Development of Strengthening Layers Against Localized Impact Loading

Due to their pronounced brittleness, existing RC structures need impact strengthening. Therefore, it was targeted to design a strengthening structure for the impact-facing side consisting of a cover layer distributing the impact load and a damping layer that aims to absorb impact energy and reduce the contact force between the impactor and the structure. The investigated cover layer materials were short-fiber concrete and distinct textile-reinforced concretes, which benefit from the high strength and ductility achieved by adding fibers and textiles to the concrete matrix and the internal friction between the fibers or textiles and the matrix, respectively. The examined damping layer materials were elastic concrete with waste tire rubber aggregates and lightweight concretes of various strengths and stiffnesses, which allow for densification upon the impact. The different material combinations were explored as strengthening layers against impact loading. Drop tower experiments with a solid steel impactor of \({21.66}\,{\text {kg}}\) , inducing a hard impact, were conducted to validate the performance of the strengthening layers. The deployed specimens were fully supported RC cuboids. The experiments proved the outstanding performance of a strengthening layer consisting of an infra-lightweight concrete damping layer and a short-fiber reinforced concrete cover layer, preventing damage until an impactor velocity of \({54}\,{\text {m}/\text {s}}\) .