Explorative Study into Alkali-Activated Repair Mortars Using Blast Furnace Slag and Glass Waste

The repair of concrete structures is increasing in prevalence. Conventional repair mortars are expensive materials rich in Portland cement (PC) and other organic and inorganic components that question their economic efficiency and carbon footprint. Alkali-activated materials (AAMs) are an eco-friendly alternative to PC that possess properties desirable for repair mortars. The article presents the mix design, mechanical, bond, and shrinkage properties of alkali-activated binary mortars intended for structural concrete repair. Mix optimisation based on mechanical properties of repair mortar and utilisation of glass waste (GW) is presented together with total and restrained shrinkage, pull-off bond tests, and life cycle assessment (LCA) for selected configurations. Results demonstrate good compressive and flexural strength, exceeding 45 N/mm2 and 7 N/mm2, an excellent pull-off bond strength (1.8-2.3 N/mm2) of the alkali-activated mortar to the concrete substrate, in spite of extensive shrinkage, with an order of magnitude of a couple of thousands of microstrains, which is also reported. Shrinkage appears to increase with the increase of the applied GW in the mixture. LCA revealed that alkali-activated mortars have up to 54% lower CO2 eq. emissions compared to PC-based repair mortar.