Mechanical behavior of rendering mortar exposed to high temperatures considering different specimen geometries

Mortars play a critical role in masonry structures, serving as both rendering and laying mortars that contribute to fire resistance and structural integrity. Understanding their behavior under high-temperature exposure is essential for ensuring safety and performance in fire scenarios. This study examines the mechanical response of one type of cement-lime-based rendering mortar when subjected to elevated temperatures, considering different specimen geometries. Prismatic and cylindrical specimens were tested for flexural, compressive, and splitting tensile strength after being exposed to temperatures of 200°C, 400 °C, 600°C, and 800°C. Tests were performed immediately after cooling to eliminate post-fire rehydration effects, which can influence long-term durability. A statistical analysis using one-way ANOVA and Tukey Tests was conducted to determine significant differences between specimen geometries. Results indicated that compressive strength remains stable up to 200°C before degrading at higher temperatures, whereas tensile strength decreases more rapidly. The study also developed statistical regression models to predict residual compressive and tensile strength as functions of temperature. The predictive formulation provides a useful tool for assessing the residual performance of cement-lime mortars in post-fire conditions, considering any of the studied specimen geometries. • A literature review on methodologies for testing mortars under high temperatures is conducted • Residual compressive and tensile strength of rendering mortar is determined • Influence of specimen geometry is assessed through statistical analysis • Formulation for predicting residual strength of cement-lime mortars is presented