Concrete structures are liable to be exposed to fire during their lifetime. After exposure to high temperature, the strength of concrete is determined only by its residual properties. The method of cooling, after exposure, is one of the significant factors in determining the residual properties of concrete. The compressive strength, tensile strength, stress-strain response and elastic modulus of concrete are the important properties to be considered in the design of fire resistant structures. In this paper, the behaviour of high temperature exposure of three different grades of concrete M20, M45 and M60 are considered. The specimens were subjected to high temperature regime of 100°C–900°C and were cooled by different methods. The maximum degradation of mechanical properties was observed between temperature regimes of 400°C to 600°C. High strength concrete was found to be more vulnerable compared to normal strength concrete. Mathematical models expressing the variation of different mechanical properties of concrete were developed and explained.

混凝土结构在其生命周期内容易遭受火灾。暴露于高温后，混凝土的强度仅由其残余性能决定。暴露后冷却的方法是确定混凝土残余性能的重要因素之一。混凝土的抗压强度，抗拉强度，应力应变响应和弹性​​模量是设计耐火结构时要考虑的重要特性。本文考虑了三种不同等级的M20，M45和M60混凝土的高温暴露行为。将样品置于100°C–900°C的高温环境中，并通过不同的方法进行冷却。在400℃至600℃的温度范围内观察到机械性能的最大降低。与普通强度混凝土相比，发现高强度混凝土更加脆弱。建立并解释了表达混凝土不同力学性能变化的数学模型。