Longitudinal Expansion of Reinforced Concrete Beams Subjected to Alkali-Silica Reaction

Longitudinal Expansion of Reinforced Concrete Beams Subjected to Alkali-Silica Reaction

Alkali silica reaction is the reaction between alkali in cement or other sources and certain forms of silica in aggregates. The reaction produces gel, which absorbs water and expands in volume, resulting in cracking and disintegration of concrete. A laboratory study was carried out to investigate the effect of deleterious ASR expansion on the structural behavior of reinforced concrete beams and on mechanical properties of concrete cylinders made with the same concrete mixture. The specimens were made with reactive or non-reactive aggregates. All beams had 100x150mm cross-sectional areas and internal reinforcement. The beams were 1100mm long, and reinforced with different ratios of compression and tension steels. The beams were standard cured and then to simulate in-service conditions, fourteen beams were held under load that caused flexural cracking while being conditioned. Beams and concrete cylinders were kept under long-term observation at 38° C and 100 percent relative humidity. During the long-term reaction period, concrete strain and steel strain were measured regularly. The strain of concrete beams was measured along the compression and tension zones in the middle of the beams. Steel strains were monitored by strain gauges mounted on the middle of bars. It was quite clear that the beams containing reactive aggregate showed a significant increasing measured strain. Increase in compression steel with constant tension steel showed significant effective on tension expansion. On the contrary, an increase in tension steel with constant compression steel showed insignificant effective on compression expansion. The effect of ASR on mechanical properties and expansion of concrete cylinders was more significant than on expansion of reinforced concrete beams.