Performance evaluation of hot mix asphalt containing recycled concrete aggregates treated by physical and chemical methods

Hot mix asphalt (HMA) can be formulated with recycled aggregates derived from construction and demolition waste, thereby reducing reliance on natural aggregates. This represents a novel approach to resource management within the construction industry. However, the low-quality coarse recycled concrete aggregates (CRCAs) produced by simple crushing cannot meet the construction technical requirements of asphalt pavement. In this study, two methods, including high-temperature mechanical grinding (HM-CR) and the chemical agent tetraethyl orthosilicate (TEOS) solution infiltration (TS-CR), were used to treat and strengthen the CRCAs. Basic physical indices were tested before and after the treatment, including apparent specific gravity, water absorption, crushing value, mortar adhesion, and asphalt adhesion. Scanning electron microscopy (SEM) and X-ray fluorescence spectrometry (XRF) were employed to analyze the microscopic properties as well as the chemical composition. Results showed that high-temperature mechanical grinding at 400°C with 500 rpm emerged as the most effective physical treatment method, while impregnation with a TEOS mixture with a concentration of 1:6 for 24 hours was recommended as the most effective chemical treatment method. CRCAs treated with the above physical and chemical treatments were incorporated into AC-20 hot mix asphalt at 0 %, 15 %, 30 %, and 45 % by the mass of hot mix asphalt. The hot mix asphalt containing treated recycled concrete aggregates underwent tracking tests through high-temperature wheel tracking, low-temperature trabecular bending, Marshall immersion, freeze-thaw splitting, four-point bending beam fatigue, and IDEAL-CT cracking tests. Results revealed that the addition of CRCAs improved the high-temperature stability of hot mix asphalt to a certain extent. HM-CR improved the low-temperature cracking resistance, water stability, and mechanical properties of hot mix asphalt containing treated recycled concrete aggregates. When the content of CRCAs was controlled below 30 %, the performance of hot mix asphalt met the requirements of the specification.