Influence of Surface Finish on Sorptivity on Concrete

Abstract

Long-term durability of highway structures is, and will for the forseeable future, be a major problem facing engineers. Movement of deleterious ionic species in solution through the cover region and the resulting corrosion and spalling is a worldwide problem, particularly with the heavy use of deicing salt for winter maintenance. In connection with the durability of the concrete cover, it is not the strength that is of interest but other properties, such as the continuity and tortuosity of pores and the absorption and diffusion characteristics of air- and water-filled pores. Since the surface of concrete is subjected to drying action, it has a nonuniform water content that is generally less than saturation. As a consequence, the problem of water movement through the cover is one of unsaturated flow, and involves capillary suction forces. Many factors influence the surface-absorption characteristics of concrete. In this paper, attention is directed toward investigating the influence of surface finish and casting procedures. Samples were cured under normal laboratory conditions, and absorption characteristics are quantified in terms of cumulative volume gain and depth of penetration. It is shown that the top and bottom surfaces of concrete samples display different sorptivity characteristics. Typical results are given.