Abstract
It is well known that serious deterioration generally occurs when concrete is exposed to the combined effects of seawater and frost action. With the aim of improving the freezing thawing resistance of concrete subjected to such condition, exposure tests were performed at tidal zone of Okhotsk Sea coast for 20 years. The concrete specimens for exposure test were different the air content and curing period. The air contents are Non AE, 4％, 6％, 8％. The specimens were water curing for 28 days or water curing for 5 days. The specimens were water curing for 5 days and then placed in air dry condition in a laboratory. And, the freeze-thaw tests were performed by using specimens of same proportion to exposure test.
The results were that, the specimens（curing for 28 days）with an air content of 4％, 6％ and 8％ showed an increase in the dynamic modulus elasticity, and a small increase in the percentage of mass loss. The scaling ratio is smaller for specimens with air content of 6％, 8％ than specimens with air content of Non AE, and 4％.
For the specimens that were curing for 5 days, the dynamic modulus elasticity was increased more than for the specimens that were curing for 28 days and the scaling ratio was small. In the case of specimens with air content of 8％ and curing for 5days, the scaling ratio was the smallest of any other case.
The deterioration was different when the results of exposure test were compared with the results freeze-thaw test. Based on the freeze-thaw test result, the specimens with air contents of Non AE, 4％, 6％, 8％ showed a decrease in the dynamic modulus elasticity and an increase in the percentage of mass loss. When specimens with air content 4％, 6％, 8％ were subjected to exposure test, the dynamic modulus elasticity and percentage of mass loss had not changed with elapsed year.
