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Experimental Investigation on Engineering Properties of Concrete Incorporating Reclaimed Asphalt Pavement and Rice Husk Ash Mulusew Aderaw Getahun 1,2, * 1 2 3 4

*

ID

, Stanley Muse Shitote 3 and Zachary C. Abiero Gariy 4

Civil Engineering Department, Pan African University Institute for Basic Sciences, Technology and Innovation (PAUSTI), 62000 00200 Nairobi, Kenya Ethiopian Roads Authority, Addis Ababa 1770, Ethiopia Civil Engineering Department, Rongo University, Rongo 103-40404, Kenya; [email protected] Civil Engineering Department, Jomo Kenyatta University of Agriculture and Technology (JKUAT), Nairobi 5505, 00100, Kenya; [email protected] Correspondence: [email protected]; Tel.: +251-912-914-229

Received: 11 June 2018; Accepted: 9 July 2018; Published: 23 August 2018

Abstract: Waste generation from agricultural and construction industries is growing at an upsetting rate that causes a heavy burden on landfill facilities. On the other hand, the construction industry is exhausting natural resources thereby posing environmental problems. This study investigates the potential use of agro-industrial waste such as rice husk ash (RHA) and construction waste like reclaimed asphalt pavement (RAP) as promising construction materials. The durability and physical and mechanical properties of concrete were assessed by partially replacing cement and virgin aggregates with RHA and RAP, up to 20% and 50%, respectively. A total of 22 mixes were studied, twelve of which were devoted to studying the collective effects of RHA and RAP on the engineering properties of concrete. Based on experimental results, RHA and RAP decreased slump, compacting factor, density, water absorption and sorptivity. RHA increased compressive and tensile splitting strength, whereas RAP decreased compressive and tensile splitting strength. Comparable strength and favorable sorptivity values were obtained when 15% RHA was combined with up to 20% RAP in the concrete mix. Thus, utilizing RHA and RAP as concrete ingredients can contribute to solid waste management, engineering and economic benefits. Keywords: slump; compacting factor; density; water absorption; sorptivity; durability; compressive strength; tensile splitting strength; volumes of permeable void spaces

1. Introduction The construction industry consumes about 40% of the global energy; is the largest global consumer of raw materials; and is responsible for 25–40% of the world’s total CO2 emissions and 28% of solid waste in the form of construction debris [1]. Over 10 billion tons of Portland cement concrete (PCC) is produced annually worldwide due to its versatility, durability and sustainability [2,3]. However, its production consumes a substantial amount of energy and raw materials. The cement production alone is both energy and resource intensive. It was attested that every ton of cement production consumes about 4 GJ of energy and 1.7 tons of raw materials and releases approximately 0.73–0.99 ton of CO2 [2,4–7]. Moreover, PCC production consumes more than 8 billion tons of aggregates each year [6]. Consequently, an increasing demand for concrete will continue reducing natural stone deposits significantly thereby poses a threat on the environment [7–9]. Concurrently, a substantial quantity of construction and agro-industrial solid wastes disposal is posing a huge threat to the environment [10–12]. For example, road maintenance and rehabilitation Buildings 2018, 8, 115; doi:10.3390/buildings8090115

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activities have been generating a large amount of valuable asphalt pavement materials that are either discarded along the generation point or hauled off to the disposal site [13–15]. Similarly, according to the FAO 2017 [16] report, the global paddy production in 2017 was forecasted to amount to 756.7 million tons. Assuming annual rice production remains the same, 254.5 million tons of rice husks is available for disposal every year worldwide. Thus, agro-industrial solid waste disposal is another serious concern unless we find a preferred alternative use. In order to curb these concerns, the cement and concrete industry could be an ideal home for construction and industrial wastes. Recently, waste materials such as crushed concrete, asphalt pavement and crushed glasses are some of the recycled materials which have been used as a coarse and/or fine aggregate in concrete production [17,18]. In addition, numerous researches devoted to find alternatives for cement replacement [19–23]. Thus, utilizing RAP and rice RHA as aggregate and cement partial replacements, respectively, is in harmony with this approach. The concern on how to use RAP has gained a remarkable curiosity in the United States due to the increasing demand for sustainable construction materials use [24]. But, in underdeveloped and developing countries where recycling materials is not a culture, a tremendous amount of RAP and RHA materials are usually discarded in landfills [13]. Previous studies [25–28] revealed and consistently reported that utilizing RAP in PCC caused reductions in compressive, flexural, and tensile splitting strength compared to PCC containing virgin aggregates. The findings from past studies showed that the decrease in strength of PCC containing RAP was largely instigated by the effects of porosity in the interfacial transition zone (ITZ) and preferential asphalt cohesion failure [29–31] However, previous studies [27–30] exhibited that concrete containing RAP had better ductility, toughness and fracture properties compared to normal concrete. Huang et al. [26] reported that RAP could initiate crack propagation and lead to the formation of a prolonged crack pattern allied to the higher dissipation of energy. Hence, there is a need to improve the strength of concrete containing RAP in order to maximize the utilization of RAP materials in construction applications. RHA was found to enhance the concrete properties by filler and pozzolanic effects [12,32]. The enhancement in strength is believed to be an advantage from the high silica content of RHA, which, in itself, possesses little cementitious value, but when calcium hydroxide reacts with RHA in the presence of water, a cementitious complex is formed [33]. The hydration of tricalcium silicate (C3 S) gives 61% calcium-silicate-hydrate (C-S-H) and 39% calcium hydroxide; the hydration of dicalcium silicate (C2 S) results in 82% C-S-H and 18% calcium hydroxide, where up to 15% of the weight of Portland cement is hydrated lime [34]. Calcium hydroxide has no contribution to concrete strength, but rather has detrimental effects on the durability of concrete. Thus, RHA can provide an opportunity to alter the free lime (Calcium hydroxide) to a C-S-H gel that makes the concrete strong [35]. Therefore, the main objective of this study was to investigate the collective effects of RHA and RAP on the physical and mechanical properties of concrete. The engineering properties of RHA-inclusive concrete were assessed in the first phase. Then, the effects of RAP on wet and hardened concrete properties were investigated. Finally, the combined effects of RHA and RAP on engineering properties of concrete were assessed. Thus, utilizing RAP in combination with RHA for concrete production can contribute to engineering benefits, economic savings, solid waste management and environmental protection. 2. Material and Methods 2.1. Materials Materials used for this study were fine reclaimed asphalt pavement (FRAP), course reclaimed asphalt pavement (CRAP), fine virgin aggregate (FVA), course virgin aggregate (CVA), ordinary Portland cement (OPC) type I, rice husk ash (RHA), water, Sika ViscoCrete 3088 superplasticizer (SVCSP) and Sikament NNG superplasticizer (SNNGSP). Figure 1 depicts aggregates (CRAP, CVA,


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FRAP, and FVA) and cementitious materials (cement and RHA). All materials were obtained from different parts FVA (river (river sand) sand) and different parts of of Kenya. Kenya. FVA and VCA VCA were were purchased purchased from from Masinga Masinga and and Molongo Molongo districts of of Kenya respectively. The The RAP RAP was was obtained obtained from from an an old old distressed distressed flexible flexible pavement, pavement, districts Kenya respectively. Ruaka-Banana-Limuru Road Road (D407), (D407), sampled sampled at at the the section section near near Tigoni, Tigoni, Kiambu Kiambu County County of of Kenya. Kenya. Ruaka-Banana-Limuru The road was constructed about 21 years ago without major rehabilitation. RHA was collected from The road was constructed about 21 years ago without major rehabilitation. RHA was collected from the dump Mwea RiceRice Milling Factory. Cement and superplasticizers were bought Bamburi the dumpsite siteofof Mwea Milling Factory. Cement and superplasticizers were from bought from Cement and Sika Kenya Limited respectively. Tap water was used for mixing. Bamburi Cement and Sika Kenya Limited respectively. Tap water was used for mixing.

Figure 1. Materials. Figure 1. Materials.

2.2. Methods 2.2. Methods The methods adopted and followed for this study are discussed in the subsequent section. The The methods adopted and followed for this study are discussed in the subsequent section. most important test methods are summarized in Table 1. The most important test methods are summarized in Table 1. Table 1. Test methods adopted. Table 1. Test methods adopted.

Test on Constituent Materials Test on Constituent Materials Test Performed Standard Used Test Performed Standard Used Sieve analysis BS EN 933-1 Sieve analysis BS Aggregate specific gravity (SG) BSEN EN933-1 1097-6 Aggregate specific gravity (SG) BS EN 1097-6 Fineness modulus ASTM C136 Fineness modulus ASTM C136 cement and SGSG ASTM C188 cement andRHA RHA ASTM C188 Aggregate water absorption BS EN 1097-6 Aggregate water absorption BS EN 1097-6 Aggregates density ASTM C29 Aggregates density ASTM C29 Voids in aggregates ASTM C29 ACV IS 2386-IVC29 Voids in aggregates ASTM AIV IS 2386-IV ACV IS 2386-IV AIV IS 2386-IV 2.2.1. Test Methods for Material Characterization

Tests on Fresh and Hardened Concrete Tests on Fresh and Hardened Concrete Test Performed Standard Used Test Performed Standard Used Slump BS EN 12350-2 Slump BS EN Compacting factor BS 12350-2 1881-103 Compacting factor BS 1881-103 Fresh density BS EN 12350-6 Fresh density BS EN 12350-6 Compressive strength ENEN 12390-3 Compressive strength BSBS 12390-3 Tensile strength BS EN 12390-6 Tensile strength BS EN 12390-6 Water absorption ASTM C642 Water absorption ASTM C642 Sorptivity ASTM C1585 Permeable voids ASTM C642 Sorptivity ASTM C1585 Hardened density ASTM C642 Permeable voids ASTM C642 Hardened density ASTM C642

2.2.1.Aggregate Test Methods for Material Characterization sampling was carried out in accordance with BS EN 932-1 (1997) [36] requirements to get representative samples for the batch. of the aggregates was determined in requirements line with BS EN Aggregate sampling was carried outGrading in accordance with BS EN 932-1 (1997) [36] to 933-1 (2012) [37] procedures using test sieves of the sizes complying with BS ISO 3310-2 (2013) get representative samples for the batch. Grading of the aggregates was determined in line with[38]. BS The RAP (2012) material was obtained using through and of old existing pavement, and(2013) then EN 933-1 [37] procedures testripping sieves of themilling sizes complying with BS ISO 3310-2 crushed manually and finally sieved using 5 mm sieve in order to separate into FRAP (grain size [38]. The RAP material was obtained through ripping and milling of old existing pavement, and then less than 5 mm) and CRAP (grain size greater than 5 mm). RHA was sieved using 0.10 mm sieve. crushed manually and finally sieved using 5 mm sieve in order to separate into FRAP (grain size less The and water ofthan coarse and fine aggregates wereusing determined as sieve. per BSThe EN thanspecific 5 mm) gravity and CRAP (grainabsorption size greater 5 mm). RHA was sieved 0.10 mm 1097-6 (2013) [39]. Bulk density and voids in aggregates were determined in line with the procedures specific gravity and water absorption of coarse and fine aggregates were determined as per BS EN defined(2013) in ASTM [40]. Aggregate and impact tests were performed to the 1097-6 [39]. (2003) Bulk density and voidscrushing in aggregates were determined in line withaccording the procedures procedures specified in IS 2386: Part IV (2002) [41]. defined in ASTM (2003) [40]. Aggregate crushing and impact tests were performed according to the procedures specified in IS 2386: Part IV (2002) [41]. 2.2.2. Mix Design and Mixing Procedures 2.2.2.The Mixmix Design andfor Mixing Procedures design 25 MPa Portland cement concrete (PCC) was done in accordance with BS EN 206 (2014) [42] and BS EN 8500-2 (2012) [43]. A total of 22 mixtures were prepared. Table 2 portrays The mix design for 25 MPa Portland cement concrete (PCC) was done in accordance with BS EN the particulars of studied mixture proportions. In all the mixtures, 254 kg/m3 of water and water 206 (2014) [42] and BS EN 8500-2 (2012) [43]. A total of 22 mixtures were prepared. Table 2 portrays the particulars of studied mixture proportions. In all the mixtures, 254 kg/m3 of water and water to cementitious material ratio of 0.65 were kept constant. The first phase of the study was replacing cement by 5, 10, 15 and 20% RHA (by weight of cement) to assess the effect of RHA on wet and


