DETECTION OF NEAR SURFACE DAMAGE AND CRACKS IN MASS CONCRETE BY ACOUTICAL AND ELECTROMAGNETIC NDT TECHNIQUES
J. Rhazi, O. Dous, R. Al-Wardany, G. Ballivy
Research Group on NDT and Instrumentation
Depatment of Civil Enginnering
Université de Sherbrooke
IREQ - Research Institute of Hydro-Québec
Varennes (Québec) Canada
The research reported in the paper examines the applicability of the Rayleigh wave dispersion method, more widely known as the spectral analysis of surface waves method (SASW), for nondestructive evaluation of deterioratedconcrete dams. Laboratory investigations were conducted on five concrete slabs (1 m*1 m*0.3 m) of different mechanical properties to evaluate the relationship between the propagation velocity of Rayleigh waves and the quality of concrete. The experiments were also conducted on three concrete slabs of 3 m * 3 m * 0.8 m to detect and characterize the extent in depth of various near surface damages that were induced in these slabs.
The paper also examines the detection of fracture in concrete by the seismic reflection and the ground penetration radar techniques. The experiments were conducted on a concrete slab of 3 m * 3 m * 4 m. An inclined horizontal crack was induced in the slab at 3.4 m depth by hydraulic fracture. The NDT tests were performed from the top of the slab for different crack widths (0.5 mm, 1 mm, 2 mm, 3 mm, 4 mm and 5 mm) and different conditions of the crack (air filled and water filled).