Nano-mechanical properties of alkali-silica reaction (ASR) products in concrete measured by nano-indentation

•Nano-indentation and SEM analysis identified two ASR products (i) rosette-like (with crystalline characteristics), and (ii) granular (with amorphous characteristics).•There is slightly lower Ca/Si and hardly any Na in the rosette-like ASR product compared to the granular ASR product.•Nearly equal K/Si ratios are observed in the rosette-like and granular phases.•Elastic modulus varied from 13.7 to 42.7 GPa (average = 27.4 GPa) for the rosette-like phases.

This paper presents a study on the nano-mechanical properties of alkali-silica reaction (ASR) products formed in laboratory-prepared concrete specimens. The nano-mechanical properties (elastic modulus and hardness) of the ASR products were investigated by nano-indentation, and scanning electron microscopy (SEM) was used to investigate the corresponding material phases. The combined nano-indentation and SEM analysis identified two types of ASR products with distinct morphologies and compositions: a rosette-like ASR product and a granular ASR product. The nano-mechanical properties obtained from the nano-indentation tests were correlated with the two nanostructural morphologies. The findings provide insight into the correlation between nano-mechanical properties and nanostructure and improve our fundamental understanding of the mechanical behavior and durability of ASR-affected concrete.