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Controlled Low Strength Materials (CLSM) Utilizing Fly Ash and Bottom Ash
Djwantoro Hardjito
Department of Civil Engineering Petra Christian University
Surabaya, Indonesia e-mail:
djwantoro.h@peter.petra.ac.id
Cheng Wee Chuan Department of Civil and
Construction Engineering Curtin University of Technology,
Sarawak Campus Miri, Sarawak, Malaysia
Jonie Tanijaya
Department of Civil Engineering Paulus Christian University
Indonesia Makassar, Indonesia
Abstract— Due to the increasing demand for electricity in Sarawak and the development of Sarawak Corridor of Renewable Energy (SCORE), Sarawak government had prompted to build more coal-fired power station as energy source. Thus, waste products of this energy source, such as fly ash and bottom ash have increased instantaneously. Disposal of these waste products will become very costly and may cause major environmental issues, such as land pollution. One of the ways to reduce these waste products is to utilize them as construction materials. This paper presents the results of parametric study on Controlled Low-Strength Materials (CLSM) utilizing fly ash and bottom ash from Sejingkat, Kuching. The properties of CLSM that had been investigated included hardening time, flowability, bleeding and segregation, density of hardened CLSM and unconfined compressive strength at CLSM age of 3 days, 7 days, 14 days, 28 days and 60 days. CLSM mixtures were designed by varying the proportion of cement, fly ash and bottom ash. CLSM mixtures were casted into cylinder moulds with the size of 39mm × 78mm (dia). From the experimental results, hardening time of CLSM was found to be in between 5 to 6.5 hours. In order to achieve good flowability, the water/ cement ratio used in CLSM was found to be very high, with the highest w/c ratio can be more than 8.0. With the increase of fillers, especially fly ash, bleeding and segregation condition of CLSM are improved. With various mixing proportion of CLSM, compressive strength of CLSM is controlled between 1.0MPa to 8.3MPa, in order to suit the requirement of different applications, such as excavatable backfill and structural backfill. With this range of strength, CLSM can be used as alternative material to solve the soft soil problems in Sarawak, especially in Northern Sarawak.
Keywords- Fly Ash; Bottom Ash; CLSM; Hardening Time; Flowability; Bleeding and Segregation; Density; Compressive Strength; Backfill; Soft Soil Problems
I. INTRODUCTION
A. Overview of Project Controlled Low Strength Materials (CLSM) is a self
compacted, cementitious materials used primarily as backfill in place of compacted fill. CLSMs are defined by ACI 229R
as materials that result in a compressive strength 8.3MPa or less [1]. It is also known as flowable fill, unshrinkable fill, controlled density fill and other various names.
In this project, bottom ash and Class F Fly Ash from Kuching Coal Fired Power Station in Sejingkat, Kuching are utilized in CLSM. The production of these by-products is increasing due to the development of coal-fired plants under the development of Sarawak Corridor of Renewable Energy (SCORE) to secure the electricity demand of Sarawak [2]. Disposal of these by-products will eventually become very costly and may cause major environmental issues, such as land pollution. Therefore, alternative methods of handling these by-products, such as utilizing them in concrete to produce CLSM, need to be thought of.
Northern part of Sarawak, like Miri and Brunei, has a major problem with soft soil. The soil is very soft and is not suitable for building foundation as it may cause structural failures, such as differential settlement of buildings, potholes and other problems [3]. To solve the problems, engineers have to replace the soft soil with better soil or have to treat the soil by mixing it with cement and then followed by compaction. However, these solutions might be very costly and tedious.
CLSM might be an alternative solution in the above problems because the materials can be easily obtained locally and sometimes can be more economical. This is because CLSM is generally made out of concrete materials mixed with by-products, which can be manufactured in batching plant. Furthermore, CLSM is flowable and self-compacted materials, so it does not require compaction after backfilling. This makes CLSM to be more economical.
