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Each year around 200 million tons of demolition wastes are produced from aging U.S. infrastructures. Of that amount, 100 million tons are portland cement concrete debris. Disposal of these wastes in landfills has been a traditional solution, but environmental regulations, costs, and a lack of landfill areas have hindered safe disposal. These problems have led to a search for alternate ways of reusing demolition wastes by recycling. Recycling the concrete waste not only reduces the waste disposal problem but also reduces the quarrying of virgin aggregate. The incorporation of recycled concrete as a hot-mix asphalt (HMA) aggregate can be a viable option in terms of costs and environmental considerations. This use of recycled concrete aggregate (RCA) as an HMA aggregate can be beneficial for constructing low-volume roads. RCA differs from virgin aggregates in that there is cement paste on the surface of the recycled concrete. In this study, 5% RCA was evaluated as an HMA aggregate. Mix designs were conducted, and the effect of RCA on the volumetrics of HMA was evaluated. The mix design results indicated that RCA is absorptive, and that as the percentage of recycled concrete increased in the mix, the optimum asphalt content increased linearly. The statistical regression model showed that RCA had significant effects on the volumetrics of the mix.

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The use of recycled concrete aggregate (RCA) in asphalt mix is a sustainable construction practice, provided that the addition of RCA does not adversely affect the performance of the asphalt mix. In this study, the effects of RCA on the performance behavior of hot mix asphalt (HMA) were examined. The mixes were produced by blending RCA with virgin aggregate at six different percentages (0 %, 20 %, 40 %, 60 %, 80 %, and 100 %). The mix design results indicate that the RCA is highly absorptive, and that as the percentage of RCA in the mix increases, the optimum asphalt content increases significantly. In terms of performance behavior, the addition of RCA to the HMA mix reduced the modulus, resistance to rutting, fatigue, thermal cracking, and resistance to moisture damage of the asphalt mix. Considering the performance behavior and the need for a higher asphalt content, the use of RCA as HMA aggregate is not recommended, even though all the RCA mixes met the volumetric requirements. More important, the findings in this study indicate that the absorbed asphalt might play a significant role at high temperatures, likely because of expansion of the asphalt.