Construction and Building Materials 169 (2018) 237–251

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Construction and Building Materials

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Mechanical, environmental and economic performance of structuralconcrete containing silica fume and marble industry waste powder

https://doi.org/10.1016/j.conbuildmat.2018.02.1920950-0618/� 2018 Elsevier Ltd. All rights reserved.

Abbreviations: AP, acidification potential; ECM, evaluation of concrete mixes;Eco, economic; Env, environmental; FP, fossil fuel depletion potential; GWP, globalwarming potential; Mec, mechanical; MWP, marble waste powder; OPC, OrdinaryPortland cement; RAC, recycled aggregate concrete; SF, silica fume.⇑ Corresponding author.

E-mail addresses: khodabakhshian.ali@mail.um.ac.ir (A. Khodabakhshian),jb@civil.ist.utl.pt (J. de Brito), Ghalehnovi@ferdowsi.um.ac.ir (M. Ghalehnovi),E.asadi@mail.um.ac.ir (E. Asadi Shamsabadi).

Ali Khodabakhshian a, Jorge de Brito b, Mansour Ghalehnovi a,⇑, Elyas Asadi Shamsabadi a

aDepartment of Civil Engineering, Ferdowsi University of Mashhad, Mashhad, IranbCERIS-ICIST, Department of Civil Engineering, Architecture and Georresources, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal

h i g h l i g h t s

� Studying the effect of the MWP and SF on the mechanical properties of concrete.� 16 concrete mixes containing MWP and SF as partial replacement of OPC are investigated.� The mechanical, economic and environmental performances of concrete are evaluated.

a r t i c l e i n f o

Article history:Received 5 December 2017Received in revised form 18 February 2018Accepted 25 February 2018

Keywords:Marble waste powderSilica fumeCementMechanical performanceEnvironmental analysisEconomic analysisConcrete

a b s t r a c t

Marble waste powder (MWP) is an inert material that is obtained as an industrial by-product during saw-ing, shaping, and polishing of marble and causes serious environmental problems. This paper describesthe procedures and results of a laboratory investigation of mechanical properties carried out on 16 con-crete mixes containing MWP and silica fume (SF) as partial replacement of ordinary Portland cement(OPC). OPC was partially replaced at different ratios of SF (0%, 2.5%, 5%, 10%) and MWP (0%, 5%, 10%,20%). In all concrete mixes, constant water/binder ratio of 0.45 and target initial slump of S2 class(50–90 mm) were used. Workability and bulk density tests were carried out on fresh concrete, whilecompressive strength, splitting tensile strength and modulus of elasticity tests were performed to eval-uate some relevant properties of concrete in the hardened state. Eventually, all of the concrete mixeswere evaluated in terms of economic, environmental and mechanical approaches.It was found that the mechanical properties of concrete containing MWP tend to decline for replace-

ment ratios over 10% but satisfactory results were obtained below that level. Regarding the use of SF,it was observed that it improves the mechanical performance of concrete with MWP by offsetting thedecline of its properties relative to conventional concrete. The comparison of the concrete mixes in termsof different approaches has shown that the optimized mix occurs when MWP and SF are used simulta-neously. The proper use of MWP as a replacement for cement would have environmental benefits andboost the viability of the marble stone industry.

� 2018 Elsevier Ltd. All rights reserved.

1. Introduction

The increase in concrete consumption will escalate cementdemand. India’s annual cement production is about 370 Mt,

manufactured by about 139 major and 365 smaller plants. It isexpected to increase up to 550 Mt by 2020 [1].

The cement industry is one of the industrial producers of carbondioxide (CO2), creating up to 5% of worldwide man-made emis-sions of this gas, of which 50% are from the chemical process and40% from burning fuel. Cement manufacture contributes green-house gases both directly through the production of CO2 when cal-cium carbonate is thermally decomposed, producing lime and CO2

and also through the use of energy, particularly from the combus-tion of fossil fuels [2].

In developing countries, the methods used to recycle and re-usewaste materials should be investigated in order to benefit from

238 A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251

natural resources effectively. Reuse of construction and demolitionwaste is one of the most important goals of the construction indus-try. Conversion of raw materials, used or waste materials providessignificant energy savings by reducing the number of industrialprocesses in the production of materials [3].

Marble waste powder (MWP) is a by-product that the marbleindustry generates in large amounts during sawing and shapingof the marble elements. MWP is mostly not being recycled norused in the industry. The presence of MWP in the hardened cementpaste has a filler effect and reduces the paste’s porosity. Today sil-ica fume (SF) is known as a by-product of silicon metal and ferro-silicon alloy industry instead of a waste product and its utilizationin concrete technology has increased recently [4].

1.1. Research significance

According to the results of past investigations, the use of MWPas partial replacement of Ordinary Portland cement (OPC) can leadto reduced mechanical performance of concrete at high replace-ment levels. SF is used for two purposes: to eliminate the disadvan-tages relative to conventional concrete that come from using MWPand to further reduce cement content while retaining an accept-able concrete performance.

Up to now, few researchers have investigated the compressivestrength of concrete with MWP and SF with different incorporationratios. The lack of detailed investigation to determine the optimalcombined content of MWP and SF as partial replacement of OPC inthe production of concrete, in terms of mechanical performancebut taking into account environmental and economic reasons, ledto this study.

In this research, the effects of the use of MWP and SF as partialreplacement of cement on the mechanical properties of concretemixes were examined extensively. Part of the innovation of thisresearch lies in the wider incorporation ratio range analysed todetermine the optimal content of MWP and/or SF as partialreplacement of cement regarding the mechanical, environmental,economic performance of concrete, simultaneously and separately.This study completes that of Khodabakhshian et al. [5], focused onthe durability performance.

2. State of the art

The literature related to the effect of MWP and SF on themechanical properties of concrete was reviewed to gain a betterknowledge of the behaviour of concrete containing MWP and SF.Concerning the effect of MWP with a pozzolanic material, Ergun[6] carried out compressive and flexural tests on concrete withsuperplasticizer containing MWP and diatomite as a partialreplacement of OPC. The author concluded that replacing theOPC with 10% diatomite, 5% MWP and 5% MWP + 10% diatomitein concrete led to the highest compressive and flexural strengthsbecause of the void filling effect of MWP and diatomite, and thepozzolanic activity of diatomite.

Rana et al. [1] studied the effect of using marble slurry ascement replacement in concrete production at substitution ratiosof 0%, 5%, 10%, 15%, 20% and 25%. These authors reported thatthe compressive and flexural strengths of concrete decreased stea-dily as the marble slurry incorporation ratios increased. This wasdue to lack of binding ability in marble slurry. The decrease instrength was not significant for 5% and 10% replacement ratios.

Aliabdo et al. [7] substituted cement and sand with marblewaste dust at ratios of 0%, 5%, 7.5%, 10% and 15%, separately foreach material. These authors concluded that marble waste dustas sand replacement has a more significant effect on compressivestrength than as cement replacement. They observed that usingup to 10% of marble waste dust as cement or sand replacement

improved the compressive strength of concrete. The substitutionratio of 15% in cement replacement led to results similar to thoseof the control mix. They also reported that replacing cement andsand with marble waste dust improved the splitting tensilestrength of concrete.