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to cementitious material ratio of 0.65 were kept constant. The first phase of the study was replacing cement by 5, 10, 15 and 20% RHA (by weight of cement) to assess the effect of RHA on wet and hardened properties of concrete. In the second phase, FVA and CVA were replaced by 10, 20, 30, 40, and 50% FRAP and CRAP (by weights of FVA and CVA) respectively to ascertain the influence of RAP on the properties of concrete. The third phase was to ascertain the collective effects of RHA and RAP on engineering properties of concrete. SNNGSP was used at 0.5, 0.85, 2, and 2.75% (by weight of cementitious material) for 5, 10, 15, and 20% RHA content respectively. SVCSP (more powerful than SNNGSP) was used at 0.5, 0.7, 0.9, and 1.1% (by weight of cementitious material) for RHA and RAP combined mixtures. Manual mixing was performed as per BS EN 1881-125 (2013) [44] with a control mechanism to prevent the loss of cementitious materials and water quantified during mixture proportioning. The chemical analysis of cement and RHA were conducted as per BS EN 196-2 (2013) [45] test method. The specific gravities of cement and RHA were done in accordance with ASTM C188 (2016) [46]. Table 2. Mix proportions for 25 MPa concrete comprising RHA and RAP. Mix Description

Cement (kg/m3 )

RHA (kg/m3 )

FVA (kg/m3 )

FRAP (kg/m3 )

CVA (kg/m3 )

CRAP (kg/m3 )

Control (5–20)% RHA (10–50)% RAP 5% RHA + (10–30)% RAP 10% RHA + (10–30)% RAP 15% RHA + (10–30)% RAP 20% RHA + (10–30)% RAP

390 (312–371) 390 371 351 332 312

0 (20–78) 0 20 39 59 78

712 712 (356–641) (499–641) (499–641) (499–641) (499–641)

0 0 (71–356) (71–214) (71–214) (71–214) (71–214)

1593 1593 (796–1434) (1115–1434) (1115–1434) (1115–1434) (1115–1434)

0 0 (159–796) (159–478) (159–478) (159–478) (159–478)

2.2.3. Test Methods for Fresh Concrete Properties Fresh concrete properties were assessed by conducting slump, compacting factor, and fresh density tests. Three replicate specimens were prepared for each test. Sampling for testing was done in accordance with procedures stipulated in BS EN 12350-1 (2009) [47]. Slump, compacting factor and fresh density was determined in accordance the procedures specified in BS EN 12350-2 (2009) [48], BS 1881-103 (1993) [49], and BS EN 12350-6 (2009) [50] respectively. 2.2.4. Test Methods for Hardened Concrete Properties Cubes of dimensions 100 mm × 100 mm × 100 mm and cylinders with a diameter of 100 mm and 200 mm long conforming to BS EN 12390-1 (2012) [51] requirements were used to make concrete specimens for compressive and tensile splitting strength test respectively. A total of 132 cube and 66 cylinder specimens were made and cured in accordance with the methods specified in BS EN 12390-2 (2009) [52] for 7 and 28 days compressive and 28 days tensile splitting strength test respectively. Three replicate specimens were prepared for each test. Compressive and tensile splitting strength of concrete were determined according to BS EN 12390-3 (2009) [53] and BS EN 12390-6 (2009) [54] test method respectively. Specimens were loaded to failure in automatic computerized testing machine conforming to BS EN 12390-4 (2000) [55]. Density, water absorption and void spaces in concrete were determined consistent with ASTM C642 (2013) [56]. Three replicate specimens were prepared for each test. A total of 66 cubes of dimensions 100 mm × 100 mm × 100 mm were made and cured for 28 days. The samples were dried in an oven for 72 h at a temperature of 105 ◦ C until the change in mass was less than 0.5%. Then, the samples were put in the water at an average temperature of 21.5 ◦ C for about 72 h until the increase in saturated surface dried mass was less than 0.5%. Finally, the specimens were placed in a receptacle, covered with tap water, and boiled for 5 h and then cooled by natural loss of heat for 15 h to a final average temperature of 22.5 ◦ C.


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Sorptivity by the concrete specimens was determined in accordance with ASTM C1585 (2013) [57] test methods. Three replicate specimens were prepared for each test. A total of 66 cubes of dimensions 100 mm × 100 mm × 100 mm were made and cured for 28 days for the sorptivity test. The specimens Buildings 2018, 8, x FOR PEER REVIEW 5 of 24 were dried in an oven at 110 ◦ C temperature for 24 h and then remained in an oven at a temperature of 100After mm ×3100 mm each × 100 specimen mm were made cured for 28adays for the sorptivity test. 50 ◦ dimensions C for 3 days. days, was and placed inside container and stored atThe an average ◦ specimens were dried in an oven at 110 °C temperature for 24 h and then remained in an oven at a temperature of 22 C for 15 days before the start of the absorption procedure. The specimens were temperature of 50 °C for 3 days. After 3 days, each specimen was placed inside a container and stored removed from the storage container and the 5 faces of the specimens were sealed properly to deter at an average temperature of 22 °C for 15 days before the start of the absorption procedure. The entrance of moisture while the opposite face left open and exposed to water. The initial weight of the specimens were removed from the storage container and the 5 faces of the specimens were sealed specimens was recorded after sealing and submerged in water about 3.5 mm above the bottom face. properly to deter entrance of moisture while the opposite face left open and exposed to water. The The initial weight gain of was forrecorded each testafter specimens at interval of time 5, 10, 30 min, 1, 2, 3, 4, 5, weight thedetermined specimens was sealing and submerged in water about 3.5 mm andabove 6 h. the bottom face. The weight gain was determined for each test specimens at interval of time 5, 10, 30 min, 1, 2, 3, 4, 5, and 6 h.

3. Results and Discussion 3. Results and Discussion

3.1. Material Characterization 3.1. Material Characterization

Virgin aggregates (VA) and RAP materials were characterized in terms of gradation, fineness Virgin aggregates (VA)specific and RAP materials were characterized in termsACV, of gradation, modulus, water absorption, gravity, bulk density, void content, and AIV.fineness modulus, water absorption, specific gravity, bulk density, void content, ACV, and AIV.

Physical and Mechanical Properties of Materials Physical and Mechanical Properties of Materials

TheThe specific gravity, water absorption, bulk density, aggregate crushing value (ACV), aggregate specific gravity, water absorption, bulk density, aggregate crushing value (ACV), aggregate impact value (AIV) ofofaggregates, amongothers, others, tabulated in Table impact value (AIV) aggregates, among areare tabulated in Table 3. 3. Table Physicaland andmechanical mechanical properties of materials. Table 3. 3. Physical properties of materials. Property OPC RHA OPC RHA Fineness modulus Fineness modulus Silt Content [%] Silt Content (%) Bulkgravity specific gravity 3.12 3.12 2.03 2.03 Bulk specific Bulk gravity, specificSSD gravity, Bulk specific basis SSD basis - Apparent specific gravity - Apparent specific gravity Water Absorption (%) - Water Absorption [%] 359 Loose bulk density (kg/m3 ) 31398 ] 1398 359 Loose bulk density [kg/m 1435 470 Rodded bulk density (kg/m3 ) 3 1435 - 470 bulk density Voids inRodded loose aggregates (%) [kg/m ]Voids inaggregates loose aggregates [%]Voids in Rodded (%) - Maximum particle size (mm) Voids in Rodded aggregates 0.09 [%] - 0.10 Aggregate crushing values (%)size (mm)Maximum particle 0.09 - 0.10 Aggregate Impact values (%) Aggregate crushing values [%] Aggregate Impact values [%] Property

FVA FVA 2.65 2.65 5.19 5.19 2.43 2.43 2.52 2.52 2.68 2.68 3.95 3.95 1456 1456 1577 1577 39.33 39.33 34.31 5 34.31 5-

FRAP CVA FRAP 3.61 0.81 3.61 0.81 2.32 2.322.62 2.37 2.372.68 2.46 2.462.80 2.42 2.422.41 1318 1318 1421 1407 1407 43.09 1584 43.09 39.25 45.75 39.25 5 39.52 - 20 5 18.73 15.51

CRAP CVA -2.41 2.62 2.45 2.68 2.80 2.51 2.41 1.63 1421 1300 1584 1326 45.75 43.97 39.52 20 42.83 18.73 20 15.51 15.92 9.83

CRAP 2.41 2.45 2.51 1.63 1300 1326 43.97 42.83 20 15.92 9.83

Gradation results of coarse and fine aggregates are depicted in Figures 2 and 3 respectively. Gradation results of coarse and fine aggregates are depicted in Figures 2 and 3 respectively. As As can be seen from the figures, the grading of CVA and FVA met the grading requirements of BS 882 can be seen from the figures, the grading of CVA and FVA met the grading requirements of BS 882 (1992) [58]. (1992) [58].

Percent Pass

100 80 CVA

60

Lower Limit

40

Upper Limit

20

CRAP

0 1

10 Sieve Size (mm)

100

Figure 2. Coarse aggregate particle size distribution as per BS 882 specifications.

Figure 2. Coarse aggregate particle size distribution as per BS 882 specifications.


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Percent Pass

100 80 60 FVA

40

Lower Limit 20

Upper Limit

0 0.1

1 Sieve Size (mm)

FRAP

10

Figure 3. Fine aggregate particle size distribution as per BS 882 specifications.

Figure 3. Fine aggregate particle size distribution as per BS 882 specifications. The grading of CRAP was slightly outside the limits and while that of FRAP was within the limits specified in BS 882. is apparent fromthe thelimits figureand thatwhile CRAPthat wasof finer thanwas CVA whereas, The grading of CRAP wasItslightly outside FRAP within the limits FRAP was coarser than FVA. Similar findings were reported by previous study [28]. The fineness specified in BS 882. It is apparent from the figure that CRAP was finer than CVA whereas,ofFRAP CRAP and coarseness of FRA might be attributed to the fragmentation of CRAP materials during was coarser than FVA. Similar findings were reported by previous study [28]. The fineness of CRAP crushing and agglomeration of particles respectively and their sources as well. All coarse aggregates and coarseness of FRA might be attributed to the fragmentation of CRAP materials during crushing used in this study had 19.1 mm nominal maximum aggregate sizes. The fine aggregates particle sizes and agglomeration of particles and their sources as well. Alland coarse aggregates used in were between 0.15 and 5 mm.respectively FVA and FRAP had fineness modulus of 2.65 3.61 respectively. this study RAP had materials 19.1 mmhad nominal maximum aggregate sizes. The fine aggregates particle sizes lower specific gravity than that of virgin aggregates. This is consistent with were between andby 5 mm. FVAlower and specific FRAP had fineness of 2.65 and 3.61 respectively. the 0.15 findings [25]. The gravity of RAPmodulus may be attributed to the substantial amounts of low-density asphalt-mortar coatings on the RAP surfaces andaggregates. its source as well. The water with RAP materials had lower specific gravity than that of virgin This is consistent absorption of RAP found to be gravity lower than that of VA.beThe reason might attributed to the the findings by [25]. Thewas lower specific of RAP may attributed to thebesubstantial amounts of asphalt coating around both coarse and fine RAP that could hinder the maximum possible amount low-density asphalt-mortar coatings on the RAP surfaces and its source as well. The water absorption of water which could have been absorbed by the aggregates. RAP materials had lower loose and of RAP was found to be lower than that of VA. The reason might be attributed to the asphalt coating rodded bulk density than that of virgin aggregates. RAP materials also showed higher void space around both andaggregates fine RAPwhich that could hinderathe maximum possible amount ofthe water than thatcoarse of virgin may demand higher amount of cement paste to fill totalwhich could surface have been the aggregates. RAP[35]. materials had lower loose and rodded bulk density areaabsorbed in order toby produce quality concrete than that of aggregates. materials showedresult. higher void than that of virgin Thevirgin ACV test done on theRAP CRAP exhibitedalso the abnormal The test space specimen compressed into a single solid mass under loading. This might be due to the presence of asphalt film around RAP aggregates which may demand a higher amount of cement paste to fill the total surface area in order might bind the crushed aggregates into a single solid dense mass. The ACV and AIV values of CVA to produce quality concrete [35]. andACV CRAPtest were below maximum limit stipulated in IS 383 (2002) [59].The CRAP lower ACV and The done onthe the CRAP exhibited the abnormal result. testhad specimen compressed AIV value than that of CVA. into a single solid mass under loading. This might be due to the presence of asphalt film around RAP The specific gravity of RHA was less than that of OPC by 35%. The bulk density of RHA was might also bindabout the crushed aggregates into a single solidgravity dense and mass. The ACVofand AIV of CVA 33% of that of OPC. The lower the specific bulk density RHA mayvalues result in and CRAP were below the maximum limit stipulated in IS 383 (2002) [59]. CRAP had lower ACV a reduction of concrete density. The maximum particle size of OPC and RHA were 90 and 100 µm and AIV value than that of CVA. respectively. Table 4 depicts the chemical composition of OPC, RHA, FRAP, and FVA. The specific gravity of RHA was less than that of OPC by 35%. The bulk density of RHA was 4. The Chemical composition of cement, RHA, FRAP, anddensity FVA. of RHA may result in also about 33% of that ofTable OPC. lower the specific gravity and bulk ChemicalThe Composition (%) particle Cement size RHA FRAP and FVA a reduction of concrete density. maximum of OPC RHA were 90 and 100 µm CaO 63.38of OPC, 0.86 RHA, 2.00 FRAP, 1.03 and FVA. respectively. Table 4 depicts the chemical composition SiO2 20.62 92.97 58.85 80.00 5.06 0.93 15.6 11.00 Al2O3 Table 4. Chemical composition of cement, RHA, FRAP, and FVA. MgO 0.82 0.48 0.04 2.00 Na2O 0.16 2.43 6.20 3.20 Chemical CompoundK(%) Cement 0.53 RHA2.54 FRAP 2.50 FVA 2O 4.30 CaO 63.38 0.86 2.00 TiO2 0.85 0.16 1.03 SiO2 20.62 58.85 0.02 80.00 MnO - 92.97 0.29 Al2 O3 5.06 0.93 15.6 11.00 3.23 0.48 0.88 5.44 1.00 2.00 Fe2O3 MgO 0.82 0.04 C3A 7.90 2.43 Na2 O 0.16 6.20 3.20 2.76 2.54 4.84 SO3 K2 O 0.53 4.30 2.50 TiO 0.85 2 on ignition (LOI) Loss 2.91 - 7.40 10.00 0.90 0.16 MnO Fe2 O3 C3 A SO3 Loss on ignition (LOI)

