Expansive behavior of thick concrete slabs affected by alkali-silica reaction (ASR)

Some of the structures affected by ASR are bridges with thick concrete slabs without shear reinforcement. This implies that concrete is the only component resisting to shear forces, which might be a problem considering that ASR can progressively and significantly affect the mechanical properties of that material. A study was launched to gain a better understanding of the effects of ASR on the behaviour of thick concrete slabs without shear reinforcement. The methodology developed for this study, as well as the analyses of the deformations/expansions obtained from different surface measurements, are presented in this paper. It led to interesting observations about the heterogeneity of the deformations between slabs. The expansion was monitored extensively in the longitudinal, vertical and transversal orientation. The expansion was the greatest in the transversal orientation reaching up to 0.6-0.7%. The steel reinforcement at the base of the specimens locally limited the expansion of the slabs and as such created an expansion gradient which increased with the advancement of the alkali-silica reaction. Also, the use of lithium nitrate proved successful as a mitigation method against the development of expansion due to ASR.