Mashaly et al. [8] investigated the effect of replacing cementwith marble sludge up to 40% in concrete production. Theyreported that, when increasing marble sludge incorporation up to20%, the compressive strength of concrete increased but then itdecreased gradually for replacement ratios above 20%.

Rodrigues et al. [9] studied the mechanical performance of con-crete with various incorporation ratios of marble sludge as cementreplacement (0%, 5%, 10% and 20%). These authors concluded thatthe compressive strength of concrete decreased with increasingsubstitution ratio. The incorporation of marble sludge decreasedthe splitting tensile strength and modulus of elasticity of concreteup to 20.6% and 8.1%, respectively. However, 5% replacement ofcement with marble sludge led to an increase in splitting tensilestrength and modulus of elasticity of about 4.4% and 2.7%,respectively.

Belaidi et al. [10] investigated the effect of substitution of OPCwith marble powder and natural pozzolan up to 40% on themechanical and rheological properties of self-compacting concrete(SCC). They observed that the compressive strength of SCCdecreased with the increase of marble dust and natural pozzolancontent.

Gesoglu et al. [11] investigated the possibility of replacing OPCwith marble powder at ratios of 0%, 5%, 10% and 20% and fly ash atratios of 0% and 30% in the production of SCCs. The authors foundthat the compressive strength and splitting tensile strengths of SCCfell when replacing OPC with marble powder. Also, they observed asimilar trend for concrete mixes with fly ash and marble powder,which had lower compressive and splitting tensile strengths thanthe control concrete containing fly ash only.

Vardhan et al. [12] studied the effect of the use of marble pow-der as replacement of the OPC at ratios of 0%, 10%, 20%, 30%, 40%and 50% on the mechanical properties and microstructure ofcement mortar. The authors concluded that the compressivestrength and the technical characteristics of the resulting mixesremained unaltered when replacing cement with marble powderup to 10%.

Soliman [13] studied the effect of using marble powder as par-tial replacement of cement at ratios of 0%, 2.5%, 5%, 7.5%, 10%,12.5%, 15%, 17.5% and 20% on the properties of concrete. The authorreported that the compressive strength increased by about 25% byreplacing the marble powder up to 7.5%, whereas the compressivestrength of concrete decreased by about 26% for replacement ratiosabove 7.5%, compared to the control mix. The author also reportedthat using up to 7.5% of marble powder increased the indirect ten-sile strength and the modulus of elasticity of concrete relative tothe control mix and decreased for higher replacement ratios.

Ashish et al. [14] investigated the properties of concrete con-taining marble waste powder as a partial replacement of cementand sand at proportions of 0%, 10% and 15% separately and in com-bined form. The authors concluded that the replacement of cementand sand with MWP at a ratio of 15% decreased and increased thecompressive strength of concrete respectively. The splitting tensilestrength and flexural strength of concrete increased slightly for10% and 15% cement replacement.

According to the reviewed studies of Arel [15], using marblewaste in concrete production reduces environmental pollutionand benefits for the economy. The author reported that replacingcement with 5–10% MWP improves the mechanical properties ofconcrete, whereas reducing the costs of concrete production andthe CO2 emissions of cement production by about 17% and 12%respectively.

A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251 239

SF consists of ultra-fine (<1 mm) particles and increases thebond strength between cement paste and aggregate by makingthe interfacial zone denser. It also plays an important role inincreasing of mechanical strengths of concrete because of havingpozzolanic activity. The filling effect of SF is more dominant thanits pozzolanic effect [4].

Dilbas et al. [16] investigated the effect of SF on the mechanicaland physical properties of recycled aggregate concrete (RAC). Theauthors replaced 0%, 5% and 10% of SF with OPC and demonstratedthat SF improves the mechanical performance of RAC. They showedthat using SF is a suitable way to improve the mechanical proper-ties of structural RAC. They observed that SF has a positive effect onthe compressive strength of RAC when recycled aggregate contentis approximately 30–40%. The modulus of elasticity of naturalaggregate concrete (NAC) containing 5% SF decreased while thoseof NAC containing 10% SF and NAC without SF were approximatelyequal. They also observed that the ratio of the tensile splittingstrength to the compressive strength of RAC increased anddecreased by using the 5% and 10% SF respectively.

Gupta et al. [17] investigated the mechanical and durabilityproperties of concrete containing waste rubber fibre as a partialreplacement of fine aggregates at three levels of SF (0%, 5% and10%) as partial replacement of cement. The authors concluded thatthe compressive strength and static modulus of elasticity of con-crete containing 25% rubber fibre decreased by about 53% and34% for w/c ratio of 0.45 respectively. They observed that the com-pressive strength and static modulus of elasticity of concrete con-taining 25% rubber fibre increased by about 27% and 17% for w/cratio of 0.45 respectively with the incorporation of 10% SF. Theybelieved that this enhanced strength can be attributed to thepore-filling effect of SF.

Onuaguluchi and Panesar [18] investigated the hardened prop-erties of concrete mixes containing pre-coated crumb rubber andSF. These authors replaced 15% of OPC with SF. They concluded thatthe mechanical properties of rubberized concrete decreased as thecoated crumb rubber content of the mixes increased while the SFincorporation improved the compressive and splitting tensilestrengths of concrete containing coated crumb rubber significantly,by about 30% on average.

Shelke et al. [19] studied the compressive strength at 7 and 28days of concrete containing marble powder and SF as a partialreplacement of OPC. These authors replaced OPC with SF (0% and8%) and marble powder (0%, 8%, 12% and 16%), separately and incombined form. They reported that the optimal results of compres-sive strength is found at 8% marble powder and 8% SF: improve-ments of 1.64% and 3.92% at 7 and 28 days for cube specimensand 2.79% and 1.78% at 7 and 28 days for cylindrical specimens.They also reported that the compressive strength of concrete with16% marble powder and 8% SF at 7 and 28 days decreased, respec-tively, by 12.18% and 14.79% (cube specimens) and 20.83% and31.95% (cylindrical specimens).

Amin et al. [20] investigated the effect on the compressivestrength of ordinary concrete of replacing OPC with 30% marblepowder and 0%, 5% and 10% SF. The authors reported that thereplacement of OPC with 30% marble powder and 0%, 5% and 10%SF decreased the 90-day compressive strength up to 19%, 60%and 47% respectively.

3. Experimental programme

3.1. Materials used

The materials used to produce the 16 concrete mixes werecrushed gravel and river sand from Maat Beton Paya, marble wastepowder from Behsang, silica fume from Iran Ferroalloy Industries

Co, type II cement from Mashhad Cement Co, polycarboxylate -ether superplasticizer from Shimi Sakhteman Co, and tap water.All listed companies are located in Iran.

