RELATIONSHIP BETWEEN ALUMINA AND CHLORIDE CONTENT ON THEIR PHYSICAL AND CORROSION RESISTANCE PROPERTIES OF CONCRETE

Abstract

The relationship between alumina and chloride content on the physical and corrosion resistance properties of OPC concrete was studied. Friedel's salt was formed in situ in OPC concrete by the addition of various percentages of alumina (1% to 15%) along with 1% CaCl(2). The compressive strength data revealed that the addition of Al(2)O(3) increased the early strength of concrete. The Friedel's salt formation up to 5% Al(2)O(3) showed maximum compressive strength. The Rapid Chloride Ion Permeability Test (RCPT) revealed that the quantity of electrical charge passed for OPC concrete at 5% Al(2)O(3) showed a 50% reduction in coulombs. The 12V impressed voltage test indicated a gradual increase in anodic current flow and delayed time taken for initial crack up to 5% Al(2)O(3) addition. Potential vs time data from macrocell corrosion studies maintained the passivity of steel embedded in OPC concrete up to 5% Al(2)O(3) throughout the exposure period of 12 months. Correspondingly, the macrocell current was also considerably reduced (50%) in OPC concrete at the 5% Al(2)O(3) level. Scanning electron micrographs revealed a denser formation of Friedel's salt at the 5% Al(2)O(3) level. The XRD pattern at the 5% Al(2)O(3) level also confirmed the existence of a greater amount of Friedel's salt. The optimum percentage of alumina for the formation of Friedel's salt in OPC concrete with improved properties was found to be 5%.