Thermal Insulation Performance Optimization of Hollow Bricks Made up of 3D Printable Rubber-Cement Mortars: Material Properties and FEM-based Modelling

Sustainable construction is attracting more attention lately. It involves the design of eco-friendly building structures, the reduction of energy consumption and waste, the use of renewable and recyclable resources, and the enhancement of low-impact manufacturing methods. This paper addresses some of these sustainability questions, in the context of the use of tire recycled rubber particles as aggregates of cement mortars suitable for Additive Manufacturing (AM) processes. Specifically, the effect of rubber aggregates on physical and thermal properties was investigated, to evaluate the heat-insulating performance of the compounds. The lightweight and non-polar nature of rubber improve the thermal insulation and physical-structural properties of the material, in terms of thermal conductivity, unit weight, and porosity respectively. However, these effects are closely related to the particle size and their adhesion with the cement matrix. In the second part of the manuscript, applicability study of rubber-cement compounds based on the design and finite element method (FEM)-based thermal analysis of innovative hollow bricks is presented. Fractal cavities were investigated as a functional inner architecture to improve the thermal behavior of the component. FEM results show an increase of more than 30% in thermal resistance (RT) for fractal-based brick compared to conventional designs, demonstrating that the holes' geometric irregularity is a key feature in the thermal flow attenuation.