Cement mortars and geopolymers with the same strength class

Recycling of industrial waste materials to manufacture environmentally friendly mortars and concretes is gaining more and more interest, in particular for sustainability, rehabilitation and renovation purposes. In the present study geopolymers, which had been made using fly ash as a precursor and were subsequently subjected to curing at room temperature, were investigated. Geopolymeric and cementitious mortars with the same mechanical strength class were compared in both the fresh and hardened states. Despite the higher free shrinkage and lower adhesive strength on brick substrate, geopolymeric mortars behaved better than cement types in terms of lower dynamic modulus of elasticity, higher water vapour permeability, lower capillary water absorption and higher resistance to salt crystallisation.