Relationship Between Elastic Modulus and Permeability of Damaged Concrete

The study examined the effects of selected damage mechanisms on the dynamic elastic (Young's) modulus (E_d) and air permeability index (API) of concrete. The relationship between E_d and API in damaged concrete and the use of E_d and API to determine both the extent of damage due to various exposures and the presence and extent of damage gradients are reviewed. The E_d and API were determined by using 25-mm-thick disks sawed from high-strength and conventional- strength concrete cylinders, before and after static fatigue damage; from cores removed from a lightweight, precast, prestressed concrete beam after exposure to intense fire; and from cores removed from an elevated concrete slab after exposure to thermal shock and subsequent cryogenic temperatures. The findings of the study suggested that E_d and API were linearly related for a given set of raw materials until damage was significant, that analyzing concrete disks at 25-mm (1-in.) depths provided insight into damage gradients, and that the durability of high-strength concrete in service may have been better than conventional-strength concrete under similar stress conditions. E_d and API were found to be effective tools in the assessment of damaged concrete and gradients of damage. API was found to be particularly sensitive to fire damage and associated severe drying.