新設コンクリート部材における水分特性と表層透気性に関する研究

Abstract

Surface-layer air permeability depends strongly on the water content of concrete. Therefore, newly built structures, which contain a large amount of water, require water content evaluation during inspections. The relationships among the material age, surface-layer air permeability, relative humidity, and air permeability coefficient of newly cast concrete have been reported, but there have been few studies on the relationship between the water content and air permeability of young concrete. In this study, the effects of the water content of young concrete on surface-layer air permeability were investigated to propose a method for evaluating the durability of newly built concrete structures. To study the relationship between water behavior and air permeability in concrete in indoor and outdoor environments, specimens and actual-size walls containing embedded ceramic sensors were produced from ordinary Portland cement, Portland blast furnace cement type B, and fly ash cement. The relationships among the water content of concrete, Wenner method resistivity, and air permeability were determined. In addition, pore structure was analyzed by the mercury intrusion technique and discussed. The effects of the relationship between pore structure and water content on air permeability varied according to material age for different kinds of cement in an indoor environment. The results indicated that it is possible to evaluate the durability of concrete aged 28 days or older, for which the effects of structural changes can be removed.