Diffusion of Chlorides in Pozzolanic Concrete made with High-absorption Aggregates Exposed under Tropical Marine Environment

摘要

Due to the highly aggressive environment in the Caribbean coast, the housing infrastructure built inthis region is continually affected, with heavy losses due to the electrochemical process of corrosion ofthe reinforcing steel embedded in concrete. In order to obtain a better understanding of the diffusion ofchlorides in concrete made with highly-porous limestone, two types of cement were employed:ordinary Portland cement and pozzolanic cement. The aggregate employed was crushed limestone forboth, coarse and fine aggregate (5% absorption). Two water to cementitious materials ratios were used:0.5 and 0.7, equivalent to 35 and 20 MPa, respectively; and two curing treatments: 1-day and 14-daywet curing periods. Concrete specimens were prismatic, 15 by 15 by 20 cm. After two weeks ofcasting, concrete specimens were exposed to marine environment, at 90 m from the shoreline.Performance of the external concrete layer was determined by chloride ingress using an acid-solubleextraction method, followed by potentiometric titration with a silver ion-selective electrode. Resultsindicate that chloride concentrations were higher for the ordinary Portland cement specimenscompared with the pozzolanic cement specimens, and high enough to onset corrosion of thereinforcing steel for the 0.7 w/cm OPC specimens after only 51 months of exposure.