Physical, mechanical properties and microstructure of waste GBFS-based geopolymer incorporated with metakaolin and SiC whiskers(SiCw)

Abstract

Geopolymer, known as alternative materials to ordinary Portland cement, possess superior properties. This study employed varying dosages of metakaolin from 0 to 30 % and silicon carbide whiskers (SiCw) from 0 to 0.05 % to enhance GBFS-based geopolymer matrix. The process began with the dispersion of SiCw in an alkaline activator through magnetic and ultrasonic stirring, followed by the preparation of the geopolymer. Physical and mechanical characteristics were evaluated to reveal the improvement effects of metakaolin and silicon carbide whiskers on the geopolymer. Techniques such as FTIR, XRD, and SEM-EDS were utilized to analyze the morphology, chemical components, and mineral phases. Pore size distribution and microstructural rearrangement were assessed using MIP and 29Si NMR. Additionally, TG-DTG analysis was conducted to analyze thermal stability. The results indicated that optimal additions of metakaolin and SiCw increased interactions among gel products and induced more chemical reactions, thus exhibiting better mechanical strength and thermal properties. The water absorption and permeable porosity were also improved. The inclusion of SiCw notably provided more nucleation sites and increased the dissolved aluminum content, enriching the phase in the system.