Performance of lightweight thermal insulating mortars applied on brick substrate specimens and prototype wall

Abstract

The trend and the market of thermal mortars increased in recent years in both new and thermal retrofitting of building facades mostly due to their enhanced thermal performance. These mortars are formulated using different lightweight aggregates, thus allowing a significant reduction of both density and thermal conductivity. However, this latter aspect should not compromise either durability or mechanical performance. It is therefore of paramount importance to have reliable data on the performance of these innovative mortars, thus contributing to increase their efficiency and durability. The aim of this paper is to evaluate the thermophysical and mechanical performance of three commercially available and five experimentally designed lightweight thermal insulating mortars with several aggregates (expanded polystyrene, expanded cork, expanded clay, and silica aerogel) replacing sand in different percentages. These thermal mortars were studied on their fresh and hardened states and when applied on brick substrate specimens and a prototype wall, also evaluating the influence of the substrate on the performance of thermal mortars. Results show that lightweight thermal insulating mortars exhibited lower density, mechanical properties and thermal conductivity and higher capillary water absorption when compared to the control mortar (100 % sand aggregate). Moreover, mortars applied on the prototype wall showed enhanced mechanical properties and slightly higher thermal conductivity than those applied on brick substrate specimens. Nevertheless, all mortars with insulating aggregates (either applied on the brick substrate or prototype wall) presented a thermal conductivity lower than 0.2 W/(m.K), thus following the requirements of the EN 998-1 for thermal mortars. Results contribute towards the development of innovative and sustainable thermal insulating mortars with improved effectiveness and durability.