Structural Performance of Shear Loaded Precast EPS-Foam Concrete Half-Shaped Slabs

sustainability

Article Structural Performance of Shear Loaded Precast EPS-Foam Concrete Half-Shaped Slabs

Sanusi Saheed 1 , Farah N. A. Abd. Aziz 1 , Mugahed Amran 2,3,*, Nikolai Vatin 4 , Roman Fediuk 5, Togay Ozbakkaloglu 6, Gunasekaran Murali 7 and Mohammad Ali Mosaberpanah 8

1 Department of Civil Engineering, Faculty of Engineering, University Putra Malaysia, Serdang 43400, Selangor, Malaysia; [email protected] (S.S.); [email protected] (F.N.A.A.A.) 2 Department of Civil Engineering, College of Engineering, Prince Sattam Bin Abdulaziz University, Alkharj 11942, Saudi Arabia 3 Department of Civil Engineering, Faculty of Engineering and IT, Amran University, Quhal 9677, Amran, Yemen 4 Higher School of Industrial, Civil and Road Construction, Peter the Great St. Petersburg Polytechnic University, 195251 St. Petersburg, Russia; [email protected] 5 School of Engineering, Far Eastern Federal University, 8, Sukhanova Str., 690950 Vladivostok, Russia; [email protected] 6 Ingram School of Engineering, Texas State University, San Marcos, TX 78667, USA; [email protected] 7 School of Civil Engineering, SASTRA Deemed to be University, Thanjavur 613401, India; [email protected] 8 Civil Engineering Department, Cyprus International University, 99258 Nicosia, North Cyprus, Turkey; [email protected] * Correspondence: [email protected] or [email protected]

Received: 9 October 2020; Accepted: 12 November 2020; Published: 20 November 2020

Abstract: Precast concrete elements provide a feasible way to expedite on-site construction; however, typical precast components are massive, making their use particularly undesirable at construction sites that suffer from low load-bearing capacity or have swelling soils. This research aims to develop an optimal lightweight expanded polystyrene foam concrete (EPS-foam concrete) slab through a consideration of various parameters. The precast EPS-foam concrete half-shaped slabs were prepared with a density and compressive strength of 1980 kg/m3 and 35 MPa, respectively. Quarry dust (QD) and EPS beads were utilized as substitutions for fine and coarse aggregates with replacement-levels that varied from 5% to 22.5% and 15% to 30%, respectively. The use of EPS beads revealed sufficient early age strength; at the same time, the utilization of quarry dust in EPS-foam concrete led to a more than 30% increase in compressive strength compared to the EPS-based mixtures. Two hundred and fifty-six trial mixes were produced to examine the physical and mechanical characteristics of EPS-foam concrete. Three batches of a total of four EPS-foam concrete half-shaped slabs with spans of 3.5 and 4.5 m and thicknesses of 200 and 250 mm were prepared. Findings showed that the ultimate shear forces for the full-scale EPS-foam concrete half-shaped slabs were approximately 6–12% lower than those of the identical concrete samples with a 2410 kg/m3 average density, and 26–32% higher than the theoretical predictions. Also, it was observed that the self-weight of EPS-foam concrete was reduced by up to 20% compared to the control mixtures. Findings revealed that the prepared precast EPS-foam concrete half-shaped slabs could possibly be applied as flooring elements in today’s modern infrastructure.

Keywords: precast concrete; lightweight concrete; expanded polystyrene beads; full-scale EPS-foam concrete half-shaped slab; shear loads

Sustainability 2020, 12, 9679; doi:10.3390/su12229679 www.mdpi.com/journal/sustainability Sustainability 2020, 12, 9679 2 of 17

1. Introduction Prefabricated precast concrete slabs present numerous positive characteristics such as quality control, accurate design, the need for less-skilled labor, and fast installation and assembly, which ultimately leads to lower construction costs and a reduction in the volume of wastage at construction sites [1–3]. Several types of half-slab components such as hollow-core slabs (HoCSs), flat precast slabs (FPSs), double-tee slabs (DTSs), and multi-rib slabs (MrSs) have been industrialized, and associated investigations on their performances have been dynamically implemented. FPSs have a simple fabrication method and an easy reinforcement layout due to their thin flange design. Furthermore, they require no permanent work (e.g., installation shores) to withstand construction loads at the point of forming their topping concrete layer [4,5]. Meanwhile, HoCSs contribute to lower self-weight due to the hollows in their design geometry, and can considerably enlarge the depth of the section at specific locations where the applied load is exceptionally high [3,6–8]. However, factory-made HoCSs using an extruder machine can be quite susceptible to shear stresses at the end-boundaries of their webs; as a result, it is difficult to position shear bars on the webs [3,9,10]. In the meantime, MrSs and DTSs have different cross-sectional outlines that are quite effective at resisting positive moments as a consequence of the elimination of needless concrete segments on the bottom zone (tension side). This usually results in a thin top flange, which leads to continuation problems at the end edges of the member [11–13]. In any case, the design of half-precast concrete slabs is commonly improved by ensuring that the bottom and top flanges are varied at the ends and center of the component so that they can withstand negative and positive moments efficiently [1,11]. Moreover, the general application of precast concrete is made with either lightweight or normal concrete. Lightweight aggregates are used to form lightweight concrete (LC), which is secured from either natural or artificial sources, namely, erupting volcanoes [14] or oil palm shells (OPSs) [15,16]. Aggregates obtained from erupting volcanoes are very costly and not easy to acquire in local markets, while OPSs have high water absorption. On the other hand, artificial lightweight aggregates (e.g., expanded polystyrene (EPS) and fly ash [17–19]) can provide a feasible alternative solution. Several studies have investigated LC made with natural aggregates (vermiculite [20], scoria [14], pumice [18,21]), manufactured aggregates (e.g., expanded clay [22,23], expanded silt [17]) and industrial waste aggregates [24–27]. Additionally, quarry dust (QD), a waste of crushed rock, can be utilized as a partial substitution for river sand, and makes environmentally sustainable LC, which contributes to the enhancement of the compressive strength of concrete at an earlier age [28]. Utilization of QD as a substitution material for fine aggregates by up to 20% can result in enhancement in the ultimate load capacity of lightweight expanded polystyrene (EPS) foam-based concrete from 17 to 35 MPa, and this can be utilized for the production of structural concrete elements [29]. Despite this, precast concrete elements are usually produced using normal concrete, which results in components with a heavy weight [30]. Henceforth, the self-weight of the system becomes very important. The self-weight of slabs is responsible for 40–60% of the total deadweight of a residential house [30–33]. As such, a 10% reduction in floor slabs can result in a 5% reduction in the deadweight of the whole building [30,34,35]. Precast flooring systems without concrete toppings are popular nowadays, but they usually suffer from water leakage at the joints [16]. Furthermore, half-shaped slabs are typically chosen, as no propping is required [16]. Over the past several years, designers have been searching for eco-friendly and economical concrete products, such as foamed concrete (FC) [30,35]. Structural FC is mainly applied to lower the self-weight of buildings and deliver the most efficient structural components [36]. Light structural elements facilitate easy construction and reduce on-site work, thereby lowering the overall cost of construction [31]. Among the techniques used to lower the self-weight of precast concrete panels is the utilization of lightweight materials like EPS beads as a part of the mix design proportions. EPS beads are cheaper than other artificial aggregates and are made from a styrene monomer that is developed in oriental sweet gum plants and natural gas. EPS beads are mainly used for packaging materials and are disposed of after unpacking, which leads to a large amount of non-biodegradable Sustainability 2020, 12, 9679 3 of 17 waste. However, by employing heat treatment methods, this material can be modified to function as a lightweight aggregate. As a significant waste material in terms of ecological pollution, EPS makes up a substantial volume of solid waste in garbage dumps in several countries. Since it is none-degradable, leading considerably to the pollution of the environment, producers have become directly responsible for the collection, recycling and re-economizing this material. EPS is light in weight, has a superior thermal insulation characteristic, and has a lower cost, as a reduction in density contributes to reducing the consumption of energy during production, transport, and construction processes in comparison with traditional building materials. It is therefore endorsed within the field of sustainability. The use of sustainable developments in low-cost residential buildings has caused the construction industry to implement suitable measurements to benefit the environment, such as decreasing building energy consumption and CO2 emissions. In addition to economic and technical issues, the selection of building materials is also in the basis of the environmental aspects behind the application and use of this material. In this sense, the development of substitutive, sustainable, and ecofriendly building materials such as EPS is imperative, as it can lead to reduced risks to human well-being, contributions to economies, solutions to environmental issues, and improvements to construction industry applications towards sustainability by increasing the design and structural integrity of building materials. Therefore, this study contributes to the development of an optimal EPS-foam concrete that could be used to produce full-scale EPS-foam concrete half-shaped slabs, ultimately leading to self-weight reductions in the total self-weights of concrete structural systems of more than 20%. This study also aims to determine the ultimate shear force of the EPS-foam concrete half-shaped slabs, and compare them with identical control concrete samples made of ordinary concrete.

