The influence of sapphire substrate silicon carbide sludge on structural properties of metakaolin-based geopolymers

Abstract

This study investigated a geopolymerization system focused on the effects of the solid-to-liquid ratio (S/L) were ranging from 0.4 to 1.0, which produces geopolymers with various silicon carbide sludge (SCS) replacement levels (0–40 wt. %). The results indicated that the silicon carbide sludge metakaolin-based (SCSMB) geopolymers increased S/L ratios from 0.8 to 1.0, reducing initial and final setting times. Flexural strength of SCSMB geopolymers of the SL ratio of 0.4 increased rapidly from 1.31 to 1.70 MPa during the early stage of curing (1–14 days). For SCSMB geopolymers with 10–40% SCS replacement, peak of SiOSi bonds for geopolymers at 524 cm−1 shifted to a higher wavenumber of 527 cm−1. 29Si nuclear magnetic resonance (NMR) showed that SCSMB geopolymer with an SCS replacement ratio of 10% increased S/L ratios from 0.8 to 1.0 (56 days) and increased the fractions of Q4(3Al; 38.2%–38.4%), Q4(2Al; 28.7%–31.7%), and Q4(1Al; 13.7%–14.6%). Moreover, the peak in 29Si NMR spectra shifted to the right side (higher frequency), indicating that an increased number of aluminum tetrahedrons coordinated with silicon tetrahedrons. SCSMB geopolymers with 10% SCS replacement and an S/L ratio of 1.0 yielded highly favorable mechanical characteristics and microstructure.