Analysis of thermally treated “plastic-pozzolanic” modified mortars and their mechanical properties

The recycling of plastic waste in construction materials offers a potential pathway toward sustainability while improving thermal performance. This study examines mortars in which natural sand is partially replaced by thermally treated PET waste by a natural source (pozzolan). Three phases were conducted: (i) experimental determination of compressive strength, Young’s modulus, and thermal conductivity at different LCA replacement levels; (ii) homogenization analysis to estimate equivalent elastic and thermal parameters, compared with literature data; and (iii) numerical simulations of heat transfer through simply supported beams with 2 cm and 4 cm coatings. The results indicate that thermally treated PET incorporation reduces compressive strength relative to the control mortar, though values remain sufficient for non-structural applications such as finishing mortars (e.g., 22 MPa at 100% substitution). In contrast, thermal performance improved significantly, with conductivity decreasing from 1.5 to 0.71 W/m·K, leading to enhanced resistance to heat transfer. These findings demonstrate the potential of thermally treated PET-modified mortars as eco-efficient materials that combine adequate mechanical capacity with excellent thermal comfort.