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Properties of recycled concrete aggregate under different curing conditions

Properties of recycled concrete aggregate under different curing conditions HBRC Journal (2017) 13, 271–276 Housing and Building National Research Center HBRC Journal http://ees.elsevier.com/hbrcj Properties of recycled concrete aggregate under different curing conditions Ahmed Shaban Abdel-Hay Structural Engineering Dept., Faculty of Engineering, Beni-Suef University, Egypt Received 13 January 2015; revised 28 June 2015; accepted 15 July 2015 KEYWORDS Abstract Construction and demolition wastes are produced every day around the world. Thus the idea of using recycled concrete aggregate in new concrete production appears to be an effective uti- Concrete; lization of concrete waste. This paper presents the results of an experimental study to evaluate the Recycling; effects of recycled concrete aggregate (RCA) percentages under different curing conditions. The Curing; percentages of recycled coarse aggregate to dolomite were (0:100%, 25:75%, 50:50%, 100:0%) Recycled aggregate respectively. The concrete properties which were studied were the mechanical properties (compres- sive and splitting strength) and mass transport properties (ISAT and sorptivity). The concrete spec- imens were exposed to three different curing conditions, moist (standard), open-air, and painted specimens using the substance (Curassol 1). The coarse recycled concrete aggregates were obtained by crushing a laboratory produced primary concrete at age of 28 days. The results showed that cur- ing using paint material was the most efficient method of curing at all ages and percentages of recy- cling except at 100% recycling, where the maximum value of both compressive and tensile strengths was obtained using water curing. Also, in moist curing, full replacement of coarse aggregates gave the highest compressive strength at age of 28 days. In all cases of recycled aggregate ratios, curing using water caused a decrease in the concrete permeability. ª 2015 The Author. Production and hosting by Elsevier B.V. on behalf of Housing and Building National Research Center. This is an open access article under the CC BY-NC-ND license (http://creativecommon- s.org/licenses/by-nc-nd/4.0/). Introduction achieve an environmentally-friendly concrete. This reduces the consumption of natural resources as well as the disposal of waste concrete in landfills [1]. Thus the idea of using Crushing concrete to produce coarse aggregates for the pro- recycled concrete aggregate in new concrete production duction of new concrete is one of the common methods to appears to be an effective utilization of concrete waste. However, the strength of new concrete produced using recy- E-mail address: ahshaban2005@yahoo.com cled concrete aggregate needs to be evaluated before their Peer review under responsibility of Housing and Building National use in structures. Research Center. Many researchers studied the mechanical behavior of recy- cled concrete coarse aggregates [1–9]. Also, many authors have pointed to the possibility of using recycled aggregates to pro- Production and hosting by Elsevier duce structural concrete [10–13]. On the other hand, few of http://dx.doi.org/10.1016/j.hbrcj.2015.07.001 1687-4048 ª 2015 The Author. Production and hosting by Elsevier B.V. on behalf of Housing and Building National Research Center. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 272 A.S. Abdel-Hay them studied the effects of curing conditions on the mechanical sand with medium grade of fineness modulus of 2.73 and dolo- properties of concrete made of recycled aggregates. mite natural coarse aggregate with maximum nominal size of Curing is a treatment that avoids excessive drying and pro- 25 mm were used in all mixes. Tap water was used for mixing vides enough water content to the concrete mass in order for and curing (saturated). Table 1 shows the mix design and cement to reach the desired degree of cement hydration. The slump of the concrete used in the experimental program. curing process of concrete tries to oppose the undesired effects The coarse recycled concrete aggregate was obtained by of some environmental actions (sun radiation, air moisture and crushing a laboratory produced primary concrete at age of wind), so the effect of curing conditions on the compressive 28 days. About 250 cubes of dimension 15 * 15 * 15 cm were strength of recycled concrete is an interesting issue to be crushed to produce the recycled