Effects of alkali-silica reaction on the fracture energy of mass concrete: Experimental investigations using the wedge splitting test

Abstract

This work aims to study the effects of alkali-silica reaction (ASR) on the fracture energy of reactive mass concrete mixtures (maximum aggregate sizes of 38 mm and 76 mm), characteristic of an existing hydro-electric facility. More than 40 large concrete blocks were casted and stored in a controlled environmental chamber for more than 1100 days. The blocks as well as cylindrical reference cores were monitored in expansion. Wedge splitting (WS) tests with different notch to depth ratios, were performed at different ASR advancements to assess the evolution of mechanical and fracture parameters of concrete. Digital Image Correlation (DIC) technique was used to monitor the tests. Damage Rate Index (DRI) technique was also performed on cores extracted from the blocks, following the completion of the splitting tests. Important size and heterogeneity effects were observed on the assessed ASR expansion and fracture energy. By filtering these effects, it was possible to assess for the first time in literature the evolution of size-independent fracture energy with respect to intrinsic volumetric expansion of concrete. The findings suggest that fracture energy increases for moderate levels of expansion, due to crack branching within the splitting crack, interacting with pre-existing ASR-induced cracks. This phenomenon was not observed for the case of a few horizontally cast blocks where the splitting crack ran parallel to pre-existing ASR cracks, indicating an anisotropy in ASR damage effects on the fracture energy of concrete.