Civl070618.qxd The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 1. Introduction Reclaimed asphalt pavement (RAP) is the result of removing old asphalt pavement material. RAP consists of high quality well-graded aggregate coated with aged asphalt cement. The removal of asphalt concrete is done for reconstruction purposes, resurfacing, or to obtain access to buried utilities. The disposal of RAP represents a large loss of valuable source of high quality aggregate. Supplies of natural high quality aggregate are deplet- ing in some areas in the world, or can be costly to trans- port to the construction site. Existing portland cement concrete and asphalt concrete pavements provide a source of high quality aggregate that can be recycled. Recycling can contribute to the waste disposal and to the conserva- tion of natural resources (Yrjanson, 1989 and Kenai, et al. 2002). Kenai, et al. 2002, conducted a study on the use of recycled concrete and bricks as an aggregate in concrete. ________________________________________ *Corresponding author’s e-mail: aloraimi@squ.edu.om The study used either fine aggregate replacement or coarse aggregate replacement or both. Percentages of replacement were 25, 50, 75, and 100% of the aggregate. The study recommended limiting the amount of recycled aggregate to 75% and 50% for the coarse and fine aggre- gate, respectively. A reduction in compressive strength was reported with the increase in recycled aggregate replacement. The study found that the relationships between tensile and compressive strength for natural aggregate concrete can be used for the recycled aggregate concrete. Murshed, et al. 1997, investigated the use of combina- tions of coarse and fine RAP aggregate in normal concrete mixes and compared the results of compressive strength to conventional mixes with 0.4 and 0.5 water cement ratios. Compressive strength values were found to decrease with the increase in RAP content. The study concluded that the concrete mixes containing RAP can qualify for concrete applications such as sidewalks, driveways, curbs, and gut- ters. Recycling of Reclaimed Asphalt Pavement in Portland Cement Concrete Salim Al-Oraimi*, Hossam F. Hassan and Abdulwahid Hago Department of Civil and Architectural Engineering, P.O. Box 33, Al-Khoud, P.Code 123, Sultan Qaboos University, Muscat, Sultanate of Oman Received 18 June 2007; accepted 14 September 2007 Abstract: Reclaimed Asphalt Pavement (RAP) is the result of removing old asphalt pavement material. RAP consists of high quality well-graded aggregate coated with asphalt cement. The removal of asphalt concrete is done for reconstruction purposes, resurfacing, or to obtain access to buried utilities. The disposal of RAP represents a large loss of valuable source of high quality aggregate. This research investigates the properties of concrete utilizing recycled reclaimed asphalt pave- ment (RAP). Two control mixes with normal aggregate were designed with water cement ratios of 0.45 and 0.5. The con- trol mixes resulted in compressive strengths of 50 and 33 MPa after 28 days of curing. The coarse fraction of RAP was used to replace the coarse aggregate with 25, 50, 75, and 100% for both mixtures. In addition to the control mix (0%), the mixes containing RAP were evaluated for slump, compressive strength, flexural strength, and modulus of elasticity. Durability was evaluated using surface absorption test. Keywords: Reclaimed asphalt pavement, Concrete, Compressive strength, Elastic moduli á«à檰S’G áfÉ°SôÿG ‘ ™LΰùŸŸG »à∏Ø°S’G ∞°UôdG ôjh~J IOÉYEG ƒég ~MGƒdG~ÑY ,ø°ùM ΩÉ°ùM ,»Áô©dG ⁄É°S ::áá°°UUÓÓÿÿGG≥aGôª∏d ∫ƒ°Uƒ∏d hCG í£°ùdG á«£¨J IOÉYE’ hCG AÉ°ûfE’G IOÉYEG ¢VGôZC’ ádGRE’G á«∏ªY ºàJh .