2. Experimental Program; A Brief Description Ordinary Portland cement (OPC) (Type 2) was used in this study, as originally presented in the first part of this research (Saheed et al. [37]). The fine and coarse aggregates used were river sand and crushed granite gravel, respectively, and are detailed in the first part of this study. To produce a workable concrete, a 1% cement volume of naphthalene-based super-plasticizer was used [37]. In this study, 16 different samples were prepared, which were then divided into four series. In the first series, the four samples were prepared with 0%, 15%, 22.5%, and 30% EPS contents without quarry dust (QD). The remaining three series samples were prepared with the same amount of EPS, while 7.5%, 15%, and 22.5% QD were used as partial replacements for sand for the second, third, and fourth series, respectively. The mixed composition of the 16 samples and casting procedures are provided in the earlier study [37]. Overall, 16 concrete batches were accordingly prepared to fabricate 48 cylindrical specimens with a 100- 200-mm size and 144 cube specimens with a 100-mm size. Both cylindrical × and cubical specimens were de-molded after 24 hours and placed in a curing container with a 27 5 C ± ◦ temperature for 15, 28, and 90 days [37]. A slump test was performed on wet concrete in accordance with BS 1881 [38] to ensure an adequate workability for structural applications. The compressive test was performed on 100-mm cube samples at 7, 28, and 90 days, in accordance with BS 1881 [39], using a universal testing machine with a 5000-kN capacity with a 2.5-kN/s loading rate. The splitting tensile test was performed on cylindrical samples with 100-mm diameters and 200-mm heights in accordance with BS 1881 [39]. An ultrasonic pulse velocity (UPV) test was performed in accordance with ASTM C 597 [40] on the cube samples at 28 days before the destructive test. As mentioned above, a detailed explanation of the testing is discussed in the earlier study [37].

3. Half-shaped Slab Configuration, Preparing, Casting Process and Production The prepared slabs had spans of either 3500 or 4500 mm, and 1000-mm widths with either a 250- and 200-mm entire thickness for the 4500- and 3500-mm span slabs, respectively (see Figure 8 [37]). The span dimensions were chosen following the PCI design code (PCI manual, 2003) [41,42]. In addition, steel bars Sustainability 2020, 12, 9679 4 of 17 with 12- and 10-mm diameters and 20-mm concrete covers were used as the ribs, while 200 200 mesh × bars with 6-mm diameters were employed as the topping bars. The details of reinforcement, span, Sustainabilityconcrete type, 2020, notations10, x FOR PEER and REVIEW thickness are all tabulated in the earlier study [37]. The notations4 of are 19 given by the concrete type followed by the thickness of the slab. For instance, CC250 stands for an The notations are given by the concrete type followed by the thickness of the slab. For instance, CC250 ordinary slab with a 250-mm thickness. stands for an ordinary slab with a 250-mm thickness. 3.1. Preparing, and Casting Process and Production 3.1. Preparing, and Casting Process and Production Formwork plywood was employed to form the half-shaped slab specimens (see Figure 9 [37]). It wasFormwork initially brushed plywood with was oil employed to prevent to water form absorptionthe half-shaped during slab casting. specimens After (see that, Figure a plastic 9 [37]). layer Itwas was placed initially to brushed ensure the with reusability oil to prevent of the water formworks, absorption and during to inhibit casting. water After loss that, while a plastic casting layer the wasconcrete. placed Prior to ensure to placing the thereusability steel bars of in the the formwo formwork,rks, strainand to gauges inhibit 5 water mm in loss size while were fixedcasting on the the concrete.10- and 12-mm Prior to diameter placing reinforcementthe steel bars in bars. the Similarly,formwork, strain strain gauges gauges of 5 2 mm mm in in size length were were fixed mounted on the 10-on and the 6-mm12-mm reinforcement diameter reinforcement bars to enable bars. theSimilarly, observation strain ofgauges strains of 2 as mm the in half-shaped length were slabs mounted were onloaded. the 6-mm To fix reinforcement the strain gauges, bars theto enable reinforcement the obse bars’rvation outer of surfacesstrains as were the half-shaped refined and laterslabs wiped were loaded.with alcohol To fix to the ensure strain they gauges, were the smooth. reinforcement After that, bars’ the outer strain surfaces gauges werewere gluedrefined using and epoxylater wiped resin, withand siliconalcohol glue to ensure was utilized they were to provide smooth. protection After that during, the strain the castinggauges process.were glued using epoxy resin, and silicon glue was utilized to provide protection during the casting process. 3.2. Arrangement, Instrumenting and Setup of Shear Test 3.2. Arrangement, Instrumenting and Setup of Shear Test In total, four electrical strain gauges (ESGs) with 67-mm lengths were utilized in this test. TheseIn strain total, gaugesfour electrical were labeled strain SG1gauges to SG4(ESGs) (see wi Figureth 67-mm1). One lengths ESG waswere utilized utilized to in record this test. the strainThese strainat the gauges top of the were slab, labeled while SG1 the remainingto SG4 (see three Figure ESGs 1). One formed ESG a was rosette utilized shape to to record measure the shearstrainstrains at the topalong of the the slab, slabs’ while depths, the remaining (as illustrated three in ESGs Figure form 8 [37ed]). a rosette Furthermore, shape to strain measure gauges shear on strains the concrete along theinterfaces slabs’ anddepths, steel (as bars illustrated were also usedin Figure to monitor 8 [37]). the Furthermore, strain curves atstrain those gauges locations. on Furthermore,the concrete interfacesthe LVDT and located steel at bars a distance were also of 2used time to of monitor beam depth the strain from leftcurves support at those was locations. utilized toFurthermore, monitor the thedeflection LVDT located at a critical at a distance zone during of 2 sheartime of testing. beam depth Also, threefrom ESGsleft support of 67-mm wasconcrete utilized wereto monitor fixed justthe deflectionbelow the pointat a critical load in zone the shearduring test shear setup. testing. To record Also, the three readings ESGs duringof 67-mm testing, concrete the instruments were fixed just and belowtheir individual the point load cables in were the shear connected test setup. to a data To re loggercord throughoutthe readings the during test. testing, the instruments and their individual cables were connected to a data logger throughout the test.

FigureFigure 1. 1. LocationLocation of of strain strain gauges. gauges.

