Effect of bitumen grade on hot asphalt mixes properties prepared using recycled coarse concrete aggregate

The research aims at evaluating the effect of using recycled coarse concrete aggregates (RCA) on the basic properties of hot mix asphalt made with different grades of bitumen (60/70 and 80/100). First, recycled aggregate properties have been determined and compared to those of normal aggregates. Except for absorption, there were no significant differences between normal aggregates and RCA. Later, recycled aggregates were introduced in asphalt mixes using either 60/70 bitumen or 80/100 bitumen. In these mixes, natural coarse aggregate was partly (0%, 25%, 50% and 75%) or totally (100%) replaced by recycled aggregates. Replacement results show that the use of recycled aggregates increased the optimum bitumen content of the asphalt mixes. Properties and performance of mixes made from both grades of bitumen were compared. Although the increase of RCA percentage decreased the resilient modulus of the asphalt mixes, it increased their skid resistance. However, 60/70 bitumen increased the resilient modulus and skid resistance of the asphalt mixes compared to 80/100 bitumen. Mixes containing RCA show lower water sensitivity (stripping resistance) than RCA-free mixes. However, replacements up to 50% do not violate the 80% tensile strength ratio limit. Although the 50% replacement limit is acceptable, however, the volumetric properties were violated at this replacement ratio. Therefore, for both grades of bitumen, replacements more than 25% should not be used in hot mix asphalt for heavy traffic pavements.