Bonding performance evaluation on WTR-APAO composite modified asphalt as waterproof adhesive layer for concrete bridge

Abstract

• The preferred concrete surface depth was 0.88 mm, and the gravel covering rate at 70 %. • The optimal dosages of WRAMA, WRMA, and SMA were 1.7 kg/m 2 ,1.2 kg/m 2 and 1.2 kg/m 2 . • WRAMA has higher bonding performance than WRMA and SMA at mid and high temperatures. • WRAMA shows good resistance to water immersion, freeze–thaw cycling, and aging. • The material cost of WRAMA is 30% lower than SMA based on economic comparison. Insufficient bonding at the waterproof adhesive layer (WAL) between the concrete bridge deck and asphalt pavement surface often leads to distress on the bridge or its surfacing pavement. This study proposes a relatively novel material, WTR (Waste Tire Rubber)/APAO (Amorphous Poly Alpha Olefin) composite modified asphalt (WRAMA), as WAL and evaluates its bonding performance compared to the commonly used interlayer SBS modified asphalt (SMA) and waste tire rubber modified asphalt (WRMA). The bonding performance was evaluated using straight shear tests and pulling out tests. Firstly, the optimal concrete surface chiseling depth was explored and determined at 0.88 mm, corresponding to 2 rounds of chiseling on the concrete surface. Then the preferred gravel coverage rate was set at 70 %, and optimum asphalt dosages were determined at 1.7 kg/m 2 , 1.2 kg/m 2 , and 1.2 kg/m 2 for SMA, WRMA, and WRAMA, respectively. While all three asphalts show good impermeability at their preferred dosage, WRAMA has the highest shear and pulling strength. Secondly, the bonding performances of investigated asphalts were evaluated and compared under controlled environments, including water immersion, temperature, free-thaw cycle, and aging. The results showed that WRAMA has the slightest temperature sensitivity but the least moisture resistance than SMA and WRMA. However, the shearing and pulling strength of WRAMA after freeze–thaw and water immersion was around 0.45 MPa, still higher than SMA (around 0.40 MPa) and WRMA (around 0.39 MPa). All three asphalts have decent resistance to aging. Thirdly, a preliminary economic analysis was conducted, and the results show that the material cost of WRAMA is around 66 % of SMA. Considering the WRAMA makes use of wasted tire rubber, this research reveals that the proposed WTR/APAO composite modified asphalt is potentially a cost-effective and environmental-friendly waterproof adhesive layer.