3.23 7.90 2.76 2.91

0.88 4.84 7.40

0.29 5.44 10.00

0.02 1.00 0.90


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The sum of the silicon dioxide (SiO2 ), aluminium oxide (Al2 O3 ) and iron oxide (Fe2 O3 ) contents of RHA was 94.8%; as a result, RHA fulfilled the 70% minimum requirement of BS EN 450-1 (2012) [60] to be used as a good pozzolana. The free calcium oxide (CaO) content was less than the upper bound (1.5%) specified in BS EN 450-1 (2012). This indicates the ability of the RHA to convert the free lime (Calcium hydroxide) to a C-S-H gel [60] that makes the concrete strong. The loss on ignition (LOI) of RHA was greater than that of cement but satisfied the limits specified in BS EN 450-1 (2012) [60]. LOI denotes the amount of unburnt carbon residue in the RHA that is responsible for an increase in water demand [32] which may have an influence on the properties of fresh concrete i.e., could result in low workability. The physical and chemical properties of superplasticizers used in the study are presented in Table 5. Table 5. Properties of superplasticizers.

Property Appearance/color Density (kg/L) pH value Chemical base Dosage

Superplasticizer Sikament NNG

Sika ViscoCrete 3088

Dark brown liquid 1.2 8 Naphthalene formaldehyde sulphonate 0.5–3.0% by weight of cement

Yellowish liquid 1.06 5.5 Aqueous solution of modified polycarboxylate 0.2–2% by weight of cement

3.2. Fresh and Hardened Properties of Concrete 3.2.1. Fresh Properties of Concrete Tables 6–8 show slump, compaction factor (CF) and density of fresh concrete.

• Slump From trial mixes, it was observed that RHA caused a dramatic decrease in slump as compared to the control mix. When Sikament NNG SP was added, the slump increased by 23.33% from 60 to 74 mm at 5% RHA and 0.5% SP content. Surprisingly, it was also discovered that as the content of RHA increased, the slump decreased considerably despite increasing the dosages of SP. The slump decreased by 20, 33.33, and 75% from 60 mm to 48, 40, and 15 mm at 10, 15, and 20% RHA content with the addition of 0.85, 2, and 2.75% SP respectively. The high demand for water and the resulted lower slump might be attributed to the large specific surface area and high unburnt carbon content of RHA. Like that of RHA, the partial replacement of virgin aggregate by RAP resulted in a substantial decrease of slump as compared to the control mix. The slump decreased by 33, 47, 62, 67, and 78% from 60 mm to 40, 32, 23, 20, and 13 mm at 10, 20, 30, 40, and 50% RAP content respectively. The reduction in slump might be attributed to absorption of the mixing water by the fine dust layers around the RAP periphery and water might also be controlled by RAP particle and was not able to move freely and thus, play no role to workability. The inclusion of both RHA and RAP in the mix found to decrease the slump significantly as expected. However, there was a slight (3%) improvement in the slump when 0.5% Sika ViscoCrete 3088 SP was added to the concrete mix containing (5RHA + 10RAP) % as shown in Table 8. The slump decreased steadily as the RHA and RAP content increased regardless of increasing the SP dosages. This may be attributed to the combined effects of RHA and RAP as already discussed.


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Table 6. Fresh properties of RHA concrete mixes. Mix Designation (RHA)%

Fresh Properties

Control

(5)

(10)

(15)

(20)

60 0.935 2.480

74 0.944 2.441

48 0.912 2.408

40 0.908 2.399

15 0.758 2.386 8 of 24

Slump (mm) Compaction Factor (CF) Fresh Density (g/cm3 ) Buildings 2018, 8, x FOR PEER REVIEW

Table 6. Freshproperties properties of mixes. Table 7. Fresh ofRHA RAPconcrete concrete mixes.

Mix Designation [RHA]% Mix [5] Designation (RAP)% Control [10] [15] [20] Fresh Properties Slump (mm) Control60(10) 74(20) 48 (30)40 15 (40) Compaction Factor (CF) 0.935 0.944 0.912 0.908 0.758 Slump (mm) 20 Fresh Density (g/cm3)60 2.48040 2.44132 2.408 23 2.399 2.386 Fresh Properties

Compaction Factor (CF) 0.935 0.931 0.922 0.921 3) 2.480 2.442 2.414 2.395 Fresh Density (g/cm Table 7. Fresh properties of RAP concrete mixes.

(50) 13 0.892 2.339

0.902 2.367

Mix Designation [RAP]% Control [10] [20] [30] [40] [50] 60 40 32 23 20 13 Designation RAP) 0.892 % 0.935Mix 0.931 0.922 (RHA 0.921 +0.902 2.367 (10 2.339 (52.480 + 20) 2.442 (5 +2.414 30) 2.395 (10 + 20) + 30)

Fresh8.Properties Table Fresh properties of both RHA and RAP concrete mixes. Slump (mm) Compaction Factor (CF) Fresh Properties Fresh Density (5(g/cm + 10)3)

Slump (mm) 62.0 58.0 53.5 49.0 Table 8. Fresh properties of both RHA and RAP concrete mixes. Compaction Factor (CF) 0.953 0.948 0.943 0.937 3) Mix Designation (RHA + RAP) % 2.441 2.427 2.418 2.421 Fresh Density (g/cm Fresh Properties

[5 + 10] [5 + 20] (15 + 10) (15 + 20) Slump [mm] 62.0 58.0 Slump (mm) Factor (CF)45.00.953 41.0 Compaction 0.948 Compaction (CF) FreshFactor Density [g/cm3] 0.9342.441 0.930 2.427 3) 2.421 Fresh Density (g/cm Fresh Properties [15 + 10] 2.407 [15 + 20] Slump [mm] 45.0 41.0 Compaction Factor (CF) 0.934 0.930 Compaction Factor (CF) 3 Fresh Density [g/cm ] 2.421 2.407

Fresh Properties

•

[5 + 30] 53.5 36.5 0.943 0.924 2.418 2.397 [15 + 30] 36.5 0.924 2.397

(15 + 30)

45.0 0.932 2.411

(10 + 30) 40.5 0.927 2.401

[10 + 20] [10 + 30] [10 + 30] (20 + 10) (20 + 20) (20 + 30) 49.0 45.0 40.5 32.5 0.932 28.5 0.927 24.0 0.937 0.860 2.411 0.8552.401 0.850 2.421 2.400 [20 +2.414 10] [20 + 20] [20 + 30] 2.391 32.5 28.5 24.0 0.860 0.855 0.850 2.414 2.400 2.391

The CF values of the concrete ranged from 0.758 to 0.953 as shown in Tables 6–8; these values are • Compaction Factor (CF) within the ranges specified in BS 1881-103 [49]. The CF of RHA-inclusive concrete increased by 1% at The CFwhereas values of CF the decreased concrete ranged from as 0.758 0.953 content as shown increased in Tables 6–8; 5% RHA content, by 19% thetoRHA to these 20%. values Figure 4a and are within the ranges specified in BS 1881-103 [49]. The CF of RHA-inclusive concrete increased by Equation (1) (obtained by regression) show the relationship between slump and compaction factor. 1% at 5% RHA content, whereas CF decreased by 19% as the RHA content increased to 20%. Figure R2 and standard error (1) of estimate (SEE) of the show model 0.958 and 0.012 respectively. 4a and Equation (obtained by regression) thewere relationship between slump and compaction 2 andCF Similarly, values of RAP-inclusive concrete decreased from 0.935 to 0.892 at 50% factor. Rthe standard error of estimate (SEE) of the model were 0.958 by and5% 0.012 respectively. CF values of mix. RAP-inclusive concrete decreased (2) by 5% from 0.935 0.892 at 50% illustrate RAP contentSimilarly, relative the to the control Figure 4b and Equation (obtained bytoregression) 2 RAP content relative to the control mix. Figure 4b and Equation (2) (obtained by regression) the relationship between slump and compaction factor. R and SEE of the modelillustrate were 0.965 and the relationship between slump and compaction factor. R2 and SEE of the model were 0.965 and 0.002 0.002 respectively. 0.95

Compaction factor (Cf)


respectively.

0.90 0.85 Cf = 0.5208S0.143 R² = 0.958

0.80 0.75 0.70 5

30 55 Slump, S [mm] (a) RHA concrete

80

0.96 0.94 0.92

Cf= 0.82S0.032 R² = 0.965

0.90 0.88 0

20 40 60 Slump, S [mm] (b) RAP concrete

Figure 4. Relationship between slump and compaction factor for RHA and RAP concrete.

Figure 4. Relationship between slump and compaction factor for RHA and RAP concrete.


9 of 24


9 of 24

C f = 0.52 × S0.143


9 of 24

C slump S 0.143for fresh RHA concrete f = 0.52 where: Cf is compacting factor; and S is the in×mm C f = 0.52 × S where: Cf is compacting factor; and S is the slump in mm0.032 for fresh RHA concrete where: Cf is compacting factor; and S is the C f slump = 0.82in×mm S for fresh RHA concrete 0.143

(1)

(1)

(1)

(2)

CCf f ==0.82 0.82××SS 0.032

0.032

(2) (2)



where: Cf is the compacting factor; and S is the slump in mm for fresh RAP concrete where: Cf isCthe compacting factor; isisthe slump mmRHA forfresh fresh RAPconcrete concrete fincrease is the compacting factor;and and the slumpatin in5% mm for RAP Awhere: slight was observed inSSCF values + (10–30)% RAP content, whereas A slight increase was observed in CF values at 5% RHA + [10–30]% RAP content, whereas A slight increase was observed in CF values at 5% RHA + [10–30]% RAP content, whereas CF CFthe CF decreased marginally for the remaining mixes. Figure 5 (obtained by regression) depicts decreased marginally for thetheremaining (obtained by byregression) regression)depicts depicts the decreased marginally remaining mixes. mixes. Figure Figure 55 (obtained relationship between slumpfor and compaction factor for RHA- and RAP-inclusive concrete.2R2the and SEE relationship between slump and compaction andRAP-inclusive RAP-inclusive concrete. relationship between slump and compactionfactor factorfor for RHARHA- and concrete. R2 R andand SEESEE of the model were 0.894 and 0.013 respectively. of model the model were 0.894 and 0.013 respectively. of the were 0.894 and 0.013 respectively. 0.94 0.94 0.90

0.90

C = -0.0001S2 + 0.0117S + 0.617

Cff = -0.0001S2 + 0.0117S + 0.617 R² = 0.894 R² = 0.894

0.86

0.86

0.82

0.82

15

15

25

25

35

45

55

35 Slump,45S [mm] 55 Slump, S [mm]

65

75

65

75

Figure 5. Relationship between slump and compaction factor.

