Construction and Building Materials 135 (2017) 94–103

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Construction and Building Materials

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Feasibility study on the use of high volume palm oil clinker waste inenvironmental friendly lightweight concrete

http://dx.doi.org/10.1016/j.conbuildmat.2016.12.0980950-0618/� 2016 Elsevier Ltd. All rights reserved.

⇑ Corresponding author.E-mail address: johnson@um.edu.my (U.J. Alengaram).

Rasel Ahmmad a, U. Johnson Alengaram a,⇑, Mohd Zamin Jumaat a, N.H. Ramli Sulong a, Moruf O. Yusuf b,Muhammad Abdur Rehman c

aCentre for Innovative Construction Technology (CICT), Department of Civil Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, MalaysiabDepartment of Civil Engineering, University of Hafr Al Batin, 31991 Hafr Al Batin, Saudi ArabiacDepartment of Geology, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia

h i g h l i g h t s

� Waste palm oil clinker powder to partially replace cement in eco-friendly concrete.� 15% POC powder produced optimum result in terms of strength and water absorption.� 37% of waste materials from palm industry in the development of green concrete.� The highest compressive strength of 65 MPa obtained using low cement content.

a r t i c l e i n f o

Article history:Received 5 August 2016Received in revised form 17 October 2016Accepted 21 December 2016Available online 7 January 2017

Keywords:Lightweight concreteWaste POC powderXRD analysisCompressive strengthStress-strain behaviourWater absorption

a b s t r a c t

Huge amount of virgin materials is being used in the production of concrete and the negative impactcaused by exploitation of natural resources to our eco-system is beyond recovery. In order to producea cleaner and greener concrete, waste palm oil clinker (POC) powder, a by-product from palm oil industrywas used as filler and amorphous material in the development of sustainable and environmental friendlylightweight concrete. The utilization of POC powder as cement replacement in concrete will certainlyhave positive impact on the environment due to potential reduction in greenhouse gas emission.Further, whole replacement of virgin crushed granite coarse aggregate with coarser POC as coarse aggre-gate would enable conservation of natural resources. The properties including workability, density, com-pressive strength in different moisture contents, splitting tensile and flexural strengths, stress-straincurve, modulus of elasticity, ultrasonic pulse velocity (UPV) water absorption and sorptivity of the sus-tainable lightweight concrete were obtained and analysed. It has been found that the addition of 15%waste POC powder produced the optimummixture as the strength enhancement of compressive and flex-ural strengths of 30% and 15%, respectively, was found. In addition, the filler effect of waste POC powdercould be seen as it decreased the water absorption and sorptivity. Moreover, the use of two palm oilindustrial waste materials up to a volume of 56% in concrete as replacement to cement and coarse aggre-gate will not only reduce cost but it will spur research and commercial interests as environmentalfriendly high strength lightweight concrete could be produced using these wastes.

� 2016 Elsevier Ltd. All rights reserved.

1. Introduction cement [3]. Due to high volume of quarrying activities of natural

The construction industry consumes a huge amount of concreteand as concrete is composed of natural resources such as water,sand, gravel and crushed granites or other rocks, the overuse ofsuch natural resources has implacable consequences on globalenvironment. Research shows the annual consumption of naturalaggregates amounts to 8–12 billion tons [1,2] and 2.8 billion tons

resources for both rocks and cement production, it is not an eco-friendly activity and has significant environmental, social and eco-nomic impacts [4]. Thus in order to achieve sustainable develop-ment, one of the paramount alternatives is to use the waste andindustrial by-product materials instead of virgin materials in con-crete [5].

Further, the use of the renewable resources by concrete indus-try could lead to greener and sustainable construction materials forbetter quality of human life and to reserve natural resources forfuture generation. The lightweight aggregate concrete (LWAC)

R. Ahmmad et al. / Construction and Building Materials 135 (2017) 94–103 95

made of artificial LWAs such as expanded clay, slate, shale, or blastfurnace slag, is a type of eco-friendly construction material. Thebenefits of LWAC include reduction in dead load, minimize microcracks in concrete compared to normal concrete (NWC) due to sig-nificantly lower stiffness of lightweight aggregate in LWAC, anduniform stress distribution at the micro level in lightweight con-crete that enhances the durability in severe environments com-pared to normal weight concretes [6,7]. However, the mainconcern in the production of lightweight aggregate is the need ofenergy and its associated cost. In addition, LWAC needs morequantity of cement and cementitious materials and this leads tomore cost. This is an energy-intensive industry with energy costnormally accounting for about 40% of operational cost and itscomes from solid coal or other liquid or gaseous fossil fuel frombiomass waste are used [8].