However, due to by-product produced from different area may have different chemical composition and properties, it may have diverse effects on the properties of CLSM. Hence, it is important to carry out parametric study on CLSM utilizing the locally available by-products before its possible application in construction. This project is focused on the use of fly ash
and bottom ash from Kuching, and its effects on the properties of CLSM.
B. Objective of Research The main objectives of this research are to investigate the
hardening time of CLSM; to optimize the flowability of CLSM within the allowable range and to find out the water-cement ratio needed to achieved that flowability; to investigate bleeding and segregation condition of CLSM from various mixing proportion of CLSM and to find out the optimum proportion to minimize bleeding and segregation; to determine the density of hardened CLSM; and to elaborate the unconfined compressive strength of CLSM from various mixing proportion in order to find out suitable proportion for various applications.
C. Scope of Work This research is focused on the practical usage of fly ash
and bottom ash in CLSM for various purposes in construction industry. Properties of CLSM, such as hardening time, flowability, segregation, density of hardened CLSM, compressive strength and bleeding are investigated.
In this project, the materials used are cement, water, sand, fly ash and bottom ash from Sejingkat Kuching. The specimen moulds are self-constructed cylinders that have diameter of 39mm and height of 78mm. Research is carried out based on various mixing proportions by varying the percentage of cement (3%, 6%, 10% and 15% of total wet density) used and the percentages of fly ash and bottom ash (0%, 25%, 50%, 75%, and 100%).
II. LITERATURE REVIEW
A. Introduction on CLSM Controlled Low Strength Materials (CLSMs) is a self
compacted, cementitious material used primarily as backfill in place of compacted fill. CLSMs are defined by ACI 116R as materials that result in a compressive strength 8.3MPa or less [1]. It is also known as flowable fill, unshrinkable fill or plastic soil cement. Besides backfilling, other applications of CLSMs are void filling, bridge reclamation, conduit bedding and nuclear waste stabilization.
CLSMs can utilize the wastes or by-products such as fly ash, bottom ash, foundry sand, waste LCD glass, and quarry dust and glass cullet to reduce the use of cement and aggregates, and to improve the flowability of the fresh material. Among the by-products used, fly ash and bottom ash are the most commonly utilized in CLSMs [1]. Fly ash is actually one of the residues generated in the combustion of coal, whereas bottom ash is non-combustible constituents of coal with traces of combustible embedded in forming clinkers.
In the ACI Committee 229 (1999), the wet properties and dry properties of CLSMs are briefly stated. ACI stated that the wet density of the normal CLSM (containing fine aggregates) is approximately between 1840 to 2320kg/m3, whereas the dry density of CLSMs is roughly 1360 to 1760kg/m3 [1]. Besides that, wet CLSMs are described as flowable and self-
compacted. This means that it can be compacted by itself without any compacting work.
Generally, the compressive strength of CLSM is less than 8.3MPa. However, this strength has to be controlled to the desired strength based on the application. For example, ACI suggested the compressive strength range of 0.3 to 0.7 MPa for the applications that needs to be excavatable in the future [1]. This is because lower strength CLSMs can be easily excavated by hand tools or conventional excavation machinery, like backhoes or hydraulic excavators [4]. This is important to reduce the excavation cost in the future.
On the other hand, ACI suggested a relatively higher strength of more than 4.0 MPa for the applications such as structural fills whereby excavation is not likely to occur in the future [1]. Higher strength is required to support the structures above and to prevent itself from cracking and shrinking.
B. Materials of CLSM Conventional CLSM mixtures usually consist of water,
Portland cement, fly ash or other similar products, fine or coarse aggregates or both. It is not necessary to use the standardized materials set by ASTM or other standard requirements [1]. Selection of materials should base on availability, cost specific application, and necessary characteristics of mixture, such as strength, flowability, excavatability, and density.
1) Cement Cement is a binder material that holds all the other
materials together and contributes to the strength and cohesion for CLSM mixtures. Normally, in compliance with ASTM C 150, Type I or Type II Portland Cement will be used. Other types of cement can also be used in compliance with ASTM C 595 as long as the testing results are satisfactory.
