Proposal for Durability Verification Technique of Concrete from the Viewpoing of Deteriorated Depth Under Freezing and Thawing Action

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The frost resistance verification of concrete in JSCE has been conducted with the relative dynamic modulus of elasticity of specimen. However, the technique of frost resistance verification with the relative dynamic modulus of elasticity is made using the small specimen in limited testing conditions, and it will be not a rational technique on the design of actual concrete structure. Therefore, it may be said that the technique is similar to the conventional method to restrict the water cement ratio of concrete.On the other side, JSCE standard specification for maintenance of concrete structures enacted in 2001, specified that frost damage in concrete structure should be rationally predicted based on the deteriorated depth due to freezing and thawing action.This study aims at the basic proposal for durability verification technique on damage of concrete from deteriorated depth focusing the surface layer of concrete structures under freezing and thawing action. The research results are summarized as follows.1.Evaluation of Frost Damage on Concrete by Using Improved Pull-off MethodFrost damages of various concretes due to freezing and thawing action, were evaluated by improved pull-off method. The assessing method for frost damage of concrete with the deteriorated depth using measured pull-off strength in the cover concrete was investigated in various test conditions. In this study, the tests were conducted changing the water cement ratio, the air content, the freezing and thawing procedure, exposed area, age of concrete and so on.2.Proposal of Durability Verification Technique of Concrete by Improved Pull-off MethodThe fundamental idea for the durability verification technique is base on deteriorated depth due to freezing and thawing action judging from the tensile strength at the distance from the concrete surface by using improved pull-off method. A new verification equation using deteriorated depth of concrete was tentatively proposed.