Influences of silicon carbide fineness on thermal and mechanical properties of cement-based composites

Abstract

Cement-based composites with high thermal conductivity have important application potential in building engineering, such as ground source heat pump and high-efficiency floor heating system. In order to study the influences of silicon carbide (SiC) fineness on the thermal and mechanical properties of cement-based composites, SiC with different fineness was used to prepare cement-based composite materials (CCMs). A series of tests, including microstructure analysis, compressive and flexural strength, thermal conductivity, thermogravimetric analysis and heating simulation test were performed to investigate the thermal and mechanical properties of CCMs. The results reveal that SiC was wrapped by hydration system evenly and could keep its good structural integrity. Reducing SiC fineness could enhance the air-entraining effect, which could produce more weak interfacial areas and pores in hydration system. The degree of cement hydration reduced as the fineness of SiC reduced. Finer SiC usually led to higher thermal conductivity of CCMs, and the thermal conductivity of CCMs could be increased by 125.34% compared with the control group. The compressive and flexural strength increased first and then decreased as the fineness of SiC reduced. The heating simulation test indicates that the thermal performance of CCMs increased with reducing SiC fineness. Specially, the heating efficiency of CCM-3 increased by 21.6% compared with the control group. The results could be helpful in improving the thermal performance of heating system and reducing carbon dioxide emissions.