Dynamic and Quasi-Static Loading Behavior of Low-Strength Concrete Incorporating Rubber Aggregates and Polymer Fiber

This study evaluates low-strength concrete with rubber and polymer fiber for "forgiving" safety barriers. These barriers should absorb collision energy, reduce vehicle deceleration, and minimize accident severity. Key requirements for such concrete are: low strength, low elastic modulus, high ductility, high toughness, and minimal dispersion of large fragments upon failure. The study examined various concrete mixes with varying percentages of recycled rubber (0-20% by volume) and polymer fibers (0-1.2% by volume). Compression, flexural, and dynamic impact tests were performed to assess the additions' effect on the concrete properties. Key findings include: Recycled rubber reduces concrete strength with a low contribution to energy absorption. Polymer fibers improve concrete's elongation and toughness, increasing overall energy absorption. The number of fibers in the fracture area is crucial to energy absorption. Energy absorption under dynamic load is higher than under quasi-static load. However, as the percentage of fibers increases, the results become more similar. Quasi-static tests of fiber-reinforced concrete can be used to assess its behavior under impact loads. In conclusion, combining recycled rubber and polymer fibers in low-strength concrete can be used to produce "forgiving" safety barriers. Attention should be paid to the distribution of fibers in the concrete, as it significantly impacts energy absorption.