On the other hand, there are alternative resources for light-weight aggregate through natural lightweight aggregates whichdo not consume a significant energy compared to artificial light-weight aggregates. Some of these aggregates can be obtained fromnatural lightweight rocks. However, due to the limitation of naturalrecourses, the use of solid wastes from palm oil industry, such aspalm oil clinker (POC) and oil palm shell (OPS) could be consideredas lightweight aggregates and concretes developed using thesewastes will be more sustainable [9–11]. Also OPS has better struc-tural performance compared to crushed granite aggregate in caseof blast loading [12] and ductility [13,14]. The oil palm industryoperates in tropical region countries, like Malaysia, Indonesia,Thailand, Nigeria. Palm oil industry produces a wide variety ofwaste such as OPS, POC, palm kernel fibre etc. in large quantities[15–17]. POC is one kind of solid waste generated during powerproduction due to burning of OPS and palm kernel fibre in certainproportions [13]. POC is abundantly available and is normally trea-ted as a waste with no economic value. It is like a porous stone,grey in colour, flaky and irregular in shape [18]. Original POC(POC directly collected from oil palm mill) is in bolder size andcrushed in stone crusher to utilize it as lightweight aggregate inconcrete.

A lightweight concrete made using POC as coarse aggregate hascompressive strength in the range of 27–35 MPa and could be con-sidered as moderate strength concrete [19]. But as POC aggregateshave rough surface with lot of pores and hence it requires morepaste to have appropriate bond with matrix. Thus, use of palmoil clinker powder could lead to sustainable concrete in the devel-opment of high strength lightweight concrete. Also in the case ofproduction of POC powder no carbon di-oxide generated. Ahmmad[13] et al. showed POC contains 60% of pozzolanic silica SiO2, and8% of CaO. Huntzinger and Eatmon [20] showed that the produc-tion of a ton cement generates a ton of CO2, causing an increaseof temperature on the earth’s crust. However, the use of POC pow-der reduces cement content and hence reduces CO2 emission. So,the aim of this study is to develop a new type of high performancelightweight concrete by incorporating POC as the coarse aggregateand as waste POC powder as additional cementing and filler mate-rial to minimize CO2 emission by reducing cement content in con-crete. Currently, there is no published research article on the use ofPOC powder as cementitious material in concrete.

2. Materials and method

2.1. Raw materials

2.1.1. CementOrdinary Portland cement (OPC) cement with 3, 7 and 28-day

compressive strengths of 26, 34 and 46 MPa, respectively, wasused in all the mixtures. The specific gravity and Blaine specific

surface area of the cement used were 3.14 and 351 m2/kg,respectively.

2.1.2. Lightweight coarse aggregateThe POC was collected from the local palm oil factory. The POC

was crushed in the laboratory stone grinding machine and thensieved to different sizes between 5 and 12.5 mm then used as light-weight coarse aggregates.

2.1.3. Local mining sand as fine aggregateLocal mining sand with a specific gravity, fineness modulus and

water absorption of 2.66, 2.89 and 1.17%, respectively, was used asfine aggregate. Its grain size was in the range of 75 lm–4.75 mm.

2.1.4. Additional environmental friendly cementing and filler materialsPalm oil clinker (POC) of size below 5 mm was further ground

in Los Angeles (LA) grinding machine to increase its surface area.The POC powder has crystalline phases dominated with quartz(within 2-theta angle of 0–10�) as shown by the X-ray diffraction(XRD) result (Fig. 1). The phase of POC is majorly crystalline withfew traces of amorphosity indicated by diffusive halo between 25and 30 �C (2-theta). This could be possibly due to short range orderof CaO-MgO-Al2O3-Fe2O3-SiO2 structure within the POC asreflected in the XRF results (Table 1). The peaks in the POC diffrac-togram include the quartz (Q-SiO2), iron (F-Fe2O3), akermanite(A-CaOMgOSiO2), calcite (C-CaCO3) and wollastonite (w-CaOSiO2).

The particle size and volume of OPC and POC powder is shownin Fig. 2. It is seen that the POC particle slightly coarser than OPCwhile the more particle volume was observed in POC comparedto OPC as more volume of particle higher than 0.1 mm was foundin the former than the latter. Also, the utilization of waste POCpowder would be a boost to environmentalists as it could reduceCO2 emission and also could bring wealth from waste.

2.1.5. SuperplasticizerA high range water-reducing admixture was used as the super-

plasticizer (SP) with a quantity of 1.5% of the mass of binder in allthe mixtures.

2.1.6. WaterPortable tap water was used for mixing with the water to

cement (w/c) ratio of 0.45 to maintain the water content of189 kg/m3 for all mixtures.

2.2. Mixing proportion

POC concrete containing 420 kg/m3 OPC (mixture MPOC00)with addition of POC powder of 5%, 10%, 15% and 20% by the weightof cement is considered as variables in the mixtures. Normal min-ing sand was used as fine aggregates. Table 2 shows the details ofthe constituent materials for all mixtures. All mixtures have thesame quantity of materials except for POC powder and SP, whichwas proportioned such that the latter increased with the former.

2.3. Specimen preparation

The cement and aggregates were blended in a mixer for 5 min.Then 70% mixing water was added to the mixture and mixing con-tinued for another 5 min. The rest of the water together with SPwas added to the mixture and mixing proceeded for another5 min before the slump test was performed. The concrete speci-mens were cast in steel moulds of 100 mm cubes for compressivestrength, cylinders of 100 mm diameter and 200 mm height forsplitting tensile strength and modulus of elasticity as well asstress-strain curve. The prismatic specimens of 100 � 100 �500 mm3 were used for flexural strength tests. All the specimens

Fig. 1. XRD analysis of waste POC powder.

