Sustainable Lightweight Self-compacting Concrete Using Oil 1 Palm Shell and Fly Ash 2

10 This research investigated fresh and hardened properties of lightweight self-compacting 11 concrete (LWSCC) incorporated with oil palm shell (OPS) and fly ash (FA). Fresh concrete 12 properties including passing ability, filling ability and segregation resistance were assessed. 13 The properties fulfilled EFNARC guidelines. Incorporation of FA improved fresh properties, 14 particularly filling ability, with the slump flow value increased from 665mm to 730mm. As for 15 hardened properties, OPS-aggregate based LWSCC mixes achieved compressive strength of 16 range 18-38MPa at 28-day age while the splitting tensile strength was in the range of 1.6 to 17 2.8MPa. SEM analyses showed good bonding in the interfacial transition zones (ITZ). Micro18 pores of OPS were filled by cement hydration products and thus ITZ was enhanced. LWSCC 19 incorporated with OPS, a renewable resource from agricultural waste, and with partial FA 20 replacement, is potentially a sustainable alternative construction material. 21 22

sense to use cheaper OPS in producing SCC in order to compensate for higher cost of bigger 162 amount of cement required to achieve concrete self-compacting ability. Also, eradicating 163 concrete vibration cost in SCC can further compensate for the extra cement material cost 164 incurred. Moreover, fly ash, as supplementary cementitious material, if incorporated in 165 concrete can not only improve the fresh state properties but also reduce cost. Produced by 166 burning coal in furnaces of power plant, fly ash is considered as an industrial waste. Partial 167 substitution of cement by fly ash is gaining popularity due to its ability to improve the fresh 168 and hardened concrete properties. Bouzoubaa and Lachemi [66] reported that the use of 169 superplasticizer tended to decrease when higher level of class F fly ash replacement was made. 170 According to Khatib [67], workability improved with fly ash replacement up to 80%, by 171 keeping constant both water-binder ratio and superplasticizer content in SCC. It has been stated 172 by Ramanathan et al. [68] that partial substitution of cement with fly ash can lead to higher 173 paste volume owing to its lower density, resulting in increased paste volume. Thus, friction at the fine aggregate-paste interface is reduced. These can improve the cohesiveness and plasticity 175 of concrete, resulting in improved workability. This trend has been similarly reported by Jalal 176 et al. [69]. The hardened properties of concrete containing fly ash is highly depending on the 177 level of fly ash replacement and class of fly ash. Generally, compressive strength of fly ash 178 concrete at early age is generally lower than that of cement concrete. This has been 179 demonstrated by numerous researchers [66][67][68] and is mainly due to slow-rate pozzolanic 180 reaction of fly ash with calcium hydroxide in hydrated cement. Liu [70] also studied fly ash 181 substitution up to 80% in SCC. The study was carried out up to 180 days. 20% fly ash 182 replacement was found to be optimum in their study as the strength close to control concrete at 183 the age of 90 days. Significant strength development was observed for high level fly ash 184 replacement (above 60%) in the study. Atiş [71] also reported that 50% fly ash replacement in 185 SCC can achieve comparable strength of control concrete. 186 Indeed, it is beneficial to utilize OPS and fly ash in concrete production, and as such, further  used. Physical properties of OPC is presented in Table 1 while Table 2 shows the material 205 chemical composition. The fly ash used in this study was acquired from a coal-fired power plant in Kuching, Sarawak, 210 Malaysia and could be categorised as "Class F low calcium fly ash" in accordance to ASTM 211 C618. The coal used in fly ash production was obtained from Merit Pila coal mine in Kapit, 212 Sarawak, Malaysia. Table 2 shows chemical compositions of the cement and fly ash. Two types of fine aggregates used for this experiment were river sand and crushed OPS. OPS 226 was crushed to the size range of 600μm to 5mm. Nominal size of river sand was 600μm.

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Physical properties of these two fine aggregates are shown in Table 3. Specific gravity and 228 water absorption of the river sand were determined in accordance with ASTM C128 [76]. The 229 particle size distribution curve of river sand is shown in Figure 1.

