SGER: An Exploratory Study of a Test Device for Concrete Permeability

North Carolina State University, Raleigh NC

Investigators

Abstract

Concrete is the most widely used material for the civil infrastructure. Deterioration of concrete is a major worldwide problem. An important factor that affects the durability of concrete structure is the permeability of concrete. Low permeability reduces the entry of moisture and aggressive substances into concrete, thus provides better protection for the steel reinforcement and limits deterioration of concrete due to freezing-thawing. However, for lack of a suitable test method and device, the permeability of concrete is not routinely measured as a means of quality assessment and control. In a recent study, the PI and his co-worker conceived an innovative method to measure concrete permeability by using a simple and economical test device. The method makes use of an axi-symmetric surface air flow model to determine the concrete permeability index. Their work provided the proof of the concept and demonstrated that the test device was capable of making consistent measurements for concrete with different water-cement ratios at different ages. They also verified that air flow within one-half inch from the concrete surface was achievable. In addition, they found satisfactory correlations between the permeability index with the results of rapid chloride permeability tests and chloride penetrations from 90-day ponding tests. The objectives of this exploratory research are to further develop and refine the test method and device. More specifically, the research will address four critical issues: (1) determine the effect of the moisture content of concrete on permeability, (2) explore techniques to dry the concrete surface to a sufficient depth to eliminate the effect of moisture content, (3) improve the test device so as to increase the depth of air flow into the concrete, and (4) establish an appropriate procedure for the concrete surface preparation in the field so that the test device can be applied successfully