Table 1XRF – chemical composition of waste POC powder.

Oxides SiO2 K2O CaO P2O5 MgO Fe2O3 Al2O3 Others

Percentage proportion 60.0 12.0 8.0 5.0 5.0 4.0 4.0 2.0

0

3

6

9

12

15

0

25

50

75

100

0.1 1 10 100

Indi

vidu

al p

artic

le v

olum

e (%

)

% fi

ner

Particle diameter, (µm)

POC Powder par�cle sizeCement Par�cle SizePOC volumeCement par�cle volume

Fig. 2. Particle size distribution and individual particle volume.

96 R. Ahmmad et al. / Construction and Building Materials 135 (2017) 94–103

were compacted using vibrating table for 20 s. The concrete spec-imens were demoulded one day after casting and for each test,the average result of at least three specimens is reported. Theambient temperature of laboratory was 30 ± 3 �C with a relativehumidity of 73 ± 5%.

Table 2Mixing proportion in different percentage of POC powder (all units in kg/m3).

Mix. no Cement Water w/c ratio

MPOC00 420 189 0.45MPOC05 420 189 0.45MPOC10 420 189 0.45MPOC15 420 189 0.45MPOC20 420 189 0.45

3. Results and discussion

3.1. Density of concrete

As POC powder was used as pozzolanic and filler material, theaddition of POC powder in the concrete increased the density ofPOC concrete. Four types of densities, namely fresh, demouldeddensity after 1-day, saturated surface dry, and oven-dry sampleswere measured for all mixtures as shown in Table 3. Based onthe oven dry density, the control POC (mix MPOC00) concretewas about 21% lighter than normal weight concrete consideringits oven dry density 2400 kg/m3. Though the addition of POC pow-der in different percentages of 5%, 10%, 15% and 20% increased thedensity, yet these concretes were found about 21%, 20%, 19% and24% lighter than normal weight concrete.

Furthermore, strength is not a major consideration in floorslabs; therefore, a large amount of lightweight aggregate concreteis used to reduce the dead weight of concrete in floors of high-risebuildings [23]. In this sense, the use of POC infused concrete is asustainable alternative in that it reduces environmental wastesand could be used to produce concrete whose weight could bereduced by 23% for 20% OPC substitution. Moreover, the total vol-

POC CA Sand POC powder SP

596 837 0 6.90596 837 21 7.30596 837 42 7.60596 837 63 8.00596 837 84 8.30

Table 3Density of high performance POC lightweight concrete at different ages.

Mix No. Density (kg/m3)

Fresh Demoulded(after 1 day)

Saturated surfacedry (28-day)

Oven dry

MPOC00 2095.39 2076.57 2109.80 1896.84MPOC05 2085.44 2065.07 2101.66 1893.35MPOC10 2100.00 2083.56 2129.76 1915.07MPOC15 2120.63 2100.62 2154.16 1944.58MPOC20 1959.30 1936.42 2014.71 1828.16

R. Ahmmad et al. / Construction and Building Materials 135 (2017) 94–103 97

ume of POC lightweight concretes including POC powder amountsto 35–37% waste materials.

3.2. Workability of concrete

Fig. 3 shows the relationship between POC powder content andthe slump value. It can be seen that the increase of POC powderwith the addition of same proportion of SP increases the slump val-ues due to the fact that the hydration of POC powder may be low atinitial age as it contains 60% of silica (Table 1); further, POC mayalso contain dicalcium silicate (C2S) due to the presence of wollas-tonite (Fig. 1) that could lower the rate of hydration at the earlystages [24]. Therefore, it is expected that by increasing the amountof POC powder and increase of SP in same proportion in concretemixture results in the increase of workability. Mehta and Monteiro[23] reported that lightweight concrete with a slump value of 50–75 mm is similar in terms of case of site application to a normalconcrete with 100–125 mm slump value.

Slump (mm) = 7.9x POC Powder % + 67.6, R² = 0.94

0

50

100

150

200

250

0 5 10 15 20 25

Slum

p V

alue

, mm

POC powder content, %

Fig. 3. Relationship of slump value with POC powder.

Fig. 4. XRD result of mixture

3.3. XRD analysis result of mortar using POC powder

From Fig. 4, diffractogram in MPOC15 appears horizontal withminor peaks of unreacted quartz (SiO2) in different angle like0–18 and 27–36 (2-theta) is shown by ellipse in the figure. How-ever these peaks appeared stronger in intensity in MPOC00 systemis similar to the study of ground blast furnace slag [25]. In addition,the disappearance of some of the peaks observed in MPOC00, in theMPOC15 sample suggested that latter is more amorphous than theformer. This could be traced to the concatenation of more siliconbased compounds. The connection of more silicon compoundcaused the reorganization of the bonds existing within the adjacentsilicon atoms thereby causing silicate re-organization. The propen-sity of more silicate reactivity within the calcium compound couldresult in non-repetitive nature of the observed short ranged orderas equally observed in a previous study [25]. Thus, addition of POCpowder in paste resulted in more amorphous products due to thepresence of less silicate re-organization in the product formed.Therefore, this implies that the POC is not only performing thefunction of micro reinforcement but could contribute to the forma-tion of secondary hydration products.

