Effects of rice husk ash and fly ash on low-temperature PCM aggregate concrete: Relieving frost heave through sensible and latent heat

Temperature is one of the primary factors influencing frost heave. It is feasible to reduce and compensate for heat loss through the sensible and latent heat of concrete, thereby mitigating frost heave deformation. This paper investigated the effect of incorporating rice husk ash (RHA) and c ash (FA) into phase change material (PCM) aggregate concrete on concrete properties, especially temperature response. Specifically, the study focused on incorporating 10-20 % RHA and 5-15 % FA to reduce the temperature drop by utilizing sensible heat. The study also considered their effects on density, workability, thermal constants, and crystal compounds. The results showed that the incorporation of RHA reduced the density and workability of concrete, making it more viscous. However, the addition of FA improved the negative impact of RHA on the workability. The pozzolanic and filling effect of them increased the strength of concrete. The addition of 20 % RHA decreased the thermal conductivity and thermal diffusivity of concrete by 33.83 % and 43.49 %, respectively. The thermal impact of FA on concrete was not as pronounced as that of RHA. The time-temperature curve indicated that the temperature difference between the concrete containing 20 % RHA-15 % FA and the control concrete can reach up to 4.3 degrees C. The time taken for the concrete containing 20% RHA-15 % FA to reach the minimum temperature was delayed by 25 min compared to that of the control concrete. The XRD results revealed that the addition of RHA and FA led to the consumption of portlandite, indicating a pozzolanic reaction in RHA and FA.