3.2. Concrete mixes

The concrete mix design was made according to the volumetricmethod of ACI 211.1 [21]. Constant water/binder (cement + fines)ratio of 0.45 was used in all specimens. The MWP and SF contentswere the parameters analysed. Four families comprising 16 con-crete mixes were produced: 1) without SF; 2) with 2.5% SF; 3) with5% SF, and 4) with 10% SF. MWP was incorporated at 0%, 5%, 10%,and 20% of total binder mass in all families. Table 1 shows the des-ignation, composition, and the slump of the 16 concrete mixes. Theused standard, specimen dimensions and age of testing are sum-marized in Table 2.

Slump was determined according to ASTM C143 [22]. Wetchamber curing conditions complied with ASTM C192 [23].

4. Consolidated evaluation

The production of cement-based products is responsible for asignificant portion of global CO2 emissions. In particular, 6–7% ofglobal CO2 emissions can be attributed to the production ofcement, which requires 3 GJ of energy per tonne of clinker and isthe component of concrete that has the highest environmentalimpact [42].

According to the definition of ISO 14040, life cycle assessment(LCA) is ‘‘a compilation and evaluation of the inputs, outputs, andpotential environmental impacts of a product system throughoutits life cycle.” LCA is a measure of the environmental impacts of aproduct, process or service during the course of its service life.Developing an LCA consists of three steps as shown in Fig. 1 [43].

A life cycle inventory (LCI) consists of estimates of the materialsand energy inputs and the emissions to air, land, and water associ-ated with the manufacture of a product, operation of a process orprovision of a service. In the case of ready-mixed concrete, forexample, materials include cement, aggregate, and water [43].

The LCI results do not include the supplementary cementitiousmaterials (such as silica fume). However, the quantities of thesematerials used are included [43–45]. In this study, it has been con-sidered that SF and MWP were a waste and that no environmentalimpact due to their production needed to be allocated, which is asimplification of the reality.

4.1. Environmental evaluation

Global Warming Potential, or GWP, has been developed to char-acterize the change in the greenhouse effect due to emissions andabsorptions attributable to humans. LCAs commonly use the GWPfor a 100-year time horizon. GWP allows computation of a singleindex, expressed in grams of CO2 per functional unit of a product,which measures the quantity of CO2 with the same potential forglobal warming over a 100-year period (Eq. (1)):

Global warming index ¼ Rimi � GWPi ð1Þ

where: mi = mass (in grams) of inventory flow i, and GWPi = gramsof CO2 with the same heat trapping potential over 100 years as onegram of inventory flow i, as listed in Table 3 [45].

The contribution to acidification made by various forms ofintervention in the environment can be determined by weightingthe Acidification Potential (AP; Table 4), which is a measure ofthe propensity to release H + relative to sulphur dioxide (SO2).Atmospheric emissions (in kg) are converted, using the AP, to

Table 1Concrete mix proportions.

Mixes Substitutionratio (%)

OPC(kg/m3)

Water(kg/m3)

SF(kg/m3)

MWP(kg/m3)

Coarseaggregate (kg/m3)

Fine aggregate(kg/m3)

SP(kg/m3)

w/b Slump(mm)

Density(kg/m3)

OC (control mix) 0 400 180 0 0 1000 793 1.3 0.45 85 2380M5 5 380 180 0 20 1000 788.4 1.3 0.45 85 2387M10 10 360 180 0 40 1000 783.8 1.35 0.45 90 2359M20 20 320 180 0 80 1000 774.5 1.35 0.45 75 2347SF2.5 2.5 390 180 10 0 1000 790.7 1.45 0.45 80 2367SF2.5 M5 7.5 370 180 10 20 1000 782.7 1.45 0.45 90 2382SF2.5 M10 12.5 350 180 10 40 1000 778.1 1.425 0.45 90 2356SF2.5 M20 22.5 310 180 10 80 1000 768.8 1.425 0.45 85 2351SF5 5 380 180 20 0 1000 788.4 1.45 0.45 90 2382SF5M5 10 360 180 20 20 1000 777.1 1.45 0.45 80 2390SF5M10 15 340 180 20 40 1000 772.5 1.475 0.45 90 2345SF5M20 25 300 180 20 80 1000 763.2 1.475 0.45 90 2360SF10 10 360 180 40 0 1000 783.8 1.6 0.45 85 2377SF10M5 15 340 180 40 20 1000 765.8 1.7 0.45 90 2367SF10M10 20 320 180 40 40 1000 761.2 1.7 0.45 85 2359SF10M20 30 280 180 40 80 1000 751.9 1.825 0.45 80 2358

Table 2The used standard, tested specimens and age of testing.

Properties Standard Dimensions of specimen Age of testing

Grading size analysis ASTM C136 [24] – –Particles dry density ASTM C29 [25] – –Saturated surface dry density ASTM C127 [26] and ASTM C128 [27] – –Fineness modulus ASTM C33 [28] – –Particle size analysis ASTM E2651-13 [29] – –Chemical composition ASTM C114-15, ASTM C1240-15,

ASTM C150M-15 [30–32]– –

Specific gravity ASTM C188 [33] – –Chemical composition ASTM C25-11e2 [34] – –Mineralogical composition ASTM C1365-06 [35] – –Slump test ASTM C143 [22] – –Density ASTM C138 [36] Cylinder of 150 mm diameter and 300 mm length Fresh concreteCompressive strength BS EN 12390–1, 2 and 3 [37–39] 100 � 100 � 100 mm cube 7, 28, 56, 91 and 180 daysSplitting tensile strength ASTM C496 [40] Cylinder of 100 mm diameter and 200 mm length 28, 91 and 180 daysStatic modulus of elasticity ASTM C469 [41] Cylinder of 150 mm diameter and 300 mm length 28 days

Fig. 1. Process for developing an LCA [43].

Table 3BEES Global Warming Potential equivalency factors[45].

Flow (i) GWPi(CO2-Equivalent)

Carbon dioxide (CO2, net) 1Methane (CH4) 23Nitrous oxide (N2O) 296

240 A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251

sulphur dioxide emissions (in kg) resulting in equivalent acidifica-tion (Eq. (2)) [46]:

AcidificationðkgÞ ¼ RiAPi � emissionitotheairðkgÞ ð2Þ

Fossil Fuel Depletion Potential (FP) is at the heart of the sustain-ability debate. It is important to recognize that this impactaddresses only the depletion aspect of fossil fuel extraction, notthe fact that the extraction itself may generate impacts. Extractionimpacts, such as methane emissions from coal mining, areaddressed in other impacts, such as global warming.

Characterization factors have been developed allowing compu-tation of a single index for potential fossil fuel depletion in surplusMegajoule (MJ) per functional unit of product and assess the sur-plus energy requirements from the consumption of fossil fuels(Eq. (3)):

Fossil fuel depletion index ¼ Rici � FPi ð3Þ

where: ci = consumption (in kg) of fossil fuel i, and FPi = MJ inputrequirement increase per kilogram of consumption of fossil fuel i,as listed in Table 5 [45].

