A new method for evaluating the surface roughness of concrete cut for repair or strengthening

Abstract

Deterioration to concrete structures usually starts at the surface and progresses into the structure. The deteriorated concrete has to be removed and replaced by new repair material, which leads to a composite concrete/repair material structure. In order to ensure full structural interaction between the old and new material, it is necessary to have a good bond between them. The bond itself depends on having a clean and rough surface. The importance of surface preparation and the effect of roughness have been emphasised by many researchers. In order to study the effect of surface roughness on the bond between a repair material and the concrete substrate, the roughness of the surface needs to be measured. No standard method for measuring surface roughness of concrete has been adopted. A range of methods are available and are in use for measuring the surface texture of concrete pavements in the highway field, but no method is accepted as standard. A new method of quantifying surface roughness is proposed and compared with the only method reported in the literature. In this new method (referred to as the roughness gradient method) a new method of describing the surface roughness is proposed. The surface of the cut concrete is defined as a series of irregular waves. The roughness parameter is dependent on the peak-to-trough depth and the respective wavelength. The method adopted using the ‘roughness gradient’ (R.G.) gave a better indication of the treated surfaces used in testing concrete repairs. Visual observation of the treated surfaces seemed to be in agreement with the R.G. parameters, while the method reported in the literature failed to define the roughness of the surface of the whole substrate in an accurate and comprehensive way.