Effect of confinement on properties and characteristics of alkali-silica reaction gel

Alkali-silica reaction (ASR) can develop between certain types of aggregates and the cement paste, leading to cracks in concrete. The degree of damage depends on the amount of local confinement existing in the material. This paper studies how steel microfibers can generate confinement of the resulting ASR gel and investigates the effect of confinement on formation and characteristics of the ASR gel. The ASR products near the reaction sites were present in both solid and liquid form. The chemical composition of these products was determined by microprobe analysis and by inductive coupled plasma spectroscopy for the solid and liquid products, respectively. Viscosity measurements of the liquid alkali-silicate solution were also performed. The experimental study provides evidence that crack control due to steel microfibers leads to a chemo-mechanical confinement of the ASR gel. This type of confinement not only reduces the volumetric expansion but also reduces the formation of the ASR gel and the reactivity of the reactive aggregate.