¥ô£dG øe â∏Ø°SC’G äÉ≤ÑW ádGREG á«∏ªY øe ™LΰùŸG »à∏Ø°SE’G ∞°UôdG èàæj ΩÉcôdG QOÉ°üe øe Q~°üŸ GQ~g OGƒŸG √òg øe ¢ü∏îàdG πãÁh ,â∏Ø°SC’ÉH ≈£¨e IOƒ÷G ¤ÉY ΩÉcQ ≈∏Y ™LΰùŸG »à∏Ø°SE’G ∞°UôdG …ƒàëj Ée ÉÑdÉZh .¥ô£dG â– áfƒa~ŸG á«e~ÿG á«fÉ°SôÿG äÉ£∏ÿG øe ÚàYƒª› º«ª°üàH ∂dPh ,™LΰùŸG »à∏Ø°SE’G ∞°UôdG ΩÉcQ øe áYƒæ°üŸG áfÉ°SôÿG ¢üFÉ°üN á°SGQO åëÑdG Gòg ∫hÉæàj ^IOƒ÷G ‹É©dG¤G AÉŸG áÑ°ùf ¿ƒµJ %50 h %25 h , áFÉŸG ‘ ôØ°U âfÉc É¡æe πc ‘ …OÉ©dG ΩÉcôdG¤G ™LΰùŸG »à∏Ø°S’G ∞°UôdG ΩÉcQ áÑ°ùf ¿G ɪc ,%50 á«fÉãdG áYƒªÛG ‘h %45 É¡æe ¤h’G ‘ â檰S’GG 50 Éeƒj 28 ~©H É¡H •É¨¶f’G OÉ¡LEG ≠∏H ~b (áFÉŸG ‘ ôØ°U) ™LΰùŸG »à∏Ø°S’G ∞°UôdG ΩÉcQ ≈∏Y …ƒà– ’ »àdG äÉ£∏ÿG ¿CG ~Lh , äÉ£∏ÿG QÉÑàNEÉHh . %100 h %75 h ,áfhôŸG πeÉ©eh , AÉæëf’G OÉ¡LGh , •É¨¶f’G OÉ¡LGh , •ƒÑ¡dG QÉÑàNG â檰 J ô°û©dG äÉ£∏ÿG ≈∏Y äGQÉÑàNG I~Y âjôLG ~bh . á«fÉã∏d ∫ɵ°SÉH Éé«e 33h ¤hÓd π°ùcÉH Éé«e .»ë£°ùdG ¢UÉ°üàe’G ᣰùJƒH äÉ£∏ÿG √òg áeƒÁO º««≤J ” ɪc áá««MMÉÉààØØŸŸGG ääGGOOôôØØŸŸGGGG.áfhôŸG πeÉ©e ,•É¨° fE’G Iƒb ,áfÉ°SôÿG ,™LΰùŸG »à∏Ø°S’CG ∞°UôdG : 38 The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 Limbachiya, et al. 2000, used recycled concrete as an aggregate in high strength concrete. Results indicated that up to 30% of recycled concrete aggregate had no effect on strength. At higher percentages, there was a gradual reduction in strength. The study presented a method to adjust the water cement ratio to overcome this reduction in strength. The study concluded that the high strength concrete made with recycled concrete aggregate can have equivalent engineering and durability performance to nor- mal high strength concrete. Jankovic, 2002, in his study, compared the effect of polymer admixture with a percentage of 0, 4, and 8 % on concrete made with combinations of recycled brick and river sand. The study concluded that there is no effect of polymer on compressive and flexural strength. However, the polymer provided some improvement in water resist- ance and frost resistance. The study recommended using the concrete made from recycled blocks in thermal insula- tors, and in bearing walls for buildings. This paper presents the results of a study conducted on the evaluation of using RAP in concrete mixes. Two mix grades are designed. Coarse aggregate is replaced with the coarse fraction of the RAP aggregate with various per- centages including 0, 25, 50, and 75%. Mix properties including: slump, compressive and flexural strength, elas- tic modulus and surface absorption are presented. 2. Experimental Program Aggregates used in the concrete mix consisted of 20 mm coarse aggregate (CA), fine aggregate (FA) and recy- cled asphalt concrete pavement (RAP). As a result of the cold milling operation, the RAP is in the form of loose particles coated with aged asphalt cement. RAP was sep- arated by sieving on the 5 mm sieve size into coarse and fine RAP. Normal portland cement type I was used. The aggre- gate and RAP gradation are shown in Fig. 1. The physical properties of aggregate and RAP are shown in Table 1. Two normal portland cement concrete control mixes (with no RAP aggregate) were designed with ratios of 1: 1.9 : 2.9 : 0.5 and 1 : 1.7 : 2.5 : 0.45 for cement to fine aggregate to coarse aggregate to water. The cube compres- sive strength after 28 days of water curing resulted in 33 and 50 MPa for the