2) Fly Ash Fly Ash is actually one of the residues generated in the
coal combustion. Fly Ash is used in CLSM to improve the flowability. Besides that, fly ash is also used to reduce bleeding, shrinkage and permeability as well as to increase the strength of CLSM [5].
Although fly ash has become an important construction material, especially in high strength concrete, approximately 70 to 75 percent of fly ash generated annually is still disposed in landfill as these fly ash does not meet the specification for use in Portland Cement concrete, due to high content of unburned carbon, as measured by the loss on ignition (LOI) test [6]. This is because higher unburned carbon contents increase water demand in concrete, causing water/ cement ratio to increase, thus reduce the strength of the concrete. Moreover, unburned carbon will also significantly increase chemical admixture demand, which will cause the total cost of concrete to increase. However, CLSM has no problem with the higher unburned carbon in the fly ash. Hence, CLSM is possibly the best solution to the environmental issues caused by fly ash landfill.
3) Bottom Ash
Bottom ash is another by-product material of coal combustion. Bottom ash is formed by large non-combustible particles that cannot be carried by the hot gases. These large non-combustible particles are put into crusher to reduce the particle size to approximately 75 microns to 25milimeters [6]. Since the size of bottom ash is similar to fine aggregates and it has relatively no cementitious properties compared to fly ash, it is used in CLSM as the fine aggregates.
Under the microscope, bottom ash particles are typically porous and angular in shape. Water will be absorbed and retained on the porous surface of bottom ash, while excessive water will be drained off [7]. Drained off water may cause the free water in CLSM to be excessive. This will actually cause bleeding condition in CLSM.
4) Water According to ACI Committee 229, water that is
acceptable for concrete mixtures is acceptable for CLSM mixtures. More information on water quality requirements can be obtained from ASTM C 94 standard.
5) Aggregates Aggregates are often the main part of CLSM mixtures.
The type, grading, and shape of aggregates can affect the physical properties of CLSM, such as flowability and compressive strength. Aggregates used in CLSM have to fulfill either one of the following specification:
a) ASTM C 33 specification aggregates within specified gradations;
b) Pea gravel with sand; c) 19mm minus aggregate with sand; d) Native sandy soils, with more than 10% passing a
75µm sieve; e) Quarry waste products, generally 10mm minus
aggregates [1].
III. EXPERIMENTAL PROGRAM
A. Mixing, Flowability Test, Casting, De-mould and Curing Before mixing, the materials were prepared in correct
amount according to proportion. This was done by measuring the mass of materials needed. After obtaining the correct amount of materials, all the materials except water were put into the Hobart mixer machine. Then, the partial of the water was placed into the mixer and start mixing for 1 minute. After that, the remaining water was placed into the mixer and the mixing was continued for 15 minutes. If the visual flowability of CLSM is too low, then additional water can be added. The additional amount of water used will be recorded.
After 15 minutes of mixing, the CLSM mixture was ready for flowability test. The equipments needed for this test were inverted slump cone, scoop, base plate and measuring tape. The CLSM mixture was loaded into the inverted slump cone until it was full. Then, the inverted slump cone was lifted up to allow the CLSM mixture to flow and form a circle. The diameter of the circle was measured with measuring tape. If
the diameter of the circle is within the range of 475mm and 750mm, flowability of the CLSM is acceptable [8].
After the flowability test, the CLSM mixture was filled into 15 fabricated cylinder moulds. No compaction is needed because CLSM is a self-compacted material. The filled CLSM mixture was left to harden indoor with room temperature of approximately 25 degree Celsius.
CLSM mixture hardened within 5 to 6.5 hours, but it could not be de-moulded within three days after casting. This is because hardened CLSM was still very fragile and could be easily crushed during de-moulding from the cylinder moulds. After three days, the hardened CLSM were de-moulded by using the Universal Testing Machine. Some of the hardened CLSM would be tested for 3 days compressive strength. The remaining of hardened CLSM would be cured by placing the hardened CLSM into the curing chambers.