coarse aggregates using mix studied. design No.1 (Table 1). After crushing of these cubes, the max- Two different qualities of recycled aggregates were used by imum nominal size of recycled coarse aggregate used in mixes Fernando et al. [14] to make concrete with 0.65 water/cement 2, 3 and 4 was 25 mm. From the results of slump shown in ratio. The recycled aggregates were added with their natural Table 1, it is noticed that all mixes were very dry especially moisture and replaced different percentages of the coarse mix numbers 3 and 4. This means that the used mixes needed aggregates (0%, 20%, 50% and 100%). The concrete speci- an admixture to improve the concrete workability. ADDICRETE mens were exposed to two different environments (standard BVF was used as an admixture with dosage 1.0% of cement curing and open air curing). The results showed that the 7- weight and the resulting slump shown in Table 1. day strength increases with the percentage of replacement, this behavior was more evident for the standard curing environ- Curing condition ment. The 28-day compressive strengths of concretes with recy- cled aggregates were found similar to the ones obtained with After 24 h from mixing, the specimens were cured in three con- natural aggregates regarding the standard curing condition. ditions, open-air curing in laboratory atmosphere, standard Fonseca, et al. [15] studied the influence of different curing curing and painted curing for 3, 7 and 28 days respectively. conditions on the mechanical properties of recycled concrete Five specimens were cured in each condition. The concrete coarse aggregate concrete. Four concrete mixes were produced cubes were painted using Curassol 1. The paint was sprayed using different replacement ratios, along with four different on the surface of concrete after casting directly, thus closing curing methods. It was concluded that compressive strength the pores and maintaining adequate moisture to interact with did not seem to be affected by recycled concrete coarse aggre- cement. Curassol 1 is a material that satisfies ASTM C309- gate incorporation for a given curing condition when com- 81 class B type 1 with a density of 0.8 kg/liter for type 1. pared to conventional concrete. In other words, compressive strength seems to be reasonably insensitive to curing condition. Testing procedures However, there is a lack of information regarding the effect of recycled aggregate concrete on mass transport of concrete Compressive strength of hardened concrete was measured at such as initial surface absorption test (Isat) and sorptivity. the age of 3, 7 and 28 days on 150 mm cubic specimens (5 spec- Moreover, there is still a need to signify the impact of various imens in each case). 28-day splitting tensile strength was mea- curing conditions on properties of concrete made with differ- sured on five 100 · 200 mm cylindrical specimens. Sorptivity ent percentages of recycled aggregate. test was carried out on 100 mm concrete cubes according to In the present study the effects of different curing condi- the test details described in Ref. [16]. Fig. 1 shows the sorptiv- tions (moist–standard curing, open air and painted) on the ity test. The test was performed on three specimens at the age mass transport (ISAT sorptivity) and mechanical properties of 28 days, and then the average was calculated using the fol- (compressive strength and splitting strength) of recycled con- lowing equation [16]: crete were investigated. 1=2 I ¼ A þ ST Experimental program where A, is constant, Four concrete mixes were produced using different replace- I is increase in mass in g/mm , ment ratios of recycled coarse aggregate to dolomite T is the time, measured in minutes, at which the weight is (0:100%, 25:75%, 50:50%, 100:0%) respectively. The four determined, and 1/2 mixes were then exposed to three different curing methods S is the sorptivity in mm/min . (open Air, Saturated, and Painted). After the curing period, hardened concrete tests were performed to determine the con- Initial surface absorption test (ISAT) was carried out on crete properties such as mechanical properties (compressive 100 mm concrete cubes. The apparatus is shown in Fig. 2 and and splitting strength) and mass transport properties (ISAT test details are described in Ref. [17]. The test was performed and sorptivity). on three specimens at the age of 28 days and the flow rates in ml/m /sec were calculated using the following equation: Materials and mix design F ¼ð60  D  0:01=tÞ where Four different concrete