New Deterioration Index of Durability and Strength Evaluation of Structural Concrete under Freezing and Thawing Action

Abstract

The existing freezing and thawing test method of structural concrete leaves much room for improvement from the viewpoint of materials science research; that is, the concrete specimen is too large and heavy and the testing procedure is so time-consuming that the test itself cannot be practically used for evaluation of durability. Thus, the authors have reported that the standard cylindrical specimen (∅10×20cm)is the best type for the quality control of concrete and that the accelerative test method using the exposure temperature of ±5°C has been developed. The surface defect ratio has been defined on the basis of the fact that the gradual process of surface deterioration, namely, the popping-out, is fundamentally related to the internal destruction of concrete. This paper deals with the relationship between the relative dynamic modulus of elasticity, the number of freezing and thawing cycles, and the surface defect ratio. Thus it proposes a practical evaluation method of the compressive strength of structural concrete, which uses a new durability index of the surface defect ratio.