Assessment of thermo-mechanical performance of lightweight fibre-reinforced LECA concrete for enhanced energy efficiency

Abstract

This study investigates the thermo-mechanical behaviours of lightweight fibre-reinforced LECA concrete. The correlation between fibre composition, porosity and temperature has been analysed, leading to the development of prediction models for each thermal property. The models effectively capture the variability of the heterogeneous concrete, exhibiting R² values > 0.98. The findings reveal superior mechanical performance in concrete containing 1–1.5 % steel fibre (STF). Furthermore, nonlinear fluctuations resulting from variations in thermal pathways are observed with intermittent changes in thermal properties, particularly when STF >0.5 %. In all cases examined, the STF concrete consistently exhibits higher thermal and mechanical properties compared to hybrid STF + PPF concrete. While the intricate interplay between STF and the concrete matrix renders it ideal for tailored applications, the stable thermal response of the hybrid fibre concrete showcases beneficial performance in thermal efficiency, characterised by lower thermal conductivity and diffusivity relative to STF concrete. Nonetheless, the optimal performances, based on the combined thermo-mechanical responses, were identified in concrete with the least porosity at 0.5 %STF and 0.75 %STF +0.2 %PPF, yielding an increase of 8.7 % and 4.2 % in compressive and tensile strength, respectively, compared to the plain concrete. Furthermore, the hybrid fibre concrete shows a 5 % reduction in thermal conductivity and diffusivity relative to STF concrete, coupled with increased specific heat and thermal effusivity at elevated temperatures in both concrete, signifying the exceptional energy performance efficiency of LECA concrete across varying temperatures.