A Study on the Mechanisms of Acceleration of Alkali-silica Reaction in Reinforced Concrete Structure Subjected to Cathodic Protection

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Reinforced concrete beams with different water : cement ratios, 0.2 m by 0.3 m by 2 m, were made from the non-reactive river sand and the reactive andesitic coarse aggregate. After 28 days of the curing time, reinforced concrete beams were exposed outdoors, and the cathodic protection current of 50 mA/m^2 was applied to the steel reinforcement of RC beams. The expansion and cracking were monitored for about 3 years in order to investigate whether or not the cathodic protection may really accelerate the alkali-silica reaction of concrete around the steel cathode. After 3 years of the exposure time, the flexural loading test was carried out for ASR damaged RC beams.The main results obtained in this study are as follows ;(1) The concrete cylinders deteriorated due to the occurrence of ASR cracks in spite of the total alkali content of less than 3 kg/m^3 when they were exposed to a natural environment.(2) The cathodic protection current significantly increased the expansion and cracking of the RC beams containing alkali-reactive aggregates.(3) The surface treatment by the epoxy-type coating was not effective in controlling the expansion due to ASR especially when the cathodic protection was applied.(4) The load-bearing capacity in bending of the RC beams did not change independently of the degree of deterioration due to ASR cracks when the cathodic protection was not applied.(5) The load-bearing capacity in bending of the RC beams was 10 to 20 % lower due to the decrease in the bond strength around the steel cathode when the cathodic protection was applied for a long period.