Natural hydraulic lime mortars: influence of the aggregates

Natural hydraulic lime specifications changed with the 2010 version of standard EN 459-1 and new natural hydraulic limes appeared in the market. The characteristics of mortars depend on many different parameters such as the type of binder, the type of aggregates, the use of fillers and of superplasticizers applied in the mortars´formulations; also on mixing and curing conditions. In this paper mortars with a Portuguese NHL3.5 were formulated with binder:aggregate volumetric proportions1:3, varying the aggregates type and proportions between them. Two coarse sands, a medium sand, a river sand, a finer sand, a calcareous filler and a ceramic powder were used, being the two last mentioned aggregates by-products from industry. Standardized prismatic mortar samples and samples of mortar applied on a brick surface were prepared and conditioned in two different situations: following standard EN 1015-11 and at 65% relative humidity but with daily water spray during the first days. Mortars were characterized in the fresh state and at the age of 28 days. Results showed the influence namely of the curing, particularly in terms of water capillary, and of the fillers. They also showed that NHL3.5 mortars seem to be adequate for old masonries conservation and repair and, in some situations, they can be an alternative to air lime based mortars.