Shotcrete based on composite cement using industrial waste

Reinforced shotcrete was developed and studied for strengthening underground structures. The article novelty lies in the fact that for the first time shotcrete was developed using composite cements, including aluminosilicates from enriched ash-to-slag mixtures. Slight slump flow decrease (47 cm) was observed with aluminosilicate content of 35 wt. %. The effect of increasing compressive strength of shotcrete on composite cement was manifested with an increase in content of aluminosilicates to 35 wt. (56 % higher) and 62 % higher flexural strength. This is confirmed by the high ratios of strength properties in the first day to those at the age of 28 days: compressive strength 0.27 (0.23 for clinker compositions without additives), flexural strength 0.30 (0.26 for clinker compositions). The effectiveness of using the developed shotcrete for strengthening load-bearing structures of underground objects was proven with increase in strength by more than 2 times, which is explained by both high strength of the resulting repair composition and monolithic contact zone between old and new concrete layers. Developed shotcrete can provide the necessary degree of strengthening of load-bearing structures of underground objects, and thickness of the repair layer of 6 cm (with proper soil consolidation) allows using of underground structures as protective objects.