Suitability assessment of non-destructive testing for mechanical property estimation of concrete with wind turbine wastes

Abstract

The simultaneous use of Coarse Recycled Aggregate (CRA) and Raw-Crushed Wind-Turbine Blade (RCWTB) in concrete enables the recycling and revaluation of two wastes from wind-farm decommissioning. Verification of the validity of Non-Destructive Testing (NDT) for field control of the concrete mixes produced with these wastes is key to extending its possibilities of use, as is the application of NDT in concrete monitoring. This research evaluates the suitability of Ultrasonic Pulse Velocity (UPV) and rebound index to estimate the mechanical properties of concrete made with up to 100% CRA and 10% RCWTB. From an experimental approach, both NDT properties decreased when adding both wastes, although rebound index exhibited a higher experimental variability. These experimental results were subsequently analyzed through two statistical procedures. First, an analysis through response surface methodology was conducted, whose models revealed that the directions of maximum variation (gradients) for UPV, modulus of elasticity, compressive strength and tensile splitting strength were aligned, especially for high waste contents. Second, a regression analysis determined that only these three mechanical properties could be properly estimated using these NDT properties, since Poisson’s coefficient and flexural strength largely depended on the stitching of the cementitious matrix, influenced by the fibers from glass fiber-reinforced polymer contained in RCWTB. UPV was always the NDT property that yielded more accurate estimations, while rebound index only improved the estimation quality of compressive strength, although a reduction of its measured value is recommended to avoid strength overestimations. In general, non-linear multiple regression models provided accurate and reliable predictions.