Use of laser interferometry for measuring concrete substrate roughness in patch repairs

• Concrete was removed from 12 slab specimens using Remote Robotic Hydro-erosion (RRH).
• Concrete was removed from 48 slab specimens using an electric chipping hammer.
• Laser interferometry was used to create 3D digital surface profiles of all 60 slabs.
• Four roughness parameters were used to measure the roughness of the excavated slabs.
• Results show that RRH provides rougher surfaces compared to the electric hammer.

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 through the use of a prototype non-contact (optical) laser interferometry measuring device. Laboratory results show that the above equipment can be used to characterise substrate roughness and confirm the ability of RRH to create rougher surfaces as opposed to chipping hammers.