test and the following conclusions are drawn

(1) rough the fiber-transparent soil model it is foundthat when the fiber content is within 3sim45 kgm3 thedistribution of BF is uniform and it forms a densenetwork structure in which agglomeration appearsand has a small ratio of pores which is beneficial toimproving the bending toughness of the shotcreteconcrete

(2) According to the comparison test of the bendingtoughness of the square slab it is found that when thefiber content is 45 kgm3 it had the best reinforcingeffect Compared with the control group the peakload and absorption capacity increased by 5667and 63696 respectively and the maximum crackwidth decreased by 3210

(3) e SEM analysis indicated that the three-dimen-sional random distribution of BF forms a stable load-bearing skeleton in the shotcrete improves the stressdistribution in the shotcrete matrix reduces thecrack driving force and restrains the generation anddevelopment of microcracks Excessive fiber

incorporation can increase fiber agglomerationduring stirring and spraying which may make BFand shotcrete matrix not fully bonded and affect thetoughness of basalt fiber shotcrete

(4) BF shotcrete has achieved a good support effect in adeep soft rock underground engineering test thebasalt fiber shotcrete support effect is improvedcompared with plain shotcrete and the ability ofrestraining the deformation of surrounding rock isenhanced e convergence displacement of theplain shotcrete support section is 247mm in 35 dayswhile the convergence displacement of the roadwayin the basalt fiber shotcrete support section with afiber dissolution of 45 kgm3 is only 021mm

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

is study was supported by the National Natural ScienceFoundation of China (51874123 and 51834001) the Scientificand Technological Research Projects of Henan ProvinceChina (182102310012) and Support Plan for Scientific andTechnological Innovation Talents in Colleges and Univer-sities of Henan Province China (19HASTIT047)

References

[1] J C Wang F Liu and L Wang ldquoSustainable coal mining andmining sciencesrdquo Journal of China Coal Society vol 41 no 11pp 2651ndash2660 2016 in Chinese

[2] E S Bernard ldquoAge-dependent changes in post-crack per-formance of fibre reinforced shotcrete liningsrdquo Tunnellingand Underground Space Technology vol 49 pp 241ndash248 2015

[3] M Khooshechin and J Tanzadeh ldquoExperimental and me-chanical performance of shotcrete made with nanomaterialsand fiber reinforcementrdquo Construction and Building Mate-rials vol 165 pp 199ndash205 2018

[4] J M Guo and Y S Zhang ldquoApplication research on mine-used high performance polymer modified concreterdquo Journalof Mining amp Safety Engineering vol 28 no 4 pp 660ndash6652011 in Chinese

[5] C High H M Seliem A EL-Safty and S H Rizkalla ldquoUse ofbasalt fibers for concrete structuresrdquo Construction andBuilding Materials vol 96 pp 37ndash46 2015

[6] F Akhlaghi R Eslami-Farsani and S Sabet ldquoSynthesis andcharacteristics of continuous basalt fiber reinforced alumi-num matrix compositesrdquo Journal of Composite Materialsvol 47 no 27 pp 3379ndash3388 2012

[7] V I Kostikov Soviet Advanced Composites Technology SeriesFibre Science and Technology Basalt Fibres and Articles Basedon ltem pp 581ndash605 Springer Moscow Russia 1995

[8] S M R Khalili M Najafi and R Eslami-Farsani ldquoEffect ofthermal cycling on the tensile behavior of polymer composites

021039

088099

107

247

The a

mou

nt o

f con

verg

ence

(mm

)

5 10 15 20 25 30 35 400Time (d)

00

05

10

15

20

25

30

0kgm3

3kgm3

6kgm3

15kgm3

45kgm3

75kgm3

Figure 10 Convergence deformation curve of bottom drainageroadway

8 Advances in Civil Engineering

reinforced by basalt and carbon fibersrdquo Mechanics of Com-posite Materials vol 52 no 6 pp 807ndash816 2017

[9] W W Hu H W Liu D F Zhao and Z B Yang ldquoAppli-cations and advantages of basalt assembly in constructionindustryrdquo Advanced Materials Research vol 332ndash334pp 1937ndash1940 2011

[10] R N Turukmane S S Culhane and A M Daberao ldquoBasalt-technical fiber for civil applicationsrdquo Technische Textilienvol 61 no 2 pp 69ndash71 2018

[11] R H Wu ldquoe application of basalt fiber in building ma-terialsrdquo Advanced Materials Research vol 450-451 pp 499ndash502 2012