B. Hardening Time Test Hardening time of CLSM was tested by using vicat
penetrometer. After mixing, the CLSM mixture was loaded in the penetrometer cast. Bleeding of the specimen had to be removed from the surface of specimen prior testing the specimen. Vicat needle was left to fall and the reading of penetration was recorded every 15 minutes. The CLSM mixture was considered hardened when the penetration of the vicat needle is less than 25mm.
C. Bleeding Test Bleeding test was measured by measuring the difference in
CLSM height due to water evaporation. In order to obtain the height reduction of the CLSM specimen, the new reduced height of CLSM specimens were measured on the third day after casting with Vernier Caliper.
The reduction of height over the total height of the CLSM specimen is considered as the percentage of bleeding. The percentage of bleeding can be calculated with the following expression:
% bleeding = (h1 – h2)/ h1 ×100 (1) Where,
h1 = initial height of CLSM specimens during casting
h2 = new measured height of hardened CLSM specimens after 3 days
D. Segregation Test There is no Standard Testing method for CLSM
segregation available. Thus, segregation of the CLSM specimen was tested visually. First of all, CLSM specimens were split into half after the compressive strength test. The split surface was then observed for obvious segregation condition. If there is any stratification exists, it is considered that there is segregation within the CLSM specimens.
E. Density of Hardened CLSM Density of hardened CLSM specimens was measured by
measuring the mass of the hardened CLSM, and then divided
by thCLSMThe dusing
F. CC
measare seloads1kN rstreng90 daspecithat tthe wobtainspeci
Thmachvalueaccorthe compdividspeci
G. MTh
paramamouof samixtuof thpropomass the cpercebotto75%
Prbleedstrengand bCLSMCLSMdemofrom and Discu
A. HH
3% cplottecan o
e volume of thM specimens wdiameter and tg Vernier Calip
Compressive StrCalifornia Bear
ure the unconfeveral rings av
s that the rings ring, 4.5kN ringth of CLSM ways. Prior to tmen had to be the loading of
whole surface oned reflects thmens.
he value obtahine does not de obtained has rding to respecload required
pressive strengtding the load
mens.
Mix Design andhe mixing pr
meters, such aunt of sand andand used was ure, whereas mhe total mass ortion was vari
of CLSM. Bycement, waterentage of masm ash (BA) band 100%.
IV. roperties of C
ding, segregatigth are discussbottom ash havM. Hence, the aM over fly aonstrate the ex
test results oftabulated into
ussions will be
Hardening TimeHardening time cement contented into graph, observed that h
he CLSM speciwas measured the height of thper.
rength Test ring Ratio (Cfined compressvailable for CBcan sustain ar
ng, 10kN ring was tested for testing, the cosmoothed and
f CBR machinof CLSM speche true compre
ained from thdirectly show th
to be comparctive load mead needed to th of CLSM sp
with the co
d Proportion roportion was as the total md the amount of
set to be 25mass of initial w
of CLSM. Aied from 3%, 6y subtracting thr and sand s was divided
by varying the
RESULTS AN
CLSM such as ion, density ased. From the ve significantlanalysis focuse
ash and bottomxperimental ref three sampleo tables and done based on
e of CLSM test has been ct and 6% cemas shown in Fhardening time
imens measureby using weig
he CLSM wer
CBR) machinesive strength ofBR machine.
