Development of thermal energy storage lightweight structural cementitious composites by means of macro-encapsulated PCM

Abstract

The aim of this paper is to develop a structural lightweight concrete with function of indoor temperature control feature using thermal energy storage aggregates (TESA). TESA were made of porous structural lightweight aggregate (LWA) impregnated with liquid phase change materials (PCM) and coated with epoxy resins and silica fume. The macro-encapsulated technique was used to incorporate the PCM into the LWA through vacuum impregnation. The basic properties of TESA concrete including compressive strength, splitting tensile strength, elastic modulus, water absorption and drying shrinkage were assessed. The thermal performance of TESA concrete was studied by using a self-designed environmental chamber. The thermal stability and reliability of PCM after 500 thermal cycles were investigated by thermogravimetry analysis (TGA) and differential scanning calorimeter (DSC) tests. The microstructure of TESA concrete was also examined via scanning electron microscopy (SEM) analysis. The test results showed that the compressive strength of TESA concrete decreased with increase in TESA content. However, the compressive strength and elastic modulus of TESA concrete were higher than those of coated/uncoated LWA concrete samples. The water absorption and drying shrinkage of TESA concrete reduced because of the reliable coating system as well as the PCM contribution in reducing thermal cracks during the hydration process. The thermal performance test results showed that using TESA concrete could reduce the energy consumption by lowering the indoor temperature. The SEM results confirmed that there was no PCM leakage after the thermal cycles, indicating the integrity of the coating system in TESA concrete. Finally, it is suggested that the concrete mixture 100TESA can be used in structural concrete to serve both structural and thermal functions.