mixes were produced: a control con- F: flow rate (ml/m .sec), crete mix and three recycled aggregate concretes with replace- D: number of divisions read on tube, and ment ratios of 25%, 50% and 100%. One type of cement was t: time (sec). used in this study, Portland cement (OPC). Natural siliceous Properties of recycled concrete aggregate 273 Table 1 Mix proportions used for experimental program. Mix W/C Cement Sand Coarse Dolomite Recycled Slump without Slump with No. ratio (kg) (kg) aggregates (kg) (%) aggregates (%) admixture (mm) admixture (mm) 1 0.55 400 600 1200 100 0 60 140 2 0.55 400 600 1200 75 25 40 115 3 0.55 400 600 1200 50 50 15 100 4 0.55 400 600 1200 0 100 5 60 Mechanical properties Compressive strength In this study, tests were conducted on specimens that have been cast with different ratios of recycled aggregates while maintaining same water cement ratio (0.55). It was found that the compressive strength of concrete cured in water was higher than that which have been cured in air when the percentage of recycled aggregates were 0% and 100%. On the contrary, it was found that the specimens with recycled aggregate of 25% and 50%, which were cured in air, provided higher com- pressive strength than that cured in water, at ages of 3, 7 and 28 days. However the case of curing using Paint material gave values of compressive strength higher than the other curing methods, in all cases and at all ages, except in the case of (100%) recycled aggregate which provided the maximum value of the compressive strength in the case of curing with water as Fig. 1 Sorptivity test. shown in Figs. 3–5 and Table 2. Splitting strength The splitting tensile strength of the tested specimens showed Results and discussion that the case of concrete that have been cast using 50% recy- cled aggregate, and cured using Paint material provided the In this section the results of the tested specimens are presented maximum value as shown in Table 3 and Fig. 6. This result concerning each curing condition. Then a comparison between all cases of curing in terms of their effects on the ratios of recy- cled aggregates in concrete mixes as well as on properties of concrete such as mechanical and mass transport properties is discussed. Fig. 3 Compressive strength for various recycled aggregate Fig. 2 ISAT device. ratios at age of 3 days. 274 A.S. Abdel-Hay Table 2 Compressive strength for different curing conditions, kg/cm . Type Age of Air Water Painted specimens (day) curing curing curing Control (3 days) 181 183 194 Recycled 191 177 229 (25%) Recycled 212 208 271 (50%) Recycled 237 249 259 (100%) Control (7 days) 223 225 261 Recycled 262 255 269 (25%) Recycled 259 226 320 (50%) Recycled 245 296 278 (100%) Fig. 4 Compressive strength for different recycled aggregate ratios at age of 7 days. Control (28 days) 264 283 350 Recycled 281 280 329 (25%) Recycled 300 242 349 is in agreement with the result of compressive strength shown (50%) in Table 2. Recycled 255 308 287 (100%) Mass transport Sorptivity The test results of sorptivity on tested specimens showed that Table 3 Splitting strength of (10 * 20) cylinder specimens at the samples that have been cured using water have lower val- age of 28 days, kg/cm . ues of sorptivity in all cases than the samples that have been cured in air, as shown in Fig. 7. This means that water curing Type Specimens Specimens Specimens cured improves the permeability of recycled concrete aggregates. cured in air cured in water by painting Control 26.5 28.1 30.3 Initial Surface Absorption Test (ISAT) Recycled 30.5 32.8 26 (25%) When the ISAT test was performed on tested specimens, it was Recycled 28.9 27.6 31.1 found that the specimens that have been cured using water (50%) have lower values of flow in all cases than those that were Recycled 28.2 26.5 27.9 (100%) Fig. 6 Splitting strength for various recycled aggregate ratios at Fig. 5 Compressive strength for different recycled aggregate age of 28 days. ratios at age of 28 days. Properties of recycled concrete aggregate 275 3. In moist curing, full replacement of coarse aggregates gave the highest compressive strength at age of 28 days. 4. Curing with Paint material is beneficial in all cases and ages than water or air curing except in the case of full replace- ment where the maximum value of the compressive and ten- sile strengths in this case, was obtained at curing using water. 