two mixes, respectively. The mixes were referred to as Mix 30 and Mix 50. The coarse aggregate was selected to be replaced with Aggregate Coarse Agg. Fine Agg. Coarse RAP Fine RAP Bulk SG 2.78 2.57 2.35 2.40 Bulk SG (SSD) 2.81 2.65 2.40 2.45 Apparent SG 2.84 2.78 2.5 2.5 Absorption (%) 1.8 1.5 1.8 1.6 LA Abrasion (%) 19.5 - 26.4 - Table 1. Aggregate and RAP physical properties 0 20 40 60 80 100 0.0 0.1 1.0 10.0 100.0 Sieve Size (mm) Pe rc en ta ge P as si ng (% ) . RAP 20 mm Coarse Agg. Fine Agg. Coarse RAP Fine RAP Figure 1. Grain size distribution for aggregate and RAP 39 The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 coarse RAP aggregate as it constitutes a higher percentage in the mix. The percentages of replacement were 0 (con- trol), 25, 50, 75, and 100 %, by weight of the coarse aggre- gate. Table 2 shows the mix quantities for the two mixes. The aggregate weights are based on saturated surface dry (SSD) condition. The fresh concrete mixes were tested for slump (ASTM C143-98) and unit weight (ASTM C138). Twelve 100 mm cubes, three 150 mm cubes, three 150 by 300 mm cylinders, and three 100 by 100 by 500 mm prisms were cast for each mix. All specimens were subjected to water curing. The 100 mm cube specimens were tested for com- pressive strength according to British standards (BS) (BS 1881-116) after 7, 14, 28, and 90 days of curing. The cylinders were tested for both modulus of elasticity (ASTM C469-94) and compressive strength (ASTM C873) after 28 days of curing. The prisms were tested for flexural strength (ASTM C78) after 28 days of curing. The 150 mm cubes were used to evaluate the durability of the mixes by the surface absorption test (BS 1881-208) after 56 days of curing. 3. Results and Discussion 3.1. Fresh Concrete Properties Table 3 shows the slump and unit weight for the two mixes for different percentages of RAP replacement. The table indicates a reduction in the slump value from 163 to 20 mm for Mix 30 and from 55 to 5 mm for Mix 50 with the increase in the percentage of RAP replacement from 0 to 100%. In general, the unit weight shows the same trend for both mixes as it decreases with the increase in percentage of RAP content. 3.2. Compressive Strength Figure 2 shows the results of the cube compressive strength (fcu) test after 7, 14, 28, and 90 days of curing for the different percentages of RAP replacement for Mix 30. The figure indicates the expected gain in strength with age. The figure also shows the reduction in strength with the increase in RAP content. Figure 3 shows the cube compressive strength (fcu) results for Mix 50. The figure also shows the gain in strength with curing and the reduc- tion in strength with the addition of RAP for all mixes. Quantity (kg/m 3) Mix RAP % Cement Fine Agg. Coarse Agg. Coarse RAP Water 30 0 380.0 730.0 1100.0 0.0 190.0 25 380.0 730.0 825.0 275.0 190.0 50 380.0 730.0 550.0 550.0 190.0 75 380.0 730.0 275.0 825.0 190.0 100 380.0 730.0 0.0 1100.0 190.0 50 0 425.0 714.3 1070.0 0.0 191.4 25 425.0 714.3 802.9 267.1 191.4 50 425.0 714.3 535.7 534.3 191.4 75 425.0 714.3 267.1 802.9 191.4 100 425.0 714.3 0.0 1070.0 191.4 Table 2. Mix quantities RAP Percentage Mix Parameter 0 25 50 75 100 30 Slump, mm 163 95 90 85 20 Unit Weight, kg/m 3 2458 2405 2392 2357 2323 50 Slump, mm 55 43 20 12 5 Unit Weight, kg/m 3 2442 2458 2435 2389 2377 Table 3. Slump and unit weight for different RAP content mixes 40 The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 For the 28 days