3.4. Compressive strength

Fig. 5 shows scanning electron microscopy image for surfacetexture of POC aggregate. The compressive strength developmentof all mixtures up to 56 days is shown in Fig. 6. The test resultsrevealed that POC concrete containing POC powder in 5%, 10%and 15% improves compressive strength compared to the controlPOC (MPOC00) concrete which is similar improvement of GBFSused concrete [25]. The increasing of compressive strength is inthe range of 53–67% at the age of 1-day compressive strength inmixture MPOC05, MPOC10 and MPOC15 compared to the controlmixture. On the other hand, the 7-, 28-, and 56-day compressivestrengths were 19–24%, 17–30% and 14–26%, respectively, higherthan the control mixture. The mixture MPOC15 produced the high-est 28-day compressive strength of about 57 MPa which is 29%higher compared to the control concrete with the density increaseonly 2% compared to the control mixture MPOC00.

However, the mixture MPOC20 showed decrease in compres-sive strength compared to the mixture MPOC15 and this couldbe attributed to the addition of more POC powder which is similarby adding more GBFS in previous study [25]. Based on the com-pressive strength, the addition of 15% of POC powder is consideredoptimum as 36% by volume of waste material could be included inthe form of POC as coarse aggregate and as powder. It should be

MPOC00 and MPOC15.

Fig. 5. Surface texture and SEM of POC aggregate.

20

30

40

50

60

70

0 10 20 30 40 50 60

Cub

e co

mpr

essi

ve st

reng

th, (

MPa

)

Age, (day)

MPOC00MPOC05MPOC10MPOC15MPOC20

Fig. 6. Compressive strength of POC concrete in different age.

98 R. Ahmmad et al. / Construction and Building Materials 135 (2017) 94–103

noted that POC aggregate is porous [26] and hence the strengthand stiffness of POC is low [6]. Therefore, the addition of POC pow-der as filler would enable the concrete to achieve maximum com-paction by filling the pores as well as becoming active aspozzolanic materials and enhance the compressive strength [13].In addition, due to porous surface texture, the POC has a larger sur-face area than aggregates of the similar size (Fig. 5).

Addition of POC powder for reducing effective w/c ratio has apositive impact by improving the concrete strength. In addition,the water absorption of POC aggregate is beneficial in that it is usedfor internal curing, which indicates the process of concrete aggre-gates holding water and releasing it during cement hydration [27].In addition, internal curing reduces autogenous shrinkage and per-meability thereby increasing the durability of concrete by preven-tion of micro cracks.

The comparison of the control mixture (MPOC00) with POC con-crete containing 20% POC powder (mix MPOC20) showed a negligi-ble compressive strength variation of 1–6% at all ages. The lowerstrength gain could be attributed due to fluidity of concrete withthe slump values of 218 mm; this could result in more voids andlow density of the concrete and subsequent strength reduction.However, the development of LWAC of grade 45 at 28-day madewith 420 kg/m3 of cement with 37% volume of POC as waste mate-rials could be compared to the sample prepared using 450 kg/m3 ofOPC and expanded clay to achieve LWAC of grade 30 [28]. It is aknown fact that production of artificial lightweight aggregatesneeds a lot of energy and expensive raw materials that are onlyavailable in certain geographic areas [29].

Aslam et al. [30] reported that grade 45 lightweight concretecould be made by using waste oil palm shell (OPS) and POC ascoarse aggregate with normal sand as fine aggregate; however they

reported that the use of 480 kg/m3 OPC was required. In contrast, itis seen from this study that LWAC of grade 45 can be producedusing POC as lightweight aggregates with or without POC powder(mixes MPOC00 and MPOC20) to the extent of 15% reduction incement content. The use of 15% POC powder in POC concrete signif-icantly increases the compressive strength by 30%. The comparisonof 28-day compressive strength of mixture MPOC00 with thestrengths of mixtures MPOC05, MPOC10, MPOC15 shows 17%,29% and 30% respectively, higher compressive strength. In addi-tion, the 56-day compressive strengths of the mixtures MPOC05,MPOC10, MPOC15 were about 14%, 19% and 26% higher comparedto the control mixture MPOC00. This is because at this age, thecement particles hydration products (portlandite) could undergoa secondary hydration reaction with POC because of its pozzolanic-ity to produce additional calcium-silicate-hydrate (C-S-H) asshown in Fig. 4. Also, the pozzolanic strength activity index hasbeen calculated by indirect method [fcu(pozzolan mixture)]/[fcu(reference)]as shown by Thorstensen and Fidjestol [31]. The 28-day pozzolanicstrength activity index values obtained for the mixtures MPOC05,MPOC10, MPOC15 and MPOC20 are 1.16, 1.28, 1.30 and 1.02,respectively. The highest pozzolanic strength activity index hasbeen obtained for the mixture MPOC15 that contained 15% ofPOC powder and this could be considered as the optimummixture.Moreover, it has been reported [26] that cube compressivestrength as high as 63 MPa (56-day) was obtained for lightweightconcrete that contained POC as lightweight aggregate and it shouldbe noted that higher cement content of 466 kg/m3 was used in thatresearch compared to 420 kg/m3 in the present work. And withlower cement content the compressive strength of 65 MPa(Fig. 6) was achieved and this could be attributed to the additionof POC powder in the concrete due to filler and pozzolanic effects.So this could lead to the usage of POC powder as cement replace-ment material and its direct influence on CO2 emission due tothe production of cement can’t be ignored.

