Quantitative comparison of chipping- and hydrodemolition-induced microscopic damage evolution in concrete substrates

The present study quantitatively evaluates the severity of chipping- and hydrodemolition-induced damage in concrete substrates. The concrete substrate layer was removed with a pneumatic breaker (BR) or a waterjet (WJ). The X-ray computed tomography (CT) method was used to microscopically investigate the porosity, crack width and its connectivity in the concrete substrates. This analysis indicates that damage depth was significantly greater in the concrete samples prepared with the BR, compared with the WJ. After this analysis was completed, additional concrete material was placed on these surfaces with these different preparation methods. Subsequently, concrete bending tests were performed on sample cores obtained from these prepared concrete blocks. From these tests, the flexural strength and fracture surface location were examined. Combining the above-mentioned results, it is concluded that concrete chipping and removal with the BR can severely damage the concrete substrate contrasted with the WJ, thus resulting in a decrease in its flexural strength.