Influence of thermal shock by brush cooling of concrete in fire situations

ABSTRACT In situations of abrupt temperature differences, as the residential fires, these structures must support the thermal chock. Thus, this is paper aims to assess the behavior of concrete exposed to high temperatures and subsequent abrupt cooling. For this we analyzed this effect on the characteristic resistences with fck of 25, 35 and 40MPa. The analyzies observed the resistence losses and the colorations of the concretes. The samples were submitted to the temperature of 300, 600, 900 and 1200°C for 90 minutes and tempered in freshwater. The strength were compared to the reference samples and to the theory to estimate the strength of the concrete exposed to abrupt cooling. The results show that concretes with Fck equal to 35 and 40MPa present lower strength when compared to the concrete with fck equal to 25MPa. On the other hand, at 900 and 1200°C, the percentage of strength lost is the same as 25MPa. However, at temperatures of 900 and 1200°C, the loss percentage is equal to the concrete with fck of 25MPa. That is, the higher the strength is, the higher the lost rate and the higher the incidence appearance of craks when heated and cooled.