Laboratory investigations of activated recycled concrete aggregate for asphalt treated base

• We analyze the mineral composition of RCA and observe surface morphology by SEM.
• We select the best activator out of three used to activate RCA.
• We prove that substituting natural aggregate by RCA in ATB is feasible.

Asphalt treated base ATB-25 was designed containing recycled concrete aggregate (RCA), which was pretreated with three types of activators in various amount. Crushed value, water absorption, density and adhesion with asphalt of RCA were tested. Four mixtures of ATB-25 were designed containing different contents of RCA: 0%, 30%, 60% and 100%. Marshall test, rutting test, water stability test and low-temperature bending test were conducted to evaluated road performances of above mixtures. It was found that the voids and microfractures existing in RCA led to large water absorption and crushed value and low density and strength. Application of activator effectively decreased crushed value and water absorption and enhanced adhesiveness with asphalt due to closing of voids in RCA. The activation effect of organic silicon resin was superior to that of metatitanic resin acceptor and silane resin acceptor. Because of asphalt absorption by microfractures, asphalt content and oil absorption of ATB increased as RCA content increasing. While effective asphalt content of different mixture were basically the same, indicating that RCA and natural aggregate had the same effective thickness of asphalt film. Residual Marshall Stability, tensile strength ratio and low-temperature bending strain of ATB decreased with RCA content increasing. Low-temperature bending strain decreased to 1728.5με when RCA content increased to 100%, which was less than the required value of specification of China. No obvious relationship was found between dynamic stability and RCA content, but dynamic stability of all ATB mixtures containing RCA satisfied the requirement in specification of China. ATB-25 mixtures containing less than 60% of RCA satisfied all the requirements of specification of China.