Elucidating The Crack Resistance Of Alkali-Activated Slag Mortars Using Coupled Fracture Tests And Image Correlation

The resistance of alkali silicate-activated slag mortars to crack propagation is explored. With increasing SiO2-to-alkali oxide ratio (M-s) of the activating solution (between 1.0 and 2.0), the flexural strengths, fracture energies, and the strain energy release rates (crack resistance, G(R)) are noted to increase. The G(R) values, especially of the systems with M-s of 1.5 and 2.0, are higher than that of ordinary portland cement (OPC) mortar. In contrast, the fracture process zone (FPZ) was observed to be smaller for the alkali-activated slag mortars, with higher localized strains. Similarly, the FPZs also shrink with increasing M-s. These responses are related to the differences in the reaction products in these systems. The fundamental differences in the fracture response of these binder systems are elucidated through tracking the FPZ development. The crack extension-crack tip opening displacement relations and its relationship with the inelastic strain energy release rates are also used to bring out the differences between the binder systems.