Effect of deleterious ASR expansion on the structural behavior of reinforced concrete elements.

摘要

A laboratory study has been carried out to investigate the effect of expansion and cracking due to alkali silica reaction (ASR) on mechanical properties and structural behavior of plain and reinforced concrete specimens. The specimens were conditioned by immersion in an alkali solution over a period of one year to accelerate ASR. Two beams were pre-cracked and held under load that caused flexural cracking while being conditioned.; It was found that visible cracks appeared on reactive specimens after four to seven months of the conditioning, when length expansion due to ASR was approximately 400 to 500 microstrain. ASR expansion of the reinforced specimens, compared with that of the plain specimens, was greatly reduced due to the restraint provided by the reinforcement. Cracking due to ASR exhibited a random pattern in the plain specimens, while the dominant cracking in the reinforced specimens was oriented in the direction parallel to the reinforcement.; Before ASR cracking, change in mechanical properties of the reactive cylinders was insignificant, but after cracking, the compressive strength, splitting tensile strength and dynamic modulus of the cylinders were significantly reduced. However, the flexural loading capacity of the reactive reinforced beams was nearly the same as that of the corresponding non-reactive reinforced beams.; ASR gel swelling was modeled by exerting an internal pressure on the interface between aggregate particles and cement matrix. A two-dimensional analysis of stress induced by ASR was made using the ANSYS finite element analysis computer program. Based on this model, it was found that for unrestrained ASR expansion, 300 psi internal pressure from the gel swelling was sufficient to induce a tensile stress that would cause concrete cracking. The stress distribution in concrete was non-uniform. Before cracking, the maximum tensile stress was localized around aggregate particles.; In addition, condition assessment and repair of structures exhibiting ASR deterioration were discussed. Finally, suggestions for further research were provided.