Cement-cork mortars for thermal bridges correction. Comparison with cement-EPS mortars performance

Abstract

The aim of this paper is to demonstrate the advantage of cork-mortars for renderings when compared to EPS-mortars, from a thermal characteristics point of view, namely in steady and unsteady conditions. It was intended to develop specific rendering mortars able to be applied in thermal bridges to reduce condensation effects and heat transfer in buildings envelopes. The impact of this solution is significant, especially in building typologies as framed reinforced concrete structures. Cement mortars and cement-EPS mortars are used as a reference as their properties are easily recognized compared to cement-cork mortars, which are made with by-products from the cork industry. Several studies were made concerning fresh and hardened state behaviour of mortars, namely: rheological and mechanical properties, microstructure evolution with time and thermal behaviour. For a cement based mortar, different cork dosages (from 0% to 80%) were tested (as sand replacement by mass). Microstructural analyses show that the mechanical properties of cement-cork blends are not only controlled by cork’s low density, but also by interaction of cork extractives with the cement hydration process. Thermal conductivity presents a linear decrease for an increasing cork dosage in mortars. Concerning the effect on thermal delay, cork-mortars seem to behave better than EPS-mortars.