This document discusses the fire resistance of concrete and the effects of fire on its strength. It states that concrete has low thermal conductivity and does not burn, making it highly fire resistant compared to steel. The temperature must exceed 250C before seeing effects on a concrete structure. Additionally, the document discusses how the type of aggregate and its thermal expansion properties, along with the amount of silica content, impact how well concrete can withstand high temperatures. It provides details on how concrete strength is reduced at various temperature levels as the water and calcium hydroxide contained in the concrete dehydrate or deteriorate.