AfterAfter 28 28 days days of of curing, curing, the the prepared prepared slabs slabs were were positioned positioned on on the the testing testing frame frame and and their their sides sides werewere glazed white to allow for easy monitoring of the cracks during testing. The The precast EPS-foam concreteconcrete half-shaped slabsslabs werewere installed installed with with a a simple simple support support 100 100 mm mm from from their their free-end free-end edges edges and andloaded loaded at 2 timesat 2 times the beam the beam depth depth from thefrom support, the supp asort, shown as shown in Figure in2 Figurea,b, where 2a, b, d iswhere the thickness d is the thicknessof the slab. of Tothe apply slab. theTo apply load, athe spreader load, a beamspreader was beam used, was as shown used, inas Figureshown2 inb, andFigure the 2b, beam and was the beamlinked was to a linked load cell to a with load a cell 1500-kN with capacity.a 1500-kN A ca hydraulicpacity. A jack hydraulic was employed jack was toemployed impose the to appliedimpose theload applied on the load slabs on at the a rate slabs of at 0.1 a kNrate/s. of Prior0.1 kN/s to testing,. Prior to a testing, trial loading a trialwas loading performed was performed two times two to timesascertain to ascertain an intact an slab intact setup slab and setup stable and readings stable fromreadings the instruments.from the instruments. Consequently, Consequently, the specimens the specimenswere loaded were at 2-kN loaded increments, at 2-kN increments, and at each and increment at each increment the load was the kept load constant was kept for constant 15–35 sfor before 15– 35the seconds LVDT and before EGS the readings LVDT were and recorded.EGS readings At the were same recorded. time, the At cracks the thatsame appeared time, the were cracks marked that appeared were marked and their sizes were determined by means of a handheld microscope with X40 amplification and a lowest count of 0.02 mm. The specimens were then loaded up until failure.

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sizes were determined by means of a handheld microscope with X40 amplification and a lowest count and their sizesof 0.02 were mm. determinedThe specimens were by means then loaded of aup handheld until failure. microscope with X40 ampliﬁcationCommented and a [M1]: lowest count of 0.02 mm. The specimens were then loaded up until failure.

Figure 2. Typical setup of shear test. Figure 2. Typical setup of shear test (a) schematic of testing device and (b) experimental test setup. 4. Results and Discussions 4. Results and Discussions 4.1. Properties of EPS-foam Concrete 4.1. Properties ofAs EPS-foam presented Concretein the first part of this research (Saheed et al. [37]), replacing large aggregates with expanded polystyrene beads (30%) reduced the workability of concrete due to its hydrophobic As presentedproperties in and the an firstincrease part in the of surface this researchof the expanded (Saheed polystyrene et al. beads [37]), [37] replacing. Additionally large, 15% aggregates with expandedand polystyrene30% substitution beadss of aggregate (30%) reduced reduced the specific the workability gravity of EPS of-foam concrete concrete due by 5.8% to its and hydrophobic properties and18%, an respectively, increase compared in the surface with that of of thethe ordinary expanded cement polystyrene concrete [37].beads A higher [37 compressive]. Additionally, 15% strength was observed at seven days in the case of EPS-foam concrete compared to traditional and 30% substitutions of aggregate reduced the specific gravity of EPS-foam concrete by 5.8% and concrete. This may have been be because of the thermal resistance of EPS-foam concrete maintaining 18%, respectively, compared with that of the ordinary cement concrete [37]. A higher compressive strength was observed at seven days in the case of EPS-foam concrete compared to traditional concrete. This may have been be because of the thermal resistance of EPS-foam concrete maintaining the heat of hydration and subsequently upsurging the activity of the clinker minerals [37]. There was not much strength gain in EPS-foam concrete compared to traditional concrete, which experienced a great improvement in compressive strength as a result of the use of QD as a partial substitute for fine aggregates. Replacing sand with QD by 7.5% and 22.5% increased the strength of the reference concrete by almost 13% and 16%, respectively, at an age of 28 days. This may be attributable to the behavior of small particles of QD that fill the pores. When substituting with 22.5% QD, the strength dropped by about 10% compared to the 15% substitution, at which EPS-foam concrete reached its maximum compressive strength [37]. The same trend was observed for 90-day-old samples. The maximum compressive strength was observed in the mixtures of EPS-foam concrete with 30% EPS and 15% QD, resulting in a 35.7-MPa compressive strength at a dry density of 1980 kg/m3. The splitting tensile Sustainability 2020, 12, 9679 6 of 17 strength of EPS-foam concrete experienced a reduction as the EPS bead replacement increased. Tensile strength increased with a 15% QD substitution, then decreased when the substitution was increased to 22.5% [37]. The compressive strength obtained from the UPV exhibited a decreasing trend with increases in the EPS content. Different sample series showed different treatments as the compressive stress ranges varied from 55 to 35.1 MPa, 53.7 to 33.9 MPa, 58.6 to 35.1 MPa, and 53.2 to 34.5 MPa for the series-1, -2, -3, and -4 samples. Consequently, the maximum compressive strength was observed in the sample containing 0% EPS and 15% QD.

4.2. Precast EPS-foam Concrete Half-Shaped Slabs The shear test results were reported in terms of load-deﬂection behavior, strain on concrete surfaces, and crack patterns for two types of concrete (i.e., control concrete and EPS-foam concrete). For each concrete type, two slabs with thicknesses of 200 and 250 mm were prepared. Each half-shaped slab was tested twice, once on each end, giving two repetitive results. A total of four half-shaped slabs were tested, having two diﬀerent spans (3.5 and 4.5 m) for each of the 200- and 250-mm thicknesses, respectively. The half-shaped slab specimens were notated as CC200A, CC200B, EPS200A, EPS200B, CC250A, CC250B, EPS250A, and EPS250B.

4.2.1. Load-Deflection Profiles Figure3 illustrates the load-deflection relationship for the slabs with a 200-mm thickness. The load-deflection profiles for the tested samples followed the uncracked response up to the cracking load, after which the load-deflection profile followed the cracked response due to a reduction in stiffness caused by cracking, as seen in Figure3. Eventually, as yielding of the reinforcements took place due to an increase in load, the load-deflection profiles reached a plateau, indicating a rapid increase in deflection with little or no increase in applied load, followed by a drop after failure. The uncracked load-deflection responses for the CC and EPS specimens were almost identical; interestingly, however, the cracked response for the EPS specimen was different from that of the CC sample, where the EPS-foam concrete specimen had less stiffness compared to the latter. It was also observed that the deformation behavior of the EPS slabs had a slightly lower range than the ones for CC slabs due to the CC slabs being more ductile than the EPS slabs. In particular, the pattern of the load deflection profile after the first cracks appeared resembled the research findings reported by Ibrahim et al. [43]. In addition, the observed failure loads differed slightly, as the destruction load of sample CC200A was 6% higher than that of sample EPS200A. The maximum deflections of all specimens were within the range of 22.2 to 28 mm after the first crack formed. Furthermore, CC200 failed in shear-compression only, while EPS200 failed through de-bonding and shear-compression, as given in Table1. The theoretical and experimental shear capacities of CC200 and EPS200 were compared together (in compliance with BS8110 (1985)), and are summarized in Table1. It is apparent that the experimental capacity for the slabs was greater than the corresponding theoretical calculations according to BS 8110. Moreover, the capacity ratio for EPS200 was 7–14% lower than that of CC200, indicating that the ordinary concrete slabs achieved a greater shear capacity. Finally, it can be seen from the Figure3 that the toughness (the area under the load-deformation curve) of EPS200 was less than CC200, indicating a lower load bearing capacity. Sustainability 2020, 12, 9679 7 of 17 Sustainability 2020, 10, x FOR PEER REVIEW 7 of 19

