The effect of aggregate size and type of binder on microstructure and mechanical properties of NHL mortars

• Effect of binder type and packing density of aggregates on strength and porosity.
• Correlation between dynamic modulus of elasticity and compressive strength.
• Exponential correlation between compressive strength and mean pore radius.
• Effect of pores below 0.5 μm to compressive strength.

Natural hydraulic limes are used as an alternative to cement-based binders in mortars and renders for the repair and maintenance of historic structures as well as in new building. This paper discusses the role of the binder type, the grain size and the packing density of aggregates on the physico-chemical and mechanical characteristics of hydraulic lime mortars. Empirical formulae connecting the compressive strength with: (a) dynamic modulus of elasticity and (b) mean pore radius, have been extracted and discussed. Overall, the results have indicated that the microstructure of the binder and the packing density aggregates are the parameters that dominate the performance of the hydraulic mortars and therefore should be seriously considered during field applications.