[12] T I Kovalrsquo ldquoInvestigation of the reliability of bridge elementsreinforced with basalt plastic fibersrdquo Mechanics of CompositeMaterials vol 53 no 4 pp 479ndash486 2017

[13] X Wang Z Wu G Wu H Zhu and F Zen ldquoEnhancementof basalt FRP by hybridization for long-span cable-stayedbridgerdquo Composites Part B Engineering vol 44 no 1pp 184ndash192 2013

[14] K Krayushkina O Prentkovskis A Bieliatynskyi et alldquoPerspectives on using basalt fiber filaments in the con-struction and rehabilitation of highway pavements and air-port runwaysrdquo lte Baltic Journal of Road and BridgeEngineering vol 11 no 1 pp 77ndash83 2016

[15] S L Ma B Peng and Z Huang ldquoTest and analysis of basaltfiber reinforced concretersquos mechanical properties and pave-ment performancerdquo Advanced Materials Research vol 671-674 pp 1291ndash1296 2013

[16] M Wlodarczyk and I Jedrzejewski ldquoConcrete slabsstrengthened with basalt fibres - experimental tests resultsrdquoProcedia Engineering vol 153 pp 866ndash873 2016

[17] G Y Cui D Y Wang S Z Ni et al ldquoModel tests bearingcharacteristics of basalt fiber reinforced concrete tunnel lin-ingsrdquo Chinese Journal of Geotechnical Engineering vol 39no 2 pp 311ndash318 2017 in Chinese

[18] S K Sateshkumar P O Awoyera and T KandasamyldquoImpact resistance of high strength chopped basalt fibre-reinforced concreterdquo Revista De La Construccion vol 17no 2 pp 240ndash248 2018

[19] A Bentur and S Mindess Fiber Reinforced CementitiousComposites Taylor amp Francis Group Abingdon UK 2007

[20] D P Dias and C aumaturgo ldquoFracture toughness ofgeopolymeric concretes reinforced with basalt fibersrdquo Cementand Concrete Composites vol 27 no 1 pp 49ndash54 2005

[21] J Sim C Park and D Y Moon ldquoCharacteristics of basaltfiber as a strengthening material for concrete structuresrdquoComposites Part B Engineering vol 36 no 6-7 pp 504ndash5122005

[22] L F Zhang Y L Yin J W Liu et al ldquoMecha-nical proportiesstudy on basalt fiber reinforced concreterdquo Bulletin of theChinese Ceramic Society vol 33 no 11 pp 2834ndash2837 2014in Chinese

[23] D J Pickel J S West and A Alaskar ldquoUse of basalt fibers infiber-reinforced concreterdquo ACI Materials Journal vol 115no 6 pp 867ndash876 2018

[24] T Ayub N Shafiq and M F Nuruddin ldquoMechanicalproperties of high-performance concrete reinforced withbasalt fibersrdquo Procedia Engineering vol 77 pp 131ndash139 2014

[25] K Attia W Alnahhal A Elrefai and Y Rihan ldquoFlexuralbehavior of basalt fiber-reinforced concrete slab strips rein-forced with BFRP and GFRP barsrdquo Composite Structuresvol 211 pp 1ndash12 2019

[26] F Abed and A R Alhafiz ldquoEffect of basalt fibers on theflexural behavior of concrete beams reinforced with BFRPbarsrdquo Composite Structures vol 215 pp 23ndash34 2019

[27] Q SWang and H Yao ldquoApplication of reinforced concrete insoft rock tunnel at great depthrdquo Journal of Mining amp SafetyEngineering vol 25 no 2 pp 184ndash187 2008 in Chinese

[28] P Iyer S Y Kenno and S Das ldquoMechanical properties offiber-reinforced concrete made with basalt filament fibersrdquoJournal of Materials in Civil Engineering vol 27 no 11Article ID 04015015 2015

[29] H G Li W Z Sun Q L Qiu et al ldquoStudy on flexuraltoughness property of basalt fiber concrete mixed with steelfiberrdquo Journal of Highway and Transportation Research andDevelopment vol 33 no 9 pp 78ndash83 2016 in Chinese

[30] D Li and Y N Ding ldquoEffect of steel fiber on biaxial flexuralproperty of TRC with basalt fiber mesh in slab testrdquo ActaMateriae Compositae Sinica vol 20 no 1 pp 78ndash82 2017 inChinese

[31] EFNARC European Specification for Sprayed concreteLoughborough University Louthborough UK 1996