re stated on theand 28kN ring3 days, 7 day
ontact surface d even. This wane was equallycimens and ensessive strength
he dial gauge he compressivered with the caasuring rings. A
make the specimen will bontact surface
designed by mass of CLSMf initial water u
5% of total mwater used wasAs for cemen6%, 10% and 1he total mass proportions, t
d between fly e ratio from 0%
D DISCUSSIONS
hardening timand unconfined
experimental ly affecting theed mainly on thm ash ratio. sults, each das. The data is
then plottedn the graphs plo
carried out for ment content. TFigure 1. Frome for 3% cem
ed. The mass ofghing machinere measured by
e was used tof CLSM. ThereThe maximume rings, such asg. Compressiveys, 28 days and
of the CLSMas to make surey distributed tosure the resultsh of the CLSM
on the CBRe strength. Thealibration charAfter obtainingspecimen faile calculated by
e area of the
fixing a fewM mixture, theused. The mass
mass of CLSMs set to be 15%nt content, the5% of the totaof CLSM withthe remainingash (FA) and
%, 25%, 50%
S me, flowabilityd compressiveresults, fly ashe properties ofhe properties ofTo effectively
ata is collectedthen averaged
d into graphsotted.
specimen withThe results are
m the graph, wement mix varies
f e. y
o e
m s e d
M e o s
M
R e rt g l, y e
w e s
M % e
al h g d
%,
y, e h f f y d d s.
h e e s
from 5 tcement mhardeningthese harrange. Ovwith the d
This mbottom asactually excessivespecimenbefore thwater traphardeningtime incre
Fig
Besidcontent inof CLSMof CLSMbinds agcement ahence theis the reacement co
B. FlowaFlowa
the flowaas showndiameter within thflowabilitexperimespecimen
Figureash: bottoResults sflowabilitBA ratio BA ratio.mixture, t
to 6.5 hours, mix varies frog time range srdening timesverall results sdecrease in fly
might be due sh particles. Thtrap water tha
e of free water n [7]. Althoughe hardening tipped in the porg time of the Ceases as the bo
gure 1: Hardening
des that, from n CLSM mixtu
M. As the cemenM is lower. Cggregates and added, the hyde strength gainason why the hontent is increa
ability of CLSMability is anothability test, resun in Figure 2.
of CLSM by he range of 4ty mixture for
ent, water contn in order to ach
e 2 also showom ash ratio foshow that the rty decreases gand increases
. It indicates ththe more water
whereas the om 4 to 6 houstated in ACI c
are reasonablshow that the hAsh: bottom A
to the unevenhe porous propat is released and eventually
gh water due ime testing, theres of bottom a
CLSM specimeottom ash conte
Time versus Fly A
Figure 1, it cure is also affent content is hement is a cefine particles
dration reactionn of the CLSMhardening timeased.
M her important pults are collectAccording toinverted slum
75 to 750mmr most of the tent of CLSMhieve the requi
ws the water coor 3%, 6%, 10required water gradually fromdrastically fro
hat the higher Fr is needed to a
hardening timurs. Comparincommittee reply within the hardening timeAsh ratio by m
n surface and pperties of botto
during mixiny causing bleeto bleeding iere is still excash. This slowens. Hence, theent increased.
Ash: Bottom Ash R
can be seen thecting the hardigher, the hard
ementitious mas together. Wn will also in
M will also be fe of CLSM is
property of CLted and plotted Tripathi [8],
mp cone test nm in order to
field applicatiM was adjusted
ired flowability
ontent needed 0% and 15% ce
content to achm 0:100 to 25:om 25:75 to 10FA: BA ratio uachieve good f
me for 6% g with the ort (1999), acceptable e increases ass.
porosity of om ash will ng, causing eding to the s removed
cessive free ws down the e hardening
Ratio
hat cement dening time dening time aterial that With more ncrease and faster. This reduced as
LSM. From d into graph
the spread needs to be have good ion. In this d for every y.
versus fly ement mix. hieve good :75 of FA: 00:0 of FA: used in the flowability.
