Comparative Analysis of Residual Mechanical Properties between Normal and Lightweight Aggregate Concrete High Temperatures: A Review

In response to increasing demands for structural weight reduction in high-rise buildings and the need to ensure fire safety, this study compares the changes in the mechanical properties of normal and lightweight aggregate concrete under high-temperature exposure. A systematic database was constructed and analyzed based on existing literature data. The results indicate that normal aggregate concrete exhibits a higher mass loss rate than lightweight aggregate concrete. This behavior is attributed to the thermal stability of lightweight aggregates, which undergo high-temperature heat treatment during the manufacturing process, resulting in a stable chemical structure. In terms of residual compressive strength, lightweight aggregate concrete showed higher residual strength than normal aggregate concrete in the temperature range of 400 to 600 °C. This is because the porous structure of lightweight aggregates provides pathways for the release of internal vapor pressure and exhibits a lower coefficient of thermal expansion, thereby minimizing the interfacial transition zone (ITZ) stress caused by thermal expansion mismatch between the aggregate and cement paste. By contrast, the elastic modulus is strongly influenced by aggregate density and material stiffness. Normal aggregate concrete, which has a denser internal structure, demonstrated a higher residual elastic modulus than lightweight aggregate concrete. These findings suggest that although lightweight aggregate concrete experiences a reduction in elastic modulus, it is a favorable material in terms of spalling resistance and strength retention during fire exposure when appropriate structural considerations are applied.