80 70 60 50 40

Load kN 30

20 CC200A CC200B 10 EPS200A 0 0 5 10 15 20 25 30 Deflection mm

Figure 3. Load-midspandeflectionrelationshipfortestspecimenswitha200-mmthickness. CC200A=control Figure 3. Load-midspan deflection relationship for test specimens with a 200-mm thickness. CC200A concrete specimens; EPS200A = expanded polystyrene (EPS)-foam concrete specimens. = control concrete specimens; EPS200A = expanded polystyrene (EPS)-foam concrete specimens. Table 1. Experimental shear force and mode of failure. The maximum deflections of all specimens were within the range of 22.2 to 28 mm after the first crack formed. Furthermore,Specimen CC200 Fu failed, kN in shear-compression Mode of Failure only, while EPS200 failed through de- bonding and shear-compression,CC200B 71.9as given in Table 1. The theoretical and experimental shear CC200A 65.8 capacities of CC200 and EPS200 were compared togetherShear-compression (in compliance with BS8110 (1985)), and are summarized in TableCC250B 1. It is apparent 81.1 that the experimental capacity for the slabs was greater than CC250A 93.7 the corresponding theoreticalEPS250A calculations 82.2 accordin Shear-compressiong to BS 8110. Moreover, the capacity ratio for EPS200 was 7–14% lowerEPS200A than that 61.8 of CC200, Shear-compression indicating that andthe de-bondingordinary concrete slabs achieved a greater shear capacity. Finally, it can be seen from the Figure 3 that the toughness (the area under the load-deformation curve) of EPS200 was less than CC200, indicating a lower load bearing capacity. The load-deflection relationships for the 250-mm slabs are shown in Figure4. Again, a similar behavior to the 200-mm slabs was observed, where the deflection increased gradually along the Table 1. Experimental shear force and mode of failure. uncracked response until the first crack formed at approximately 47 kN for specimen CC250 and 26.7 kN for specimenSpecimen EPS250. F Thisu, kN represented a first-crack Mode strength of Failure reduction of 55% for EPS250 when comparedCC200B with CC250. Subsequently,71.9 the load-deflection profiles followed the cracked response until reinforcementCC200A yielding could65.8 take place, which was followed by failure of the specimens and Shear-compression immediate unloading.CC250B From the81.1 deflection profiles, it is clear that the CC250 specimen was a bit stiffer than its EPSCC250A counterpart, and93.7 that the pattern of the load-deflection curves was similar to that of Sarbini et al.EPS250A [44]. The maximum82.2 deflections of all specimens Shear-compression were within the range of 14.8 to 20.6 mm, whichEPS200A was less than 18 61.8L/d. In addition, Shear-compressionboth CC250 and EPS250 and de-bonding failed in shear-compression (Table2), and the ultimate shear-load of CC250A was 12% greater than that of specimen EPS250A. The theoreticalThe load-deflection and experimental relationships shear capacities for the 250-mm of the CC250 slabs and are EPS250shown samplesin Figure are 4. listedAgain, in a Table similar2. Thebehavior experimental to the shear200-mm capacity slabs forwas specimen observed, CC250 where was the 51%deflection higher increased than the theoretical gradually capacity,along the whileuncracked the experimental response until shear the strengthfirst crack of formed specimen at approximately EPS250 was 32.6%47 kN higherfor specimen than the CC250 calculated and 26.7 theoreticalkN for specimen shear capacity. EPS250. In This addition, represented the experimental a first-crack shear strength strength reduction of specimen of 55% EPS250-A for EPS250 was 12%when lowercompared than the with experimental CC250. Subsequently, shear capacity the load-deflect of specimenion CC250A, profiles but followed 25% higher the cracked when comparedresponse until to thereinforcement theoretical shear yielding load. Therefore,could take the place, shear capacitywhich was of EPS followed precast by slabs failure was adequateof the specimens when related and toimmediate the theoretical unloading. shear capacity From the of normaldeflection concrete. profiles, This it is shows clear that that the the CC250 theoretical specimen shear calculationwas a bit stiffer of normalthan its concrete EPS counterpart, is practical and for EPS-foamthat the pattern concrete. of Itthe can load-deflection also be observed curves the was load similar bearing to of that EPS of wasSarbini less thanet al. CC250A, [44]. The as maximum the under deflections curve area of of all load-deformation specimens were ofwithin EPS250 the was range clearly of 14.8 smaller to 20.6 thanmm, CC250A. which was less than 18 L/d. In addition, both CC250 and EPS250 failed in shear-compression (Table 2), and the ultimate shear-load of CC250A was 12% greater than that of specimen EPS250A. The theoretical and experimental shear capacities of the CC250 and EPS250 samples are listed in Table

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2. The experimental shear capacity for specimen CC250 was 51% higher than the theoretical capacity, while the experimental shear strength of specimen EPS250 was 32.6% higher than the calculated theoretical shear capacity. In addition, the experimental shear strength of specimen EPS250-A was 12% lower than the experimental shear capacity of specimen CC250A, but 25% higher when compared to the theoretical shear load. Therefore, the shear capacity of EPS precast slabs was adequate when related to the theoretical shear capacity of normal concrete. This shows that the theoretical shear calculation of normal concrete is practical for EPS-foam concrete. It can also be observed the load bearing of EPS was less than CC250A, as the under curve area of load-deformation Sustainability 12 of EPS2502020 was, clearly, 9679 smaller than CC250A. 8 of 17

100 90 80 70 60 50 Load kN 40 30 20 CC250A CC250B 10 EPS250A 0 0 5 10 15 20 25 30 Deflection mm

Figure 4. Load-midspan deflection relationship for the test specimen with a 250-mm thickness. Figure 4. Load-midspan deflection relationship for the test specimen with a 250-mm thickness. Table 2. Comparison of experimental and theoretical shear forces. Table 2 Comparison of experimental and theoretical shear forces. Ultimate Shear Force, V (kN) Capacity Ratios = Name of Sample (a/d) Ratio Experimental valve UltimateExperimental Shear Force, Theoretical V Name of (a/d) CapacityTheoretical Ratios valve = (kN) 𝐄𝐱𝐩𝐞𝐫𝐢𝐦𝐞𝐧𝐭𝐚𝐥 𝐯𝐚𝐥𝐯𝐞 SampleCC200A Ratio 2.0 65.8 49 1.3 CC200B 2.0Experimental 71.9 Theoretical 49 𝐓𝐡𝐞𝐨𝐫𝐞𝐭𝐢𝐜𝐚𝐥 1.4 𝐯𝐚𝐥𝐯𝐞 CC200ACC250A 2.0 2.0 65.8 93.7 49 62 1.5 1.3 CC250B 2.0 81.1 62 1.3 CC200B 2.0 71.9 49 1.4 EPS200A 2.0 61.8 49 1.2 CC250AEPS250A 2.0 2.0 93.7 82.2 62 62 1.3 1.5 CC250B 2.0 81.1 62 1.3 EPS200A 2.0 61.8 49 1.2 4.2.2. Concrete Strain Curves EPS250A 2.0 82.2 62 1.3 The load-strain curves for the concrete topping of the tested slabs are shown in Figure5. It is clear that4.2.2. the Concrete strain increased Strain Curves gradually as the applied load increased, and negative strains were recorded that indicated compression of the topping concrete. Furthermore, no crushing failure was observed at The load-strain curves for the concrete topping of the tested slabs are shown in Figure 5. It is the ultimate shear load, as the strains were between 250 to 550 µ, which is much smaller than the clear that the strain increased gradually as the applied load increased, and negative strains were maximum crushing strain of 3000 µ. It can be seen that EPS200A detected a large strain just before the recorded that indicated compression of the topping concrete. Furthermore, no crushing failure was failure load, possibly due to that the location of the concrete strain gauge, which was absorbing large observed at the ultimate shear load, as the strains were between 250 to 550 µϵ, which is much smaller amounts of energy prior to the fracture and thus affording an opportunity to take remedial action before than the maximum crushing strain of 3000 µϵ. It can be seen that EPS200A detected a large strain just an actual fracture could occur. The completely different natures of the control sample and the EPS-foam before the failure load, possibly due to that the location of the concrete strain gauge, which was concrete can be seen by comparing the load-strain curves. Samples EPS200A and EPS250A were capable absorbing large amounts of energy prior to the fracture and thus affording an opportunity to take of withstanding heavy loads (75–95 kN), but they experienced brittle behavior, showing ultimate remedial action before an actual fracture could occur. The completely different natures of the control strains of 250–300 µ. Specimens CC250A and CC250B, on the other hand, were able to withstand much higher strains without failure (up to 500 µ), but at the same time had a minimum breaking load is 60 kN. The results obtained can be explained by the different microstructures of these two specimens; namely, traditional concrete is denser and stronger, while expanded polystyrene concrete is less dense and more elastic. This latter microstructure is due to a lower interfacial bond-strength resulting from the hydrophobic nature of EPS aggregate, as well as the compressibility of EPS aggregate, which increases the crashing rate of EPS-foam concrete and subsequently increases the topping concrete strain of EPS-foam concrete. Sustainability 2020, 10, x FOR PEER REVIEW 9 of 19

