This study is aimed to estimate the frost damage of concrete under natural weatering conditions. An empirical formula based on the meteorological factors was obtained by means of multiple regression analysis of the results of freezing-and-thawing tests which were carried out under several experimental conditions to evaluate the effects of the freezing-and-thawing conditions (lowest temperature, keeping time of lowest temperature, cooling rate) and the curing conditions of concrete (water content). The formula describes the number of equivalent freezing-and-thawing cycles to ASTM C666 A. Applying meteorological data in some cities of Japan to this formula, the number of equivalent cycles in one year and the length of service life were calculated. The correspondence of estimated value to the results of exposure test for 15 years was investigated.