•

Fresh Density

Figure 5. Relationship between slump and compaction factor. Figure 5. Relationship between slump and compaction factor.

• • Fresh Density Fresh Density The fresh density of RHA-inclusive PCC decreased by 3.8% from 2480 to 2386 kg/m3 as the RHA

Density = 2.480(RHA)0.024 R² = 0.990

2.45

2.50

2.40

Density = 2.480(RHA)0.024 R² = 0.990

2.45

2.35

2.40

2.30 0

2.35 2.30

5 10 15 RHA Content [%]

20

DensityDensity [g/cm3] [g/cm3]

Density [g/cm3]

Density [g/cm3]

content in the mix increased from 0 to 20%. The reduction in density might be 2386 due tokg/m the fact 3 as the The RHA-inclusive PCC decreased byfresh 3.8% to Thefresh freshdensity density of RHA-inclusive PCC decreased by 3.8% fromfrom 2480 2480 to 2386 kg/m3 as the RHA that the particle density of RHA (2.03) was lower than that of cement particle density (3.12). The RHA content theincreased mix increased 0 toThe 20%. The reduction in freshmight density might be due content in theinmix from 0from to 20%. reduction in fresh density be due to the fact to relationship between fresh density and RHA content (obtained by regression) is depicted in Figure that the particle density of RHA (2.03) was lower than that of cement particle density (3.12). The the fact that the particle density of RHA (2.03) was lower than that of cement particle density (3.12). 6a. R2 and SEE of the model were 0.990 and 0.008 respectively. relationship between freshfresh density and RHA (obtained by regression) depicted Figure in The relationship between density and content RHA content (obtained by regression) is in depicted The mix containing RAP exhibited relatively lower fresh density compared tois the mix containing 2 and SEE 2 and 6a. Rvirgin ofSEE the The model were 0.990 and 0.008 respectively. Figure 6a. Raggregates. of the model were 0.990 and 0.008 respectively. fresh density of RAP-inclusive mix decreased by 5.7% from 2480 to 2339 kg/m3 The mix containing RAP exhibited relatively density toto thethe mix containing as the RAP content inRAP the mix increased from 0 tolower 50%. fresh The reduction incompared density might be attributed The mix containing exhibited relatively lower fresh densitycompared mix containing 3 virgin aggregates. The fresh density of RAP-inclusive mix decreased by 5.7% from 2480 to 2339 kg/m the fact thatThe specific FRAP and CRAP were lowerbythan those of 2480 both to FVA and virgin to aggregates. freshgravities density of ofboth RAP-inclusive mix decreased 5.7% from 2339 kg/m3 as the RAP content in the mix increased from 0 to 50%. The reduction in density might be attributed Figure (obtained by regression) givesreduction the relationship between fresh as the CVA RAP respectively. content in the mix 6b increased from 0 to 50%. The in density might be density attributed to and RAP Content. R2 gravities and SEE ofofthe model were 0.993 and 0.005 respectively. to the fact that specific both FRAP and CRAP were lower than those of both FVA and the fact that specific gravities of both FRAP and CRAP were lower than those of both FVA and CVA CVA respectively. Figure 6b (obtained by regression) gives the relationship between fresh density respectively. Figure 6b (obtained by regression) gives the relationship between fresh density and RAP and RAP 2Content. R2 and SEE of the model were 0.993 and 0.005 respectively. Content. R2.50 and SEE of the model were 0.993 and 0.0052.50 respectively. Density = -0.003(RAP) + 2.474 R² = 0.993

2.45

2.50 2.40

Density = -0.003(RAP) + 2.474 R² = 0.993

2.45 2.35 2.30 2.40 2.25 2.35

2.30

0

20 40 RAP Content [%]

2.25 (b) RAP concrete 0 20 40 5 10 15 20 Figure 6. Fresh density for RHA and RAP concrete. RAP Content [%] RHA Content [%]

60

(a) RHA concrete

0

(a) RHA concrete

(b) RAP concrete

Figure 6. Fresh density for RHA and RAP concrete. Figure 6. Fresh density for RHA and RAP concrete.

60


10 of 24


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Density [cg/cm3]

The fresh density for mixes containing both RHA and RAP is graphically depicted in Figure 7. The fresh density for mixes containing both RHA and RAP is graphically depicted in Figure 7. It was observed that the mixes containing both RHA and RAP had lower fresh density compared to It was observed that the mixes containing both RHA and RAP had lower fresh density compared to the control mix. The mix incorporating 20% RHA + 30% RAP showed 3.6% reduction in fresh density the control mix. The mix incorporating 20% RHA + 30% RAP showed 3.6% reduction in fresh density relative to that of the control mix. The reduction in fresh density might be attributed to the collective relative to that of the control mix. The reduction in fresh density might be attributed to the collective effects pertaining to RHA and RAP as has been explained. effects pertaining to RHA and RAP as has been explained. 2.52 2.48 2.44 2.40 2.36 2.32

RHA and RAP Content [%] Figure 7. Fresh density for both RHA- and RAP-inclusive concrete. Figure 7. Fresh density for both RHA- and RAP-inclusive concrete.

3.2.2. Hardened Properties of Concrete 3.2.2. Hardened Properties of Concrete Table 9 shows the compressive strength (CS), tensile splitting strength (TSS), bulk dry density, Table 9 shows (w), the compressive strength tensile splitting (TSS), bulk dry density, water absorption permeable void spaces (CS), (v), and sorptivity (k) ofstrength the concrete. water absorption (w), permeable void spaces (v), and sorptivity (k) of the concrete. Table 9. Hardened properties of concrete. Table 9. Hardened properties of concrete.

CS (MPa) TSS (MPa) 7 Days 28 Days 28 Days w [%] v [%] K [mm/h1/2] CS (MPa) TSS (MPa) Control 17.34 (0.41) 26.72 (0.42) 2.13 (0.13) 7.24 (0.18) 17.33 1.961/2(0.02) w (%) v (%)(0.01) K (mm/h ) Mix Description 7 Days Days 28 Days RHA5% 19.42 (0.61) 27.9028(0.75) 2.19 (0.20) 7.19 (0.30) 17.09 (0.29) 1.92 (0.06) Control (0.41) 29.60 26.72 (0.42) 2.13 (0.06) (0.13) 7.24 (0.18) 17.33 (0.01) (0.02)(0.25) RHA10% 20.1317.34 (0.71) (0.73) 2.26 7.16 (0.18) 17.02 (0.60) 1.96 1.90 RHA5% (0.61) 30.05 27.90 (0.75) 2.19 (0.01) (0.20) 7.19 (0.30) 17.09 (0.29) (0.06)(0.78) RHA15% 21.2319.42 (0.41) (0.79) 2.29 7.15 (0.11) 16.90 (0.40) 1.92 1.80 RHA10% 20.13 (0.71) 29.60 (0.73) 2.26 (0.06) 7.16 (0.18) 17.02 (0.60) 1.90 (0.25) RHA20% 20.90 (0.80) 29.13 (0.32) 2.25 (0.09) 7.15 (0.01) 16.77 (0.03) 1.75 (0.11) RHA15% 21.23 (0.41) 30.05 (0.79) 2.29 (0.01) 7.15 (0.11) 16.90 (0.40) 1.80 (0.78) RAP10% 16.7520.90 (0.20) (0.90) 1.87 6.86 (0.30) 16.86 (0.18) 1.75 1.82 RHA20% (0.80) 20.87 29.13 (0.32) 2.25 (0.06) (0.09) 7.15 (0.01) 16.77 (0.03) (0.11)(0.20) RAP20% 16.1416.75 (0.40) (0.0.5) 1.69 6.74 (0.09) 16.61 (0.08) 1.82 1.30 6.86 (0.30) 16.86 (0.18) RAP10% (0.20) 19.56 20.87 (0.90) 1.87 (0.07) (0.06) (0.20)(0.02) RAP30% 14.5116.14 (0.40) (0.08) 1.50 6.65 (0.19) 16.28 (0.64) 1.30 1.16 6.74 (0.09) 16.61 (0.08) RAP20% (0.40) 17.86 19.56 (0.0.5) 1.69 (0.01) (0.07) (0.02)(0.13) 6.65 (0.19) 16.28 (0.64) RAP30% (0.40) 16.36 17.86 (0.08) 1.50 (0.10) (0.01) (0.13)(0.03) RAP40% 12.7314.51 (0.60) (0.07) 1.39 6.54 (0.20) 15.98 (0.47) 1.16 0.91 6.54 (0.20) 15.98 (0.47) RAP40% (0.60) 14.87 16.36 (0.07) 1.39 (0.04) (0.10) (0.03)(0.01) RAP50% 11.0812.73 (0.30) (0.12) 1.26 6.45 (0.30) 15.68 (0.65) 0.91 0.69 6.45 (0.30) 15.68 (0.65) RAP50% 11.08 (0.30) 14.87 (0.12) 1.26 (0.04) 0.69 (0.01) [5RHA + 10RAP]% 18.37 (0.75) 23.00 (0.68) 2.05 (0.03) 6.69 (0.15) 16.94 (0.16) 1.88 (0.27) [5RHA + 10RAP]% 18.37 (0.75) 23.00 (0.68) 2.05 (0.03) 6.69 (0.15) 16.94 (0.16) 1.88 (0.27) [5RHA + 20RAP]% 16.90 (0.38) 21.42 (0.47) 1.85 (0.10) 6.65 (0.04) 16.79 (0.05) 1.81 (0.08) [5RHA + 20RAP]% 16.90 (0.38) 21.42 (0.47) 1.85 (0.10) 6.65 (0.04) 16.79 (0.05) 1.81 (0.08) [5RHA[5RHA + 30RAP]% (0.84)(0.84) 19.42 (0.54) 1.77 6.62 (0.08) 16.53 (0.08) 1.69 1.69 + 30RAP]% 15.00 15.00 19.42 (0.54) 1.77 (0.04) (0.04) 6.62 (0.08) 16.53 (0.08) (0.05)(0.05) [10RHA + 10RAP]% (0.84)(0.84) 25.12 (0.66) 2.12 6.68 (0.01) 16.92 (0.11) 1.80 1.80 [10RHA + 10RAP]% 19.66 19.66 25.12 (0.66) 2.12 (0.06) (0.06) 6.68 (0.01) 16.92 (0.11) (0.55)(0.55) [10RHA + 20RAP]% 17.00 17.00 23.62 (0.07) 2.09 (0.01) (0.01) 6.49 (0.18) 16.72 (0.24) (0.18)(0.18) [10RHA + 20RAP]% (0.97)(0.97) 23.62 (0.07) 2.09 6.49 (0.18) 16.72 (0.24) 1.65 1.65 [10RHA + 30RAP]% 16.65 (0.38) 4(0.61) 1.80 (0.03) 6.20 (0.10) 16.64 (0.06) (0.17) [10RHA + 30RAP]% 16.65 (0.38) 20.420.4 4(0.61) 1.80 (0.03) 6.20 (0.10) 16.64 (0.06) 1.41 1.41 (0.17) [15RHA + 10RAP]% 20.02 (0.55) 27.62 (0.54) 2.22 (0.25) 6.33 (0.06) 16.78 (0.02) 1.87 (0.35) [15RHA + 10RAP]% 20.02 (0.55) 27.62 (0.54) 2.22 (0.25) 6.33 (0.06) 16.78 (0.02) 1.87 [15RHA + 20RAP]% 19.54 (0.24) 25.01 (0.56) 2.10(0.03) 6.32 (0.05) 16.76 (0.10) 1.61 (0.07)(0.35) [15RHA + 20RAP]% (0.24)(0.13) 25.01 (0.56) 2.10(0.03) 6.32 (0.05) 16.76 (0.10) 1.47 1.61 [15RHA + 30RAP]% 19.54 17.14 21.69 (0.12) 1.89 (0.01) 6.30 (0.07) 16.60 (0.17) (0.29)(0.07) [20RHA + 10RAP]% 17.14 18.95 25.48 (0.14) 2.15 (0.01) (0.05) 6.30 (0.13) 16.81 (0.45) (0.46)(0.29) [15RHA + 30RAP]% (0.13)(0.50) 21.69 (0.12) 1.89 6.30 (0.07) 16.60 (0.17) 1.92 1.47 [20RHA + 20RAP]% 22.19 (0.92) 1.99 (0.01) 6.25 (0.08) 16.88 (0.52) (0.04) [20RHA + 10RAP]% 18.95 17.30 (0.50)(1.04) 25.48 (0.14) 2.15 (0.05) 6.30 (0.13) 16.81 (0.45) 1.89 1.92 (0.46) [20RHA + 30RAP]% 16.38 (0.43) 20.20 (0.93) 1.79 (0.06) 6.25 (0.11) 16.48 (0.03) 1.65 (0.06) [20RHA + 20RAP]% 17.30 (1.04) 22.19 (0.92) 1.99 (0.01) 6.25 (0.08) 16.88 (0.52) 1.89 (0.04) Average value for(0.43) three replicate and(0.06) standard 6.25 deviation [20RHA + 30RAP]% 16.38 20.20 specimens (0.93) 1.79 (0.11) (in parentheses). 16.48 (0.03) 1.65 (0.06) Mix Description