sample and the EPS-foam concrete can be seen by comparing the load-strain curves. Samples EPS200A and EPS250A were capable of withstanding heavy loads (75–95 kN), but they experienced brittle behavior, showing ultimate strains of 250–300 µɛ. Specimens CC250A and CC250B, on the other hand, were able to withstand much higher strains without failure (up to 500 µɛ), but at the same time had a minimum breaking load is 60 kN. The results obtained can be explained by the different microstructures of these two specimens; namely, traditional concrete is denser and stronger, while expanded polystyrene concrete is less dense and more elastic. This latter microstructure is due to a lower interfacial bond-strength resulting from the hydrophobic nature of EPS aggregate, as well as Sustainabilitythe compressibility2020, 12, 9679 of EPS aggregate, which increases the crashing rate of EPS-foam concrete9 ofand 17 subsequently increases the topping concrete strain of EPS-foam concrete. 100 90 80 70 60 50

40 Load kN 30 20 10 0 -600 -500 -400 -300 -200 -100 0 100 Strain (µϵ) FigureFigure 5. 5.Topping Topping concrete concrete strain strain results. results.

RosetteRosette strain strain gauges gauges were were glued glued on on the the critical critical shear shear position position ofof thethe slabsslabs halfwayhalfway betweenbetween the pointpoint of of load load application application and and the the support. support. Each Each rosette rosette gauge gauge measured measured strain strain readings readings at at 45 45 degrees degrees in bothin both horizontal horizontal and verticaland vertical directions, directions, and theand results the results are shown are shown in Figures in Figures6–8 for 6–8 the for 200-mm the 200-mm slabs andslabs Figures and 9Figures–11 for 9–11 the 250-mm for the 250-mm slabs. High slabs. strain High values strain werevalues expected were expected to be recorded to be recorded by the rosette by the strainrosette gauges, strain followed gauges, by followed breaking by of thebreaking gauges of as the shear gauges cracks as intercepted shear cracks them. intercepted Considering them. the 200-mmConsidering slab specimens, the 200-mm strain slab observations specimens, strain of the ob entireservations tested of samples the entire showed tested lower samples strain showed values (belowlower 300 strainµ) values as the ﬁrst(below cracks 300 formed.µϵ) as the However, first cracks as the formed. loads passedHowever, 40 kN,as the higher loads strain passed values 40 kN, up tohigher 2500 µ strainwere values observed up forto 2500 sample µϵ EPS200Awere observed (Figure for8). sample Generally, EPS200A both EPS200 (Figure and 8). CC200Generally, showed both Sustainability 2020, 10, x FOR PEER REVIEW 10 of 19 similaritiesEPS200 and in shearCC200 strain showed distributions, similarities and in highshear strain strain values distributions, were recorded and high prior strain to failure. values were recorded prior to failure. Samples CC200A (Figure70 9) and CC200B (Figure 10) showed the highest susceptibilities to vertical deformations, both in terms of maximum load and maximum stress, amounting to 65 kN and 800-1100 µɛ, respectively.60 On the other hand, the EPS200A (Figure 8) and EPS250A (Figure 11) samples showed the highest susceptibilities to 45-degree deformations. In this case, the maximum ɛ Horizontal loads were 60–80 kN at strains50 of 1200–2100 µ . Samples CC250A (Figure 9) and CC250B (Figure 11) showed uniform behaviors only for loads at 45 degrees, while instability45 of behavior was noted for other loads up to the appearance of negative strains. Interesting results were observable for the 40 vertical EPS200A sample (Figure 8), where no horizontal or vertical strains were recorded with an increase in load from 0 to 43 kN, then horizontal strains increased sharply to 400 kN while the vertical strains 30

did not change at all.Load kN

0 -200 0 200 400 600 800 1000 1200 Strain (µϵ)

Figure 6. Load versus rosette strain on CC200A. Figure 6. Load versus rosette strain on CC200A.

50 Horizontal 45 40 vertical Load kN 30

0 -200 0 200 400 600 800 1000 Strain (µϵ)

Figure 7. Load versus rosette strain on CC200B.

Sustainability 2020, 10, x FOR PEER REVIEW 10 of 19

Horizontal 50 45 40 vertical

30 Load kN

0 -200 0 200 400 600 800 1000 1200 Strain (µϵ)

Sustainability 2020, 12, 9679 Figure 6. Load versus rosette strain on CC200A. 10 of 17

50 Horizontal 45 40 vertical Load kN 30

0 -200 0 200 400 600 800 1000 Strain (µϵ) Sustainability 2020, 10, x FOR PEER REVIEW 11 of 19 Figure 7. Load versus rosette strain on CC200B. Figure 7. Load versus rosette strain on CC200B. 70

50 Horizontal 45 40 vertical 30 Load kN

0 -400 0 400 800 1200 1600 2000 2400 Strain (µϵ)

Figure 8. Load versus rosette strain on EPS200A. Figure 8. Load versus rosette strain on EPS200A. Samples CC200A (Figure9) and CC200B (Figure 10) showed the highest susceptibilities to verticalFigures deformations, 9–11 show the both load-strain in terms of maximumcurves for load the andCC250 maximum and EPS250 stress, amountingsamples. In to 65general, kN and stain observation800–1100 ofµ the, respectively. tested samples On the othershowed hand, lower the EPS200A strain values (Figure 8(below) and EPS250A 100 µϵ) (Figure before 11 the) samples first crack formed.showed As the the highestload passed susceptibilities 45 kN, hi togher 45-degree strain deformations. values of up Into this 1200 case, µϵ thecould maximum be observed, loads were and, as µ before,60–80 EPS250 kN at and strains CC250 of 1200–2100 slabs showed. Samples similarity CC250A in terms (Figure of9 shear) and CC250Bstrain di (Figurestributions, 11) showed with high uniform behaviors only for loads at 45 degrees, while instability of behavior was noted for other loads strain values recorded before failure. In addition, based on visual observations during testing, EPS- foam concrete samples were more compressible and able to withstand stress after failure due to the EPS aggregate, which caused a strain with increased absorption (and no destruction) compared to conventional concrete samples. 80

60 Horizontal 50 45 40 vertical

Load kN 30

0 -200 0 200 400 600 800 1000 1200 1400 Strain (µϵ) Figure 9. Load versus rosette strain on CC250A.

