Abstract：The common concrete and the concrete dipped in 3.5% sodium chloride solution imitating seawater are subjected to freezing and thawing tests of 0，25，50，75 and 100 times，respectively. The effects of the freezing and thawing cycles on compressive strength，module of elasticity and stress-strain relation of concrete are investigated and the relevant simple formulae are established. A research on microstructure of concrete under various freezing and thawing cycles proved that with the increase of cycles，there will be more cracks in cement slurry，and concretes of various water ratios are affected differently by freezing and thawing cycles.