The effect of moisture in concrete could be seen from the28-day compressive strengths of concrete tested in SSD and ODconditions as shown in Table 4. Further, the relationship betweenOD specimens of cube and cylinders is also shown in Table 4.The cube compressive strengths of OD specimens of POC concretewere higher in the range of 9–24% compared to SSD specimens andthis is similar to the previous study using OPC cement in normalconcrete [32]. Also, the water pressure developed in concreteunder SSD condition concrete after crack caused water dischargethrough the concrete cracks as shown in Fig. 7. This uniform waterpressure might influence in the reduction of compressive strengthof specimens in SSD condition. As there is no water pressure in ODconcrete specimens, it has higher compressive strength is similarto the previous study [32]. The POC lightweight concrete’s ovendried cylinder compressive strength was found nearly 79–89% of

Table 428-day compressive strength of POC high strength LWC in SSD and OD conditions.

Mix No. Cube compressive strength, f cu (MPa) Cylinder compressivestrength (OD), f 0c (MPa)Saturated surface

dry (SSD) conditionOven dry(OD)condition

MPOC00 44.21 52.47 46.84MPOC05 51.10 55.44 47.17MPOC10 56.70 61.86 49.51MPOC15 57.10 62.12 53.30MPOC20 45.15 56.05 47.19

Table 5Tensile strength of POC lightweight concrete.

Mix No. Splitting tensilestrength, f t(MPa)

Splitting tensilestrength/compressivestrength ratio at28 days (%)

Flexuralstrength, f r(MPa)

7 day 28 day 7 day 28 day

MPOC00 3.29 4.29 9.71 4.75 5.82MPOC05 3.68 4.34 7.60 5.44 6.49MPOC10 3.62 4.25 7.50 5.47 6.69MPOC15 3.66 4.63 8.11 5.58 6.72MPOC20 3.15 3.87 8.84 4.83 5.54

R. Ahmmad et al. / Construction and Building Materials 135 (2017) 94–103 99

the respective cube compressive strength though for normalweight concrete the cylinder compressive strength is found about65–85% of the cube compressive strength [33]. However, in caseof high strength (above 100 MPa) normal weight concrete thereis no significance change in compressive strength in case of cubeand cylinder specimen [33].

3.5. Tensile strength

The measured splitting tensile and flexural strengths for allmixtures are shown in Table 5. The minimum 28-day splitting ten-sile strength requirement for lightweight concrete to be used instructural elements is 2.0 MPa [34]. As can be seen in Table 5, allthe mixtures produced splitting tensile strengths of more than2.0 MPa at the ages of both 7- and 28-day. As shown the 7-daycompressive strength of concretes containing POC powder up to15% (50–52 MPa) is about 90% of the 28-day compressive strength(56–57 MPa) and this shows that all these mixtures achieved thestrength grade required for high strength lightweight concrete.Therefore, a structural member made of these lightweight aggre-gate concretes can be exploited at an early age of 7 days. Theincrease in the splitting tensile strength rate from 7 days to 28 dayswas 17–30% for all mixtures. It should be noted that the increase inthe rate of all compressive strengths from 7 to 28 days was 9–12%.

Therefore, it can be seen that the increase in the rate of splittingtensile strength with time is more significant than the compressivestrength. Table 5 clearly shows that the inclusion of POC powderup to 15% in POC concrete increases the tensile strength. ThePOC aggregate has different shapes with small pores in the rangeof 10.4–1200 lm [13] with lot of pores less than the minimumsand particle size of 75 lm. The particle size of POC powder variesbetween 0.43 lm and 112 lm as shown in Fig. 2. Thus, the smallerPOC particles could fill the voids within the pores of POC coarseaggregate and enhance the bond which in turn increases thestrength. Similar to the compressive strength, in the case of thesplitting tensile strength an addition of 15% of POC powder is opti-

(a)

Fig. 7. (a) surface in SSD condition and (b) water dis

mum. However, the results show that the splitting tensile strengthreduces in case of addition of POC powder in excess of 15% as itwould create more voids.

