An experimental investigation of the behavior of two-way reinforced concrete slabs strengthened with additive materials, steel fiber and steel plate under low-velocity impact loading

The aim of this study is to improve the impact performance of reinforced concrete elements using different additive materials. For this purpose, the effect of different additive materials on the static and impact properties of concrete was experimentally investigated. The studied additive materials are nano additive materials (nano-SiO2, nano-Al2O3, nano-Fe2O3), fibers (steel fiber, PET fiber, polypropylene fiber) and waste tire rubbers (fine and coarse tire rubbers). Additive materials were used separately and in different combinations. A total of 39 concretes were produced and tested. The effect of additive materials on the unit weight, static properties (compressive strength, split tensile strength, flexural strength and flexural toughness properties), microstructural properties and impact performance of concrete was researched. The concretes were also evaluated using cost and desirability function analyses. The results showed that the concretes with highest performance in nano additive materials group, fibers group and waste tire rubbers group are concrete containing 0.5% nano-Fe2O3, concrete containing 1% steel fiber and concrete containing 10% fine tire rubber, respectively. The effect of different combinations of these three additive materials on the performance of concrete was also investigated. Among all the studied concretes, concrete containing %1 steel fiber was observed to have the highest overall performance. This concrete, along with the reference concrete, was used to produce RC plates of different types. These are RC plates manufactured from reference concrete, steel fiber reinforced concrete and functionally graded concrete, and RC plates containing steel plates. A total of 9 RC plates were prepared and tested using drop weight test. In the test, the impact load-time, acceleration-time and displacement-time histories and crack pattern of each specimen were investigated. Cost analysis of the RC plates was also conducted. The results showed that use of steel plates, especially at the back surface, along with steel fibers led to a remarkable increase in the impact performance of RC plates. The highest impact performance was found in RC plate containing one steel plate at the front surface and one at the back surface. Finite element models of the RC plates were also generated using Abaqus software. Finally, numerical results were compared with the experimental ones and evaluated.