Value-added utilization of recycled concrete in hot-mix asphalt

摘要

The feasibility of partial substitution of granite aggregate in hot-mix asphalt (HMA) with waste concrete aggregate was investigated. Three hybrid HMA mixes incorporating substitutions of granite fillers/fines with 6 percent, 45 percent untreated, and 45 percent heat-treated concrete were evaluated by the Marshall mix derign method: the optimum binder contents were found to be 5.3 percent, 6.5 percent and 7.0 percent of grade Pen 60/70 bitumen, respectively. All three hybrid mixes satisfied the Marshall criteria of the Singapore Land Transport Authority (LTA) W3B wearing course specification. The hybrid mix with 6 percent concrete fillers gave comparable resilient modulus and creep resistance as the conventional W3B mix, while hybrid mixes with higher concrete substitutions achieved better performance. X-ray diffraction (XRD) showed the distinct presence of free lime in the heat-treated concrete, while the scanning electron microscope (SEM) provided an in-depth perspective of the concrete grains in the HMA matrix. The results suggest feasible use of waste concrete as partial aggregate substitution in HMA.