As can be seen from Fig. 8, the slope of the flexural strength wasmore than that for the splitting tensile strength. This shows thatthe increasing rate in the flexural strength was more for the split-ting tensile strength and the positive effect of adding POC powderin POC concrete was more pronounced in the flexural strength thanin the splitting tensile strength. Generally, the splitting tensilestrength/compressive strength ratio of normal weight concretevaries in the range of 8–14% [35]. The 28-day splitting tensilestrength/compressive strength ratio of all mixtures varied between7.5 and 9.7%. However, it should be noted that compared to OPSbased lightweight concrete [36], the tensile strength/compressivestrength ratio was higher for the POC lightweight aggregate con-crete of equivalent grade.

Fig. 9 shows relationship between splitting tensile strength andcompressive strength. The strong correlation of this relationshipshows that Eq. (1) can be used for predicting splitting tensilestrength from compressive strength.

f t ¼ 0:21f 0:752cu ð1Þwhere, f t is splitting tensile strength (MPa), f cu is cube compressivestrength (MPa).

Shafigh et al. [37] proposed Eq. (2) for lightweight concrete withcube compressive strength in the rage of 34–53 MPa. Eq. (3) wasalso proposed by ACI 318-05 for normal weight concrete withcylinder compressive strength in the range of 21–83 MPa.

f t ¼ 0:4887f 0:5cu ð2Þ

f t ¼ 0:59f 0:5cy ð3ÞAs can be seen in Fig. 9, POC lightweight concretes produced in

this study has higher splitting tensile strength compared to pre-dicted values based on Eq. (2); however, the predicted values based

(b)

Water

charge through concrete crack in SSD condition.

3

4

5

6

7

40 45 50 55 60

Tens

ile st

reng

th, M

Pa

Compressive strength, fcu (MPa)

Fig. 8. Relationship (28 day) of tensile strength with compressive strength of POCLWC.

ft = 0.21fcu0.7519

R² = 0.82

3

3.5

4

4.5

5

40 45 50 55 60

Split

ing

Tens

ile st

reng

th, f

t, (M

Pa)

Compressive strength, fcu, (MPa)

This studyPredicted from equation (2)Predicted from equation (3)

Fig. 9. Relationship of splitting tensile strength with compressive strength of POCLWC.

100 R. Ahmmad et al. / Construction and Building Materials 135 (2017) 94–103

on ACI code (Eq. (3)) show closer to the experimental values. Thiscomparison shows that POC lightweight concrete has about 20%higher splitting tensile strength than OPS lightweight concrete atthe same compressive strength.

3.6. Stress-strain behaviour

Stress-strain relationship of structural concrete is an importantcharacteristic of concrete to predict the behaviour of structural ele-ments. From the stress-strain curve the properties of concrete suchas various forms of the modulus of elasticity, strain at peak stressand ultimate strain could be obtained. Fig. 10 shows the typical

0

20

40

60

0 0.0005 0.001 0.0015 0.002 0.0025 0.003

Stre

ss, f

c' (M

Pa)

Strain,

MPOC00

MPOC05

MPOC10

MPOC15

MPOC20

Fig. 10. Stress-strain behaviour of POC LWC at 28-day adding POC powder.

stress-strain curve for all the mixtures. The strain at the peak stress(e0) of these mixtures was found to be in the range of 0.0023–0.0027. POC concretes containing additional POC powder showedalmost same e0 with that of the control POC concrete (mixMPOC00). For instance, the stress currying capacity increases upto 21% with the addition of 15% POC powder then it decreases onthe addition of 20% POC powder. A reliable numerical stress–strainrelationship was determined by Popovics [38] in 1973, wherein thestress r (psi) at a given strain e is estimated by a function of theultimate stress r0ðpsiÞ, the corresponding strain e0 in Eq. (4).

e0 ¼ 2:7x10�4r1=40 ð4Þ

Using Eq. (4) the strain obtained at ultimate stress is in therange of 0.023–0.025. It can be seen that the POC concretes showedapproximately 35–53% greater strains at peak stress than NWCstrain range 0.0015–0.002 [39]. The stress-strain curve of light-weight and normal weight concretes tested at a constant rate ofstrain showed that at the same compressive strength, lightweightconcrete has a higher e0 value than normal weight concrete byabout 33% [40]. The higher strain capacity of a concrete showsthe ability of concrete to absorb movement, which causesimproved resistance to cracking due to the restrained lengthchange [41]. The ultimate compressive strain (eu) of normal weightconcrete is in the range of 0.002–0.003 [42]. However, the value forlightweight concrete is 0.003–0.0035 [42]. Therefore, the eu valuesof the POC mixtures adding varying percentage of POC powderwere within the ranges of normal weight concrete [13].

