SELF-INDUCED STRESS AND RESULTANT CRACKS IN REINFORCED ULTRA HIGH-STRENGTH CONCRETE COLUMN: Part 1 Experimental study on the effect of temperature history

In this research, reinforced concrete (RC) columns with ultra-high strength concrete were tested with regard to self-induced stress by autogenous shrinkage and temperature history. Parameters of experiment are reinforcement ratio, and temperature of fresh concrete. As a result, 1) ultra-high strength concrete containing silica fume exhibit temperature dependent autogenous shrinkage i.e. the higher peak temperature in early ages brings the larger autogenous shrinkage and the higher temperature of fresh concrete yields the smaller autogenous shrinkage, 2) surface crack was observed in a full scale RC column with reinforcement ratio of 3.3% placed in winter due to the larger autogenous shrinkage, 3) internal crack, which can not be observed from an outward appearance, was detected in the same specimen due to temperature dependent autogenous shrinkage, and this can be explained by the larger autogenous shrinkage at the center part of specimen than that in surrounding area. On the other hands, no such crack was seen in the same size specimen placed in summer.