5. Increasing the recycled aggregates ratio causes a decrease in the concrete permeability by ISAT in case of curing in air. 6. In all cases of recycled aggregates ratios, curing in water causes a decrease in the concrete permeability. Conflict of interest The author declares that there are no conflict of interests. References [1] Valeria Corinaldesi, Mechanical and elastic behaviour of Fig. 7 Sorptivity for various recycled aggregate ratios. concretes made of recycled-concrete coarse aggregates, Constr. Build. Mater. 24 (2010) 1620, 1620-1616. [2] Rasiah Sriravindrarajah, Neo Derek Huai Wang, Lai Jian Wen Ervin, Mix Design for pervious recycled aggregate concrete, Int. J. Concr. Struct. Mater. 6 (4) (2012) 246, 246-239. [3] Belen Gonzalez-Fonteboa, Fernando Martinez-Abella, Javier Eiras-Lopez, Sindy Seara-Paz, Effect of recycled coarse aggregate on damage of recycled concrete, Mater. Struct. 44 (2011) 1759–1771. [4] J.-Zh. Xiao, J.-B. Li, Ch. Zhang, On relationships between the mechanical properties of recycled aggregate concrete: an overview, Mater. Struct. 39 (2006) 664, 664-655. [5] Amnon. Katz, Properties of concrete made with recycled aggregate from partially hydrated old concrete, Cem. Concr. Res. 33 (2003) 703–711. [6] C.S. Poon, Z.H. Shui, L. Lam, H. Fok, S.C. Kou, Influence of moisture states of natural and recycled aggregates on the slump and compressive strength of concrete, Cem. Concr. Res. 34 (2004) 31–36. [7] Arundeb Gupta, Saroj Mandal, Somnath Ghosh, Direct compressive strength and elastic modulus of recycled aggregate Fig. 8 (ISAT) for various recycled aggregate ratios. concrete, Int. J. Civ. Struct. Eng. 2 (1) (2011) 292–304. [8] Shi-cong Kou, Chi-sun Poon, Francisco Agrela, Comparisons of cured in the air as shown in Fig. 8. This indicates that perme- natural and recycled aggregate concretes prepared with the ability increased in case of curing in air, and increasing the addition of different mineral admixtures, Cement Concr. recycled aggregates ratio in the mixes led to decreasing the Compos. 33 (2011) 788–795. concrete permeability by ISAT in case of curing in air. [9] Katrina Mc Neil, Thomas H.-K. Kang, Recycled concrete The painted specimens were not tested pertaining to, both aggregates: a review, Int. J. Concr. Struct. Mater. 7 (1) (2013) Sorptivity and Initial Surface Absorption Test because the 61–69. [10] F.I. AL-Zahraa, M.T. El-Mihilmy, T.M. Bahaa, Flexural painted material caused the specimens to be almost strength of concrete beams with recycled concrete aggregates, impermeable. J. Eng. Appl. Sci. 57 (5) (2010) 355–375. [11] Cathleen Hoffmann, Sandy Schubert, Andreas Leemann, Conclusions Masoud Motavalli, Recycled concrete and mixed rubble as aggregates: influence of variation in composition on the concrete properties and their use as structural material, Constr. Build. According to the results that have been reached, it can be con- Mater. 35 (2012) 701–709. cluded that: [12] Ashraf M. Wagih, Hossam Z. El-Karmoty, Magda Ebid, Samir H. Okba, Recycled construction and demolition waste 1. In all the studied cases of curing (air, water, paint), increas- as aggregate for structural concrete, HBRC J. 9 (2013) 193– ing the concrete age led to an increase in its compressive strength. [13] M. Etxeberria, A.R. Mari, E. Vazquez, Recycled aggregate 2. The best ratio of recycled aggregates to natural aggregates is concrete as structural material, Mater. Struct. 40 (2007) 529– the mixing ratio of 50% and that when they are cured in air or painted, the maximum value of the compressive strength [14] Fernando Lopez Gayarre, Carlos Lopez-Colina Perez, Miguel and tensile strength was obtained at age of 28 days. A. Serrano Lopez, Alberto Domingo Cabo, The effect of curing 276 A.S. Abdel-Hay condition on the compressive strength of recycled aggregate [16] J.F. Young, A review of the pore stricter of cement paste and concrete, Construct. Build. Mater. 53 (2014) 260–266. concrete and its influence of permeability, Am. Concr. Inst. SP [15] N. Fonseca, J. de Brito, L. Evangelista, The influence of 108 (1) (1988) 1–18. curing condition on the mechanical performance of concrete [17] A.A. Rahman, F.P. Glasser, Comparative studies of the made with recycled concrete waste, Cement Concr. Compos. 33 carbonation of hydrated cement, Adv. Cement Res. 2 (6) (2011) 637–643. 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Properties of recycled concrete aggregate under different curing conditions

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Taylor & Francis
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© 2015 Housing and Building National Research Center. Production and hosting by Elsevier B.V.