Average value for three replicate specimens and standard deviation (in parentheses).

• •Compressive Strength (CS) Compressive Strength (CS) test resultsofofPCC PCCmixtures mixturescontaining containing RHA RHA are thethe CSCS test results are depicted depictedin inFigure Figure8a. 8a.RHA RHAenhanced enhanced 7-days 12.0, 16.1,22.4, 22.4,and and20.5% 20.5%at at 5, 5, 10, 10, 15, and relative to to thethe 7-days CSCS byby 12.0, 16.1, and 20% 20%RHA RHAcontent contentrespectively respectively relative control mix.Similarly, Similarly,the the28-days 28-daysCS CS was was also also enhanced enhanced by In In this study, control mix. by4.4, 4.4,10.8, 10.8,12.5, 12.5,and and9.0%. 9.0%. this study, the highest 7 and 28-days CS gain was observed at 15% RHA content. the highest 7 and 28-days CS gain was observed at 15% RHA content. The 7 and daysCS CStest testresults resultsof of RAP RAP inclusive inclusive concrete AA dramatic The 7 and 2828days concreteare aredepicted depictedininFigure Figure8b. 8b. dramatic reduction in CS was observed with an increment of RAP content in the concrete mixtures. The 7 and reduction in CS was observed with an increment of RAP content in the concrete mixtures. The 7 and


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11 of 24

28-days CS decreased by 36.1 and 44.3%, relative to the control mix, respectively, at 50% RAP content. CS decreased byresults 36.1 andfound 44.3%,in relative to thestudies control [23,28,29]. mix, respectively, at 50% RAPincontent. This Buildings is28-days consistent with the previous The reduction CS might be 2018, 8, x FOR PEER REVIEW 11 of 24 This is consistent with the results found in previous studies [23,28,29]. The reduction in CS might be attributed to the collective effect of higher porosity and asphalt cohesion failure, which occurs instead attributed to the collective effect of higher porosity and asphalt cohesion failure, which occurs instead CS decreased 36.1 and 44.3%, relative to the control mix, respectively, at 50% content. of the28-days adhesive failure ofby the cement-asphalt interface or cohesive failure of the ITZ RAP [26,27].

CS [MPa] CS [MPa]

CS [MPa] CS [MPa]

of the adhesive failure of the cement-asphalt interface or cohesive failure of the ITZ [26,27]. This is consistent with the results found in previous studies [23,28,29]. The reduction in CS might be attributed cohesion failure, which occurs instead 35 to the collective effect of higher porosity and asphalt 30 of the adhesive failure of the cement-asphalt interface or cohesive failure of the ITZ [26,27]. 7-day 28-day 7-day 28-day 25 30 35 30 20 25 7-day 28-day 7-day 28-day 25 30 15 20

25 15 20

0

5 10 RHA [%]

15

20

20 10 15

0

10

20

30

40

50

RAP Content [%]

10 (a) RHA concrete RAP concrete 0 (b)10 20 30 40 50 0 5 10 15 20 RAP Content [%] Figure RHA [%]8. Compressive strength for RHA and RAP concrete. Figure 8. Compressive strength for RHA and RAP concrete. (a) RHA concrete (b) RAP concrete The relationship between RHA content and the 28-days CS given in Figure 9a (obtained by Figuremodel 8.RHA Compressive strength for RHA and RAP concrete. regression). The regression had R2 and SEEthe values of 0.950 0.444inrespectively. CS The relationship between content and 28-days CSand given Figure 9a The (obtained by decreased linearly with RAP content as shown in Figure 9b. A similar trend was found by previous 2 regression). The regression model had R and SEE values of 0.950 and 0.444 respectively. The CS The relationship between analysis, RHA content 28-days CS given in 9a (obtained by study [61]. From the regression linearand formthe relationship, Equation (3) Figure was found. R2 and SEE decreased linearly with RAP content as shown in Figure 9b. A similar trend was found by previous 2 and SEE values of 0.950 and 0.444 respectively. The CS regression). regression model values of theThe model were 0.902 andhad 1.476Rrespectively. studydecreased [61]. From the regression analysis, relationship, Equation (3) was found. R2 and SEE linearly with RAP content aslinear shownform in Figure 9b. A similar trend was found by previous − 0.21× RAP (3) c = f co values of the were 0.902 and 1.476f linear respectively. study [61].model From the regression analysis, form relationship, Equation (3) was found. R2 and SEE values were 0.902 1.476 respectively. the 28-days CS ofand the RAP-inclusive concrete in MPa; f is the 28-days CS of the mix where:off theismodel 15

c

f c = f co − 0.21 × RAP

co

with no RAP content in MPa; and RAP fisc the asphalt pavement content in %. = freclaimed co − 0.21× RAP

(3)

(3)

where: f c is the CS ofCS the concrete 28-days 30 ininMPa; is fthe 28-days of2 RAP-inclusive the RAP-inclusive concrete MPa;f cof cois the is the 28-daysCS CSof ofthe the mix mix with where: f c 28-days c = -0.0156(RHA) + 0.451RHA + fc = in fco-0.21(RAP) no RAP content in MPa; and RAP is the reclaimed asphalt pavement content %. 26.504 35 CS, fc [MPa] CS, fc [MPa]

CS, fc [MPa] CS, fc [MPa]

with no RAP content in MPa; and RAP is the reclaimed25 asphalt pavement content in %. R² = 0.95 R² = 0.902 20 30 30 fc = -0.0156(RHA)2 + 0.451RHA + fc = fco-0.21(RAP) 15 26.504 35 25 25 10 R² = 0.95 R² = 0.902 20 30 5 20 15 0 20 40 60 0 10 20 30 25 RAP Content [%] RHA Content [%] 10 (b) RAP concrete (a) RHA concrete 5 20 0 content and 20 CS. 40 60 between RHA and RAP 0 10Figure 9. Relationship 20 30 RAP Content [%] RHA Content [%]

RAP concreteconcrete at 7 and Figure 10 portrays compressive strength of both RHA- and(b) RAP-inclusive (a) RHAthe concrete 28-days. The partial replacement of cement by RHA improved the CS of RAP-inclusive concrete Figure 9. Relationship between RHA and RAP content and CS. Figurebe 9. credited Relationship between RHA and content and CS. moderately. This might to the development of RAP additional C-S-H gel due to the high reactive silica content of RHA and/or filler effect. Mixtures incorporating (10RHA + 10RAP)%, Figure 10 portrays the compressive strength of both RHA- and RAP-inclusive concrete at 7 and (15RHA + 10RAP)%, (15RHA + 20RAP)% and (20RHA + 10RAP)% showed comparable strength. The Figure 10 portrays compressive strength of both RHA- and RAP-inclusive concrete at 7 and 28-days. The partial the replacement of cement by RHA improved the CS of RAP-inclusive concrete maximum strength (27.62 MPa) obtained at 15% RHA and 10% RAP combination. Thus, it is evident moderately. This might be credited to the development of additional C-S-H gel due to the high 28-days. The partial replacement of cement by RHA improved the CS of RAP-inclusive concrete that treatment of RAP by RHA possibly will be an effective way to enhance the mechanical properties reactive silica content be of credited RHA and/or filler effect. Mixtures incorporating (10RHA 10RAP)%, moderately. This might to the development of additional C-S-H gel +due to the high of RAP incorporating concrete. (15RHA + 10RAP)%, (15RHA + 20RAP)% and (20RHA + 10RAP)% showed comparable strength. The reactive silica content of RHA and/or filler effect. Mixtures incorporating (10RHA + 10RAP)%, maximum strength (27.62 MPa) obtained at 15% RHA and 10% RAP combination. Thus, it is evident (15RHA + 10RAP)%, (15RHA + 20RAP)% and (20RHA + 10RAP)% showed comparable strength. that treatment of RAP by RHA possibly will be an effective way to enhance the mechanical properties The maximum strength (27.62 MPa) obtained at 15% RHA and 10% RAP combination. Thus, it is of RAP incorporating concrete.

evident that treatment of RAP by RHA possibly will be an effective way to enhance the mechanical properties of RAP incorporating concrete.




CS [MPa] CS [MPa]

20

12 of 24

7-day

30

30

12 of 24

12 of 24

28-day

7-day

28-day

10 20 0 10

0 RAH and RAP Content [%]

RAH and RAP Content [%]

Figure10. 10.Compressive Compressive strength for RHA both and RHA and RAP inclusive Figure strength for both RAP inclusive concrete. concrete. Tensile Splitting Strength (TSS) Figure 10. Compressive strength for both RHA and RAP inclusive concrete. • • Tensile Splitting Strength (TSS)

2.0

TSS [MPa]

STS [MPa] STS [MPa]

TSS [MPa]

