Role of aggregates in durability of air lime mortars influence of curing conditions

Abstract eng:
Ancient mortars have proved to be durable and reliable materials even when submitted to severe conditions of salts and high humidity. This study intends to contribute to the rediscovery of the role of aggregate on the durability of lime mortars, namely in terms of its mineralogy and its’ behaviour in different curing conditions with salt water contact. Aerial lime mortars, with a binder: aggregate mass ratio of 1:3, prepared with different types of sands (basaltic, granitic and siliceous) were subjected to saline conditions, with the intent to simulate a maritime environment and sea water spraying. The mortars were analysed by physical, mechanical, mineralogical and microstructural characterisation. The main phases detected in the mortars are related to the minerals of the sands (quartz, feldspar and mica) and the aerial lime (portlandite, calcite and monocarboaluminate and chloroaluminate). The aluminate compounds can be associated to the occurrence of pozzolanic reactions between alumina rich minerals of the sands and the lime. The bulk density is higher in the samples cured in laboratory, with the highest values obtained in mortars with basaltic aggregate. All mortar samples present an increase of bulk density related, according to XRD and TGA-DTA analysis, to the mortars carbonation progress. The results of this work evidence better performance of basaltic sand.

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