A Study of the Behavior of Hybrid Fiber Reinforced Concrete Slabs Exposed to Impact Loading

Abstract

he most accurate and reliable approach to investigating concrete slabs structural behavior under impact loading is to conduct impact experiments. This research has the aim of providing a better understanding of the behavior of Hybrid Fiber Reinforced Concrete (HFRC) slabs under impact loading. Experimental work was conducted to study how to enhance the impact resistance of HFRC slabs which are commonly encountered in modern buildings. The focus is on preventing their collapse by increasing their ductility and energy dissipation by strengthening them with steel and Polypropylene (PP) fibers. In this research a study of the behavior of hybrid fiber reinforced concrete slabs under impact loads was carried out by casting and testing eight hybrid fiber reinforced concrete slabs with dimensions of 1700x1700x100 mm and with two fiber volume ratios of 0.5 % and 1.0 %. The tests were carried out at Structural Laboratory of the University of Putra Malaysia. The free-fall impact tests were conducted with a 200-kilogram hammer and two different drop heights (1m and 2m). The relationships between impact loads, displacements, and strains were established from the recorded tests results. The dynamic responses gained during tests, as well as the failure modes detected, had been thoroughly analyzed. The tests findings show that, when appropriately built, hybrid-fiber reinforcement can greatly improve the overall impact resistance of concrete slabs, stop crack growth, and thereby reduce the size of the damaged area. Under impact force, the slab specimen with a mix of 1% steel fibers and 0.5% PP fibers performed best improvement of integrity after failure and impact resistance with an increase 30.79%. The load tests showed that hybrid fiber reinforcement contributes to increasing load capacity and ductility of the slab. In addition, the dissipated energy of the reference slab was doubled in the hybrid reinforced concrete slab. Also, applying the strengthening technique led to a change in the crack pattern from one opened hair crack to multiple cracks in the tension face. However, hybrid fiber reinforcement results in a considerable reduction (by up to 68%) in compressive strength.