compressive strength, the reduction in strength is indicated in Fig. 4 for both mixes. The figure indicates approximately 10% higher reduction in strength for Mix 50 compared with Mix 30. At 100% RAP replacement, the reduction is approximately 58 % for both mixes. Figures 5 and 6 show the development of cube com- pressive strength at different curing periods for both mixes and different RAP percentage. The figures show the ratio of the compressive strength at different curing periods to the compressive strength at 28 days of curing (develop- ment ratio). The development of strength was generally the same for both mixes. The results are similar to the reported typical values for the gain in strength for normal concrete (Mehta and Monteiro, 1993; Neville, 1987). The compressive strength for cylinders (fcyl) after 28 days of curing as well as the ratio of fcyl to fcu are shown in Table 4. The results indicate the reduction in strength with the increase in RAP content, which is consistent with the decrease in the case of cube specimens. The ratio of fcyl to fcu ranged from 0.77 to 0.89 for all specimens. 3.3. Flexural Strength Table 5 shows the flexural strength (modulus of rup- ture) (fr) results for the prisms after 28 days of curing. Predicted values based on the ACI Code equations (Mehta and Monterio, 1993) and the cylinder compressive strength (fcyl) are also shown, in addition to the ratio of (fr/fcyl). A general trend of reduction in strength with the increase in RAP content can be seen. The modulus of rup- 10 15 20 25 30 35 40 45 50 55 60 0 25 50 75 100 Percent of RAP Replacement C om pr es si ve S tre ng th (M Pa ) . 7 Days 14 Days 28 Days 90 Days Figure 2. Compressive strength for Mix 30 10 15 20 25 30 35 40 45 50 55 60 0 25 50 75 100 Percent of RAP Replacement C om pr es si ve S tre ng th (M Pa ) . 7 Days 14 Days 28 Days 90 Days Figure 3. Compressive strength for Mix 50 41 The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 0 10 20 30 40 50 60 70 0 20 40 60 80 100 120 Percent of RAP Replacement C om p. S tre ng th R ed uc tio n (% ) . Mix 30 Mix 50 Figure 4. Percentage reduction in compressive strength 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 1.40 0 14 28 42 56 70 84 98 Curing period (days) St re ng th D ev el op m en t ( f cu/ f cu 28 ) . 0% RAP 25% RAP 50% RAP 75% RAP 100% RAP Figure 5. Strength development ratio for cube compressive strength (Mix 30) 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 0 14 28 42 56 70 84 98 Curing period (days) St re ng th D ev el op m en t ( f cu/ f cu 28 ) . 0% RAP 25% RAP 50% RAP 75% RAP 100% RAP Figure 6. Strength development ratiofor cube compressive strength (Mix 50) 42 The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 ture decreased from 4.0 to 2.7 MPa for an increase in RAP replacement of 100% for Mix 30, about 33% reduction in strength. For the higher strength mix (Mix 50), the mod- ulus of rupture decreased from 5.5 to 3.9 MPa for the 100% RAP replacement, which amounts to 29% reduc- tion. The modulus of rupture results obtained from the lab- oratory tests are shown to be in agreement with the range given by the ACI equations. Moreover, the ratio of (fr/fcyl) for both mixes and for the different percentages of RAP replacement agrees with typical reported values for nor- mal concrete (Mehta and Monterio, 1993). 