Spot laser ranging system for analysing surface features of concrete: a case in characterising concrete frost damage.

Surface damage of concrete induced by freezing and thawing (F-T) cycles in cold regions is characterised by peeling and pits as features of the damaged concrete surface, which needs characterising before repairing. A spot laser ranging system was established with high accuracy, and its ability to detect concrete surface features was evaluated. A 50 mm × 50 mm zone on a surface of C30 concrete specimen, with 2550 measurement points in it, was defined to obtain vertical displacements and other parameters. Mean vertical displacement of measurement points increase with F-T cycles. Effectiveness of the proposed method to characterise concrete surface damage is verified by significant regression relationship between mean vertical displacement and mass of scaling substances per unit area. Analysis of other parameters reveals that frost pit's depth increases within initial 8 F-T cycles, while its cross-sectional area increases in the subsequent 12 F-T cycles. However, in the final 8 F-T cycles, frost pit's cross-sectional area increases more significantly. Thus, the system is well performed in detecting frost pits on concrete surface non-destructively. The insights prolongate application of laser technology, which provides a new perspective to study the evolution of surface damage of concrete subjected to F-T cycles. [ABSTRACT FROM AUTHOR]