Sustainability 2020, 10, x FOR PEER REVIEW 11 of 19

50 Horizontal 45 40 vertical 30 Load kN

0 Sustainability 2020, 12, 9679 11 of 17 -400 0 400 800 1200 1600 2000 2400 Strain (µϵ) up to the appearance of negative strains. Interesting results were observable for the EPS200A sample (Figure8), where no horizontal or vertical strains were recorded with an increase in load from 0 to 43 kN, then horizontal strainsFigure increased 8. Load sharplyversus rosette to 400 strain kN while on EPS200A. the vertical strains did not change at all. FiguresFigures 9–119– 11show show the the load-strain load-strain curves curves for for the the CC250 CC250 and and EPS250 EPS250 samples. In In general, general, stain observationstain observation of the tested of the samples tested samples showed showed lower lowerstrain strain values values (below (below 100 100µϵ)µ before) before the the first ﬁrst crack formed.crack As formed. the load As passed the load 45 passed kN, hi 45gher kN, strain higher values strain valuesof up ofto up1200 to µ 1200ϵ couldµ could be observed, be observed, and, as before,and, EPS250 as before, and EPS250 CC250 and slabs CC250 showed slabs similarity showed similarity in terms inof termsshear ofstrain shear di strainstributions, distributions, with high strainwith values high strainrecorded values before recorded failure. before In failure. addition In addition,, based on based visual on visual observat observationsions during during testing, testing, EPS- foamEPS-foam concrete concrete samples samples were more were morecompressible compressible and andable able to withstand to withstand stress stress after after failure failure duedue to to the EPS theaggregate, EPS aggregate, which which caused caused a strain a strain with with increa increasedsed absorption absorption (and(and no no destruction) destruction) compared compared to to conventional concrete samples. conventional concrete samples. 80

60 Horizontal 50 45 40 vertical

Load kN 30

0 -200 0 200 400 600 800 1000 1200 1400 Strain (µϵ) Sustainability 2020, 10, x FOR PEER REVIEW 12 of 19 FigureFigure 9. 9. LoadLoad versus versus rosette strainstrain on on CC250A. CC250A. 90 80 Horizontal 45 70 vertical 60 50

40 Load kN 30 20 10 0 -500 -300 -100 100 300 500 700 900 1100 Strain (µϵ)

FigureFigure 10. Load 10. Load versus versus rosette rosette strain strain on on CC250B. CC250B.

100 90 80 70 Horizontal 60 45 50 vertical

Load kN 40 30 20 10 0 -200 0 200 400 600 800 Strain (µϵ)

Figure 11. Load versus rosette strain on EPS250A.

4.2.3. Steel Bar Strain Curves Figures 12 and 13 show the moment-strain distributions of the main bars for the 200- and 250- mm precast half-shaped slabs; respectively. Initially, the moment-strain curves followed an elastic behavior until the opening of the first crack; subsequently, the steel strain was augmented consistently until the steel yielded at about 1172 and 1071 µε for the CC200 and EPS200 specimens, and 366 and 407 µε for the CC250 and EPS250 specimens, respectively. After yielding of the bars, the load-strain curve followed the strain-hardening response, and failure ultimately took place at 2025 and 2408 µε for the CC200 and EPS200 specimens, and 1177 and 1310 µε for the CC250 and EPS250 specimens, respectively. All EPS-foam concrete slabs showed a slower rise in strain in comparison with the half-shaped concrete reference slabs due to the former’s inherent higher ductility and ability to engross extra energy. It could also be observed that EPS-foam concrete was able to attain its full strain capacity under the shear load. Moreover, the topping steel strain was augmented elastically

Sustainability 2020, 10, x FOR PEER REVIEW 12 of 19

90 80 Horizontal 45 70 vertical 60 50 40 Load kN 30 20 10 0 -500 -300 -100 100 300 500 700 900 1100 Strain (µϵ)

Sustainability 2020, 12, 9679 12 of 17 Figure 10. Load versus rosette strain on CC250B.

100 90 80 70 Horizontal 60 45 50 vertical

Load kN 40 30 20 10 0 -200 0 200 400 600 800 Strain (µϵ)

Figure 11. Load versus rosette strain on EPS250A. Figure 11. Load versus rosette strain on EPS250A. 4.2.3. Steel Bar Strain Curves 4.2.3. Steel Bar Strain Curves Figures 12 and 13 show the moment-strain distributions of the main bars for the 200- and 250-mm precastFigures half-shaped 12 and slabs;13 show respectively. the moment-strain Initially, the distributions moment-strain of the curves main followed bars for anthe elastic 200- and behavior 250- mmuntil precast the opening half-shaped of the ﬁrstslabs; crack; respectively. subsequently, Initiall they, the steel moment-strain strain was augmented curves followed consistently an elastic until behaviorthe steel yieldeduntil the at aboutopening 1172 of and the 1071 firstµ forcrack; the CC200subsequently, and EPS200 the specimens,steel strain and was 366 augmented and 407 µ consistentlyfor the CC250 until and the EPS250 steel yi specimens,elded at about respectively. 1172 and After 1071 yieldingµε for the of CC200 the bars, and the EPS200 load-strain specimens, curve andfollowed 366 and the 407 strain-hardening µε for the CC250 response, and EPS250 and failure specimens, ultimately respec tooktively. place After at 2025yielding and of 2408 theµ bars,for the the load-strainCC200 and EPS200curve followed specimens, the and strain-hardening 1177 and 1310 µresponse,for the CC250and failure and EPS250 ultimately specimens, took place respectively. at 2025 andAll EPS-foam2408 µε for concrete the CC200 slabs and showed EPS200 a slower specimens, rise in strainand 1177 in comparison and 1310 µ withε forthe the half-shaped CC250 and concreteEPS250 specimens,reference slabs respectively. due to the All former’s EPS-fo inherentam concrete higher slabs ductility showed and abilitya slower to engrossrise in strain extra energy.in comparison It could withalso bethe observed half-shaped that concrete EPS-foam reference concrete slabs was due able to the to attain former’s its fullinherent strain higher capacity ductility under and the ability shear toload.Sustainability engross Moreover, extra 2020, the10energy., x topping FOR ItPEER could steel REVIEW also strain be was observed augmented that EPS-foam elastically concrete until reaching was able 95% to of attain the ultimate its13 full of 19 strainshear load.capacity The under topping the shear bars didload. not Moreover, yield in eitherthe topping the reference steel strain concrete was augmented or EPS-foam elastically concrete until reaching 95% of the ultimate shear load. The topping bars did not yield in either the reference half-shaped slabs. concrete or EPS-foam concrete half-shaped slabs. 80 70

Load, kN 30

20 CC200A 10 EPS200A 0 0 500 1000 1500 2000 2500 3000 Strain, (µϵ)

FigureFigure 12. 12.Steel-reinforcement Steel-reinforcement load-strain load-strain relationship relationship of of specimens specimens CC200A CC200A and and EPS200A. EPS200A.

40 Load, kN 30

20 CC250B 10 EPS250B

0 0 250 500 750 1000 1250 1500 Strain, (µϵ) Figure 13. Steel-reinforcement load-strain relationship of specimens CC250B and EPS250B.

