Comparison between cementitious and geopolymeric mortars with the same mechanical strength class

In the perspective of environmental sustainability for the rehabilitation and restoration of masonry buildings, the properties of geopolymeric mortars were studied and compared with those of traditional cement-based ones with the same mechanical strength class and workability. To this aim, four different geopolymeric and cement mixtures were manufactured in order to obtain mortars belonging to R1  10MPa, R2  15MPa, R3  25 MPa and R4  45 MPa strength class. In particular, geopolymeric mixtures were prepared with a sodium silicate/sodium hydroxide equal to 1:1, by using different concentration of the solutions, and sand/fly ash proportion equal to 2.7:1. The respective four cementitious mortar mixtures were prepared with water/cement equal to 0.5, 0.65, 0.9 and 1.1 by weight. Geopolymer mortars behave better than cement ones in terms of lower elastic modulus, higher water vapour permeability, lower capillary water absorption and higher resistance to salt crystallization.