[32] X D Wang W Z Zhen and Y Wang ldquoInternal force re-distribution of umbonded prestressed concrete edge-sup-ported sl-absrdquo Journal of Harbin Institute of Technologyvol 47 no 2 pp 1ndash8 2015 in Chinese

[33] Z C Deng ldquoFlexural toughness and characterization methodof hybrid fibers reinforced ultra-high performance concret-erdquoActa Materiae Compositae Sinica vol 33 no 6 pp 1274ndash1280 2016 in Chinese

[34] S Cao E Yilmaz and W D Song ldquoEvaluation of viscositystrength and microstructural properties of cemented tailingsbackfillrdquo Minerals vol 8 no 8 p 352 2018

[35] S M Song J H Liu and X Q Zhang ldquoPerformance of thecement matrix composite material with rubber powderrdquoJournal of Wuhan University of Technology vol 19 no 1pp 77ndash80 2014

Advances in Civil Engineering 9

maximum deformation (7 days) of the plain sprayed con-crete retaining structure is 144mm When the BF content is3 kgm3 and 45 kgm3 the deformation of the roadway isonly 012mm in the first 7 days e total convergencedisplacement of the plain sprayed concrete at 35 days is247mmWhen the BF content is 45 kgm3 the convergencedisplacement of the bottom drainage roadway is 021mm Inthe stirring and spraying process the uniformly distributedBF will form a stable bearing structure inside the basalt fibershotcrete matrix thereby improving the resistance of theroadway to deformation

5 Conclusions

In this paper the effect of BF on the flexural toughness ofshotcrete square slab is studied e fiber-reinforcedmechanism is analyzed by means of a synthetic fiber-transparent soil model and SEM technology combined witha field test and the following conclusions are drawn

(1) rough the fiber-transparent soil model it is foundthat when the fiber content is within 3sim45 kgm3 thedistribution of BF is uniform and it forms a densenetwork structure in which agglomeration appearsand has a small ratio of pores which is beneficial toimproving the bending toughness of the shotcreteconcrete

(2) According to the comparison test of the bendingtoughness of the square slab it is found that when thefiber content is 45 kgm3 it had the best reinforcingeffect Compared with the control group the peakload and absorption capacity increased by 5667and 63696 respectively and the maximum crackwidth decreased by 3210

(3) e SEM analysis indicated that the three-dimen-sional random distribution of BF forms a stable load-bearing skeleton in the shotcrete improves the stressdistribution in the shotcrete matrix reduces thecrack driving force and restrains the generation anddevelopment of microcracks Excessive fiber

incorporation can increase fiber agglomerationduring stirring and spraying which may make BFand shotcrete matrix not fully bonded and affect thetoughness of basalt fiber shotcrete

(4) BF shotcrete has achieved a good support effect in adeep soft rock underground engineering test thebasalt fiber shotcrete support effect is improvedcompared with plain shotcrete and the ability ofrestraining the deformation of surrounding rock isenhanced e convergence displacement of theplain shotcrete support section is 247mm in 35 dayswhile the convergence displacement of the roadwayin the basalt fiber shotcrete support section with afiber dissolution of 45 kgm3 is only 021mm

Data Availability

e data used to support the findings of this study areavailable from the corresponding author upon request

Conflicts of Interest

e authors declare that there are no conflicts of interestregarding the publication of this paper

Acknowledgments

is study was supported by the National Natural ScienceFoundation of China (51874123 and 51834001) the Scientificand Technological Research Projects of Henan ProvinceChina (182102310012) and Support Plan for Scientific andTechnological Innovation Talents in Colleges and Univer-sities of Henan Province China (19HASTIT047)

References

[1] J C Wang F Liu and L Wang ldquoSustainable coal mining andmining sciencesrdquo Journal of China Coal Society vol 41 no 11pp 2651ndash2660 2016 in Chinese

[2] E S Bernard ldquoAge-dependent changes in post-crack per-formance of fibre reinforced shotcrete liningsrdquo Tunnellingand Underground Space Technology vol 49 pp 241ndash248 2015

[3] M Khooshechin and J Tanzadeh ldquoExperimental and me-chanical performance of shotcrete made with nanomaterialsand fiber reinforcementrdquo Construction and Building Mate-rials vol 165 pp 199ndash205 2018

[4] J M Guo and Y S Zhang ldquoApplication research on mine-used high performance polymer modified concreterdquo Journalof Mining amp Safety Engineering vol 28 no 4 pp 660ndash6652011 in Chinese

