Influence of alkali-silica reaction on the physical, mechanical, and structural behaviour of reinforced concrete

Alkali-silica reaction (ASR) is one of the major concrete deterioration mechanisms in the world. Cracking in concrete structures due to ASR has been observed worldwide. In Denmark numerous concrete structures have been built with a critical amount of ASR-reactive aggregate, mostly as porous opaline and porous calcareous opaline flint in the fine aggregate fraction. During the last few decades, an increasing number of bridges in Denmark have been severely damaged due to ASR. In the most severe cases, the ASR-damaged bridges have been demolished and reconstructed due to uncertainty about their residual load-carrying capacity. The decisions to demolish and reconstruct these bridges have been based on visual appearance of drilled concrete cores and rough estimates of their residual loadcarrying capacity. Research into the mechanical properties of drilled cores and the residual load-carrying capacity of ASR-damaged flat slab bridges in service is very limited. This PhD thesis contributes to the documentation and better understanding of the influence of ASR on the physical and mechanical properties of ASR-damaged concrete, and on the residual load-carrying capacity of an actual ASR-damaged flat slab bridge. The ASR-damaged concrete originated from ASR-damaged flat slab bridges in service and from laboratory-casted and laboratory-accelerated reinforced slabs. In this study, slab segments from three ASR-damaged slab bridges without shear reinforcement were examined. All the examined slabs had following features in common: (a) significant amount of ASR cracks were observed on and inside the slabs, (b) the ASR cracks were oriented parallel to the plane of the slabs, and (c) ASR occurred in the fine aggregate fraction. In this PhD study, both the compressive strength and tensile strength of drilled cores, from all slabs, were found to be negatively influenced by ASR. However, the compressive and tensile strength depended on the orientation of the ASR cracks inside the cores. It was found that the compressive strength in ...