ISSN
1687-4048
DOI
10.1016/j.hbrcj.2015.07.001
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Abstract

HBRC Journal (2017) 13, 271–276 Housing and Building National Research Center HBRC Journal http://ees.elsevier.com/hbrcj Properties of recycled concrete aggregate under different curing conditions Ahmed Shaban Abdel-Hay Structural Engineering Dept., Faculty of Engineering, Beni-Suef University, Egypt Received 13 January 2015; revised 28 June 2015; accepted 15 July 2015 KEYWORDS Abstract Construction and demolition wastes are produced every day around the world. Thus the idea of using recycled concrete aggregate in new concrete production appears to be an effective uti- Concrete; lization of concrete waste. This paper presents the results of an experimental study to evaluate the Recycling; effects of recycled concrete aggregate (RCA) percentages under different curing conditions. The Curing; percentages of recycled coarse aggregate to dolomite were (0:100%, 25:75%, 50:50%, 100:0%) Recycled aggregate respectively. The concrete properties which were studied were the mechanical properties (compres- sive and splitting strength) and mass transport properties (ISAT and sorptivity). The concrete spec- imens were exposed to three different curing conditions, moist (standard), open-air, and painted specimens using the substance (Curassol 1). The coarse recycled concrete aggregates were obtained by crushing a laboratory produced primary concrete at age of 28 days. The results showed that cur- ing using paint material was the most efficient method of curing at all ages and percentages of recy- cling except at 100% recycling, where the maximum value of both compressive and tensile strengths was obtained using water curing. Also, in moist curing, full replacement of coarse aggregates gave the highest compressive strength at age of 28 days. In all cases of recycled aggregate ratios, curing using water caused a decrease in the concrete permeability. ª 2015 The Author. Production and hosting by Elsevier B.V. on behalf of Housing and Building National Research Center. This is an open access article under the CC BY-NC-ND license (http://creativecommon- s.org/licenses/by-nc-nd/4.0/). Introduction achieve an environmentally-friendly concrete. This reduces the consumption of natural resources as well as the disposal of waste concrete in landfills [1]. Thus the idea of using Crushing concrete to produce coarse aggregates for the pro- recycled concrete aggregate in new concrete production duction of new concrete is one of the common methods to appears to be an effective utilization of concrete waste. However, the strength of new concrete produced using recy- E-mail address: ahshaban2005@yahoo.com cled concrete aggregate needs to be evaluated before their Peer review under responsibility of Housing and Building National use in structures. Research Center. Many researchers studied the mechanical behavior of recy- cled concrete coarse aggregates [1–9]. Also, many authors have pointed to the possibility of using recycled aggregates to pro- Production and hosting by Elsevier duce structural concrete [10–13]. On the other hand, few of http://dx.doi.org/10.1016/j.hbrcj.2015.07.001 1687-4048 ª 2015 The Author. Production and hosting by Elsevier B.V. on behalf of Housing and Building National Research Center. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 272 A.S. Abdel-Hay them studied the effects of curing conditions on the mechanical sand with medium grade of fineness modulus of 2.73 and dolo- properties of concrete made of recycled aggregates. mite natural coarse aggregate with maximum nominal size of Curing is a treatment that avoids excessive drying and pro- 25 mm were used in all mixes. Tap water was used for mixing vides enough water content to the concrete mass in order for and curing (saturated). Table 1 shows the mix design and cement to reach the desired degree of cement hydration. The slump of the concrete used in the experimental program. curing process of concrete tries to oppose the undesired effects The coarse recycled concrete aggregate was obtained by of some environmental actions (sun radiation, air moisture and crushing a laboratory produced primary concrete at age of wind), so the effect of curing conditions on the