Thermal stability and physico-mechanical assessment of volcanic pozzolan-based concrete at elevated temperatures

Abstract

The development of sustainable construction materials with high fire resistance is a critical challenge in civil engineering. This experimental study investigates the synthesis, characterization, and high-temperature performance of lightweight concrete produced with natural volcanic pozzolan aggregates. Conventional fine and coarse aggregates were partially or fully replaced with volcanic pozzolan at rates of 0 % (CPz0), 25 % (CPz25), 50 % (CPz50), 75 % (CPz75), and 100 % (CPz100). Specimens were exposed to temperatures ranging from 25 °C to 800 °C to assess the impact of thermal treatment on their physico-mechanical properties. The results indicate that thermal degradation primarily affects concretes containing conventional limestone aggregates (CPz0 and CPz25), with the formation of microcracks and damage at the paste–aggregate interface observed from 400 °C. Mass loss and compressive strength reductions were strongly correlated with the principal components identified through Principal Component Analysis (PCA). Increasing the substitution rate with volcanic pozzolan improved thermal stability and preserved mechanical performance, even at elevated temperatures where limestone-based concretes exhibited significant degradation. These findings demonstrate the feasibility of using natural volcanic pozzolan to produce fire-resistant concretes, offering a promising solution for durable and high-performance construction applications in thermally demanding environments.