4.3. Crack Patterns The location of crack patterns was carefully recorded and studied. The cracks on the EPS-foam concrete and reference half-shaped slab specimens showed similarities in terms of the gradual crushing of concrete, appearance of multiple crack lines during deflection, and lack of an explosion at failure. An example of the slab crack pattern observed can be seen in Figure 14, where the crack patterns are noticeable at each load increment. The observed cracks in the tested precast EPS-foam concrete half-shaped slabs are comparable to those exhibited in one-way reinforced concrete slabs [45,46]. Moreover, the failure mode of all samples was shear-compression, and two specific failure patterns were observed, including shear cracking and interface failure. For instance, sample CC200- A failed through shear cracking as the shear cracks spread from the base of the slab to the point of support at approximately 34 degrees, which is beneath the 45 degrees specified in BS8110 [47]. In

Sustainability 2020, 10, x FOR PEER REVIEW 13 of 19

until reaching 95% of the ultimate shear load. The topping bars did not yield in either the reference concrete or EPS-foam concrete half-shaped slabs. 80

Load, kN 30

20 CC200A 10 EPS200A 0 0 500 1000 1500 2000 2500 3000 Strain, (µϵ)

SustainabilityFigure2020, 12 12., 9679 Steel-reinforcement load-strain relationship of specimens CC200A and EPS200A. 13 of 17

40 Load, kN 30

20 CC250B 10 EPS250B

0 0 250 500 750 1000 1250 1500 Strain, (µϵ) FigureFigure 13. 13.Steel-reinforcement Steel-reinforcement load-strain load-strain relationship relationship of of specimens specimens CC250B CC250B and and EPS250B. EPS250B.

4.3. Crack Patterns 4.3. Crack Patterns The location of crack patterns was carefully recorded and studied. The cracks on the EPS-foam The location of crack patterns was carefully recorded and studied. The cracks on the EPS-foam concrete and reference half-shaped slab specimens showed similarities in terms of the gradual crushing concrete and reference half-shaped slab specimens showed similarities in terms of the gradual of concrete, appearance of multiple crack lines during deflection, and lack of an explosion at failure. crushing of concrete, appearance of multiple crack lines during deflection, and lack of an explosion An example of the slab crack pattern observed can be seen in Figure 14, where the crack patterns at failure. An example of the slab crack pattern observed can be seen in Figure 14, where the crack are noticeable at each load increment. The observed cracks in the tested precast EPS-foam concrete patterns are noticeable at each load increment. The observed cracks in the tested precast EPS-foam half-shapedconcrete half-shaped slabs are comparableslabs are comparable to those exhibitedto those exhibited in one-way in one-way reinforced reinforced concrete concrete slabs [45 ,slabs46]. Moreover,[45,46]. Moreover, the failure the mode failure of allmode samples of all was sample shear-compression,s was shear-compression, and two specific and two failure specific patterns failure werepatterns observed, were observed, including including shear cracking shear andcracking interface and failure.interface For failure. instance, For sampleinstance, CC200-A sample CC200- failed throughA failed shear through cracking shear ascracking the shear as cracksthe shear spread cracks from spread the basefrom of the the base slab of to the the slab point to ofthe support point of Sustainabilityatsupport approximately 2020 at ,approximately 10, x FOR 34 degrees,PEER REVIEW 34 which degrees, is beneath which is the beneath 45 degrees the 45 specified degrees in specified BS8110 [in47 ].BS8110 In addition,14 [47].of 19 In the shear cracks cut across the rosette-shaped strain gauges, as shown in Figure 14 and all specimens addition,exhibited the similar shear shearcracks cracks cut across despite the di rosette-shafferent failureped loads.strain gauges, As for the as locationshown in of Figure the shear 14 and cracks all in specimensthe CC200 exhibited specimen, similar all cracks shear formed cracks on despite the rib ofdiffe therent slab failure and propagated loads. As graduallyfor the location upwards of asthe the shearloading cracks on in the the tested CC200 samples specimen, increased. all cracks Cracks formed were on the prolonged rib of the along slab and the propagated concrete’s topping gradually and upwardsthere was as the no de-bonding,loading on the which tested indicates samples decent increased. composite Cracks work. were prolonged along the concrete’s topping and there was no de-bonding, which indicates decent composite work. a b

Major shear cracks (Think cracking pattern) Major shear cracks (Thin cracking pattern)

Figure 14. Shear failure of slab (a) CC200A and (b) EPS200A. Figure 14. Shear failure of slab (a) CC200A and (b) EPS200A. Moreover, shear failure at the concrete interface occurred due to de-bonding of the topping layer fromMoreover, the precast shear unit failure (Figure at 15the), concrete and a diagonal interface crack occurred along due the heightto de-bonding of the slabs of the was topping clearly layer visible. fromSample the precast EPS200A unit failed (Figure as a15), result and ofa diagonal interface crack shear along from the height extreme of endthe slabs up to was the clearly point of visible. loading Sample EPS200A failed as a result of interface shear from the extreme end up to the point of loading and shear cracking, as shown in Figure 14. Interface shear failure could be seen with 90–95% of the ultimate shear force applied. This mode of failure was similar to that observed by Girhammar [48], where de-bonding of the topping concrete took place with approximately 90-95% of the ultimate shear load applied. Despite both EPS200 and CC200 failing as a result of shear cracking, de-bonding of the topping concrete in the former was a significant difference between the two when considering the modes of failure.

De-bonding of topping concrete

Figure 15. Interface failure of EPS200A.

Furthermore, because the de-bonding of the topping concrete occurred at 95% of the ultimate load, the shear cracks shared the same pattern. The failure mode of the 250-mm precast half-shaped slabs was similar for both the normal and EPS-foam concrete slabs (Figure 16a). For CC250, shear cracks extended from the point of load application to about 100 mm from the supports. The crack cut across the rosette strain gauge to the base of the topping concrete, then to the point of load application (see Figure 16a, b). The shear crack of sample EPS250 started 100 to 110 mm away from the support. The crack cut across the 45-degree rosette strain gauge, and extended towards the topping concrete, ending at the point of load application. The ultimate failure load was relatively different for samples CC250A (Figure 13a) and EPS250A (Figure 13b), but the crack patterns were quite similar, regardless the type of concrete used to cast the EPS-foam concrete slabs.

Sustainability 2020, 10, x FOR PEER REVIEW 14 of 19 addition, the shear cracks cut across the rosette-shaped strain gauges, as shown in Figure 14 and all specimens exhibited similar shear cracks despite different failure loads. As for the location of the shear cracks in the CC200 specimen, all cracks formed on the rib of the slab and propagated gradually upwards as the loading on the tested samples increased. Cracks were prolonged along the concrete’s topping and there was no de-bonding, which indicates decent composite work. a b

Major shear cracks (Think cracking pattern) Major shear cracks (Thin cracking pattern)

Figure 14. Shear failure of slab (a) CC200A and (b) EPS200A.

Sustainability 2020, 12, 9679 14 of 17 Moreover, shear failure at the concrete interface occurred due to de-bonding of the topping layer from the precast unit (Figure 15), and a diagonal crack along the height of the slabs was clearly visible. Sampleand shear EPS200A cracking, failed as shownas a result in Figure of interface 14. Interface shear from shear the failure extreme could end be up seen to the with point 90–95% of loading of the andultimate shear shear cracking, force as applied. shown Thisin Figure mode 14. of Interfac failuree was shear similar failure to thatcould observed be seen bywith Girhammar 90–95% of [the48], ultimatewhere de-bonding shear force of applied. the topping This concrete mode of took failur placee was with similar approximately to that observed 90–95% by of theGirhammar ultimate shear[48], whereload applied. de-bonding Despite of the both topping EPS200 concrete and CC200 took failing place as with a result approximately of shear cracking, 90-95% de-bonding of the ultimate of the sheartopping load concrete applied. in Despite the former both was EPS200 a signiﬁcant and CC200 di ﬀfailingerence as between a result theof shear two whencracking, considering de-bonding the ofmodes the topping of failure. concrete in the former was a significant difference between the two when considering the modes of failure.

De-bonding of topping concrete

FigureFigure 15. 15. InterfaceInterface failure failure of of EPS200A. EPS200A.

