Nondestructive testing of concrete using highly nonlinear solitary waves

In this article, we describe the capability of a nondestructive evaluation (NDE) method at determining the strength of concrete surfaces. The method uses highly non-linear solitary waves (HNSWs) propagating inside a metamaterial in contact with the concrete to be tested. The metamaterial consists of a chain of spherical particles, and is part of a built-in transducer designed to excite and detect HNSWs. The NDE method exploits the dynamic interaction between the metamaterial and the concrete, and the hypothesis is that this interaction depends on the stiffness of the specimen being inspected. In this study, we tested this hypothesis by assembling two kinds of transducer and by casting cylinders with different water-to-cement ratios. The results show that the time of flight of the HNSWs is inversely proportional to the modulus of elasticity of the concrete. Once fully developed, the proposed NDE method may easily assess concrete surfaces.