Ultrasound Applications in the Safety Assessment of Concrete Structures

The safety assessment of concrete structures involves regular inspections to evaluate the real condition of the structure. A concrete structure is subjected to cracking whenever the developed tensile stresses due to deterioration processes or structural loads surpass the tensile strength of the material. While some cracks may only affect aesthetics, others may impair the durability and serviceability of the concrete structure. When monitoring cracking, nondestructive techniques (NDT) are commonly used. The use of stress wave propagation methods such as ultrasound allows one to indirectly evaluate the cracking process in a convenient and fast approach. This paper discusses the application of ultrasound to assess the integrity of concrete structures subjected to cracking of different nature. In particular, plastic shrinkage cracking and the crack repair with epoxy were evaluated through ultrasound. Ultrasound energy parameters were able to indicate the extent of plastic shrinkage cracking in small mortar and concrete slabs in laboratory conditions. The ultrasonic diffusion method was evaluated for its potential use to verify the epoxy filling of surface cracks. The results obtained here expand the already wide range of applications in which ultrasound can be used to evaluate the integrity of concrete structures. Keywords: ultrasound, nondestructive testing, wave parameters, crack repair, diffuse ultrasound