Numerical and Experimental Investigation of Thermal and Mechanical Performance in Cement Mortars with Recycled Glass Aggregates

Abstract

This study investigates the production and characterization of cement-based composites reinforced with recycled expanded glass aggregates (rEGA) as a partial replacement for natural sand. The primary aim is to enhance the thermal insulation properties of the composite while maintaining acceptable mechanical strength. Experimental tests, including compressive strength and thermal conductivity measurements, were conducted on various rEGAmortar mixtures, and numerical simulations were employed to model heat transfer within the composites. Regression analysis was applied to the numerical data to quantify the nonlinear relationship between rEGA volume fraction and thermal conductivity, revealing a strong correlation supporting the numerical findings. The results demonstrate that the inclusion of rEGA significantly improves the thermal insulation properties of the mortar. The thermal conductivity of the control sample was 1.23 W/mK, whereas the sample with 30 wt% rEGA content showed a significantly reduced value of 0.113 W/mK. However, the compressive strength of the mortar decreased with increasing rEGA content. After 28 days of curing, the control sample exhibited a compressive strength of 37.6 MPa, while the sample with 10 wt% rEGA showed 21 MPa. Despite the reduction in early strength, the pozzolanic properties of rEGA contributed to improved late age strength development. In addition to thermal and mechanical testing, microstructural analyses were also conducted using SEM to evaluate the impact of rEGA on the cement matrix. The study focused on identifying the structural formations, such as ettringite and calcium-silicate-hydrate gels, and the influence of rEGA's porous structure on thermal conductivity and strength development. Numerical simulations confirmed the experimental findings, showing that higher rEGA content reduced the effective thermal conductivity by disrupting heat flux pathways. These results highlight the potential of rEGA as a sustainable and energy-efficient additive in construction materials, supporting waste recycling and improving building insulation performance.