Temperature-dependent effect of nanoscale phase change materials on fresh and hardened cement-based mortar

As smart and innovative materials, temperature-dependent phase change materials (PCMs) can be used to produce environmentally friendly energy-saving concrete. In this study, the fresh and hardened concrete properties of mortars incorporating PCMs in different ratios (0%, 2.5% and 5%) were experimentally investigated. Rheological properties such as slump flow, specific viscosity and yield stress were determined at different temperatures (20–50°C). Time-dependent physical, mechanical and thermal properties such as ultrasound pulse velocity (UPV), electrical resistivity, dynamic modulus of elasticity and compressive and flexural strengths were determined. Thermogravimetric analysis and thermal conductivity tests were also carried out. The experimental findings showed that the workability and hardened properties of mortars decreased with the addition of PCM. However, the rheological properties of the fresh mortar changed depending on the temperature due to the PCM absorbing heat. Therefore, the fresh properties of mortar with PCMs can be controlled by temperature. It was also found that the phase change of mortars with PCM could be obtained by measuring the electrical resistivity or UPV at different temperatures.