Durability and compatibility of lime-based mortars: The effect of aggregates.

Abstract

In order to fully perform their functions and be durable, mortars for renders and plasters are requested to have a set of characteristics that can vary with the type of exposure to external environmental actions and the type of substrate. Generally, they need moderate strength, high deformability, some water protection capability, and good adhesion to the substrate. To be used in rehabilitation works, especially for application on old buildings, with structural masonry walls, it is of utmost importance that mortars are compatible with pre-existent materials. The presence of water and its movement inside the pore structure of the mortars are among the most significant causes of degradation. However, several authors consider that the main factors for durability and good performance of lime-based mortars are mostly related with the good quality of the binder and the use of adequate aggregates with appropriate particle size distribution. Accelerated weathering tests are the easiest, quickest, and most commonly used way of studying the durability of a construction material exposed to given environmental conditions. This paper intends to study the effect of ageing, on the properties and durability of air lime mortars, using aggregates of different lithological natures. For this purpose, different mortars compositions are made and exposed to an accelerated weathering test under defined conditions. The obtained characteristics are discussed and finally compared with the results obtained with the same mortars tested in laboratory conditions. The effect of the aggregate type on the durability of mortars is highlighted and discussed. Some remarks are made about the fields of application of these mortars.