Abstract
Changes of the length of concrete specimens during freezing and thawing within the temperature range from 20℃ to 30℃ were measured by using a new testing apparatus. The tensile strength of the specimens were measured after 13 alternate freezing and thawing cycles. The new term, "the degree of expansion by frost (DEF)", was defined as a measure of frost resistance of concrete. Slow and rapid freezing and thawing tests were made for finding out the relation between DEF and the dynamic modulus of elasticity. A diluvial gravel, a crushed stone and several kinds of artificial lightweight aggregates, which show various properties to freezing and thawing, were used as coarse aggregates. Test results are as follows; 1) Oven-dry specimens give uniform thermal expansion, however, the saturated specimens using high water absorptive aggregates show abnormal expansion during freezing. And DEF of the specimens after 13 alternate freezing and thawing cycles gives value from 1000×(10)^<-6> to 3000×(10)^<-6>. In this case, the decrease in the tensile strength exceeds 50% of the initial strength. In case of low water absorptive aggregates, no expansion during freezing is observed, and increase in DEF and decrease in the tensile strength are very small. 2) DEF will indicate the grade of frost damage of Concrete, as there is a relation between DEF and the decrease in the splitting tensile strength or in the dynamic modulus of elasticity. However, the relationship between DEF and dynamic modulus of elasticity varies due to the difference of water-cement ratio.
