CATHODIC PROTECTION CURRENT ACCELERATES ALKALI-SILICA REACTION

Results from a study on the effect of cathodic protection (CP) current on the enhancement of alkali-silica reaction are presented in this pa per Steel embedded in mortar specimens made of high alkali cement and reactive crushed Pyrex glass were subjected to 215 and 1076 ma/m2 (20 and 100 ma/ft2) cathodic protection current at the steel surface. CP c urrent densities of 215 and 1076 ma/m2 (based on the reinforcing steel surface area) advanced the cracking time by 40 and 60 percent, respec tively, compared to cracking time in specimens which were not current treated. 34 and 15 percent reductions in compressive strength due to i ncreased alkali-silica reaction occurred when the specimens were expos ed to 1076 and 215 ma/m2, respectively, for 80 days. Hardness of morta r adjacent to the steel is reduced with increase in current densities at the steel surface. CP current has no effect on the tensile strength and ductility of low strength reinforcing steel in concrete. Results obtained from a simple staining technique suggested the formation of h igher alkali-silica gel contents near the steel at a higher current de nsity.