The Effect of RHA as a Supplementary Cementitious Material on the Performance of PCM Aggregate Concrete

The thermal insulated cement matrix further enhances the thermal insulation of PCM aggregate concrete, consequently reducing energy consumption. In this paper, 0–15% rice husk ash (RHA) was used as a replacement for cement. The effect of the substitution amount of RHA on the workability, mechanical properties, thermal properties, and pore structure of concrete was investigated. The results showed that the density of concrete decreased after replacing cement with RHA. The workability of concrete decreased with the increase in RHA content. The filling effect and pozzolanic effect of RHA resulted in an initial increase and subsequent decrease in the mechanical properties of the concrete. After the cement was replaced by 10% RHA, the concrete exhibited the highest compressive strength and splitting tensile strength. The high porosity of RHA reduced the thermal conductivity of concrete by 12.29%. The temperature response indicated that the temperature difference between 15% RHA concrete and the reference concrete can reach up to 1.2 °C, potentially reducing the energy demand. The NMR results showed that the total pore volume was minimal with a 10% RHA admixture. The capillary pore volume increased slightly with the increase in RHA substitution due to the presence of numerous micron-sized pores within the RHA. The micropore and macropore volumes exhibited a decreasing and then increasing trend.

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