Natural hydraulic lime for blended cement mortars: Behavior from fresh to hardened states

This paper presents the influence of natural hydraulic lime (NHL) on the behavior of cement-based materials at fresh and hardened states. Two reference mortars with and without limestone filler (LF) and with water-to-cement ratio of 0.6 were considered. For each reference mixture, cement was replaced by NHL with increasing mass proportions of 12.5%, 25% and 50%, while maintaining a constant paste volume. The freshly mixed pastes and mortars were tested for rheology, hydration process and setting properties. Moreover, plastic and drying shrinkage and compressive strength were also measured. The methodology shows that the substitution of cement by NHL affects the rheological behavior and the compressive strength, but improves the homogeneity of the mixtures. The incorporation of NHL also generated an expansion period resulting in a significant decrease in plastic shrinkage, and mitigated long-term drying shrinkage. The effects of substitution of cement by NHL during fresh and hardened states are presented along with the analysis of underlying mechanisms. The findings of this paper highlight the benefits of using NHL to optimize mortars' mix-design in terms of workability, mechanical properties and delayed behavior.