Mechanical properties of natural hydraulic lime-based mortars

One hundred eighty different mortars made with a natural hydraulic lime (NHL) and different kinds of aggregates were prepared to be used in restoration works. The factors affecting the mechanical behaviour have been studied at long-term test. Compressive and flexural strengths of the specimens were discussed according to curing time, binder/aggregate ratios, attributes of the aggregates and porosity. Three phases of hardening have been established as a function of the chemical composition: C3S contributes to the strength at early ages. C2S and the carbonation process give their strengths at long term. Specimens with larger binder amounts have shown higher porosity and strength. The characteristics of the aggregates have been correlated with the strength and porosity. Limestone aggregates contribute to the strength. Rounded-shaped aggregates increasing large pores cause a strength reduction, hence their use is not advisable. Aggregates with small grain size show a good cohesion at the interface improving the strength. (C) 2004 Elsevier Ltd. All rights reserved.