Yuki USUI
Development of simple verification method which evaluates cracking resistance of concrete material against shrinkage
Takumi SHIMOMURA
Fly ash is one of ECO material because we can reduce the usage of natural resource by utilizing fly ash in concrete. However, we have cleared that cracking resistance for shrinkage in fly ash concrete was lower than that of normal concrete when concrete is cured only 7 days.
To maintain shrinkage cracking resistance of fly ash concrete, test for drying shrinkage cracking of restricted concrete (JIS A 1151) were conducted in this study. Experimental factors were curing condition and restraint condition. As results of test, it is cleared that cracking resistance of fly ash concrete is same as that of normal concrete if concrete is cured longer then 28 days or restraint steel ratio is lower than 5% To prevent shrinkage crack of fly ash concrete, we should take care about the time of demolding and the degree of restraint .
Then, we developed numerical program that can estimate the risk of shrinkage cracking in concrete in this study. Shrinkage strain and induced tension stress in concrete are calculated with use of numerical models. Then, cracking probability is calculated statistically in this program. The influence of curing time and the type of concrete on shrinkage cracking resistance can be evaluated by extracting the maximum probability of cracking along drying time.
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