© 2015 Taylor & Francis Group, London. This paper presents the investigation on an in-situ assessment technique for durability performances of cover concrete based on the relationship between air permeability coefficients and moisture content. First, an assessment technique for the quality of cover concrete using insitu air permeability tests in conjunction with moisture content measurements was examined. Durability performances of concrete specimens subjected to different curing conditions at an early age were subsequently studied via accelerated tests. Finally, this study exemplified the application of the assessment technique to existing RC structure.