Effects of healing agent on shape memory, mechanical and self-healing properties of joint filler on cement concrete pavement

To improve the self-healing performance of joint filler on cement pavement and determine the healing agent content for preparing titanium dioxide/ shape memory polyurethane (TiO2/SMPU) composite as joint filler, the influences of PCL content on different properties of TiO2/SMPU joint filler were investigated before and after the two-stage uniaxial training, as well as after free recovery. Results indicate that the shape memory transition temperature of TiO2/SMPU joint filler and melting temperature of healing agent of thermoplasticpolycaprolactone (PCL) meet the requirements of two-stage uniaxial training and two-step self-healing of TiO2/ SMPU joint filler. Also, SMPU matrix has a good compatibility with PCL particles, and there are no chemical reactions between PCL and TiO2/SMPU. The physical cross-linking reactions between PCL and SMPU matrix occur during the self-healing at high temperature, providing a basis for PCL to repeat the self-healing. After the two-stage uniaxial training, TiO2/SMPU joint filler shows satisfactory shape memory performance, but when PCL content is more than 10%, TiO2/SMPU joint filler shows lower shape memory effects. Additionally, the two-stage uniaxial training method improves the mechanical properties and repeated self-healing ability of TiO2/SMPU joint filler after the two-step self-healing method. Finally, the PCL content of 10% is suggested to prepare TiO2/SMPU joint filler of expansion joint after the two-stage training to reduce the damages of cement concrete pavement.