GWP, AP and FP for each ingredient of concrete (includingcement, aggregates, water and superplasticizer) were obtainedfrom previous studies [44,47–66]. According to gathered data, for-mulas 4, 5 and 6 were derived (these formulas allow determiningthe carbon footprint, the quantity of hydrogen ion emissions withthe same potential acidification effect and the energy requirements

Table 4Classification factors for the effect score [46].

Flow (i) APi(SO2-Equivalent)

Sulphur dioxide (SO2) 1.00Nitrogen monoxide (NO) 1.07Nitrogen dioxide (NOx as NO2) 0.70Ammonia (NH3) 1.88Hydrogen chloride (HCl) 0.88Hydrogen fluoride (HF) 1.60

Table 5BEES Fossil Fuel Depletion Potential characterization factors [45].

Flow (i) FPi (surplus MJ/kg)

Coal (in ground) 0.25Oil (in ground) 6.12Natural gas (in ground) 7.80

A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251 241

from the consumption of fossil fuels until concrete productionstage without considering transportation). In some cases, the worstscenario is considered and for some ingredients the median of dif-ferent studies is considered. Also, Flower and Sanjayan [67]reported that the effect of admixture on the environmental assess-ment can be ignored, but in this study the effect of superplasticiz-ers is considered. The LCI data for cement, aggregates, water andsuperplasticizer are given in Tables 6 and 7.

GWPi ¼ ð0:885� CiÞ þ ð0:0032� AiÞþ ð0:0025�WiÞ þ ð1:11� SPiÞ ð4Þ

APi ¼ ð0:0053� CiÞ þ ð0:00002� AiÞþ ð0:0045�WiÞ þ ð0:00481� SPiÞ ð5Þ

FPi ¼ ð1:49� CiÞ þ ð0:0063� AiÞ þ ð0:01�WiÞþ ð83:97� SPiÞ ð6Þ

where: GWPi is the GWP score of concrete mix i; APi is the AP scoreof concrete mix i; FPi is the energy input requirement increase perkilogram of consumption of fossil fuel of concrete mix i; Ci is thecement content of concrete mix i (kg/m3); Wi is the water contentof concrete mix i (kg/m3); Ai is the aggregate content of concretemix i (kg/m3); and SPi is the superplasticizer content of concretemix i (kg/m3).

Each index value was calculated for each mix. Since all threefactors are very important, their weight factors were assumed tobe the same. After normalizing the calculated index values, theenvironmental index for each concrete mix was obtained basedon Eqs. (7) and (8) [68]:

EnvScorei ¼Xp

k¼1

IAScoreik ð7Þ

where: EnvScorei is the environmental performance score for build-ing product alternative i; p is the number of environmental impact

Table 6LCI data for cement, aggregates, water and superplasticizer.

Production (kg) Emissions to air (kg)

GWP (CO2-eq) AP (SO2-eq)

Cement 0.885 0.0053Aggregates 0.0032 0.00002Water 0.0025 0.0045Superplasticizers 1.11 0.00481

categories; IAScoreik is the weighted and normalized impact assess-ment score for alternative i with respect to environmental impact k:

IAScoreik ¼IAik � IVwtk

MaxfIA1k; IA2k; :::; IAmkg � 100 ð8Þ

where: IVwtk is the impact category importance weight for impactk; m is the number of product alternatives; IAmk is the raw impactassessment score for alternative m with respect to environmentalimpact k.

4.2. Economic assessment of concrete mixes

The cost of materials used in production is obtained from sellersreports. Based on their reports, the following normalized formula isderived from Eq. (9):

Costi ¼ ð1� CiÞ þ ð5� SFiÞ þ ð0:0034�WiÞ þ ð0:1� AiÞþ ð45� SPiÞ ð9Þ

where: costi is the normalized cost to produce concrete mix i of 1m3; Ci is the cement content of concrete mix i (kg/m3); SFi is the sil-ica fume content of concrete mix i (kg/m3); Wi is the water contentof concrete mix i (kg/m3); Ai is the aggregate content of concretemix i (kg/m3); and SPi is the superplasticizer content of concretemix i (kg/m3).

4.3. Consolidated index

According to Bement [69], in developing countries, the weightof economic index and environmental index are considered thesame. On the other hand, for the performance evaluation of con-crete mixes, compressive strength is one of the most important cri-teria. So the weigh coefficient of all three indexes considered is thesame. But different weight coefficient can be considered due tolocation and time. Eventually, for simultaneous economic,mechanical and environmental evaluation of each concrete mix,the following formulas (Eqs. (10–13)) are used:

ECMi ¼ MecinEnvScorein þ Costin

ð10Þ

EnvScorein ¼ EnvScoreiMAXEnvScore1; EnvScore2; :::; EnvScorem

ð11Þ

Costin ¼ CostiMAX Cost11;Cost2; :::;Costmgf ð12Þ

Mecin ¼ MeciMAXMec1;Mec2; :::;Mecm

ð13Þ

where ECMj is the consolidated index of economic, environmentaland mechanical performance of concrete mix i; EnvScorein is thenormalized environmental score of concrete mix i; costin is the nor-malized economic score of concrete mix i; Mecin is the normalized28-day compressive strength score of concrete mix i; and m is thenumber of concrete mix alternatives.

5. Results and discussion

5.1. Natural aggregates, Portland cement, marble waste powder andsilica fume properties

The results of the physical properties of fine and coarse aggre-gates, sieve analysis and the chemical and physical properties ofthe OPC, MWP and SF are presented in Tables 8–10.

On average, the particle size of the MWP and SF are finer thanOPC by about two and twelve times, respectively. This difference

Table 7Energy inventory elements for cement, aggregates, water and superplasticizer.

Production (kg) Energy (MJ) FP(MJ/kg)

Coal Oil Natural gas

Cement 3.37 0.00003 0.083 1.49Aggregates 0.0001 0.001 0.00002 0.0063Water – – – 0.01Superplasticizers 1.7 3.2 8.2 83.97

Table 8Physical properties of fine and coarse aggregates.

Aggregates Relativedensity (SSD)

Dry density(kg/m3)

Finenessmodulus

Coarse aggregates 2.675 1620 –Fine aggregates 2.645 1650 2.86

Table 9Sieve analysis of OPC, SF and MWP.

Cumulative passing material (%) Size grading (mm)

OPC MWP SF

10% 1.583 0.991 0.30550% 8.668 4.747 0.68787% 19.850 12.866 10.262Median 8.668 4.747 0.687

Table 10Chemical and physical properties of OPC, MWP and SF.