[5] C High H M Seliem A EL-Safty and S H Rizkalla ldquoUse ofbasalt fibers for concrete structuresrdquo Construction andBuilding Materials vol 96 pp 37ndash46 2015

[6] F Akhlaghi R Eslami-Farsani and S Sabet ldquoSynthesis andcharacteristics of continuous basalt fiber reinforced alumi-num matrix compositesrdquo Journal of Composite Materialsvol 47 no 27 pp 3379ndash3388 2012

[7] V I Kostikov Soviet Advanced Composites Technology SeriesFibre Science and Technology Basalt Fibres and Articles Basedon ltem pp 581ndash605 Springer Moscow Russia 1995

[8] S M R Khalili M Najafi and R Eslami-Farsani ldquoEffect ofthermal cycling on the tensile behavior of polymer composites

021039

088099

107

247

The a

mou

nt o

f con

verg

ence

(mm

)

5 10 15 20 25 30 35 400Time (d)

00

05

10

15

20

25

30

0kgm3

3kgm3

6kgm3

15kgm3

45kgm3

75kgm3

Figure 10 Convergence deformation curve of bottom drainageroadway

8 Advances in Civil Engineering

reinforced by basalt and carbon fibersrdquo Mechanics of Com-posite Materials vol 52 no 6 pp 807ndash816 2017

[9] W W Hu H W Liu D F Zhao and Z B Yang ldquoAppli-cations and advantages of basalt assembly in constructionindustryrdquo Advanced Materials Research vol 332ndash334pp 1937ndash1940 2011

[10] R N Turukmane S S Culhane and A M Daberao ldquoBasalt-technical fiber for civil applicationsrdquo Technische Textilienvol 61 no 2 pp 69ndash71 2018

[11] R H Wu ldquoe application of basalt fiber in building ma-terialsrdquo Advanced Materials Research vol 450-451 pp 499ndash502 2012

[12] T I Kovalrsquo ldquoInvestigation of the reliability of bridge elementsreinforced with basalt plastic fibersrdquo Mechanics of CompositeMaterials vol 53 no 4 pp 479ndash486 2017

[13] X Wang Z Wu G Wu H Zhu and F Zen ldquoEnhancementof basalt FRP by hybridization for long-span cable-stayedbridgerdquo Composites Part B Engineering vol 44 no 1pp 184ndash192 2013

[14] K Krayushkina O Prentkovskis A Bieliatynskyi et alldquoPerspectives on using basalt fiber filaments in the con-struction and rehabilitation of highway pavements and air-port runwaysrdquo lte Baltic Journal of Road and BridgeEngineering vol 11 no 1 pp 77ndash83 2016

[15] S L Ma B Peng and Z Huang ldquoTest and analysis of basaltfiber reinforced concretersquos mechanical properties and pave-ment performancerdquo Advanced Materials Research vol 671-674 pp 1291ndash1296 2013

[16] M Wlodarczyk and I Jedrzejewski ldquoConcrete slabsstrengthened with basalt fibres - experimental tests resultsrdquoProcedia Engineering vol 153 pp 866ndash873 2016

[17] G Y Cui D Y Wang S Z Ni et al ldquoModel tests bearingcharacteristics of basalt fiber reinforced concrete tunnel lin-ingsrdquo Chinese Journal of Geotechnical Engineering vol 39no 2 pp 311ndash318 2017 in Chinese

[18] S K Sateshkumar P O Awoyera and T KandasamyldquoImpact resistance of high strength chopped basalt fibre-reinforced concreterdquo Revista De La Construccion vol 17no 2 pp 240ndash248 2018

[19] A Bentur and S Mindess Fiber Reinforced CementitiousComposites Taylor amp Francis Group Abingdon UK 2007

[20] D P Dias and C aumaturgo ldquoFracture toughness ofgeopolymeric concretes reinforced with basalt fibersrdquo Cementand Concrete Composites vol 27 no 1 pp 49ndash54 2005

[21] J Sim C Park and D Y Moon ldquoCharacteristics of basaltfiber as a strengthening material for concrete structuresrdquoComposites Part B Engineering vol 36 no 6-7 pp 504ndash5122005

[22] L F Zhang Y L Yin J W Liu et al ldquoMecha-nical proportiesstudy on basalt fiber reinforced concreterdquo Bulletin of theChinese Ceramic Society vol 33 no 11 pp 2834ndash2837 2014in Chinese

