Assessment of concrete cover quality is necessary for proper maintenance of concrete structures. Concrete durability is evaluated primarily based on chloride penetrability, neutralization and other external factors. The present study attempts to analyze concrete quality and its mass transfer resistance performance by measuring the air permeability and its relation with concrete durability indicators like chloride diffusion and neutralization. The applicability of air permeability as a durability indicator is validated using concrete with different materials, parameters and curing conditions. The tests are conducted on laboratory prepared concrete as well as for concrete exposed to actual marine conditions. From the experimental results, it is found that air permeability coefficient, neutralization coefficient and chloride ion diffusion coefficient have high correlation. It is suggested that air permeability could be considered as an alternative to estimate mass transfer resistance of concrete and as a concrete durability indicator.

No abstract

No abstract

In this research, an apparatus for a simple freezing and thawing test using liquid nitrogen that enables measurement to be carried out even in actual structures has been developed based on existing research studies as a new testing method replacing the freezing and thawing test of concrete defined in the Japanese Industrial Standards (JIS), and a reviews was made of its practicality. The results indicated that, when used in conjunction with ultrasonic measurement equipment, the apparatus for a simple freezing and thawing test using liquid nitrogen was capable of evaluating the degradation of concrete surfaces part after only a small number of cycles and was greatly effective in practical application.

The effect of Superabsorbent polymer (SAP) admixture in patch repair materials on the adhesion to the base concrete and the protection performance of reinforcing bars was investigated. In the experiment, one side of RC joint specimens were exposed to water. Water leakage from the interface between the base concrete and the repair material was reduced in the SAP specimen compared to the conventional Polymer modified mortar specimen. In addition, the half-cell potential and polarization resistance of the SAP specimens showed noble and high values, respectively, indicating the inhibition of corrosion of reinforcing bars.