Air permeability of joint between existing and newly placed concrete subjected to sustained and repeated tensile stresses

Air permeability of joint between new and old concrete under tensile stress is investigated with mechanical properties of joint experimentally. Treatment roughening the joint surface is made by shot blast method and green cut method. Static, sustained and repeated tensile stresses are applied to specimen, respectively. When viewed in terms of the increasing ratio of air permeability coefficient of specimen in loaded condition to that of specimen in unloaded condition, the increasing ratio for joint is larger compared to that for concrete without joint. Changes in air permeability coefficient and elastic modulus of joint subjected to repeated tensile stress are related to each other by defect rate.(author)