Stress-strain curves for high strength concrete at elevated temperatures

The effects of high temperature on the strength and stress-strain relationship of high strength concrete (HSC) were investigated. Stress-strain curve tests were conducted at various temperatures (20, 100, 200, 400, 600, and 800degreesC) for four types of HSC. The variables considered in the experimental study included concrete strength, type of aggregate, and the addition of steel fibers. Results from stress-strain curve tests show that plain HSC exhibits brittle properties below 600degreesC, and ductility above 600degreesC. HSC with steel fibers exhibits ductility for temperatures over 400degreesC. The compressive strength of HSC decreases by about a quarter of its room temperature strength within the range of 100-400degreesC. The strength further decreases with the increase of temperature and reaches about a quarter of its initial strength at 800degreesC. The strain at peak loading increases with temperature, from 0.003 at room temperature to 0.02 at 800degreesC. Further, the increase in strains for carbonate aggregate HSC is larger than that for siliceous aggregate HSC.