ABSTRACT
ABSTRACT Polymer concrete (PC) is a construction material with high compressive strength and bending strength. Moreover, PC provides both compressive strength and bending strength by using concrete alone, so it is used instead of reinforced concrete as a construction material of underground structures. At present, destructive inspection is the only means for accurately calculating bending strength. The problems with destructive inspection are twofold: it necessarily damages the shape and function of the structure under inspection, and it is expensive. Accordingly, to avoid those problems, it is desirable to perform inspection on anon-destructive manner. Therefore, in this study, by devising a new inspection method, namely, the first nondestructive-inspection method for measuring bending strength of a PC structure, we are aiming to significantly improve inspection work in terms of time and cost. In this study, by applying a bending-fracture test with a deteriorated sample, we experimentally demonstrated that the bending strength and elastic modulus of PC are empirically correlated, and we estimated bending strength on the basis of ultrasound velocity which reflects elastic modulus. In-situ experiments were conducted with 52 resin-concrete manholes, and the velocity of a longitudinal elastic wave propagating on the surface and the bending strength of the manholes obtained by a destructive test were plotted, and a correlation of R2 = 0.80 between those two parameters was found. In this manner, it was possible to verify that the bending strength of PC can be estimated by the proposed means of nondestructive inspection.
