Use of digital image analysis to determine fracture properties of alkali-activated mortars

•The fracture properties of three alkali-activated mortars are studied.•Low values of fracture energy might be associated with the presence of unreacted FA.•The fracture energy depends on the type of aggregate used.•Digital image correlation can be used to estimate the size of the FPZ. Results of three-point bending tests on notched beams cast with three alkali-activated mortars that differ by the type and size of the aggregates are presented. Digital image correlation is used to estimate the size of the fracture process zone. The fracture energy is computed by means of the work-of-fracture method and found to be strongly dependent on the type of aggregate used and does not differ whether the LDVT or DIC load-deflection curves are used. Finally, low values of the fracture energy in alkali-activated mortars might be associated with the presence of unreacted fly ash.