compressive 28 days. About 250 cubes of dimension 15 * 15 * 15 cm were strength of recycled concrete is an interesting issue to be crushed to produce the recycled coarse aggregates using mix studied. design No.1 (Table 1). After crushing of these cubes, the max- Two different qualities of recycled aggregates were used by imum nominal size of recycled coarse aggregate used in mixes Fernando et al. [14] to make concrete with 0.65 water/cement 2, 3 and 4 was 25 mm. From the results of slump shown in ratio. The recycled aggregates were added with their natural Table 1, it is noticed that all mixes were very dry especially moisture and replaced different percentages of the coarse mix numbers 3 and 4. This means that the used mixes needed aggregates (0%, 20%, 50% and 100%). The concrete speci- an admixture to improve the concrete workability. ADDICRETE mens were exposed to two different environments (standard BVF was used as an admixture with dosage 1.0% of cement curing and open air curing). The results showed that the 7- weight and the resulting slump shown in Table 1. day strength increases with the percentage of replacement, this behavior was more evident for the standard curing environ- Curing condition ment. The 28-day compressive strengths of concretes with recy- cled aggregates were found similar to the ones obtained with After 24 h from mixing, the specimens were cured in three con- natural aggregates regarding the standard curing condition. ditions, open-air curing in laboratory atmosphere, standard Fonseca, et al. [15] studied the influence of different curing curing and painted curing for 3, 7 and 28 days respectively. conditions on the mechanical properties of recycled concrete Five specimens were cured in each condition. The concrete coarse aggregate concrete. Four concrete mixes were produced cubes were painted using Curassol 1. The paint was sprayed using different replacement ratios, along with four different on the surface of concrete after casting directly, thus closing curing methods. It was concluded that compressive strength the pores and maintaining adequate moisture to interact with did not seem to be affected by recycled concrete coarse aggre- cement. Curassol 1 is a material that satisfies ASTM C309- gate incorporation for a given curing condition when com- 81 class B type 1 with a density of 0.8 kg/liter for type 1. pared to conventional concrete. In other words, compressive strength seems to be reasonably insensitive to curing condition. Testing procedures However, there is a lack of information regarding the effect of recycled aggregate concrete on mass transport of concrete Compressive strength of hardened concrete was measured at such as initial surface absorption test (Isat) and sorptivity. the age of 3, 7 and 28 days on 150 mm cubic specimens (5 spec- Moreover, there is still a need to signify the impact of various imens in each case). 28-day splitting tensile strength was mea- curing conditions on properties of concrete made with differ- sured on five 100 · 200 mm cylindrical specimens. Sorptivity ent percentages of recycled aggregate. test was carried out on 100 mm concrete cubes according to In the present study the effects of different curing condi- the test details described in Ref. [16]. Fig. 1 shows the sorptiv- tions (moist–standard curing, open air and painted) on the ity test. The test was performed on three specimens at the age mass transport (ISAT sorptivity) and mechanical properties of 28 days, and then the average was calculated using the fol- (compressive strength and splitting strength) of recycled con- lowing equation [16]: crete were investigated. 