SF MWP OPC Chemical and physical composition

90–95 0.12 21.63 SiO2 (%)0.6–1.2 0.09 4.27 Al2O3 (%)0.3–1.3 0.21 3.45 Fe2O3(%)– N.D – TiO2 (%)0.5–1.5 55.64 63.25 CaO (%)0.5–2 0.08 2.77 MgO (%)0.3–0.5 0.01 – Na2O (%)0.02–0.07 – – MnO (%)0.2–0.5 N.D. – K2O (%)0.2–0.4 – – C (%)– – 5.48 C3A (%)– – 2.02 SO3 (%)0.04 – – P2O5 (%)0.4–3 43.76 1.5 Loss of ignition (%)0.01–0.4 – – Moisture (%)6.8–8 – – pH1.9 2.5 3.2 Specific gravity (gr/cm3)20–25 – – Specific surface (m2/gr)300–500 – – Bulk density (kg/m3)– 0.19 – Water absorption (%)– 450–600 – Compressive strength (kgf/cm2)1230 – – Melting point (�C)Spherical – – ShapeAmorphous – – Structure

242 A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251

in OPC, MWP and SF particle size can lead to better voids filling inconcrete and improvement of its mechanical properties.

The XRD patterns of MWP and SF showed that the calcite(CaCO3) is the main crystalline mineral of the MWP and SF is anamorphous (non-crystalline) material.

The figures related to the size distribution of coarse and fineaggregates and sieve analysis of OPC, MWP and SF and XRDpatterns of the MWP and SF are presented in Khodabakhshianet al. [5].

5.2. Fresh concrete tests

5.2.1. SlumpThe slump test is a means of assessing the workability or consis-

tency of fresh concrete. In this study, the superplasticizer contentwas adjusted in order to keep the slump test results within the lim-its stipulated (80 ± 10 mm). Fig. 2 shows that the decrease of OPCcontent using MWP and SF instead does affect this property. Asfor concrete mixes containing MWP and SF, as the replacementratio increased, the superplasticizer content also increased, indi-cating that this replacement together with constant w/c ratioreduces the workability of concrete because of the high fineness,amount and low density of SF and MWP. Khayat and Aitcin [70],Mazloom et al. [71] and Gesoglu et al. [11] reached similar conclu-sions in their studies.

5.2.2. Bulk densityThe bulk density and relative bulk density of fresh concrete,

right after the mixes production, are illustrated in Table 1 andFig. 3. The density of fresh concrete is mostly indifferent to thedecrease of OPC content using MWP and SF instead. The densityof concrete containing 5% MWP (M5) slightly increases due to bet-ter particle size distribution by MWP, whereas the densitydecreases at more than 5% substitution ratio because of the lowerspecific gravity of MWP relative to OPC. Rodrigues et al. [9] reachedsimilar conclusions in their study. The replacement of 2.5% SF ledto a decrease in the bulk density, whereas 5% and 10% replacementdid not lead to significant changes in concrete’s bulk density.

5.3. Hardened concrete tests

5.3.1. Compressive strengthThe cube compressive strength of concrete mixes at 7, 28, 56, 91

and 180 days is given in Fig. 4.Effect of SF incorporation. Chemical analysis indicated that the

OPC and SF have different compositions and are principally com-posed of calcium and silica, respectively. After 28 days, the poz-zolanic activity of SF is visible. For instance, at 28 days thecompressive strength of mixes SF10, SF5 and SF2.5 rose approxi-mately 24%, 25% and 23% in comparison with the results after 7days, by contrast, a percentage increase of control mix is 13%.When the values of SFx specimens compared with the control con-crete, it could be seen that the specimens containing SF had highercompressive strength than that of the control concrete. The sameresults can be found in previous researches [16–18,71].

The rate of strength is dependent on the combination of clinkerhydration and the pozzolanic activity of SF. Overall, the mostimportant factors that have influence on the compressive strengthdue to the contribution of SF can be categorized as follows: (i) thepozzolanic reaction of SF with calcium hydroxide that caused theconcrete to be more homogeneous and dense, (ii) the filler effectof SF that improved the initial porosity of the mix due to theobstruction of pores, (iii) using a SP admixture to decrease waterdemand in the production of concrete, and (iv) the dilution effect

60

65

70

75

80

85

90

95

Slum

p (m

m)

Concrete mixes

Fig. 2. Slump test results.

0.975

0.98

0.985

0.99

0.995

1

1.005

1.01

Rel

ativ

e bu

lk d

ensi

ty

Concrete mixes

Fig. 3. Relative bulk density of fresh concrete.

OC M5 M10 M20 SF2.5 SF2.5M5 SF2.5M10 SF2.5M20 SF5 SF5M5 SF5M10 SF5M20 SF10 SF10M5 SF10M10 SF10M207 days 46 49 45 40 48 47 45 40 48 50 44 39 53 50 44 4028 days 52 54 51 47 59 57 54 49 60 61 55 50 66 63 60 5656 days 55 57 53 49 65 64 59 54 66 65 60 56 68 69 65 5991 days 60 63 59 54 68 69 64 58 71 71 65 59 74 74 70 63180 days 62 64 60 54 71 71 65 59 73 72 66 60 77 76 71 64

3035404550556065707580)

MPa

(

Com

pres

sive

stre

ngth

Concrete mixes

Fig. 4. Compressive strength.

A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251 243

that leads to less hydrated compounds due to the less clinker con-tent of the blended cement.

The relative strength was the ratio of the strength of the con-crete with SF and/or MWP to that of the control specimen at thesame age. As seen in Fig. 5, the relative compressive strength ofthe concretes (SF2.5, SF5, SF10) containing SF ranged from 1.04to 1.15 at 7 days, 1.13 to 1.27 at 28 days, 1.18 to 1.24 at 56 days,1.13 to 1.24 at 91 days, and 1.15 to 1.24 at 180 days.

Effect of MWP incorporation. Chemical analysis indicated thatthe main component of MWP is calcium. MWP had higher surfacearea than OPC because of the fineness of MWP used. A slightincrease in the compressive strength can be seen at 5% replace-ment of OPC with MWP. MWP particles acted as the nucleus forhydration and catalyzing process which resulted in higher com-pressive strength results. The usage of MWP reduced the porosityin concrete matrix physically, and had an important binding

OC M5 M10 M20 SF2.5 SF2.5M5 SF2.5M10 SF2.5M20 SF5 SF5M5 SF5M10 SF5M20 SF10 SF10M5 SF10M10 SF10M207 days 1.00 1.07 0.98 0.87 1.04 1.02 0.98 0.87 1.04 1.09 0.96 0.85 1.15 1.09 0.96 0.8728 days 1.00 1.04 0.98 0.90 1.13 1.10 1.04 0.94 1.15 1.17 1.06 0.96 1.27 1.21 1.15 1.0856 days 1.00 1.04 0.96 0.89 1.18 1.16 1.07 0.98 1.20 1.18 1.09 1.02 1.24 1.25 1.18 1.0791 days 1.00 1.05 0.98 0.90 1.13 1.15 1.07 0.97 1.18 1.18 1.08 0.98 1.23 1.23 1.17 1.05180 days 1.00 1.03 0.97 0.87 1.15 1.15 1.05 0.95 1.18 1.16 1.06 0.97 1.24 1.23 1.15 1.03

0.70

0.80

0.90

1.00

1.10

1.20

1.30

Rel

ativ

e co

mpr

essi

ve st

reng

th

Concrete mixes

Fig. 5. Relative compressive strength.

