An evaluation of cooling Portland cement mortars exposed to high temperature, by using firefighting foam

Abstract

The purpose of this study was to investigate the effects of cooling Portland cement mortars exposed to high temperature, with synthetic high-expansion firefighting foam. In this experimental study, mortar samples produced with Portland cement CEM I 42,5R, Rilem-Cembureau sand and tap water were first subjected to water curing for 28, 90 and 180 days and then exposed to 20°C, 150°C, 300°C, 500°C and 700°C for 3 hours, respectively. Cement mortars exposed to high temperatures were cooled with high expansion firefighting foam and the resulting flexural strength and compressive strengths were evaluated according to hydration period and temperature parameters. Subsequently, 180-day cement mortar samples exposed to high temperature were cooled using air, water, and foam cooling methods. It was determined that the air cooling method resulted in a higher compressive strength than water or foam cooling. The flexural strength, compressive strength, ultrasonic pulse velocity, and mass loss percentage values, obtained by the different cooling methods and exposure temperatures employed, were then analysed. It was determined that samples exposed to 500°C, cooling with firefighting foam, yielded a compressive strength of 9% higher, compared to water cooling. SEM images of 180-day Portland cement mortars exposed to 20°C, 300°C and 700°C and subsequently air, water and foam cooled, respectively, were obtained and analysed.