The 28-days TSS of the mixtures containing RHA is represented in Figure 11a. There was a 28-days TSS of the mixtures RHA is represented in Figure 11a. There was a gradual • TheTensile Splitting (TSS)containing gradual increment in TSSStrength with increasing the RHA content up to 15%. The TSS peaked at 15% RHA increment in TSS with increasing the RHA content up 15%.inclusive The TSSconcrete peakedshowed at 15%better RHA and then and then 15%mixtures RHA. However, still RHA 20%toRHA Thedecreased 28-days beyond TSS of the containing is represented in Figure 11a. There was a decreased beyond 15% However, stillin 20% RHA inclusive showed better strength strength than the control mix.with The increment strength was 2.8, 7.5, 5.6% 5, 10, 15, and gradual increment in RHA. TSS increasing the RHA content up6.1, to concrete 15%.and The TSSatpeaked at 15% RHAthan 20% RHA content respectively, relative to the control mix. TSS increased in a second-order the control mix. The increment in strength was 2.8, 6.1, 7.5, and 5.6% at 5, 10, 15, and 20% RHA content and then decreased beyond 15% RHA. However, still 20% RHA inclusive concrete showed better 2 = 0.96 and SEE = 0.018). The trend for TSS polynomial with RHA content as depicted in Figure 11a (R respectively, relative to the control mix. TSS increased in a second-order polynomial with RHA content strength than the control mix. The increment in strength was 2.8, 6.1, 7.5, and 5.6% at 5, 10, 15, and was similar to that of CS. The increment in TSS might be ascribed to the development extra of C-S-H 2 as depicted in content Figure 11a (R = 0.96relative and SEE 0.018). The trend TSS wasinsimilar to that of CS. 20% RHA respectively, to = the control mix. TSSfor increased a second-order gel due to the active silica content of RHA. RHA content as depicted in Figure 11a (R2 = 0.96 = 0.018). Thetotrend for TSSsilica Thepolynomial increment with in TSS might be ascribed to the development extraand of SEE C-S-H gel due the active TSS decreased linearly with increasing the RAP content as can be seen in Figure 11b (R2 = 0.98 was similar to that of CS. The increment in TSS might be ascribed to the development extra of C-S-H content of RHA. and SEE = 0.052). TSS decreased by 12.2, 20.7, 29.6, 34.7, and 40.8% for 10, 20, 30, 40, and 50% RAP gel due to the active silica content of RHA. the RAP content as can be seen in Figure 11b (R2 = 0.98 TSS decreased linearly with increasing respectively. The decrement pattern for TSS was similar to that of the CS. However, the rate of2 TSS decreased linearly with increasing the RAP 34.7, content as40.8% can be seen in20, Figure 11band (R = 0.98 and SEE =reduction 0.052). TSS decreased by 12.2, 10,is 30, 40, strength in the TSS mixtures was 20.7, lower29.6, compared and to the CS’s.for This consistent with 50% RAP and SEE = 0.052). TSS decreased by 12.2, 20.7, 29.6, 34.7, and 40.8% for 10, 20, 30, 40, and 50% RAP previous study respectively. The[26]. decrement pattern for TSS was similar to that of the CS. However, the rate of strength respectively. The decrement pattern for TSS was similar to that of the CS. However, the rate of reduction in the TSS mixtures was lower compared to the CS’s. This is consistent with previous strengthf reduction in the This is+ 2.23 consistent with 2 TSS mixtures was lower 2.2 compared to the fct=CS’s. -0.17(RAP) study2.3 [26]. ct = -0.018(RHA) + 0.14(RHA) + 1.99 previous study [26]. 1.9 R² = 0.98 R² = 0.96 2.2 2 + 0.14(RHA) + 1.99 2.2 f f = -0.018(RHA) 1.6 ct= -0.17(RAP) + 2.23 ct 2.3 2.1 1.3 1.9 R² = 0.98 R² = 0.96 2.2 2.0 1.0 1.6 5 10 15 20 2.1 0 0 10 20 30 40 50 1.3 RHA Content [%] RAP Content [%] (a) RHA concrete (b) RAP concrete 1.0 0 5 10 15 20 0 10 20 30 40 Figure 11. Splitting RHA Content [%] strength for RHA and RAP concrete. RAP Content [%]

50

(a) RHA concrete (b) RAP concrete From regression analysis, a power form relationship was found between the 28 days TSS and CS of RHA inclusive concrete as shown in Equation (4) and Figure 12a (R2 =0.99 and SEE= 0.004). Figure11. 11.Splitting Splitting strength strength for concrete. Figure forRHA RHAand andRAP RAP concrete. 0.6

(4) = 0.28× f From regression analysis, a powerfform relationship was found between the 28 days TSS and CS ct

c

From regression analysis, a power form relationship was found 2between the 28 days TSS and CS of RHA concrete as shown in Equation (4) and Figureconcrete 12a (R =0.99 and SEE= 0.004). 2 =0.99 where: and fct are the 28-days CS and of the RHA inclusive MPa f c inclusive of RHA inclusive concrete as shown inTSS Equation (4) and Figure 12a (Rrespectively, andinSEE= 0.004). 0.6 The exponential form relationship was found = between 28 days TSS and CS of RAP inclusive (4) 0.28 the 0.6 ct SEE = 0.0526). concrete as presented in Figure 12b (R2 = 0.97 and f ct = 0.28× f c c Equations (5) and (6) were obtained by regression. where: f c and fct are the 28-days CS and TSS of the RHA inclusive concrete respectively, in MPa

f

×f

(4)

where: f c and fct are the 28-days CS and TSS of the RHA inclusive concrete respectively, in MPa. The exponential form relationship was found between the 28 days TSS and CS of RAP inclusive The exponential form relationship between the Equations 28 days TSS and(6) CSwere of RAP inclusive concrete as presented in Figure 12b (R2 was = 0.97found and SEE = 0.0526). (5) and obtained 2 concrete as presented in Figure 12b (R = 0.97 and SEE = 0.0526). Equations (5) and (6) were obtained by regression. by regression. f ct = −0.17 × RAP + 2.23 (5)


13 of 24


13 of 24

f ct = −0.17 × RAP + 2.23


(5)

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0.93 0.93 (6) f ct 0.105× f ct== 0.105 × ff cc f ct = −0.17 × RAP + 2.23 (5) where: are the 28-days and the RAP inclusive concrete respectively, MPa where: f c andf cf ctand are the CS andCS TSS ofTSS theof RAP inclusive concrete respectively, ininMPa. f 28-days ct

2.25 2.30 2.20 2.25 2.15 2.20 2.10 2.15 26

f

1.9 2.5

R² = 0.99 fct = 0.28fc0.6 R² = 0.99

1.6 2.2

R² = 0.97 fct = 0.105fc0.93

1.3 1.9

R² = 0.97

1.0 1.6

27

28

29

30

31

CS, fc [MPa]

2.10

(6)

2.5 are the 28-days CS and TSS of the RAP inclusive concrete0.93 respectively, in MPa fct = 0.105fc fct = ct0.28fc0.6 2.2 TSS, fct [MPa] TSS, fct [MPa]

STS, fct [MPa] STS, fct [MPa]

2.30 where: f c and

0.93

f ct = 0.105× f c

(6)

1.3 10 1.0

15 20 CS, fc [MPa]

25

30

(b) RAP concrete 15 20 25 30 FigureCS, 12. Relationship between CS and TSS for RHA and CS, RAPfc concrete. [MPa] fc [MPa] Figure 12. Relationship between CS and TSS for RHA and RAP concrete. (b) RAP concrete (a) RHA concrete The experimental results of TSS of both RHA and RAP inclusive PCC and its relationship with 12. Relationship between CSand and TSS RHA and by RAP concrete. The experimental results of and TSS 14 of respectively. both RHA inclusive PCC and relationship with CS CS are depicted inFigure Figures 13 TSSRAP wasforimproved 4.7% atits 15% RHA and 10% RAP content compared to the specimen’s which was similar the15% CS results. TSS10% and RAP are depicted in Figures 13 and 14control respectively. TSSresult was improved by 4.7%toat RHA and Thepositively experimental results of2 =TSS of and bothSEE RHA and RAP inclusive PCC andasitsshown relationship with CS were correlated 0.928 = 0.065) with a power function in Equation content compared to the control(Rspecimen’s result which was similar to the CS results. TSS and CS CS are depicted in Figures 13 and 14 respectively. TSS was improved by 4.7% at 15% RHA and 10% were (7). positively correlated (R2 = 0.928 and SEE = 0.065) with a power function as shown in Equation (7). RAP content compared to the control specimen’s result which was similar to the CS results. TSS and 0.68 = 0.235 × f with f ct SEE (7) CS were positively correlated (R2 = 0.928 and = 0.065) a power function as shown in Equation c 26

(a) RHA concrete 27 28 29

30

10

31

f ct = 0.235 × f c0.68

(7). Buildings 2018, 8, x FOR PEER REVIEW

TSS, fct (MPa) TSS (MPa) TSS (MPa)

2.5 2.0

0.68

f ct = 0.235 × f c

(7)

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(7)

2.5

1.5

2.5 2.0 1.0

2.0 1.5 0.5

1.5 1.0 0.0

1.0 0.5 0.5

0.0

0.0

RHA and RAP Content (%)

Figure 13. Tensile splitting strength for RHA and RAP RHA and RAP Content (%) inclusive concrete.

RHA and RAP Content (%) Figure 2.413. Tensile splitting strength for RHA- and RAP-inclusive concrete. Figure 13. Tensile splitting strength for RHA and RAP inclusive concrete. TSS, fct (MPa) TSS, fct (MPa) TSS, fct (MPa)

Figure 13. Tensile splitting RHA and RAP inclusive concrete. 0.680 fctstrength = 0.235fcfor 2.3 2.2 R² = 0.928 2.2 2.4 fct = 0.235fc0.680 = 0.928 0.680 2.0 2.1 fct =R² 0.235fc 2.2 R² = 0.928 2.0

1.8 1.9 2.0 1.8 1.6 1.7 1.8 15 17 19 21 23 25 27 29 1.6 CS, fc (MPa) 17 19 21 23 25 27 29 1.6 15 Figure 14. Relationship and for 23 RHA and25RAP inclusive concrete. fcCS (MPa) 15 17between 19TSSCS, 21 27 29

CS, f (MPa)

Figure. 14. Relationship between TSS and cCS for RHA- and RAP-inclusive concrete.



Figure 14. Relationship between TSS and CS for RHA and RAP inclusive concrete.

Figure 14. Relationship between TSS and CS for RHA and RAP inclusive concrete. Water Absorption

The water absorption after immersion (wi) and after immersion and boiling (wi&b) decreased with increasing RHA content as shown in Figure 15a. The minimum relative percentage of reduction in water absorption were 0.7 and 1.2% for wi and wi&b respectively at 5% RHA content whereas, the maximum relative percentage of reduction in water absorption were 1.3, and 2.0% for wi, and wi&b respectively at 20% RHA content. This reduction could be due to the fact that the finer HHA particles might have filled the pore spaces in the concrete. The water absorption is correlated to RHA content in a power function as shown in Equations (8) and (9). The wi&b values are slightly higher than those


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• Water Absorption Buildings 2018, 8, x FOR PEER REVIEW

14 of 24

The water absorption after immersion (wi ) and after immersion and boiling (wi&b ) decreased • Water Absorption with increasing RHA content as shown in Figure 15a. The minimum relative percentage of reduction in water absorptions were 0.7 and for wi(w and w after respectively 5%boiling RHA (w content, whereas the The water absorption after 1.2% immersion i) andi&b immersion at and i&b) decreased maximum relative percentage in water absorption were 1.3,percentage and 2.0%offor wi , and wi&b with increasing RHA contentof asreduction shown in Figure 15a. The minimum relative reduction in wateratabsorptions 0.7 and 1.2% for wi andcould wi&b respectively at 5% RHA whereas respectively 20% RHAwere content. This reduction be due to the fact thatcontent, the finer HHAthe particles maximum relative percentage of reduction in water absorption were 1.3, and 2.0% for w i , and w i&b might have filled the pore spaces of the concrete. The water absorption is correlated to RHA content in respectively at 20% RHA content. This reduction could be due to the fact that the finer HHA particles a power function as shown in Equations (8) and (9). The wi&b values are slightly higher than those might have filled the pore spaces of the concrete. The water absorption is correlated to RHA content of wi . in a power function as shown in Equations (8) and (9). The wi&b values are slightly higher than those The water absorption of RAP inclusive concrete decreased with increasing RAP content, as can of wi. be seen from Figureabsorption 15b. Theofminimum wi concrete and wi&b were 6.4, and 6.9%, with percentage The water RAP inclusive decreased with increasing RAP relative content, as can reduction of 10.94 and 6.20% respectively ati 50% RAP content. The reductions in water absorption be seen from Figure 15b. The minimum w and w i&b were 6.4, and 6.9%, with relative percentage mightreduction be due toofthe lower waterrespectively absorptionatof50% RAP aggregates compared to in that of virgin aggregate. 10.94 and 6.20% RAP content. The reductions water absorption mightpossible be due toreason the lower waterbe absorption of RAP aggregates compared to that of virgin aggregate. The other might due to the melted asphalt and dust layer engulfed around the The other reason might be concrete due to the[62]. melted dust layer engulfedtoaround the aggregate couldpossible fill void spaces in the Theasphalt water and absorption is related RAP content in aggregate could fill void spaces in the concrete [62]. The water absorption is related to RAP content a power function as shown in Equations (10) and (11). The wi&b values were somewhat higher than in a power function as shown in Equations (10) and (11). The wi&b values were somewhat higher than those of wi . those of wi.

wi = 7.36(RHA)-0.012 R² = 0.973 wi&b = 7.24(RHA)-0.008 R² = 0.983

7.4 7.3 7.3 7.2 7.2 7.1 7.1

7.6 Water absoption, w [%]

Water absorption, w [%]

7.4

wi = 7.38(RAP)-0.033 R² = 0.965 wi&b = 7.214(RAP)-0.062 R² = 0.989

7.4 7.2 7.0 6.8 6.6 6.4 6.2

0


(a) RHA inclusive concrete

20

0

10

20 30 40 RAP Content [%]

50

(b) RAP inclusive concrete

Figure 15. Water absorption by RHA and RAP concrete.