[23] D J Pickel J S West and A Alaskar ldquoUse of basalt fibers infiber-reinforced concreterdquo ACI Materials Journal vol 115no 6 pp 867ndash876 2018

[24] T Ayub N Shafiq and M F Nuruddin ldquoMechanicalproperties of high-performance concrete reinforced withbasalt fibersrdquo Procedia Engineering vol 77 pp 131ndash139 2014

[25] K Attia W Alnahhal A Elrefai and Y Rihan ldquoFlexuralbehavior of basalt fiber-reinforced concrete slab strips rein-forced with BFRP and GFRP barsrdquo Composite Structuresvol 211 pp 1ndash12 2019

[26] F Abed and A R Alhafiz ldquoEffect of basalt fibers on theflexural behavior of concrete beams reinforced with BFRPbarsrdquo Composite Structures vol 215 pp 23ndash34 2019

[27] Q SWang and H Yao ldquoApplication of reinforced concrete insoft rock tunnel at great depthrdquo Journal of Mining amp SafetyEngineering vol 25 no 2 pp 184ndash187 2008 in Chinese

[28] P Iyer S Y Kenno and S Das ldquoMechanical properties offiber-reinforced concrete made with basalt filament fibersrdquoJournal of Materials in Civil Engineering vol 27 no 11Article ID 04015015 2015

[29] H G Li W Z Sun Q L Qiu et al ldquoStudy on flexuraltoughness property of basalt fiber concrete mixed with steelfiberrdquo Journal of Highway and Transportation Research andDevelopment vol 33 no 9 pp 78ndash83 2016 in Chinese

[30] D Li and Y N Ding ldquoEffect of steel fiber on biaxial flexuralproperty of TRC with basalt fiber mesh in slab testrdquo ActaMateriae Compositae Sinica vol 20 no 1 pp 78ndash82 2017 inChinese

[31] EFNARC European Specification for Sprayed concreteLoughborough University Louthborough UK 1996

[32] X D Wang W Z Zhen and Y Wang ldquoInternal force re-distribution of umbonded prestressed concrete edge-sup-ported sl-absrdquo Journal of Harbin Institute of Technologyvol 47 no 2 pp 1ndash8 2015 in Chinese

[33] Z C Deng ldquoFlexural toughness and characterization methodof hybrid fibers reinforced ultra-high performance concret-erdquoActa Materiae Compositae Sinica vol 33 no 6 pp 1274ndash1280 2016 in Chinese

[34] S Cao E Yilmaz and W D Song ldquoEvaluation of viscositystrength and microstructural properties of cemented tailingsbackfillrdquo Minerals vol 8 no 8 p 352 2018

[35] S M Song J H Liu and X Q Zhang ldquoPerformance of thecement matrix composite material with rubber powderrdquoJournal of Wuhan University of Technology vol 19 no 1pp 77ndash80 2014

Advances in Civil Engineering 9

reinforced by basalt and carbon fibersrdquo Mechanics of Com-posite Materials vol 52 no 6 pp 807ndash816 2017

[9] W W Hu H W Liu D F Zhao and Z B Yang ldquoAppli-cations and advantages of basalt assembly in constructionindustryrdquo Advanced Materials Research vol 332ndash334pp 1937ndash1940 2011

[10] R N Turukmane S S Culhane and A M Daberao ldquoBasalt-technical fiber for civil applicationsrdquo Technische Textilienvol 61 no 2 pp 69ndash71 2018

[11] R H Wu ldquoe application of basalt fiber in building ma-terialsrdquo Advanced Materials Research vol 450-451 pp 499ndash502 2012

[12] T I Kovalrsquo ldquoInvestigation of the reliability of bridge elementsreinforced with basalt plastic fibersrdquo Mechanics of CompositeMaterials vol 53 no 4 pp 479ndash486 2017

[13] X Wang Z Wu G Wu H Zhu and F Zen ldquoEnhancementof basalt FRP by hybridization for long-span cable-stayedbridgerdquo Composites Part B Engineering vol 44 no 1pp 184ndash192 2013

[14] K Krayushkina O Prentkovskis A Bieliatynskyi et alldquoPerspectives on using basalt fiber filaments in the con-struction and rehabilitation of highway pavements and air-port runwaysrdquo lte Baltic Journal of Road and BridgeEngineering vol 11 no 1 pp 77ndash83 2016

[15] S L Ma B Peng and Z Huang ldquoTest and analysis of basaltfiber reinforced concretersquos mechanical properties and pave-ment performancerdquo Advanced Materials Research vol 671-674 pp 1291ndash1296 2013