3.7. Modulus of elasticity

The moduli of elasticity of the MPOC00, MPOC05, MPOC10,MPOC15 and MPOC20 mixtures were 23.4, 29.0, 32.5, 35.1 and26.4 GPa, respectively. This showed that the addition of 5%, 10%,15% and 20% POC powder of cement weight as filler and cementingmaterials increases the modulus of elasticity by 24%, 39%, 50% and13%, respectively, compared to control mixture MPOC00. It can beseen that except for mixture MPOC20, the increase in the modulusof elasticity for the other mixtures was significant. This increase ofMOE of POC lightweight concrete indicates the stiffness of concreteelement also increases that could result in lower deflection in thestructural element. The modulus of elasticity of lightweight aggre-gates is lower than normal weight aggregates and is often less thanmortar, ranging mainly from 5 to 15 GPa [43]. Therefore, it isexpected that increasing the volume of POC powder as filler andcementing material improves the stiffness of concrete and this inturn enhances the modulus of elasticity. Generally, the modulusof elasticity of structural lightweight concrete ranges between 10and 24 GPa based on strength and density of concrete [43] whereasfor normal weight concrete it ranges from 14 to 41 GPa [35]. Thetest results of this study showed that the modulus of elasticity ofPOC concrete increases with the addition of POC powder. The fol-lowing Eqs. (5) and (6) were proposed for the modulus of elasticityof concrete by the ACI code [44] and CEB/FIP manual [43],respectively.

Ec ¼ 0:043w1:5c

ffiffiffiffif 0c

qð5Þ

Ec ¼ kðf 0cÞ1=3ðwc=2400Þ2 ð6Þ

In this equation, Ec is the predicted modulus of elasticity (MPa);wc is air-dry density (kg/m3); f 0c is the cylinder compressivestrength (MPa) and k is a constant taken as 9.5 in CEB/FIP manual.The predicted values of modulus of elasticity of POC concrete usingACI model gives closer prediction compared to CEP/FIP model codeas shown in Table 6.

Fcu = 0.045(UPV)4.78

R² = 0.93

20

30

40

50

60

70

3.65 3.85 4.05 4.25 4.45 4.65

Com

pres

sive

stre

ngth

, fcu

(MPa

)

UPV (km/s)

Fig. 11. Relationship of UPV with compressive strength.

R. Ahmmad et al. / Construction and Building Materials 135 (2017) 94–103 101

3.8. UPV-compressive strength relationship

The time of travel of an ultrasonic pulse passing through theconcrete to be test is defined as ultrasonic pulse velocity (UPV).The time of travel between initial on set and the reception of thepulse is measured electronically. This test as a measure of non-destructive test, carried out to ascertain the quality of concrete.Results of UPV test are presented in Table 7. The addition of POCpowder up to 15% in the concrete enhanced the UPV of the con-crete mixtures in comparison to control mixture. However, anincrease in POC powder to 20% shows a decrease of UPV due tomore pores. At the age of 28 days, the UPV of control mixturewas recorded 4.39 km/s. At this age, a slight increase in UPV inthe concrete mixtures of MPOC05, MPOC10, and MPOC15 wasobserved compared to control mix-MPOC00. But in case ofMPOC20 the UPV is 2.7% lower than the control mixture. Improve-ment in UPV was observed with age but the deviation decreaseswith increased age of concrete and POC powder content up to15% is considered optimum. It has been stated that concrete withUPV values within the range of 3.66–4.58 km/s are considered asconcrete with ‘‘good” condition [40]. In general, it can be seen thatthe UPV of the control concrete and POC concrete adding POC pow-der increased with increase in compressive strength and the valueswere found within the range of 3.70–4.52 km/s. In addition, in caseof OD condition of concrete due to elevated temperature of con-crete the internal water is evaporated so the UPV reduce eventhe concrete structure not changed.

From the results, it is evident that the specimens of adding POCpowder have a positive effect on the UPV values of POC concrete. Itwas found that UPV can be correlated with its corresponding cubecompressive strength, as shown in Fig. 11, with a R2 value of 0.93.Eq. (7)is proposed to estimate the cube compressive strength basedon the UPV values.

f cu ¼ 0:045ðUPVÞ4:78 ð7Þwhere, f cu represents the cube compressive strength (MPa) and UPVrepresents the transverse ultrasonic pulse velocity (km/s).

3.9. Water absorption

The 24 and 72 h water absorption values for all mixtures areshown in Fig. 12. This figure clearly shows that compared to thecontrol mixtures, the water absorption of POC powder based con-

Table 7UPV of POC concrete containing different percentage of POC powder in km/s.

Mix No. On water cured specimens

1-day 3-day 7 day

MPOC00 3.70 4.18 4.26MPOC05 3.91 4.18 4.32MPOC10 3.90 4.24 4.31MPOC15 3.95 4.28 4.35MPOC20 3.80 4.06 4.12

Table 6Experimental and predicted modulus of elasticity values.