Figure 15. Water absorption by RHA and RAP concrete.

w i = 7.36× RHA wi = 7.36 × RHA−0.012 −0.008 w i&b = 7.24× RHA −0.008 wi&b = 7.24 × RHA − 0.033 w i = 7.38× RAP wi = 7.38 × RAP−−0.033 0.062 −0.012

w i&b = 7.214×RAP wi&b = 7.214 × RAP−0.062

(8)

(8)

(9) (10) (11)

(9) (10) (11)

where: w i is the water absorption after immersion in %; wi&b is the water absorption after where:immersion wi is the and water absorption after immersion %;content wi&b isinthe absorption after immersion boiling; RHA and is the rice huskin ash %; water and RAP is reclaimed asphalt pavement content %.the rice husk ash content in %; and RAP is reclaimed asphalt pavement and boiling; RHA andinis content inThe %. water absorption of RHA and RAP inclusive concrete at 28 days are depicted in Figure 16. Both w i and wi&b decreased as RHA and RAP content increased. The relative percentage reduction The water absorption of RHA and RAP inclusive concrete at 28 days are depicted in Figure 16. of wi&b (13.7%) was lower than both that of RHA inclusive concrete (1.30%) and RAP inclusive Both wi and wi&b decreased as RHA and RAP content increased. The relative percentage reduction of concrete (10.94%). The least wi, and wi&b found were 6.25, and 7.06% respectively at 20% RHA and wi&b (13.7%) was lower than both that of RHA inclusive concrete (1.30%) and RAP inclusive concrete 30% RAP combination. The maximum relative percentage of reduction in absorption were 13.7 and (10.94%). The least wi , and least wi&babsorptions. found wereThe 6.25, and 7.06% respectively at might 20% RHA and 4.2% for the respective reduction of water absorption be due to 30% the RAP combination. maximum relative percentage of reduction in absorption were 13.7 and 4.2% for the collectiveThe effect of RHA and RAP discussed above.

respective least absorptions. The reduction of water absorption might be due to the collective effect of RHA and RAP discussed above.


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Water absoption [%] Water absoption [%]


15 of 24

7.5

Wi

Wi&b


15 of 24

7.0

7.5 6.5

Wi

Wi&b

7.0 6.0 6.5 5.5 6.0 5.5

RHA and RAP Content [%] Figure 16. Water absorption by both RHA- and RAP-inclusive concrete.

•

Figure 16. Water absorption by both RHA- and RAP-inclusive concrete. RHA and RAP Content [%] Volume of Permeable Void Spaces in Hardened Concrete

• Volume ofvolume Permeable Void Spaces in Hardened Concrete Figure 16. Water absorption by RHAand RAP-inclusive concrete.decreased slightly The of permeable void spaces inboth hardened RHA inclusive concrete withvolume increment of RHA. The voids decreased by 3.22% from 17.32 toconcrete 16.77% as the RHAslightly content with of Permeable permeable void spaces hardened RHA inclusive decreased •The Volume of Spaces inin Hardened Concrete increased from 0 to 20%. Void The reduction in void space might be attributed to the finer siliceous increment of RHA. The voids decreased by 3.22% from 17.32 to 16.77% as the RHA content increased particles which could fill a portion void in spaces that exist the concrete matrix. As can slightly be seen The volume of permeable void of spaces hardened RHAininclusive concrete decreased from 0 to 20%. The reduction in void space might be attributed to the finer siliceous particles which from increment Figure 17aofand Equation (12), adecreased power function wasfrom found as atogood fit (R 0.970 and SEE = with RHA. The voids by 3.22% 17.32 16.77% as2 =the RHA content could0.026) fill a to portion of void spaces that in the concrete matrix. As can be seen from Figure 17a and correlate RHA content withexist the voids. increased from 0 to 20%. The reduction in void space might be attributed to the finer siliceous 2 = 0.970 and SEE = 0.026) to correlate RHA Equation (12), a power function was found asspaces a good fit exist (R Figure 17bcould depicts volume permeable void spaces in RAP inclusive concrete. is seen clear particles which fill the a portion ofofvoid that in the concrete matrix. As canItbe content with voids. from the the figure that Equation voids decreased exponentially an increment of fit RAP The SEE voids from Figure 17a and (12), a power function with was found as a good (R2content. = 0.970 and = decreased by 9.47% from 17.32 to 15.68% as the RAP increased from 0 toconcrete. 50%. The It reduction Figure depicts thecontent volume of permeable void content spaces in RAP inclusive is clear from 0.026) to17b correlate RHA with the voids. in void space could be due the lower water of RAP aggregates compared toisthat of Figure 17b depicts the to volume of permeable void spaces inof RAP inclusive concrete. It clear the figure that voids decreased exponentially withabsorption an increment RAP content. The voids decreased virgin aggregates and oozed out asphalt film which could fill a portion voids spaces in concrete. from the figure that voids decreased exponentially with an increment of RAP content. The voids by 9.47% from 17.32 to 15.68% as the RAP content increased from 0 to 50%. The reduction in void space As beto seen from Equation an exponential function obtained from regression analysis to by 9.47% from 17.32(13), to 15.68% asof theRAP RAP contentwas increased from 0 to 50%. reduction coulddecreased becan due the lower water absorption aggregates compared to that ofThe virgin aggregates correlate RAP could content voids (R2 =water 0.995 absorption and SEE = 0.024). in void space bewith due the to the lower of RAP aggregates compared to that of

and oozed out asphalt film which could fill a portion of voids spaces in concrete. As can be seen from virgin aggregates and oozed out asphalt film which could fill a portion of voids spaces in concrete. Equation (13), an exponential function was obtained from regression analysis to correlate RAP content 17.5 As can be seen2 from Equation (13), an exponential function was obtained fromvregression analysis to = 17.6e-0.019RAP 17.3 (R = 0.995 and -0.019 with the voids SEE = 0.024). v = 17.33 (RAP) 2 17.0

R² = 0.995

17.1

R² = 0.97

16.9 17.3 16.7 17.1

v = 17.33 (RAP)-0.019 R² = 0.97

16.5 16.9 16.7

0

Voids, v Voids, [%] v [%]

Voids, v Voids, [%] v [%]

correlate RAP content with the voids (R = 0.995 and SEE = 0.024).

v = 17.6e-0.019RAP R² = 0.995 10 20 30 40 RAP Content [%]

50

(b)0RAP10 inclusive 20 concrete 30 40 5 10 15 20 Figure 17. Voids in RHA and RAP concrete. RAP Content [%] RHA Content [%]

50


20

16.5 (a) RHA inclusive concrete

0

16.5 17.5 16.0 17.0 15.5 16.5 15.0 16.0 15.5 15.0


v = 17.33×RHA −0.019

0


Figure 17. Voids in RHA and RAP concrete.

Figure 17. Voids in RHA−0.019 and×RAP RAP concrete.

v = 17.36×e

(12) (13)

−0.019 v = 17.33 where: v is the volume of permeable void spaces×RHA %; and RHA is the rice husk ash content (12) in %; −0.019 v = 17.33 ×in RHA (12) and RAP is the reclaimed asphalt pavement content −in %. ×RAP (13) v = 17.36×e−0.019 ×RAP A relationship between voids and absorption RHA concrete was determined as shown (13) v water = 17.36 × e 0.019for in Figure 18a and Equations (14) and (15). According to the correlation found, water absorption where: v is the volume of permeable void spaces in %; and RHA is the rice husk ash content in %; where:v is the volume of permeable void spaces in %; and RHA is the rice husk ash decreased as the void in concrete Water absorption by RAP content concretein %; and RAP is exponentially the reclaimed asphalt pavement content decreased. in %. and RAP theexponentially reclaimed asphalt pavement content in %. decreased with voids in water concrete as shown inRHA Figure 18b, and Equations (16)as and (17). Aisrelationship between voids and absorption for concrete was determined shown

A relationship between voids RHA concrete was determined as shown in Figure 18a and Equations (14)and andwater (15). absorption According tofor the correlation found, water absorption in Figure 18a and Equations According to theWater correlation found, water absorption decreased exponentially as (14) the and void (15). in concrete decreased. absorption by RAP concrete decreased exponentially with voids in concrete as shown in Figure 18b, and Equations (16) and (17).


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decreased exponentially as the void in concrete decreased. Water absorption by RAP concrete decreased exponentially with voids in concrete as shown in Figure 18b, and Equations (16) and (17). 16 of 24

absorption WaterWater absorption [%] [%]

Buildings 7.402018, 8, x FORwPEER= REVIEW 3.87e0.037v i&b

R² = 0.93 wi&b = 3.87e0.037v R² = 0.93

7.35 7.40 7.30 7.35 7.25 7.30 7.20 7.25

wi = 4.79e0.024v R² = 0.91 wi = 4.79e0.024v R² = 0.91 17.30 17.50

absorpition WaterWater absorpition [%] [%]


16 of 24

7.6 7.6 7.2 7.2 6.8

wi&b = 3.89e0.037v R² = 0.98 wi&b = 3.89e0.037v R² = 0.98

wi = 2.25e0.067v R² = 0.95 wi = 2.25e0.067v 6.4 6.0 R² = 0.95 15.5 16.0 16.5 17.0 6.0 Permeable Voids, v [%] 15.5 16.0 16.5 17.0 (b) RAP inclusive concrete Permeable Voids, v [%] 6.8 6.4

7.15 7.20 7.10 7.15 16.70 16.90 17.10 7.10 Permiable Voids,v [%] 16.70 16.90 17.10 17.30 17.50 (a) RHA inclusive concrete Permiable Voids,v [%] FigureRHA 18. Relationship between water absorption and voids RHA and RAP concrete. inclusivebetween concrete (b)for RAP Figure(a) 18. Relationship water absorption and voids for inclusive RHA andconcrete RAP concrete. Figure 18. Relationship between water absorption and voids for RHA and RAP concrete.

0.024× v (14) w i = 4.79×e wi = 4.79 × e0.024×v (14) 0.024 0.027××vv (14) = (15) wwi&bi =4.79 3.87××ee wi&b = 3.87 × e0.027×v (15) 0.027 0.067 × v× v (15) (16) w 3.87××e e wi&b i ==2.25 wi = 2.25 × e0.067×v (16) 0.067 0.037××vv (16) (17) ww ==2.25 3.89××ee wi&bi&bi= 3.89 × e0.037×v (17) 0.037×v where: w i is absorption after immersionwini&b %;=w3.89 i&b is absorption after immersion and boiling; and v (17) ×e where:w absorption after immersion in %; w is absorption after immersion and boiling; and v is i isvolume is the of permeable void spaces in %. i&b where:of is absorption after immersion wi&b is absorption after immersion and boiling; and v the volume void spaces %. in %; ipermeable Thewvolume of permeable voidinspaces in both RHA and RAP inclusive PCC is portrayed in is the volume of permeable void spaces in %. The volume of permeable void spaces in both RHA of and RAP inclusive portrayed in Figure 19. As expected, the relative percentage of reduction voids (4.86%) in bothPCC RHAisand RAP The volume of permeable void spaces in both RHA and RAP inclusive PCC is portrayed in PCC is higher that ofpercentage RHA inclusive PCC (3.22%)ofbut lower(4.86%) than that RAPRHA inclusive Figureinclusive 19. As expected, thethan relative of reduction voids inofboth and RAP Figure 19. As expected, the relative percentage of reduction of voids (4.86%) in both RHA and RAP PCC (9.47) 1.64 and 4.61% inclusive PCC isbyhigher than thatrespectively. of RHA inclusive PCC (3.22%) but lower than that of RAP inclusive inclusive PCC is higher than that of RHA inclusive PCC (3.22%) but lower than that of RAP inclusive PCC (9.47) by 1.64 and 4.61% respectively. PCC (9.47) by 1.64 and 4.61% respectively.

