Chizuru Kiyohara

STUDY ON THE CRITERION FOR THE OCCURRENCE OF DRYING SHRINKAGE CRACKING OF CONCRETE

The purpose of this paper is to propose a criterion for the occurrence of drying shrinkage cracking of concrete. Based on the test results obtained by using the new testing apparatus in which the restraint ratio can be kept constant and the stress occurring in concrete can be directly measured, the shrinkage cracking criterion based on both stress and strain was constituted. The stress and strain at the maximum load under the stress-strain relationship were discussed as well as the static strength test, and the stress reducing factor(α: maximum restraint stress ratio) and the strain increasing factor(β: maximum restraint strain ratio) were introduced. These factors were assumed to be dependent on water-cement ratio(W/C), the age at the start of drying(T), and restraint ratio(K). Moreover, since it was considered that the effects of the internal stress due to the distribution of drying shrinkage strain was remarkable, the initial slope between the water loss and drying shrinkage strain(WSi) was discussed. Finally, both factors were expressed as a function of WSi and K. It was found that the proposed criterion was almost described the jeopardy of the occurrence of drying shrinkage cracking, although it was very difficult to predict the occurrence of cracking exactly.