244 A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251

property which was developed by hydration of calcite and C3Achemically. As shown in Fig. 4, the compressive strength decreasedwith the increasing percentage of MWP incorporation. It wasobserved that M10 and M20 specimens had lower strengths thanthe control concrete specimens due to potential reduction in thecementing materials which was commonly known as the dilutionof the pozzolanic reactions. The relative compressive strength ofthe concretes (M5, M10, M20) containing MWP ranged from 1.06to 0.87 at 7 days, 1.04 to 0.9 at 28 days, 1.04 to 0.89 at 56 days,1.05 to 0.9 at 91 days, and 1.03 to 0.87 at 180 days (Fig. 10). Similarresults were found by Ergun [6].

Effect of SF and MWP simultaneous incorporation. Test resultsshowed that up to a certain value of replacing OPC with either SFor MWP using a superplasticizer in concrete matrix had high com-pressive strength. It was thought that concrete added both SF andMWP using a superplasticizer had higher compressive strength.The relative compressive strength of the concretes containing SFand MWP ranged from 0.87 to 1.09 at 7 days, 0.94 to 1.21 at 28days, 0.98 to 1.25 at 56 days, 0.97 to 1.23 at 91 days, and 0.95 to1.23 at 180 days (Fig. 5). The concrete specimens with the highestrelative strength were 10% SF + 5% MWP (SF10M5) at 56 days andit was 1.25 with respect to the control concrete specimens. Overall,it can be argued that, although the use of MWP leads to a down-ward trend in all instances, including compressive strength, theuse of SF can eliminate disadvantages caused by MWP. Accordingto the test results, the use of 2.5% SF increased the compressivestrength of concrete containing 5%, 10% and 20% MWP by about

OC M5 M10 M20 SF2.5 SF2.5M5 SF2.5M10 SF2.5M228 days 3.32 3.35 3.57 3.18 3.12 3.1 3.22 391 days 3.4 4 3.75 3.03 3.53 3.51 3.23 3.28180 days 3.7 4.05 3.98 3.84 4.1 4 3.6 3.65

2.52.72.93.13.33.53.73.94.14.34.5

Tens

ile st

reng

th (M

pa)

Concrete

Fig. 6. Splitting tensile strengt

11%, 8% and 9% respectively. The compressive strength of concretecontaining 5%, 10% and 20% MWP increased by about 12.5%, 10%and 11% by using 5% SF. The most effective percentage of SF toincrease the strength of concrete containing MWP is 10%, with astrength increase of about 18.5%.

5.4. Splitting tensile strength

Compressive and tensile strengths are both required in thedesign of concrete structures. Tensile strength is important fornon-reinforced concrete structures such as dam under earthquakeexcitations. Other structures such as pavement slabs and airfieldrunway, which are designed based on bending strength, aredesigned to withstand tensile forces. Therefore, in the design ofthese structures, tensile strength is more important than compres-sive strength [72].

Effect of SF incorporation. The splitting tensile strength develop-ment of concrete with SF is related to the cement replacementlevel and curing age. It was observed that the replacement ofOPC with 10% SF significantly increased the splitting tensilestrength in this study. It resulted that the specimens containingSF had higher splitting tensile strength than that of the controlconcrete. The relative strength was the ratio of the strength ofthe concrete with SF or MWP to that of the control specimen atthe same age. As seen in Fig. 7, the relative splitting tensilestrength of the mixes (SF2.5, SF5, and SF10) containing SF ranged

0 SF5 SF5M5 SF5M10 SF5M20 SF10 SF10M5 SF10M10 SF10M203.82 3.7 3.72 3.1 3.94 3.71 3.87 3.154.1 3.84 3.8 3.2 4.18 3.91 3.95 3.844.25 4.15 4.3 3.65 4.3 4.2 4.15 4.15

mixes

h at 28, 91 and 180 days.

OC M5 M10 M20 SF2.5 SF2.5M5 SF2.5M10 SF2.5M20 SF5 SF5M5 SF5M10 SF5M20 SF10 SF10M5 SF10M10 SF10M2028 days 1.00 1.01 1.08 0.96 0.94 0.93 0.97 0.90 1.15 1.11 1.12 0.93 1.19 1.12 1.17 0.9591 days 1.00 1.18 1.10 0.89 1.04 1.03 0.95 0.96 1.21 1.13 1.12 0.94 1.23 1.15 1.16 1.13180 days 1.00 1.09 1.08 1.04 1.11 1.08 0.97 0.99 1.15 1.12 1.16 0.99 1.16 1.14 1.12 1.12

0.800.850.900.951.001.051.101.151.201.251.30

Rel

ativ

e te

nsile

stre

ngth

Concrete mixes

Fig. 7. Relative splitting tensile strength at 28, 91 and 180 days.

OC M5 M10 M20 SF2.5 SF2.5M5 SF2.5M10 SF2.5M20 SF5 SF5M5 SF5M10 SF5M20 SF10 SF10M5 SF10M10 SF10M2028 days 0.064 0.062 0.07 0.068 0.053 0.054 0.06 0.061 0.064 0.061 0.068 0.062 0.06 0.059 0.065 0.05691 days 0.057 0.063 0.064 0.056 0.052 0.051 0.05 0.057 0.058 0.054 0.058 0.054 0.056 0.053 0.056 0.061180 days 0.06 0.063 0.066 0.071 0.058 0.056 0.055 0.062 0.058 0.058 0.065 0.061 0.056 0.055 0.058 0.065

0.045

0.05

0.055

0.06

0.065

0.07

0.075

ft/fc

Concrete mixtures

Fig. 8. Ratio between the splitting tensile strength (ft) and compressive strength (fc).

A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251 245

from 0.94 to 1.19 at 28 days, 1.04 to 1.23 at 91 days, and 1.1 to 1.16at 180 days.

Effect of MWP incorporation. Generally, the use of MWP ascement replacement has an obvious effect on the concrete tensilestrength. Fig. 6 shows that the tensile strength increases with theincrease of MWP content up to 10% compared to the control mix.The maximum tensile strength achieved is for 5% MWP at all cur-ing ages, while the minimum concrete tensile strength is observedfor 20% MWP.

As seen in Fig. 7, the relative splitting tensile strength of themixes (M5, M10, and M20) containing MWP ranged from 0.96 to1.01 at 28 days, 0.89 to 1.18 at 91 days, and 1.04 to 1.09 at 180days. Generally, this improvement in tensile strength refers tothe low porosity and good strength of both cement paste matrixand the interfacial transition zone (ITZ).