Furthermore,Furthermore, because thethe de-bondingde-bonding of of the the topping topping concrete concrete occurred occurred at 95% at 95% of the of ultimatethe ultimate load, load,the shear the shear cracks cracks shared shared the same the same pattern. pattern. The failureThe failure mode mode of the of 250-mm the 250-mm precast precast half-shaped half-shaped slabs slabswas similarwas similar for both for theboth normal the normal and EPS-foam and EPS-foam concrete concrete slabs (Figureslabs (Figure 16a).For 16a). CC250, For CC250, shear cracksshear cracksextended extended from the from point the ofpoint load of application load applicatio to aboutn to 100about mm 100 from mm the from supports. the supports. The crack The cutcrack across cut acrossthe rosette the rosette strain strain gauge gauge to the to basethe base of the of the topping topping concrete, concrete, then then to to the the point point ofof load application (see(see Figure Figure 16a,16a,b). b). The shear crack of of sample sample EP EPS250S250 started started 100 100 to to 110 110 mm mm away away from from the the support. support. TheThe crack crack cut cut across across the the 45-degree 45-degree rosette rosette strain strain ga gauge,uge, and and extended extended towards towards the the topping topping concrete, concrete, endingending at at the the point point of of load load application. application. The The ultima ultimatete failure failure load load was was relatively relatively different diﬀerent for for samples samples CC250ACC250A (Figure (Figure 13a)13a) and and EPS250A EPS250A (Figure (Figure 13b),13b), but but the the crack crack patterns patterns were were quite quite similar, similar, regardless regardless thetheSustainability type type of of concrete2020 concrete, 10, x FORused used PEER to to ca cast REVIEWst the the EPS-foam concrete slabs. 15 of 19

a b

MajorFigure shear 16. cracksShear cracking (Thick ofcracking CC250A pattern) and EPS250A half-shapedMajor slabs: shear (a cracks) thick cracking (Thin cracking pattern, ( bpattern)) thin cracking pattern. Figure 16. Shear cracking of CC250A and EPS250A half-shaped slabs: (a) thick cracking pattern, (b) 5. Conclusions thin cracking pattern. This research study presented the findings of an experimental investigation into EPS-foam concrete half-shaped5. Conclusions slabs subjected to shear loading. The experimental campaign started with the development of structuralThis research precast study EPS-foam presented concrete the half-shaped findings of slabs an usingexperimental QD and EPSsinvestigation as partial into substitutes EPS-foam for sandconcrete and half-shaped crushed stone, slabs respectively. subjected Ato trial shear and load erroring. procedure The experimental was performed campaign to produce started EPS-foam with the concretedevelopment with of strength structural of 35 precast MPa. EPS-foam The replacement concrete of half-shaped fine and coarse slabs aggregatesusing QD and was EPSs made as testingpartial disubstitutesfferent amounts for sand of and the twocrushed (0–30% stone, and respectively. 0–22.5%, respectively). A trial and Toerror ascertain procedure that was the optimumperformed mix to throughproduce which EPS-foam to achieve concrete the with required strength design of strength,35 MPa. materialThe replacement tests (i.e., of a compressivefine and coarse test, aggregates a splitting tensilewas made test, testing and UPV different non-destructive amounts of tests)the two were (0–30% carried and out 0–22.5%, on diff respectively).erent mix proportions. To ascertain In that the process,the optimum a total mix of 256 through trial mixes which were to made achieve to investigate the required the physicaldesign strength, and mechanical material characteristics tests (i.e., a ofcompressive the EPS-foam test, concretea splitting mixtures, tensile test, and and a total UPV of no fourn-destructive EPS-foam tests) concrete were slabs carried (of out 3.5- on and different 4.5-m mix proportions. In the process, a total of 256 trial mixes were made to investigate the physical and mechanical characteristics of the EPS-foam concrete mixtures, and a total of four EPS-foam concrete slabs (of 3.5- and 4.5-m spans) with different thicknesses (200 and 250 mm) were prepared. The findings showed that the ultimate shear force for the full-scale EPS-foam concrete half-shaped slabs was 6–12% lower when compared to identical control concrete samples with a 2410-kg/m3 average density, and 26–32% higher than the theoretical calculation values according to the BS 8110 design code. Furthermore, a substantial decrease in the density of the EPS-foam concrete mixes was observed (approximately a 20% reduction when compared to the control mixtures). From the aforementioned results, it can be asserted that EPS-foam concrete has the potential to be utilized for the slab systems of sustainable buildings in the present-day construction industry. Furthermore, this study suggests several recommendations for future research works: • to concentrate on enhancing the structural behavior of EPS-foam concrete half-shaped slabs, (e.g., addressing the stiffness and allowable deflections of the design system in order to satisfy the serviceability limit state); • to further predict the feasibility of the developed precast EPS-foam concrete half-shaped slab via numerical simulations; and • to enhance the connection efficiency between precast EPS-foam concrete half-shaped slab elements.

Funding: The experimental work was funded by Universiti Putra Malaysia (Vote No: 62302). This research was supported by Peter the Great St. Petersburg Polytechnic University, Russian Academic Excellence Project ‘5-100’.

Acknowledgments: The authors gratefully acknowledge the experimental work fund provided by the Universiti Putra Malaysia and the publication support given by the Peter the Great Polytechnic University, Saint

Sustainability 2020, 12, 9679 15 of 17 spans) with diﬀerent thicknesses (200 and 250 mm) were prepared. The ﬁndings showed that the ultimate shear force for the full-scale EPS-foam concrete half-shaped slabs was 6–12% lower when compared to identical control concrete samples with a 2410-kg/m3 average density, and 26–32% higher than the theoretical calculation values according to the BS 8110 design code. Furthermore, a substantial decrease in the density of the EPS-foam concrete mixes was observed (approximately a 20% reduction when compared to the control mixtures). From the aforementioned results, it can be asserted that EPS-foam concrete has the potential to be utilized for the slab systems of sustainable buildings in the present-day construction industry. Furthermore, this study suggests several recommendations for future research works:

to concentrate on enhancing the structural behavior of EPS-foam concrete half-shaped slabs, (e.g., • addressing the stiffness and allowable deflections of the design system in order to satisfy the serviceability limit state); to further predict the feasibility of the developed precast EPS-foam concrete half-shaped slab via • numerical simulations; and to enhance the connection efficiency between precast EPS-foam concrete half-shaped slab elements. •

Author Contributions: Conceptualization, S.S., and F.N.A.A.A.; methodology, S.S., F.N.A.A.A. and M.A.; resources, F.N.A.A.A., S.S., and M.A.; Investigation, S.S., F.N.A.A.A. and M.A.; data curation, F.N.A.A.A., M.A., T.O. and G.M.; formal analysis, S.S., F.N.A.A.A., M.A., T.O., G.M. and M.A.M.; supervision, F.N.A.A.A.; Validation, S.S., F.N.A.A.A., M.A., R.F., N.V., T.O., G.M., and M.A.M.; visualization, S.S., F.N.A.A.A., M.A., R.F., N.V., T.O., G.M., and M.A.M.; writing—original draft, S.S., and M.A.; writing—review & editing, S.S., F.N.A.A.A., M.A., R.F., N.V., T.O., G.M., and M.A.M.; project administration; F.N.A.A.A., N.V., R.F., and M.A.; funding acquisition, F.N.A.A.A. and N.V. All authors have read and agreed to the published version of the manuscript. Funding: The experimental work was funded by Universiti Putra Malaysia (Vote No: 62302). This research was supported by Peter the Great St. Petersburg Polytechnic University, Russian Academic Excellence Project ‘5-100’. Acknowledgments: The authors gratefully acknowledge the experimental work fund provided by the Universiti Putra Malaysia and the publication support given by the Peter the Great Polytechnic University, Saint Petersburg, Russia, and the cooperation of the Deanship of Scientific Research at Prince Sattam bin Abdulaziz University, Alkharj, Saudi Arabia and the Department of Civil Engineering, Faculty of Engineering and IT, Amran University, Yemen, for this research. Conflicts of Interest: The authors declare no conflict of interest.

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