1=2 I ¼ A þ ST Experimental program where A, is constant, Four concrete mixes were produced using different replace- I is increase in mass in g/mm , ment ratios of recycled coarse aggregate to dolomite T is the time, measured in minutes, at which the weight is (0:100%, 25:75%, 50:50%, 100:0%) respectively. The four determined, and 1/2 mixes were then exposed to three different curing methods S is the sorptivity in mm/min . (open Air, Saturated, and Painted). After the curing period, hardened concrete tests were performed to determine the con- Initial surface absorption test (ISAT) was carried out on crete properties such as mechanical properties (compressive 100 mm concrete cubes. The apparatus is shown in Fig. 2 and and splitting strength) and mass transport properties (ISAT test details are described in Ref. [17]. The test was performed and sorptivity). on three specimens at the age of 28 days and the flow rates in ml/m /sec were calculated using the following equation: Materials and mix design F ¼ð60  D  0:01=tÞ where Four different concrete mixes were produced: a control con- F: flow rate (ml/m .sec), crete mix and three recycled aggregate concretes with replace- D: number of divisions read on tube, and ment ratios of 25%, 50% and 100%. One type of cement was t: time (sec). used in this study, Portland cement (OPC). Natural siliceous Properties of recycled concrete aggregate 273 Table 1 Mix proportions used for experimental program. Mix W/C Cement Sand Coarse Dolomite Recycled Slump without Slump with No. ratio (kg) (kg) aggregates (kg) (%) aggregates (%) admixture (mm) admixture (mm) 1 0.55 400 600 1200 100 0 60 140 2 0.55 400 600 1200 75 25 40 115 3 0.55 400 600 1200 50 50 15 100 4 0.55 400 600 1200 0 100 5 60 Mechanical properties Compressive strength In this study, tests were conducted on specimens that have been cast with different ratios of recycled aggregates while maintaining same water cement ratio (0.55). It was found that the compressive strength of concrete cured in water was higher than that which have been cured in air when the percentage of recycled aggregates were 0% and 100%. On the contrary, it was found that the specimens with recycled aggregate of 25% and 50%, which were cured in air, provided higher com- pressive strength than that cured in water, at ages of 3, 7 and 28 days. However the case of curing using Paint material gave values of compressive strength higher than the other curing methods, in all cases and at all ages, except in the case of (100%) recycled aggregate which provided the maximum value of the compressive strength in the case of curing with water as Fig. 1 Sorptivity test. shown in Figs. 3–5 and Table 2. Splitting strength The splitting tensile strength of the tested specimens showed Results and discussion that the case of concrete that have been cast using 50% recy- cled aggregate, and cured using Paint material provided the In this section the results of the tested specimens are presented maximum value as shown in Table 3 and Fig. 6. This result concerning each curing condition. Then a comparison between all cases of curing in terms of their effects on the ratios of recy- cled aggregates in concrete mixes as well as on properties of concrete such as mechanical and mass transport properties is discussed. Fig. 3 Compressive strength for various recycled aggregate Fig. 2 ISAT device. ratios at age of 3 days. 274 A.S. Abdel-Hay Table 2 Compressive strength for different curing conditions, kg/cm . Type Age of Air Water Painted specimens (day) curing curing curing Control (3 days) 181 183 194 Recycled 191 177 229 (25%) Recycled 212 208 271 (50%) Recycled 237 249 259 (100%) Control (7 days) 223 225 261 Recycled 262 255 269 (25%) Recycled 259 226 320 (50%) Recycled 245 296 278 (100%) Fig. 4 Compressive strength for different recycled aggregate ratios at age of 7 days. Control (28 days) 264 283 350 Recycled 281 280 329 (25%) Recycled 300 242 349 is in agreement with the result of compressive strength shown (50%) in Table 2. Recycled 255 308 287 (100%) Mass transport Sorptivity The test results of sorptivity on tested specimens showed that Table 3 Splitting strength of (10 * 20) cylinder specimens at the samples that have been cured using water have lower val- age of 28 days, kg/cm . ues of sorptivity in all cases than the samples that have been cured in air, as shown in Fig. 7. This means that water curing Type Specimens Specimens Specimens cured improves the permeability of recycled concrete aggregates. cured in air cured in water by painting Control 26.5 28.1 30.3 Initial Surface Absorption Test (ISAT) Recycled 30.5 32.8 26 (25%) When the ISAT test was performed on tested specimens, it was Recycled 28.9 27.6 31.1 found that the specimens that have been cured using water (50%) have lower values of flow in all cases than those that were Recycled 28.2 26.5 27.9 (100%) Fig. 6 Splitting strength for various recycled aggregate ratios at Fig. 5 Compressive strength for different recycled aggregate age of 28 days. ratios at age of 28 days. Properties of recycled concrete aggregate 275 3. In moist curing, full replacement of coarse aggregates gave the highest compressive strength at age of 28 days. 4. Curing with Paint material is beneficial in all cases and ages than water or air curing except in the case of full replace- ment where the maximum value of the compressive and ten- sile strengths in this case, was obtained at curing using water. 