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Assessment of segregation resistance of fresh concrete was done through sieve segregation test.

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The test began by allowing the mass of fresh concrete to stand still in a container for 15 minutes.

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The mass of pan was then measured as W p on weighing balance.   The method prescribed by Norma [81] was used to carry out splitting tensile strength test.

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Immersed water absorption test was conducted according to the procedure prescribed in ASTM 321 C642-13. In the experiment, the prepared sample was weighted and then allowed to oven dry 322 at 110°C for 24 hours. The sample was weighted again at room temperature after oven drying 323 process. If the difference between two successive measured weights was more than 1g, oven 324 drying process had to be repeated until the difference was less than 1g. This value was noted 325 as M1. The sample was then immersed into water for 48 hours. After the immersion, concrete 326 surface was dried using cloth. The mass was measured as M2. The water absorption was 327 computed by using Eq. (5).
Presently, there is no standard method which can be used for the mix design of LWSCC.

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Nevertheless, for this study, a method proposed by Kanadasan and Razak [64], which was 331 known as particle packing method, was adopted. This method assumed that the voids between 332 aggregates particles are filled by paste. Figure 3 shows the overall mix design procedure.

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Particle packing (PP) is defined as volume of packed aggregate particles in a unit volume [84].

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The study is targeted at determining suitable LWSCC mix design method. The method 336 recommends that PP test has to be carried out first. It is a prerequisite to pre-soak all the 337 aggregates in water for 24 hours and air dry to saturated surface dry condition (SSD). Fixed 338 amounts of fine and coarse aggregates are prepared and put into a container of known volume.

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The aggregates are mixed thoroughly so that they are well-blended. Known amount of water is

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The procedures to determinate the LWSCC mix design is presented in this section.

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Step 1: Determination of particle packing factor 349 The first step in proportioning LWSCC mix, which incorporates OPS as full coarse aggregates 350 replacement, is to determine the particle packing factor between the blended OPS as coarse 351 aggregates and river sand as fine aggregates, by using Eq. (6). The minimum paste volume necessary for lubricating aggregates so as to produce the required characteristics of flowing indicates that less paste is required as aggregates are tightly packed. The PP value is determined 356 based on the procedure described in previous section.
where PP is particle packing value and e is void ratio

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Step 2: Calculation of aggregates content

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The aggregate content of proposed LWSCC mix design can be determined from Eq. (7). The

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subscript of f/c agg in each term represents respective type of aggregate used and the ratio of 361 each aggregate to total aggregates in a unit volume of LWSCC has been considered. The main 362 concern of aggregates in this research is fine aggregate which is sand, and OPS as coarse 363 aggregate. The optimum ratio of each aggregate to total aggregates was determined from the 364 blended aggregates bulk density curve.

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W f/c agg = PP × AR f/c agg × SG f/c agg × 1000 (7) where W f/c agg is aggregate content (kg/m 3 ), AR f/c agg is ratio of aggregate to total aggregates 366 in volume and SG f/c agg is specific gravity of aggregates.

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Step 3: Calculation of cement content 368 Cement content must be chosen properly to ensure the concrete fresh properties as a SCC, 369 including filling ability, passing ability and segregation resistance, fulfil the specified 370 requirements while not to compromise the compressive strength. Good adjustment of cement 371 content will ensure sufficient amount of cement paste is available to lubricate aggregates so as 372 to attain self-compacting ability. The volume of cement can be determined using Eq. (8).
where V cement is volume of cement, W cement is cement content (kg/m 3 ) and SG cement is 374 specific gravity of cement.

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Step 4: Calculation of paste volume 376 The voids that exist in particle packing of aggregates represent the amount of paste required to 377 be filled to ensure good concrete self-compacting ability. This can be calculated by using Eq. 378 (9).
where V paste volume of paste 380 Step 5: Determination of water content 381 Water content can be calculated by water to binder (W/B) ratio using Eq. (10) and Eq. (11).

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The actual W/B needs to be validated and adjusted by trial mix.