[16] M Wlodarczyk and I Jedrzejewski ldquoConcrete slabsstrengthened with basalt fibres - experimental tests resultsrdquoProcedia Engineering vol 153 pp 866ndash873 2016

[17] G Y Cui D Y Wang S Z Ni et al ldquoModel tests bearingcharacteristics of basalt fiber reinforced concrete tunnel lin-ingsrdquo Chinese Journal of Geotechnical Engineering vol 39no 2 pp 311ndash318 2017 in Chinese

[18] S K Sateshkumar P O Awoyera and T KandasamyldquoImpact resistance of high strength chopped basalt fibre-reinforced concreterdquo Revista De La Construccion vol 17no 2 pp 240ndash248 2018

[19] A Bentur and S Mindess Fiber Reinforced CementitiousComposites Taylor amp Francis Group Abingdon UK 2007

[20] D P Dias and C aumaturgo ldquoFracture toughness ofgeopolymeric concretes reinforced with basalt fibersrdquo Cementand Concrete Composites vol 27 no 1 pp 49ndash54 2005

[21] J Sim C Park and D Y Moon ldquoCharacteristics of basaltfiber as a strengthening material for concrete structuresrdquoComposites Part B Engineering vol 36 no 6-7 pp 504ndash5122005

[22] L F Zhang Y L Yin J W Liu et al ldquoMecha-nical proportiesstudy on basalt fiber reinforced concreterdquo Bulletin of theChinese Ceramic Society vol 33 no 11 pp 2834ndash2837 2014in Chinese

[23] D J Pickel J S West and A Alaskar ldquoUse of basalt fibers infiber-reinforced concreterdquo ACI Materials Journal vol 115no 6 pp 867ndash876 2018

[24] T Ayub N Shafiq and M F Nuruddin ldquoMechanicalproperties of high-performance concrete reinforced withbasalt fibersrdquo Procedia Engineering vol 77 pp 131ndash139 2014

[25] K Attia W Alnahhal A Elrefai and Y Rihan ldquoFlexuralbehavior of basalt fiber-reinforced concrete slab strips rein-forced with BFRP and GFRP barsrdquo Composite Structuresvol 211 pp 1ndash12 2019

[26] F Abed and A R Alhafiz ldquoEffect of basalt fibers on theflexural behavior of concrete beams reinforced with BFRPbarsrdquo Composite Structures vol 215 pp 23ndash34 2019

[27] Q SWang and H Yao ldquoApplication of reinforced concrete insoft rock tunnel at great depthrdquo Journal of Mining amp SafetyEngineering vol 25 no 2 pp 184ndash187 2008 in Chinese

[28] P Iyer S Y Kenno and S Das ldquoMechanical properties offiber-reinforced concrete made with basalt filament fibersrdquoJournal of Materials in Civil Engineering vol 27 no 11Article ID 04015015 2015

[29] H G Li W Z Sun Q L Qiu et al ldquoStudy on flexuraltoughness property of basalt fiber concrete mixed with steelfiberrdquo Journal of Highway and Transportation Research andDevelopment vol 33 no 9 pp 78ndash83 2016 in Chinese

[30] D Li and Y N Ding ldquoEffect of steel fiber on biaxial flexuralproperty of TRC with basalt fiber mesh in slab testrdquo ActaMateriae Compositae Sinica vol 20 no 1 pp 78ndash82 2017 inChinese

[31] EFNARC European Specification for Sprayed concreteLoughborough University Louthborough UK 1996

[32] X D Wang W Z Zhen and Y Wang ldquoInternal force re-distribution of umbonded prestressed concrete edge-sup-ported sl-absrdquo Journal of Harbin Institute of Technologyvol 47 no 2 pp 1ndash8 2015 in Chinese

[33] Z C Deng ldquoFlexural toughness and characterization methodof hybrid fibers reinforced ultra-high performance concret-erdquoActa Materiae Compositae Sinica vol 33 no 6 pp 1274ndash1280 2016 in Chinese

[34] S Cao E Yilmaz and W D Song ldquoEvaluation of viscositystrength and microstructural properties of cemented tailingsbackfillrdquo Minerals vol 8 no 8 p 352 2018

[35] S M Song J H Liu and X Q Zhang ldquoPerformance of thecement matrix composite material with rubber powderrdquoJournal of Wuhan University of Technology vol 19 no 1pp 77ndash80 2014

Advances in Civil Engineering 9