3.4. Modulus of Elasticity The modulus of elasticity was determined according to ASTM C469-94 on the cylinder specimens before crush- ing them. The results are shown in Figs. 7 and 8 for Mix 30 and 50, respectively. For comparison, the ACI build- ing code 318-83 gives the following expression for the static modulus of for normal weight concrete (Neville, 1987). (1) where, Ec = the modulus of elasticity in GPa and fcyl = the 28 days cylinder strength in MPa. The British Standards for the structural use of concrete BS 8110: Part 2: 1985 tabulates typical values of the static modulus of elasticity based on the 28 days cube strength. An expres- sion is proposed by Neville, 1987 based on the BS stan- dards as follows: (2) where, Ec = the modulus of elasticity in GPa and fcu = the 28 days cube strength in MPa. RAP Percentage Mix Parameter 0 25 50 75 100 30 fcyl a 29.4 23.8 20.9 15.9 12.4 fcyl/fcu b 0.89 0.81 0.80 0.81 0.87 50 fcyl a 39.5 30.3 24.0 19.8 16.9 fcyl/fcu b 0.79 0.79 0.77 0.83 0.81 Table 4. Cylinder compressive strength afcyl = cylinder compressive strength in MPa, bfcyl/fcu = ratio of cube t o cylinder compressive strength RAP Percentage Mix Modulus of Rupture (fr), MPa 0 25 50 75 100 30 Laboratory 4.0 4.30 3.3 3.1 2.7 ACI Code a 3.6 3.2 3.0 2.6 2.3 ACI Code b 5.4 4.9 4.6 4.0 3.5 ACI Code c 3.4 3.0 2.8 2.5 2.2 fr/fcyl 12 15 13 16 19 50 Laboratory 5.5 4.5 3.8 4.5 3.9 ACI Code a 4.1 3.6 3.2 2.9 2.7 ACI Code b 6.3 5.5 4.9 4.4 4.1 ACI Code c 3.9 3.4 3.0 2.8 2.5 fr/fcyl 11 12 12 19 19 Table 5. Prism flexural strength (modulus of rupture) alower range = cylf66.0 , bupper range = cylf0.1 , and crecommended value = cylf62.0 . c cylE . f=470 . c cuE . f= 0 339 1 43 The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 Both expressions 1 and 2 were used as shown in Figs. 7 and 8. The results indicate a decrease in the modulus as RAP percentage is increased. The results also indicate that the obtained results fall between the values predicted from both equations up to 50% RAP replacement. For higher percentages of RAP, the modulus is lower than that given by both equations. A regression analysis was per- formed on the ten mixes to obtain equations similar to Eqs. 1 and 2, the resulting equations were as follows: (3) (4) where, Ec, fcyl and fcu are as defined before; and R2 and R2adj are the coefficient and adjusted coefficient of deter- mination, respectively. 3.5. Durability The initial surface absorption test (BS 1881-208) was performed as an indicator for the durability of the mixes. The test gives the water flow (in ml/m2/sec) into the sur- face of a dry cube specimen subjected to a head of 200 mm. Water is allowed to penetrate the surface for periods of 10, 30, 60 and 120 minutes. At the end of each period, flow measurements were made. Figure 9 shows the results for Mix 30. The figure indi- cates a reduction in surface absorption with time. The same observations apply to Fig. 10 (Mix 50). The flow at 120 minutes for Mix 30 was in the range of 0.057 to 0.093 ml/m2/sec. Lower flow values were obtained for mix 50 with values in the range of 0.043 to 0.063 ml/m2/sec. The results did not indicate a significant difference in the absorption with the increase in RAP content for both mixes. However, a lower flow was obtained for the stronger mix (mix 50) which should be anticipated. 