The eash c
ATangthat cin bosurfacmixtudecrewateradded
Balso dknowincreaout tmixtuthe flcarbobottoash aof unThusmoreCLSM
Inthe pbottoachiemixin
C. BFi
versuobser2.31%obtainfrom maximordinfill [5exper
explanation foontent causes t
According to ttermsirikul [7]
can retain and aottom ash is vece can help ture when bottoease of bottomr content in thd to maintain th
Figure 2: W
esides, more wdue to the incr
wn to have smasing flowabilihat fly ash mure due to the ply ash used [6]on has very pm ash. Due to
and the porositynburned carbon, the more fly water contentM.
n this experimeproportion of Cm ash is used
eve good flowng proportion,
leeding and Seigure 3 illustr
us fly ash: botrved that the b% to 7.25%. ned by Horigu1.5% to 6.8%
mum bleedingnary flowable f5]. Thus, the reriments are con
r this result isthe increase in
the research d], bottom ash hadsorb water. ery high, the wto decrease thom ash is adde
m ash will resuhe mixture andhe required flo
ater Content versu
water content rease of fly ashmooth and eveity of CLSM, b
may increase thpresent of high]. According toporous and units larger surf
y, the water nen in fly ash is ash with high t is needed to
ent, the optimuCLSM where d, due to the lewability. This
less friction am
egregation of Crates the bleettom ash ratiobleeding perce
Comparing tuchi, Okumura% , the results
ratio specifiedfill and 1 perceesults of bleednsidered to be v
s that the decrewater demand
done by Kasehas angular andTherefore, if th
water retained he demand fored to the mixtuult in the decr
d more water wowability.
us Fly Ash: Bottom
is needed for h content. Althen surface thabut recent resehe water demh content unbuo Kulaots et alneven surface
face area compeeded to lubriccomparativelyunburned carbachieve good
um water conte25% of fly aseast water conmay indicate
mong particles
CLSM ding percenta
o. From Figurentage of CLSMthe results wi, and Saeki [5]are quite sim
d in Japan is 3 ent for high qu
ding ratio obtaivery high.
ease of bottomd.
emchaisiri andd rough surfacehe initial wateron the uneven
r water in theure. Hence, therease of initiawill need to be
m Ash Ratio
mixtures mayhough fly ash isat will help inearch has found
mand in CLSMurned carbon in. [9], unburned
e just like thepared to bottomcant the surfacey much higherbon is used, thed flowability of
ent occurred ash and 75% ofntent needed to
that with thiswould occur.
ages of CLSMre 3, it can beM varies fromith the results], which varies
milar. Howeverpercent for theuality flowableined from both
m
d e r n e e
al e
y s n d
M n d e
m e r. e f
at f o s
M e
m s s r, e e h
From the contebottom asinitial mothe porescontent oamount oash may c
Besidis inversesame as Razak [1increase needed tincrease trequired decreasesthe free wfree wate
Fi
In thobservedused in particles voids, pexcessivesegregatiovery unlik
D. DensiFigure
versus flyhardenedash conteporosity specimenfurther inof the spebe decrea
From obtained ACI Combetween
the graph, bleent of bottom sh used indeedoisture contents of bottom asof CLSM mixtuof free water. Tcause bleeding
des that, the graely proportionthe condition 0]. The decreain aggregates
to lubricate ththe free water to hydrate cem
s as amount owater content ier is the cause o
igure 3: Bleeding P
his experiment. This is becauall the mixturhave smaller articles are l
e free water on of CLSM kely to happen
ity of Hardenede 4 shows the y ash: bottom
d CLSM at 28th
ent in the CLof bottom a
ns. Besides thatncrease the voiecimen increasased.
Figure 4, thevaries from 1
mmittee 22R 1360kg/m3 and
eding percentaash is increas
d has porous prt. The initial wsh will be addure, which evenThis is the reasg in CLSM.
aph also showsal to cement cof CLSM fo
ase of cementproportion. T
hese aggregatebetween parti
ment in order f cement usedin the CLSM mof bleeding.
