Effect of waste colemanite and PVA fibers on GBFS-Metakaolin based high early strength geopolymer composites (HESGC): Mechanical, microstructure and carbon footprint characteristics

Abstract

This study investigated the effects of polyvinyl alcohol (PVA) fiber and colemanite on the physical, mechanical and transport characteristics of GBFS-metakaolin-based geopolymer composites with high early-age strength (HESGC). The microstructure was intensified using 100, 150 and 200 kg/m3 colemanite instead of quartz powder. In addition, 0.25% and 0.50% PVA fiber were added to the blend to prevent the permeability problem in the condensed microstructure. HESGCs were cured in 3 different environments: ambient, 60 and 80 °C. The binder dosage (GBFS + Metakaolin) in HESGCs is 750 kg/m3. The alkali solution ratio is approximately 75% (according to binder amount. While the apparent porosity exceeds 10% in HESGCs subject to ambient cure, the porosity % in heat-cured HESGCs) In addition, the porosity and water absorption decrease when colemanite is used in heat cured HESGCs. Adding 0.25% PVA fiber to HESGCs creates a micro-aggregate effect, reducing porosity and water absorption relatively. It varies between 2393 kg/m3. The compressive strength (fc) of HESGCs subjected to ambient cure varies between 27.5 and 43.8, and the fc of HESGCs heat cured at 80 °C varies between 77.4 and 95.6 MPa. The flexural strength (ff) of HESGCs varies between 3.6 and 13.3 MPa. As the PVA fiber content and curing temperature increase, the ff increases. If 0.5% PVA fiber is used, the ff of HESGCs is increased between 8.3% and 89.6%0.200 kg/m3 colemanite is used in heat-cured HESGCs fc can increase up to 20%. While 0.25% PVA fiber ratio is the most suitable ratio in fc, 0.5% PVA fiber ratio is more suitable in ff. The capillary water absorption of HESGCs varies between 0.27–2.67 kg/m2. In the case of heat curing of HESGCs at 80 °C instead of ambient curing, capillary water absorption can be reduced up to 88%. Using colemanite instead of fine aggregate in microstructure investigations intensified the microstructure, but using 0.5% PVA fiber increased the porosity relatively. As a result, it has been observed that heat curing must be used in colemanite-containing HESGCs. When a heat cure is applied to HESGCs containing 0.25% PVA fiber and 200 kg/m3 colemanite, a fc of more than 12 MPa can be obtained.