VoidsVoids [%] [%]

17.5

17.0 17.5 16.5 17.0 16.0 16.5 15.5 16.0 15.5 RHA and RAP Content [%] Figure 19. Void spaces in both and RAP-inclusive concrete. RHA and RHARAP Content [%]

•

Sorptivity

Figure 19. Void spaces in both RHA- and RAP-inclusive concrete.

Figure 19. Void spaces in both RHA- and RAP-inclusive concrete. The sorptivity by RHA concrete, shown in Table 10, was obtained from the slope of the line that • Sorptivity is the best fit to the cumulative amount of water absorption (I) plotted against the square root of time • Sorptivity sorptivity by RHA shownthe in cumulative Table 10, was obtained from the slope of from the line that (t1/2), The depicted in Figures A1 concrete, and A2 shows amount of water absorption which is the best fit to the cumulative amount of water absorption (I) plotted against the square root of time the sorptivity RAP inclusive concrete wasindetermined and tabulated Table 11.slope of the line that is The sorptivityofby RHA concrete, shown Table 10, was obtainedinfrom the (t1/2), depicted in Figures A1 and A2 shows the cumulative amount of water absorption from which the best fit to the cumulative amount of water absorption (I) plotted against the square root of time the sorptivity of RAP inclusive concrete was determined and tabulated in Table 11.

(t1/2 ), depicted in Figures A1 and A2 shows the cumulative amount of water absorption from which the sorptivity of RAP inclusive concrete was determined and tabulated in Table 11.


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Table 10. Sorptivity by RHA inclusive concrete. RHA Content (%)

(0)

(5)

(10)

Buildings 2018, 8, x FOR PEER REVIEW Sorptivity, K (mm/h1/2 )

1.964 1.922 1.899 2) 0.969 0.976 0.974 Determination Coefficient (R Table 10. Sorptivity by RHA inclusive concrete. Correlation Coefficient (R) 0.984 0.988 0.987 RHA Content [%] [0] [5] [10] [15] Sorptivity, K [mm/h1/2] 1.964 1.922 1.899 1.799 Table 11. Sorptivity by RAP inclusive concrete. Determination Coefficient [R2] 0.969 0.976 0.974 0.982 Correlation Coefficient [R] 0.984 0.988 0.987 0.991 RAP Content (%) (0) (10) (20) (30)

(15)

(20)

1.799 0.982 0.991 [20] 1.746 0.977 0.988 (40)

1.746 0.977 0.988

1.964 1.301 by1.816 RAP inclusive concrete.1.164 (mm/h1/2 )Table 11. Sorptivity

0.908 Sorptivity 0.969 0.971 0.989 0.983 0.985 Determination Coefficient (R2 ) RAP Content [%] [0] [10] [20] [30] [40] [50] Correlation Coefficient (R) 0.984 0.985 0.994 0.992 0.993 1/2 Sorptivity (mm/h ) 1.964 1.816 1.301 1.164 0.908 0.694 Determination Coefficient [R2] 0.969 0.971 0.989 0.983 0.985 0.993 The effect of RHA content on the sorptivity of concrete is depicted Figure 20a. Correlation Coefficient [R] 0.984 0.985 0.994 0.992 in 0.993 0.997

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(50) 0.694 0.993 0.997

As can be seen from Equation (18), the sorptivity decreased linearly as the RHA content increased. The sorptivity of RHA sorptivity concrete depicted in Figure 20a. As can be seen decreasedThe by effect 11.1% fromcontent 1.964 on to the 1.746 mm/hof1/2 whenisRHA content increased from 0 to 20%. from Equation (18), the sorptivity decreased linearly as the RHA content increased. The sorptivity The reduction in sorptivity might be due to the fact that finer RHA particles filled up air voids decreased by 11.1% from 1.964 to 1.746 mm/h1/2 when RHA content increased from 0 to 20%. The exist in the concrete matrix, as a result of which the rate of ingress of water was inhibited. The influence reduction in sorptivity might be due to the fact that finer RHA particles filled up air voids exist in the of RAP content on the of concrete also portrayed in inhibited. Figure 20b. Sorptivity decreased concrete matrix, as asorptivity result of which the rate ofisingress of water was The influence of RAP significantly as the thesorptivity content of RAP increased. A linear relationship was found between RAP content content on of concrete is also portrayed in Figure 20b. Sorptivity decreased significantly and sorptivity, andofEquation (19) represents the same. Similar findingsRAP were reported in the previous as the content RAP increased. A linear relationship was found between content and sorptivity, and Equation represents same. Similar were reported in the was previous studies [13,27]. studies [13,27]. The(19) main reason the being given for findings the reduction in sorptivity the melted asphalt layer The main reason being given for the reduction in sorptivity was the melted asphalt layer surrounding surrounding the RAP aggregates. In addition, the authors of this paper believed that the reduction in the RAP aggregates. In addition, the authors of this paper believed that the reduction in sorptivity sorptivity might also be ascribed to the lower water absorption by the RAP aggregates compared to might also be ascribed to the lower water absorption by the RAP aggregates compared to that of the that of the virgin aggregates. 2.5

Sorptivity, k [mm/h1/2]

Sorptivity, K [mm/h1/2]

virgin aggregates.

k =ko -0.0112(RHA) R² = 0.955

2.0

1.5

1.0

2.5 k =ko -0.0263(RAP) R² = 0.9724

2.0 1.5 1.0 0.5 0.0

0.0

10.0 20.0 RHA content [%]

30.0


0

20 40 RAP Content [%]

60


Figure 20. Relationship between sorptivity and RHA, and RAP contents.

Figure 20. Relationship between sorptivity and RHA, and RAP contents.

k = k o − 0.0112 × RHA

k = k o − 0.0112 × RHA

(18)

(18)

where: k and ko are the sorptivity by RHA inclusive concrete and concrete without RHA respectively where:inkmm/h and 1/2 ko; are sorptivity RHA inclusive concrete and concrete without RHA respectively and the RHA is the rice by husk ash content in %.

in mm/h1/2 ; and RHA is the rice husk ash content in %.

k = k o − 0.0236 × RAP

(19)

k =inclusive k o − 0.0236 × RAP where: k and ko are the sorptivity by RAP concrete and concrete without RAP, respectively, (19) 1/2 in mm/h ; and RAP is the reclaimed asphalt pavement content, in %. where: k and ko are the sorptivity by RAP inclusive and concrete without RAP, respectively, Figures A3–A6 depict the cumulative amount ofconcrete water absorption (I) plotted against the square 1/2 1/2 root of time ), from which the sorptivity by both RHA and RAP inclusive in mm/h ; and(tRAP is the reclaimed asphalt pavement content, in %. concrete was determined and tabulated in Table 12.


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Figures A3–A6 depict the cumulative amount of water absorption (I) plotted against the square root of time (t1/2 ), from which the sorptivity by both RHA and RAP inclusive concrete was determined and tabulated in Table 12. Table 12. Sorptivity by both RHA- and RAP-inclusive concrete. RHA and RAP Content

Sorptivity (mm/h1/2 )

Determination Coefficient (R2 )

Correlation Coefficient (R)

Control 5% RHA + 10% RAP 5% RHA+ 20% RAP 5% RHA+ 30% RAP 10% RHA+ 10% RAP 10% RHA+ 20% RAP 10% RHA+ 30% RAP 15% RHA+ 10% RAP 15% RHA+ 20% RAP 15% RHA+ 30% RAP 20% RHA+ 10% RAP 20% RHA+ 20% RAP 20% RHA+ 30% RAP

1.964 1.883 1.808 1.688 1.801 1.653 1.411 1.867 1.610 1.474 1.919 1.891 1.646

0.9688 0.971 0.975 0.978 0.972 0.98 0.986 0.977 0.983 0.973 0.983 0.988 0.982

0.984 0.985 0.987 0.989 0.986 0.990 0.993 0.988 0.991 0.986 0.991 0.994 0.991

It is evident from experimental results that the sorptivity by RHA and RAP inclusive concrete was decreased as expected. The reduction in sorptivity ranged from 2.29 to 28.16% relative to the control specimens. The reduction in sorptivity could be due to the combined influences of RHA and RAP as already discussed. Although sorptivity value alone does not suffice to envisage the service life of a structure [63], according to the research conducted by Hinczak, Conroy, and Lewis, cited in the study [64], a concrete is said to be durable if sorptivity is less than 6 mm/h1/2 . The experimental results of this study revealed that all concrete specimens had sorptivity values under the limit specified i.e., considered as durable concrete holding other factors constant. 4. Conclusions The effects of RHA and RAP on the engineering properties of concrete were studied. Based on the experimental results obtained and the analysis and discussion made, the following conclusions can be drawn: 1. 2. 3. 4. 5. 6.

The water demand of the mix increased as the RHA and RAP content increased; as a result, the slump and compaction factor of the fresh concrete decreased significantly. The density of concrete decreased with increasing RHA and RAP content in the concrete mix. RHA-inclusive concrete exhibited an increase in both compressive and tensile splitting strength. The maximum possible strength was obtained when cement was replaced by 15% RHA. Compressive and tensile splitting strength decreased drastically as the RAP content increased beyond 20%. Comparable strength and favorable sorptivity values were obtained when 15% RHA was combined with up to 20% RAP in the concrete mix. Specimens containing both RHA and RAP exhibited lower water absorption, permeable void space and sorptivity values compared to that of the control specimens. This indicates that RHA and RAP inclusive concrete might perform better when subjected to aggressive environment.

Author Contributions: S.M.S., M.A.G. and Z.C.A.G. designed the experiments; M.A.G. performed the experiment and collected data; S.M.S. and M.A.G. analyzed the data; Z.C.A.G. facilitated resources; M.A.G., S.M.S. and Z.C.A.G. wrote the paper. Funding: The authors wish to thank the African Union Commission (AUC) and Japan International Cooperation Agency (JICA) for funding this research. Conflicts of Interest: The authors confirm that there are no known conflicts of interest.


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Buildings 2018, 8, x FOR PEER REVIEW Buildings 2018, 8, x FOR PEER REVIEW

Appendix Cumulative Water Absorption

Appendix A. Cumulative Water Absorption Appendix A. Cumulative Water Absorption

Figure A1. Cumulative water absorption by RHA Concrete.

Figure A1. Cumulative absorptionbybyRHA RHA Concrete. Figure A1. Cumulativewater water absorption Concrete.

Figure A2. Cumulative water absorption by RAP Concrete.

Figure A2. Cumulativewater water absorption Concrete. Figure A2. Cumulative absorptionbybyRAP RAP Concrete.

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Buildings 2018, 8, 115 Buildings 2018, 8, x FOR PEER REVIEW Buildings 2018, 8, x FOR PEER REVIEW

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Figure A3. Cumulative water absorption by 5% RHA and (10–30) % RAP-inclusive concrete. Figure A3.A3. Cumulative water 5%RHA RHAand and(10–30) (10–30) % RAP-inclusive concrete. Figure Cumulative waterabsorption absorption by by 5% % RAP-inclusive concrete.

Figure A4. Cumulative water absorption by 10% RHA and (10–30) % RAP-inclusive concrete.

Figure A4. Cumulative water absorption by 10% RHA and (10–30) % RAP-inclusive concrete. Figure A4. Cumulative water absorption by 10% RHA and (10–30) % RAP-inclusive concrete.

Buildings 2018, 8, 115 Buildings 2018, 8, x FOR PEER REVIEW Buildings 2018, 8, x FOR PEER REVIEW

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Figure Cumulative waterabsorption absorption by 15% 15% RHA %% RAP-inclusive concrete. Figure A5. A5. Cumulative water RHAand and(10–30) (10–30) RAP-inclusive concrete. Figure A5. Cumulative water absorption by by 15% RHA and (10–30) % RAP-inclusive concrete.

Figure A6. Cumulative water absorption by 20% RHA and (10–30) % RAP-inclusive concrete.

Figure Cumulative waterabsorption absorption by by 20% 20% RHA %% RAP-inclusive concrete. Figure A6. A6. Cumulative water RHAand and(10–30) (10–30) RAP-inclusive concrete. References References

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