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V water /V cement = W/B (10) where W/B is water to binder ratio, V water is volume of water content, W water is water content 384 (kg/m 3 ) and SG water is specific gravity of water.

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Step 6: Determination of superplasticizer dosage 386 SP is an essential constituent to allow SCC to achieve followability and passing ability.   to improve the packing of LWSCC which in turn reduced the water demand although fly ash   and sieve stability tests. Table 7 shows the fresh property test results. Further evaluation and elaboration of these results will be done in the following section.

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Percentage of concrete mix passing through 5mm sieve is expressed as segregation ratio. Figure   528 11 depicts the comparison of segregation of LWSCC at different levels of fly ash replacement.    the control mix has achieved weight some 17% lighter compared to normal granite based 566 concrete. It is noted that the density of concrete reduces with increasing replacement level of fly ash in the binder content of concrete. This reduction of density is due to the lower specific 568 gravity of fly ash compared to cement. Similar trend of results was reported by Shafigh et al.

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[50] with fly ash substitution up to 70% for normally vibrated OPS based concrete. Reduced 570 density of concrete can lead to better economic design of structure as dead load of structure is 571 decreased significantly.        Table 11. These equations are used to predict the splitting tensile 641 strength and plotted in Figure 19 for comparison purpose.     can be noticed in Figure 22 that smooth spherical fly ash particles are still present, which shows 678 that fly ash is still in the early stage of hydration as its initial shape is spherical. As such, the 679 pozzolanic reactions of fly ash and cement are not complete in the initial phase of hydration 680

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[95]. As concrete ages, decomposition of the spherical shape of fly ash gradually takes. Figure   681 23 indicates that the round-shaped fly ash particles are not as easily noticeable as the material 682 is at the age of 90 days. These observations prove that the rate of hydration in concrete is 683 reduced by fly ash. It is also noted that the aggregate surface is full of binder particles. The   695 Concrete water absorption values of all four mix designs are presented in Table 12 and 696 illustrated in Figure 24Error! Reference source not found.. The water absorption values for 697 all mixes were 6.1-7.33% at 28 day and 4.47-5.07% at 90 day. At 28-day age, control LWSCC 698 mix had the lowest water absorption value among the four mixes. It is noticed that increasing 699 the substitution of fly ash in OPS based LWSCC increases water absorption at earlier age. This 700 is because increasing of class F fly ash content in concrete reduces the hydration process at 701 earlier age. At earlier age, the hydration process in high fly ash content concrete is not complete 702 and capillary pores still exist which are permeable, resulting in higher water absorption [96].

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Several researchers [50,52] have demonstrated that the water absorption of normally vibrated 704 OPS increases with increasing of fly ash content. The study of Shafigh et al. [52] shows that 705 the water absorption of normally vibrated OPS concrete increases from 5.5% to 6.6%, 7% and 706 9.8% when fly ash content is increased from 0% to 10%, 30% and 50% respectively. 707 At 90-day age, concrete of all the four mixes shows reduction in water absorption. It is observed 708 that the water absorption at 90 day reduced by 17%, 27%, 34% and 39% for M0, M30, M40 709 and M50 respectively when compared to 28 day. At 90-day age, for concrete incorporated with 710 fly ash, the voids between particles of materials were filled with fly ash at higher percentage 711 and thus the porosity of concrete was reduced. The texture and size of the fly ash particles are 712 able to minimize the voids in between particles [97]. The results show that water absorption 713 of LWSCC decreases with age especially those with higher fly ash content. This is because the 714 interconnectivity of the pores in concrete structure is reduced by fly ash as it uses Ca(OH)2 715 from the cement and induces secondary calcium silicate to hydrate at later age [98]. However, 716 the total porosity of concrete is increased with the incorporation of fly ash. Nevertheless, the 717 ratio pore refinement to "pore size" is reduced [99].
Generally, all the concrete mixes exhibited water absorption of less than 8% at all ages. Neville

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[18] stated good concrete must possess the water absorption value of less than 10%, the result 720 of which can be determined from immersed water absorption test.