The effect of elevated temperature on the mechanical properties of concrete produced with raw perlite aggregate

Deterioration caused by elevated temperatures in the micro- and macrostructure of concrete can lead to significant reductions in its mechanical performance, making it crucial to assess the residual behavior of concrete elements after thermal exposure. This study experimentally investigates the effects of elevated temperatures (25 °C, 200 °C, 400 °C, and 600 °C) on cubic and prismatic specimens produced with two different aggregate types (raw perlite aggregate and conventional coarse aggregate) across four mixtures (C25, C40, P25, and P40). Destructive (compressive and flexural strength) and non-destructive (ultrasonic pulse velocity, scanning electron microscopy) tests were conducted before and after thermal loading. Increasing the temperature to 600 °C reduced the compressive strength of conventional mixtures by 34.91 % (C25) and 41.79 % (C40), whereas perlite-based concretes exhibited significantly lower reductions of 9.91 % (P25) and 12.80 % (P40). Mass loss remained negligible (<2 %) up to 200 °C, increased to 4–6 % for conventional mixtures and 6–11 % for perlite-based mixtures at 400 °C, and reached 25–40 % and nearly 47 %, respectively, at 600 °C. UPV results revealed a substantial degradation in internal integrity at high temperatures, with decreases of 49–60 % in conventional concretes and only 16–17 % in perlite-based mixtures at 600 °C. Although the flexural strength of P25 and P40 was initially lower at 25 °C, their post-heating performance became comparable to conventional mixtures, showing similar residual flexural behavior at elevated temperatures. SEM observations further confirmed that perlite-based concretes exhibited fewer microcracks and reduced matrix deterioration compared to conventional mixtures. Overall, the findings clearly demonstrate that raw perlite aggregate significantly enhances the thermal resistance, internal stability, and residual durability of concrete, making it a promising sustainable alternative for structures exposed to elevated temperature environments. © 2025 Elsevier Ltd