Effect of cooling methods on the residual properties of concrete exposed to elevated temperature

Abstract

One of the most damaging effects a building may suffer is a fire. Structures may be exposed to temperatures of more than 1000 °C while the fire is burning. In the course of and after the fire, structural concrete loses its rigidity and strength. The concrete's residual strength qualities may also be significantly influenced by the cooling phase's speed and cooling medium. In an attempt to compare the impact of various cooling regimes on concrete, an investigation has been made. The effects of adding polypropylene fibres and air entrainment admixtures were examined in addition to studies on traditional concrete. The water-cement ratio, cement mass and type, and aggregate type were all the same throughout the test. After cooling down from five distinct heat stages ranging from 150 to 900 °C, samples were compared to their unheated counterparts' results. Five distinct approaches, including slow cooling, forced air cooling, cooling with water mist, quenching, and the “normal” cooling under laboratory conditions, were used to study the cooling effects. The study aimed to examine integrated temperature endurance numbers, relative residual compressive strength values, and residual compressive strength values in addition to visual observation. Regulations were matched with the outcomes. The findings demonstrated that, up to 600 °C, there were no appreciable changes in the residual properties between the various cooling methods or between the different mediums with virtually the same cooling pace. The apparent disintegration of water-cooled samples was evident after cooling from 900 °C.