Thermal properties of multi-purpose mortar mixtures: experimental characterization and influencing parameters

A considerable portion of existing buildings requires renovation. In Europe, there is a growing demand for integrated renovation strategies that reduce seismic vulnerability and improve energy efficiency. Retrofitting techniques, such as composite systems, use mortars with specific properties developed to fulfil a structural function. However, these mortars can also be used to improve the energy performance of the building envelope to which they are applied. Yet, the literature on the subject is very scarce. This work presents a study on the thermal performance of multi-purpose mortars, designed to satisfy the structural application while improving the energy efficiency of renovation works with composites. An experimental study on mixtures evaluated two strategies: (1) replacement of part of the main binder with supplementary cementitious materials (SCMs), and (2) incorporation of lightweight aggregates (LWAs). Both transient and stationary methods were used to measure and compare the thermal properties of the specimens under investigation. The study revealed that, in terms of reducing thermal properties, the best results are obtained by replacing granite sand with 20 % cork granules (−80 % in thermal conductivity). In general, the use of LWAs, especially waste materials or by-products, proves to be a promising strategy, while SCMs have limited effects on the desired performance. Density and thermal inertia are critical parameters. As for the measurement methods used, the study also revealed that the parameters measured in steady or transient conditions, although consistent in trend, can vary considerably in intensity, reaching peak differences of over 80 %. • Experimental study on the thermal properties of multi-purpose mortars. • Effect of aggregates and supplementary cementitious materials on thermal parameters. • Significant decrease in thermal conductivity obtained with new aggregates. • Comparison between the transient plane source and guarded hot box methods. • Influence of thermal inertia on the transient and stationary response of mortars.