Effect of SF and MWP simultaneous incorporation. It was expectedthat concrete with both SF and MWP and a superplasticizer hadhigher splitting tensile strength than the control concrete. The rel-ative splitting tensile strength of the mixes containing SF and MWPranged from 0.90 to 1.17 at 28 days, 0.94 to 1.16 at 91 days, and0.99 to 1.16 at 180 days (Fig. 7). The concrete mix with the highestrelative strength (1.17) was 10% SF + 10% MWP (SF10M10) at 28days. The concrete mix where cement was replaced with a combi-nation of 5% SF and 10% MWP showed the highest relative increasein splitting tensile strength at 180 days and the concrete mixwhere cement was replaced with a combination of 5–10% SF and

5–20% MWP showed the highest relative increase in splitting ten-sile strength at all ages. The other concrete mixes also showed theacceptable increase in splitting tensile strength at older ages.

Fig. 8 shows the ratio between splitting tensile strength (ft) andcompressive strength (fc) for different SF and MWP ratios. Fig. 9shows the relationship between the concrete compressive strengthand its splitting tensile strength at 91 days, showing a correlationcoefficient for all specimens of 0.54. Similarly, in an experimentalstudy by Dilbas et al. [16], a low correlation coefficient (0.46)between the compressive strength and tensile splitting strengthof recycled aggregate concrete with SF was mentioned. The analy-ses point out that the correlation between compressive strengthand tensile splitting strength of specimens with MWP and SF ispoor. This poor correlation can be attributed to the different effectof the different combinations of MWP and SF on compressivestrength and splitting tensile strength. For instance, as can be seenin Fig. 9, some mixes like SF2.5My and SF10M5 showed a betterbehaviour in the compressive strength test compared to the split-ting tensile strength test. While My and SF10M20 showed a betterbehaviour in the splitting tensile strength test compared to thecompressive strength test.

5.5. Static modulus of elasticity

The test results of the modulus of elasticity of the specimens at28 days are presented in Fig. 10. In order to present the relative

246 A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251

modulus of elasticity in Fig. 11, the modulus of elasticity of eachspecimen is normalized by the modulus of elasticity of the controlspecimen. As seen in Figs. 10 and 11, the modulus of elasticity of allspecimens except M10, M20, SF2.5 M10 and SF2.5 M20 is higherthan the modulus of elasticity of the control specimen, and thevalue of the modulus of elasticity of all specimens increases stea-dily as the SF content goes from 0% to 10%. It is observed thatthe replacement of OPC with 5% MWP slightly increased the mod-ulus of elasticity in this study. Figs. 10 and 11 show that the mod-ulus of elasticity increases with the increase of MWP content up to10% compared to the control mix.

Experience also shows that the modulus of elasticity is closelyrelated to compressive strength. Therefore, the relationshipbetween the 28-day compressive strength (fc) and modulus of elas-ticity (Ec) is given in Fig. 12. The results show that there is a goodcorrelation between the compressive strength and modulus ofelasticity for all concrete mixes. As shown in Fig. 12, almost allmixes behaved similarly in both tests and have had a better

y = 0.1502x0.7642

R² = 0.5447

2.83

3.23.43.63.8

44.24.4

50 55 60 65 70 75

Tens

ile st

reng

th (M

Pa)

Compressive strength (MPa)

91 days Power

Fig. 9. Relationship between the splitting tensile stre

34.65

36.49

34.08

29.31

34.78

38.64

33.11

30.08

25

27

29

31

33

35

37

39

41

43

Stat

ic m

odul

us o

f ela

stic

ity (G

Pa)

Concrete

Fig. 10. Static modulus of

behaviour in the compressive strength test compared to the mod-ulus of elasticity test.

5.6. Environmental, economic and mechanical indexes

5.6.1. Environmental indexesThe comparative environmental impact assessment is per-

formed for the material production stage of the concrete life cycle.Figs. 13–15 show the relative GWP, AP and FP indexes, i.e. the ratiobetween the GWP, AP and FP indexes of each mix with SF and/orMWP and those of the control specimen. There is a clear decreasein GWP, AP and FP indexes with increasing MWP and SF incorpora-tion ratios. The relative GWP, AP and FP indexes of the mixes withSF and/or MWP ranged from 0.71 to 0.98, 0.79 to 0.98 and 0.81 to1.00, respectively. The relationship between the three GWP, AP andFP indexes for all the mixes is depicted in Fig. 16. As shown inFig. 16, each mix has similar results in environmental indexesassessment in comparison with the control mix. In other words,

80

0.500.600.700.800.901.001.101.201.30

OCM5

M10

M20

SF2.5

SF2.5M5

SF2.5M10

SF2.5M20SF5

SF5M5

SF5M10

SF5M20

SF10

SF10M5

SF10M10

SF10M20

Relative compressive strength (91 days)Relative tensile strength (91 days)

ngth and compressive strength of all specimens.

37.01

39.84

36.5334.96

38.72

40.65

38.8438.13

mixes

elasticity at 28 days.

Ec = 1.2906 fc0.8271

R2 = 0.7113

28

30

32

34

36

38

40

42

46.00 51.00 56.00 61.00 66.00Stat

ic m

odul

us o

f ela

stic

ity (G

Pa)

Compressive strength (MPa)

28 days Power

0.500.600.700.800.901.001.101.201.30

OCM5

M10

M20

SF2.5

SF2.5M5

SF2.5M10

SF2.5M20SF5

SF5M5

SF5M10

SF5M20

SF10

SF10M5

SF10M10

SF10M20

Relative compressive strength (28 days)Relative modulus of elasticity (28 days)

Fig. 12. Relationship between the modulus of elasticity and compressive strength of specimens at 28 days.

1.00

0.95

0.90

0.80

0.98

0.93

0.88

0.78

0.95

0.90

0.85

0.76

0.90

0.85

0.81

0.71

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

Rel

ativ

e G

WP

inde

x

Concrete mixes

Fig. 13. Relative global warming potentials (GWP) index.

1

1.05

0.98

0.85

1.00

1.12

0.96

0.87

1.07

1.15

1.051.01

1.12

1.17

1.12 1.10

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

1.1

1.15

1.2R

elat

ive

mod

ulus

of e

last

icity

Concrete mixes

Fig.11. Relative modulus of elasticity at 28 days.

A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251 247

1.00

0.96

0.92

0.84

1.00

0.96

0.91

0.83

0.98

0.93

0.90

0.81

0.950.92

0.88

0.81

0.75

0.8

0.85

0.9

0.95

1

1.05

Rel

ativ

e FP

inde

x

Concrete mixes

Fig. 15. Relative fossil fuel depletion potential (FP) index.

0.550.6

0.650.7

0.750.8

0.850.9

0.951

OC

M5

M10

M20

SF2.5

SF2.5M5

SF2.5M10

SF2.5M20

SF5

SF5M5

SF5M10

SF5M20

SF10

SF10M5

SF10M10

SF10M20

GWP index AP index FP index

Fig. 16. Relationship between the relative GWP, AP and FP indexes.

1.00

0.96

0.93

0.86

0.980.95

0.91

0.84

0.97

0.93

0.89

0.82

0.93

0.89

0.86

0.79

0.75

0.8

0.85

0.9

0.95

1

1.05R

elat

ive A

P in

dex

Concrete mixes

Fig. 14. Relative acidification potential (AP) index.