Mix No. fc’ (MPa) wc (kg/m3)

MPOC00 46.84 2109.80MPOC05 47.17 2101.66MPOC10 49.51 2129.76MPOC15 53.30 2154.16MPOC20 47.19 2014.71

crete decreases. The water absorption of concrete decreases byincreasing the POC powder up to 15% in the mixture. The waterabsorption of lightweight aggregate influences the microstructureof hardened cement paste and the interfacial zone of lightweightaggregate concrete, and because the water absorption of light-weight aggregate is higher than for normal aggregate, the percent-age of pore area in the interfacial zone increases with theabsorption of aggregate [45]. Therefore, water absorption of con-crete increases. Elyamany et al. [46] investigated the water absorp-tion of concretes made of pozzolanic fillers silica fume, andmetakaolin and they reported that pozzolanic filler materialsreduce water absorption. Therefore, in this study it is expected thatby adding POC powder as pozzolanic material in POC concrete, thepore area decreases, which causes lower absorption values of POCconcrete. Fig. 12 also shows the relationship between percentageaddition of POC powder in POC concrete and the 24- and 72-hwater absorption of concrete. If the average value of water absorp-tion of concretes be considered it can be seen that there is a poly-nomial relationship (Eq. (8)) with a strong correlation betweenwater absorption and POC powder content.

Wab ¼ 0:0023P2 � 0:0559P þ 5:9544 ð8Þ

where,Wab is water absorption (%) and P is POC powder content (%).Clarke [47] reported that water absorption cannot be used as a

measure of the durability of concrete, but that most good concretes

On oven-dried specimens

28 day 56 day 28 day

4.39 4.44 4.124.43 4.44 4.164.48 4.49 4.194.50 4.52 4.224.27 4.44 4.06

28-day modulus of elasticity (GPa)

ACI CEB/FIP manual Experimental values

28.52 26.46 23.428.45 26.32 29.029.74 27.47 32.531.39 28.80 35.126.71 24.19 26.4

Wab = 0.0023P2 - 0.0559P+ 5.9544

4

5

6

7

0 5 10 15 20

Wat

er a

bsor

ptio

n, W

ab, (

%)

POC powder content, P (%)

24 h water absorption 72 h water absorption

Fig. 12. Water absorption of POC concrete containing POC powder.

0.12

0.13

0.14

0.15

0.16

0.17

0 5 10 15 20

Sorp

tivity

, mm

/m

in

POC powder content, P (%)

10 min Sorptivity30 min sorptivity

Fig. 13. Sorptivity of POC concrete containing POC powder.

102 R. Ahmmad et al. / Construction and Building Materials 135 (2017) 94–103

have an absorption well below 10% by mass. All the POC powderbased mixtures show water absorption lower than 10%.

Fig. 13 shows the effect of addition of POC powder on the sorp-tivity of POC lightweight concrete. It can be seen that the sorptivitydecreases with the increase in POW powder content up to 15% andthen it increases and hence it can be concluded that the addition of15% POC powder is recommended for enhanced performance.

4. Conclusions

This research focused on critical analysis of feasibility study ofusing waste POC powder as additional cementitious and fillermaterial in lightweight concrete to enable it to achieve highstrength. Further, this also could serve as means of minimizing vir-gin materials and make wealth from waste. Based on the researchfindings, the following conclusions have been drawn:

a. X-ray diffraction (XRD) result shows phase of POC is majorlycrystalline with few traces of amorphosity indicated by dif-fusive halo between 25 and 30 �C (2-theta) that could possi-bly be due to short range order of CaO-MgO-Al2O3-Fe2O3-SiO2 structure within the POC.

b. The utilization of waste POC as coarse aggregate, filler andcementing materials would reduce the environmental pollu-tion. Also, the use of nearly 20% of POC powder as filler andcementitious materials would result in the reduction of CO2

in the development of 45 grade lightweight concrete.c. The slump value of POC lightweight concrete increases with

the addition of POC powder. The addition of POC powder upto 15% increases the compactness of concrete though theconcrete is 19% lighter compared to normal concrete.

d. The mix-MPOC15 achieved 28-day compressive strength of57 MPa which is 29% higher compared the control mixture(mix MPOC00). Also, the addition of waste material in con-crete could lead to sustainable concrete as it acts as bothpozzolan and filler.

e. The oven dry specimens had higher compressive strength ofabout 9–24% compared to saturated surface dry specimens.

f. The cylinder compressive strength was found 79–89% as thatof the cube compressive strength and this is higher com-pared the normal weight concrete.

g. The mixture MPOC15 produced the highest splitting tensileand flexural strengths. The splitting tensile strength to com-pressive strength ratio was in the range of normal weightconcrete.

h. With the increase of POC powder content the modulus ofelasticity improves up to 60% (mix MPOC15) compared tocontrol mixture and this could be attributed to enhancementof stiffness of concrete.

i. The ultrasonic pulse velocity shows the addition of POCpowder enhances the compactness of concrete significantly.Also water absorption and sorptivity values decrease withthe increase of POC powder content up to 15%.

j. Based on the investigation, it is recommended that 15% POCpowder that enhances the overall performance of concretecan be used as replacement of OPC.

Acknowledgments

The authors gratefully acknowledge the financial support ofUniversity of Malaya Research Grant (UMRG) No. RP037A-15AET-Enhancement Of Concrete Properties Made From Local WasteMaterials Using Nano Particles. The authors also thank lab assistantMr. Mansur Hitam for his dedicated help in this project.

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