Percentage versus F
t, there is nouse only fine ares instead of void between
less likely toexists or te
designed withn [1].
d CLSM density of haash ratio. Fro
h-day is directlLSM mixturesash that incrt, the uneven sd created in thses, the density
e density of C610kg/m3 to 1[1], the rang
d 1760kg/m3, w
age of CLSM insed. This showroperties and rwater content ded to the totantually ends upon that the use
s that bleeding content in CLSund by Nagan
t content will lhus, more waes and fillers,cles. Howeverto act as bon
d is reduced. Tmixture to incr
Fly Ash: Bottom A
o significant saggregates and
coarse aggregthe particles.
o be dislocateerrible bleedinh fine aggregat
ardened CLSMom the graph, ly proportiona. This is mainreases the vourface of botto
he specimens. Ay of hardened C
CLSM in this e1820kg/m3. Acge of CLSM whereas the res
ncreases as ws that the retains high
trapped in al moisture p with high e of bottom
percentage SM, which nathan and lead to the
ater will be , and thus r, the water nding agent This causes rease. This
Ash Ratio
segregation d fillers are gates. Fine With less ed. Unless ng occurs, tes only is
M at 28days density of
al to the fly nly due to
oid in the om ash will As the void CLSM will
experiment ccording to
density is sults found
by Hdensithose
F
E. UIn
speci60 dafollow3% ofor Cconte
Frquantcompmajoris usestrengthese can gbondewould[11].
Bto thconteCLSMthe vrequiused This preve
Futhe calso dthat iCalcilime betwethe grcomp
Horiguchi, Okuity varies frome results, the re
Figure 4: Density o
Unconfined Comn this experimmens was testeays. The data wed. Figure 5
of cement conteCLSM speciment in Figure 6,
rom all the ftity of cemenpressive strengr source of cemed to bond thegth of CLSM
particles. Thugenerate more ed together. Fud have higher
esides cementhe compressivent of fly ash M. This may bvoids betweenre cement pastas fillers, but actually impr
ents dislocation
urthermore, hicompressive strdue to the facts Silica Oxide ium Silicate Hreleased by theen aggregatesreater the bond
pressive strengt
umura, and Sam 1338kg/m3 tsults obtained
of CLSM at 28 day
mpressive Strenment, compreed for 3 days, was collected
shows the resuent. Similar pat
mens with 6%,, Figure 7 and F
figures, it cannt used will pgth. This is vementitous mate
e aggregates anis depending o
us, it is reasonstrength as p
urthermore, higstrength as it h
t, fly ash contee strength ofwill increase e due to fly ash
n larger particlte to fill [12]. Wmore on form
roves the bonn of particles d
igher fly ash crength of CLSt that fly ash h
(Si02), which ydrates (CSH)
he hydrated cems and fillers. Thding between pth of CLSM.
eki [5], the rato 2056kg/m3. seem to be ver
ys versus Fly Ash: B
ngth of CLSM essive strength7 days, 14 day
d and plotted ults of CLSM sttern of results, 10% and 15Figure 8.
n be concludeproduce CLSMery rational as erials within th
nd particles. Thon the bond fonable that morparticles are mgher cement conhas lower wate
ent also causesf CLSM specthe compressih that acts as fles, which woWith this, less
ming bonds betwnding betweendue to larger vo
content can slSM specimensas minor pozzcan be used to
) when it reactment [12]. CSHhus, the more Cparticles and th
ange of CLSMComparing to
ry similar.
Bottom Ash Ratio
h for all theys, 28 days andinto graphs as
specimens withs were obtained5% of cemen
ed that higherM with higher
cement is thehe mixture thahe compressiveormed betweenre cement used
more effectivelyntent of CLSM
er/ cement ratio
s minor effectsimens. Higherive strength offillers to reduceould otherwisecement will beween particles
n particles andoids.