5 10 15 20 25 30 35 40 0 25 50 75 100 Percentage of RAP Ec (G Pa ) . Laboratory ACI BS Figure 7. Modulus of elasticity for Mix 30 5 10 15 20 25 30 35 40 0 25 50 75 100 Percentage of RAP Ec (G Pa ) . Laboratory ACI BS Figure 8. Modulus of elasticity for Mix 50 . c cylE . f= 11065 (R2 = 0.85, R 2adj = 0.87) . c cuE . f= 1050 61 (R2 = 0.85, R 2adj = 0.87) 44 The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 4. Conclusions Reclaimed asphalt pavement was used as a coarse aggregate substitute in two different normal concrete mixes having 28 days cube compressive strengths of 33 and 50 MPa. RAP was used with 25, 50, 75, 100% replacement of coarse aggregate. The slump decreased with the increase in RAP content. The compressive and flexural strength decreased as well with the increase in RAP content. The general trend of strength development, as well as the relations between flexural strength, elastic modulus and compressive strength for the RAP mixes agreed well with that for normal concrete. The surface absorption was not significantly affected by the addition of RAP. The results indicated the viability of RAP as an aggregate in non-structural concrete applications. The percentage of RAP should be limited according to the application. Low slump should also be considered when utilizing RAP in the mixes. References ASTM C138-2000, Standard Test Method for Unit Weight, Yield, and Air Content (Gravimetric) of Concrete. ASTM C143-98, Standard Test Method for Slump of 0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450 0.500 0 10 20 30 40 50 60 70 80 90 100 110 120 130 Time, min. Fl ow , m l/m 2 / se c. 0% 25% 50% 75% 100% Figure 9. Initial surface absorption for Mix 30 0.000 0.050 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450 0.500 0 10 20 30 40 50 60 70 80 90 100 110 120 130 Time, min. Fl ow , m l/m 2 / se c. 0% 25% 50% 75% 100% Figure 10. Initial surface absorption for Mix 50 45 The Journal of Engineering Research Vol. 6, No.1, (2009) 37-45 Hydraulic-Cement Concrete. ASTM C469-94, Standard Test Method for Static Modulus of Elasticity and Poisson's Ratio of Concrete in Compression. ASTM C78-94, Standard Test Method for Flexural Strength of Concrete (Using Simple Beam with Third Point Loading). ASTM C873-99, Standard Test Method for Compressive Strength of Concrete Cylinders Cast in Place in Cylindrical Molds. BS 1881: Part 166: 1983, Method for Determination of Compressive Strength of Concrete Cubes. BS 1881: Part 208: 1996, Recommendations for the Determination of the Initial Surface Absorption of Concrete. Jankovic, K., 2002, "Using Recycled Brick as Concrete Aggregate," Proceedings of the International Conference: Sustainable Concrete Construction, Dundee, UK, pp. 232-240. Kenai, S., Debieb, F. and Azzouz, L., 2002, Mechanical Properties and Durability of Concrete made with Coarse and Fine Recycled Aggregates," Proceedings of the International Conference: Sustainable Concrete Construction, Dundee, UK, pp. 383-392. Limbachiya, M.C., Leelawat, T. and Dhir, R.K. 2000, "Use of Recycled Concrete Aggregate in High- Strength Concrete," Materials and Structures/Materieux et Constructions, Vol. 33, pp. 574-580. Mehta, P.K., Monteiro, P.J.M., 1993, Concrete: Microstructure, Properties, and Materials, McGraw Hill, New York. Murshed, D., Fahmy, M. and Taha, R., 1997, "Use of Reclaimed Asphalt Pavement as an Aggregate in Portland Cement Concrete," ACI Materials Journal, Vol. 94(3), pp. 251-256. Neville, A.M. and Brooks, J.J., 1987, "Concrete Technology," Longman Scientific & Technical, UK. Yrjanson, W.A., 1989, "Recycling of Portland Cement Concrete Pavements, Synthesis of Highway Research Practice 154," National Cooperative Highway Research Program, Transportation Research board, National Research Council, Washington, pp. 3-36.