Microstructure and compressive properties of silicon carbide reinforced geopolymer

The typical compressive strength of geopolymers and their composites is usually limited to around 80 MPa, therefore they should be further strengthened for wider applications, such as ultrahigh strength concrete and bone replacement. This paper presents a facile method for enhancing the compressive strength by incorporating silicon carbide particles (SiCp) and silicon carbide whiskers (SiCw) into a geopolymer matrix via the geopolymerization of metakaolin (MK). The effects of the reinforcement of SiCpand SiCwon the microstructure, thermal properties and compressive properties of the composites were investigated. The SEM images showed that both SiCpand SiCwwere well dispersed in the geopolymer matrix. Due to the bridging effect among the SiCwparticles, the silicon carbide whisker/geopolymer (SiCw/GP) composites possessed higher porosity and lower density, and thus lower thermal stability and thermal conductivity as compared with the silicon carbide particle/geopolymer (SiCp/GP). The mechanical tests showed that the compressive strength of SiCp/GP composites increased with the increase of SiCpconcentration. With an optimum concentration of 10 wt % of SiCp, the compressive strength of the composite was enhanced to 155 MPa, corresponding to a 100% increase as compared with the unfilled geopolymer.