ightly increases. This may beolanic materia
o produce morets with the freeH is the binderCSH producedhus increase the
M o
e d s h d
nt
r r e
at e n d y
M o
s r f e e e s. d
e e
al e e r
d, e
From cement isexcavatiowith 6% whereas structural
Fi
Fi
Fig
the experimens suitable for on purpose as i
cement is suCLSM mixtur
l backfill as it h
igure 5: Compressi
igure 6: Compressi
gure 7: Compressiv
nt results, CLgeneral purpoit has low com
uitable for roadre with 10% has higher com
ive Strength of CL
ive Strength of CL
ve Strength of CLS
LSM mixturesse backfilling
mpressive strengdway trench bcement is bes
mpressive stren
LSM with 3% Cem
LSM with 6% Cem
SM with 10% Cem
s with 3% and future
gth. CLSM backfilling; st used for
ngth [13].
ment Used
ment Used
ment Used
Bexper
1) botto
2) cemecontamoreof CL
3) waterash ra
4) occur75% to ach
5) increait is in
6) obser
7) fly asFigur
8) that propoBesidcompfly asthe lim
9) cemeexcavwith
Figure 8: Comp
ased on the rimental results
Hardening timm ash content,
From Figure ent has loweraining 3% cem cement conten
LSM will be.
From Figurer to achieve goatio increases.
Referring torred at the propof bottom ashhieve good flow
Figure 3 shases as the connversely propo
In this experrved.
Density of Hsh: bottom ashre 4.
From the comcement contenortional to thedes cement, flypressive strengsh will increasmit where fly a
From the expent is suitable vation purpose6% cement is
pressive Strength o
V. CONC
experiment cs, the following
me of CLSM i, as shown in F
1, it can be ser hardening
ment. Thus, itnt in CLSM, th
e 2, it can be ood flowability
o Figure 2, tportion of CLSh is used, as thwability.
hows that bleentent of bottomortional to cem
riment, there i
Hardened CLSMh ratio of CLS
mpressive strennt used in Ce compressive y ash content agth of CLSM sse the compresash: bottom ash
periment resulfor general pu as it has low cs suitable for
f CLSM with 15%
CLUSIONS conducted ang conclusions
increases with Figure 1.
en that CLSM time compar
t can be conche shorter the h
concluded thay increases as f
the optimum SM where 25%he least water c
eding percentam ash increased
ment content in
is no significa
M is directly pSM specimens
ngth test, it canLSM specimestrength of t
also has minorspecimens. Higssive strength oh ratio is 75: 2
lts, CLSM mixurpose backfillcompressive stroadway tren
% Cement Used
nd analysis ofare drawn:
the increase of
containing 6%ed to CLSM
cluded that thehardening time
at the requiredfly ash: bottom
water conten% of fly ash and
content needed
age of CLSMd. Besides thatCLSM.
ant segregation
proportional tos, as shown in
n be concludedens is directlythe specimensr effects on thegher content ofof CLSM unti5.
xtures with 3%ling and futuretrength. CLSMch backfilling
f
f
% M e e
d m
nt d d
M t,
n
o n
d y . e f l
% e
M ;
whereas structural
[1] ACIMat
[2] Sara200http
[3] KanBehEng
[4] The Spec
[5] HorOptof CSP-p. 3
[6] TrejDev
[7] Kasmethaggconc132
[8] TripLabTimInno(FloBaa
[9] Kulin FTestFly
[10] NagStreQuaACF
[11] Neved. E
[12] Dayand
[13] ConSep
CLSM mixturl backfill as it h
I Committee 2terial. America
awak Corridor9 Septem
p://www.sarawa
niraj, S.R. anhaviour of Orggineering, ed. C
European Gucification, Pro
riguchi, T., Htimization of CLClinker Ash an199. American07-325.
jo, D., K.J. Fvelopment using
semchaisiri, Rhod to determ
gregate for dcrete. Constru2-133.
pathi, H., et boratory Measme of Controvations in owable Fill), as, Editors. AST
aots, I., et al, 2Fly Ash and Det. in 2002 ConfAsh.
ganathan, S. anength Materialarry Dust, in TF/ VCA 2008. U
ville, A.M., 199Edinburgh Gat
y, K.W., 2006. d Specification.
ntrolled Low-Sttember]; Avail
re with 10% has higher com
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