Relative residual compressive strength is a measure used to evaluate the remaining strength of concrete after it has been subjected to specific conditions, such as high temperatures, freeze–thaw cycles, or chemical exposure. This metric is crucial for assessing the durability and longevity of concrete structures that have been exposed to harsh environments. It is calculated by comparing the compressive strength of concrete samples after exposure to a severe condition with the original strength of unexposed samples. The mechanism behind the loss of strength typically involves the degradation of the cementitious matrix and the breakdown of the bonds between the cement paste and aggregates.