5. Increasing the recycled aggregates ratio causes a decrease in the concrete permeability by ISAT in case of curing in air. 6. In all cases of recycled aggregates ratios, curing in water causes a decrease in the concrete permeability. Conflict of interest The author declares that there are no conflict of interests. References [1] Valeria Corinaldesi, Mechanical and elastic behaviour of Fig. 7 Sorptivity for various recycled aggregate ratios. concretes made of recycled-concrete coarse aggregates, Constr. Build. Mater. 24 (2010) 1620, 1620-1616. [2] Rasiah Sriravindrarajah, Neo Derek Huai Wang, Lai Jian Wen Ervin, Mix Design for pervious recycled aggregate concrete, Int. J. Concr. Struct. Mater. 6 (4) (2012) 246, 246-239. [3] Belen Gonzalez-Fonteboa, Fernando Martinez-Abella, Javier Eiras-Lopez, Sindy Seara-Paz, Effect of recycled coarse aggregate on damage of recycled concrete, Mater. Struct. 44 (2011) 1759–1771. [4] J.-Zh. Xiao, J.-B. Li, Ch. Zhang, On relationships between the mechanical properties of recycled aggregate concrete: an overview, Mater. Struct. 39 (2006) 664, 664-655. [5] Amnon. Katz, Properties of concrete made with recycled aggregate from partially hydrated old concrete, Cem. Concr. Res. 33 (2003) 703–711. [6] C.S. Poon, Z.H. Shui, L. Lam, H. Fok, S.C. Kou, Influence of moisture states of natural and recycled aggregates on the slump and compressive strength of concrete, Cem. Concr. Res. 34 (2004) 31–36. [7] Arundeb Gupta, Saroj Mandal, Somnath Ghosh, Direct compressive strength and elastic modulus of recycled aggregate Fig. 8 (ISAT) for various recycled aggregate ratios. concrete, Int. J. Civ. Struct. Eng. 2 (1) (2011) 292–304. [8] Shi-cong Kou, Chi-sun Poon, Francisco Agrela, Comparisons of cured in the air as shown in Fig. 8. This indicates that perme- natural and recycled aggregate concretes prepared with the ability increased in case of curing in air, and increasing the addition of different mineral admixtures, Cement Concr. recycled aggregates ratio in the mixes led to decreasing the Compos. 33 (2011) 788–795. concrete permeability by ISAT in case of curing in air. [9] Katrina Mc Neil, Thomas H.-K. Kang, Recycled concrete The painted specimens were not tested pertaining to, both aggregates: a review, Int. J. Concr. Struct. Mater. 7 (1) (2013) Sorptivity and Initial Surface Absorption Test because the 61–69. [10] F.I. AL-Zahraa, M.T. El-Mihilmy, T.M. Bahaa, Flexural painted material caused the specimens to be almost strength of concrete beams with recycled concrete aggregates, impermeable. J. Eng. Appl. Sci. 57 (5) (2010) 355–375. 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Struct. 40 (2007) 529– the mixing ratio of 50% and that when they are cured in air or painted, the maximum value of the compressive strength [14] Fernando Lopez Gayarre, Carlos Lopez-Colina Perez, Miguel and tensile strength was obtained at age of 28 days. A. Serrano Lopez, Alberto Domingo Cabo, The effect of curing 276 A.S. Abdel-Hay condition on the compressive strength of recycled aggregate [16] J.F. Young, A review of the pore stricter of cement paste and concrete, Construct. Build. Mater. 53 (2014) 260–266. concrete and its influence of permeability, Am. Concr. Inst. SP [15] N. Fonseca, J. de Brito, L. Evangelista, The influence of 108 (1) (1988) 1–18. curing condition on the mechanical performance of concrete [17] A.A. Rahman, F.P. Glasser, Comparative studies of the made with recycled concrete waste, Cement Concr. Compos. 33 carbonation of hydrated cement, Adv. Cement Res. 2 (6) (2011) 637–643. (1989) 49–54.

Journal

HBRC JournalTaylor & Francis

Published: Dec 1, 2017

Keywords: Concrete; Recycling; Curing; Recycled aggregate

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