Measurement and characterisation of concrete substrate roughness in patch repairs

Patch repair is one of the most common types of repair in reinforced concrete bridges. The overall success and long-term durability of a patch repair is significantly influenced by the bond developed at the interface between the concrete substrate and the repair material. In turn, the bond strength is influenced by the topography (roughness) of the substrate surface after removal of the defective concrete. However, different removal methods of defective concrete produce substrate surfaces with different topographies. Hence, the ability to measure and characterise the topography of substrate surfaces is of great importance for evaluating the effectiveness of different removal methods. In this paper the effect of two removal methods: electric chipping hammers and Remote Robotic Hydro-erosion (RRH) on the surface roughness is investigated. The paper also presents an alternative to current BS EN 1504-10 surface roughness measurement methods (sand patch and contact stylus profilometry), which overcomes some of their limitations. It employs state of the art fringe-based laser interferometry which provides a more accurate measurement and characterisation of concrete substrate surfaces. In addition, it has the potential for use in other fields of concrete bridge maintenance and rehabilitation where surface roughness is important such as FRP laminate strengthening and application of water proof coatings.