An experimental investigation of laser scabbling of concrete

• New experimental methodology, using infrared thermography.
• Scabbling behaviour differs between cement pastes, mortars and concretes.
• Air drying of specimens did not produce the expected reduction in scabbling.
• The effect of PFA in cement paste suggests permeability is a key factor.
• Scabbling is caused by processes in cement paste; and influenced by aggregates.

Laser scabbling of concrete is the process of removal of surface material using a high power laser beam. The main aim of this investigation was to establish an experimental procedure for assessing the effects of various parameters that may be critical for the effectiveness of the process, such as material composition and initial moisture content. The study shows that the key characteristics of the process can be detected by monitoring surface temperature variations. This experimental procedure is used to provide data on the effects of each parameter to explain the mechanisms that drive the process. The results suggest that scabbling is mainly driven by pore pressures in the cement paste, but strongly affected by other factors. Reducing permeability by adding PFA to the cement paste resulted in significant increase in volume removal; but reducing moisture content by air-drying of the material did not result in the expected reduction in volume removal.