Primary creep of concrete at elevated temperature

The primary creep in compression of usual and high strength concrete has been studied at various constant loads and elevated temperature for 6 hours. The creep strains, in general, increase with time under constant load and temperature. The influence of time on the creep strain is substantial within one hour from the start of the creep test. Creep strain grows gradually large, when the applied stress level increases at constant temperature. The increment of creep strain on applied stress level variation is not linear. Generally, under constant loads, the creep strain at 100 deg C is greater than the creep strain at 150∼300 deg C and the creep strain at the temperature range from 150 to 300 deg C is nearly equal. However, the creep strain at the temperature range above 400 deg C grows suddenly large. The mathematical expression of creep strain is defined as a function of stress, temperature and time. The correlation between creep strain and elasto-plastic strain is demonstrated by the stress-strain curves obtained after the completion of creep tests. (author)