248 A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251

the effect of each mix on the GWP, AP and FP changes is almost thesame in comparison with the control mix.

5.6.2. Economic indexFig. 17 shows the relative economic index, i.e. the ratio between

the economic index of each mix with SF and/or MWP and that ofthe control specimen. There is a clear increase in the relative eco-nomic index up to 1.07, 1.14, and 1.27 for SF contents of 2.5%, 5%and 10%, respectively. Furthermore, for increasing MWP incorpora-tion, the relative economic index decreases to 0.88, 0.94, 1.01, and1.16 for mixes with 0%, 2.5%, 5% and 10% SF, respectively.

5.6.3. Normalized and ECM indexesAll the three normalized environmental, economic and mechan-

ical indexes for all the mixes are depicted in Fig. 18. The figureshows that, for mixes with SF contents up to 5%, the environmentalindex is much higher than the two other indexes. However, SF con-tents over 5% lead to lower differences between these indexes tothe extent that the environmental index becomes lower than thetwo other ones for mixes with 10% SF.

Subsequently, using MWP and SF is appropriate from an envi-ronmental point of view. In all mixes an increase in the substitu-tion rate led to a downward trend of the environmental index,which is positive. Increasing the MWP and SF content leads to adescent and ascent in the graph of economic index, respectively.

OC M5 M10 M20 SF2.5 SF2.5M5 SF2.5M10 SF2.5M20 SF5 SF5M5 SF5M10 SF5M20 SF10 SF10M5 SF10M10 SF10M20Normalized Mec (28 days) 0.79 0.82 0.77 0.71 0.89 0.86 0.82 0.74 0.91 0.92 0.83 0.76 1.00 0.95 0.91 0.85Normalized Env 1.00 0.96 0.92 0.83 0.99 0.95 0.9 0.82 0.97 0.92 0.88 0.80 0.93 0.89 0.85 0.77Normalized Eco 0.79 0.76 0.74 0.69 0.84 0.82 0.79 0.74 0.89 0.87 0.84 0.79 1.00 0.98 0.95 0.91

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

1

1.05

Nor

mal

ized

inde

xes (

Mec

, Env

, Eco

)

Concrete Mixes

Fig. 18. Normalized environmental, economic and mechanical indexes.

0.440

0.4760.465 0.469

0.488 0.488 0.4840.476

0.489

0.516

0.484 0.476

0.5180.510 0.505 0.505

0.4

0.42

0.44

0.46

0.48

0.5

0.52

0.54

ECM

inde

x

Concrete Mixes

Fig. 19. Evaluation of the concrete mixes ECM index.

10.97

0.940.88

1.071.04

1.010.94

1.141.10

1.07

1.01

1.27 1.241.21

1.16

0.80.850.9

0.951

1.051.1

1.151.2

1.251.3

Rel

ativ

e ec

onom

ic in

dex

Concrete mixes

Fig. 17. Relative economic index.

A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251 249

According to the normalized indexes results, the economic index islower than the mechanical index for SF replacements up to 10%,but for 10% SF replacement the opposite occurs.

Consolidated index values for each concrete mix are depicted inFig. 19, in accordance with Eq. (13). The relative ECM index is the

ratio between the ECM index of each mix with SF and/or MWPand that of the control specimen. Fig. 20 shows the relative ECMindex and it can be said that, if the three environmental, economicand mechanical indexes are considered simultaneously, all themixes containing MWP and/or SF have better performance than

1.00

1.081.06 1.06

1.11 1.11 1.101.08

1.11

1.17

1.101.08

1.181.16 1.15 1.15

0.9

0.95

1

1.05

1.1

1.15

1.2R

elat

ive

ECM

inde

x

Concrete Mixes

Fig. 20. Relative ECM index.

250 A. Khodabakhshian et al. / Construction and Building Materials 169 (2018) 237–251

the control mix. The SF10My and SF5M5 mixes have the best per-formance and the control mix has the worst.

In general, the concrete mixes with MWP and/or SF have betterperformance than the control mix.

6. Conclusions

The use of silica fume and marble waste powder as partialreplacement of cement in the production of concrete has beeninvestigated in this study. The marble extraction industry in Iranand elsewhere produces several by-products that are normallydumped in or near the quarry site and create unacceptable envi-ronmental impacts. The LCA method allows comparing differentsolutions of concrete design from an environmental point of view.The following conclusions may be drawn from this investigation:

1. The replacement of Portland cement with 10% silica fume sig-nificantly increased the compressive strength in this study.The 5% replacement of marble waste powder with cement alsoleads to an increase in compressive strength. It was observedthat the mixes containing 10% and 20% marble waste powderhad lower strength than the control concrete. The concretemixes where cement was replaced with a combination of 10%silica fume and 5–20% marble waste powder showed highervalue in compressive strength than the control concretes at allages. As well the concrete mixes where cement was replacedwith a combination of 2.5–5% silica fume and 10–20% marblewaste powder showed a slight increase in compressive strengthat older ages.

2. The specimens with silica fume had higher splitting tensilestrength than that of the control concrete and it increased asthe marble waste powder content increased up to 10%. The con-crete mixes where cement was replaced with a combination of5–10% silica fume and 5–20% marble waste powder had highersplitting tensile strength than the control concrete at all ages.

3. The analysis shows that the correlation between compressivestrength and splitting tensile strength of mixes with MWPand SF is poor.

4. The modulus of elasticity of all specimens except the concretemixes where cement was replaced with a combination of 0–2.5% silica fume and 10–20% marble waste powder is higherthan the modulus of elasticity of the control specimen. Thevalue of the modulus of elasticity of all specimens steadilyincreased as the silica fume content increased from 0% to 10%.It was observed that the replacement of Portland cement with5% marble waste powder slightly increased the modulus of elas-ticity of the mixes.

5. There was a good correlation between the compressive strengthand modulus of elasticity for all concrete mixes.

6. The environmental (GWP, AP and FP) indexes of the control mixwere higher than those of the other mixes. The use of silicafume and marble waste powder increased and decreased theeconomic index respectively but for silica fume contents up to5% this increase was not significant.

7. If the three environmental, economic and mechanical indexesare considered simultaneously, using the ECM index, all themixes with marble waste powder and/or silica fume have betterperformance than the control mix.

8. In general terms, it was found that the mechanical properties ofconcrete with marble waste powder tend to decline for cementreplacement ratios of more than 10%. Satisfactory results wereobtained for incorporation ratios of marble waste powder upto 10%. Regarding the use of silica fume, it was observed thatit improves the mechanical performance of concrete with mar-ble waste powder by offsetting the decline of its properties rel-ative to the control concrete. The concrete mixes with marblewaste powder and/or silica fume have better performance thanthe control mix.

9. Environmentally, when 30% of cement is replaced withMWP and SF (the mix containing 10% silica fume and20% marble waste powder(, so that not only the mechani-cal properties of concrete are improved but MWP productsfrom marble stone industry are reused, the greenhousegases emissions are significantly reduced and more naturalresources are saved.

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