Behaviour of fibre reinforced concrete slabs under impact loads

Extensive use of reinforced concrete structures and composite materials in infrastructure, increases the demand of design of high strength and durable reinforced concrete structure subjected to static and impact loads. The structural design deals with various types of loads such as earthquake load, wind load, wave loads and impact occurs from various reasons such as vehicle collision, rock fall, military exercise, missile attacks etc. Construction industry is heading towards a new era with intensive use of High Performance Concrete (HPC). High performance concrete overcomes the limitations of conventional concrete. The use of HPC is not only limited to infrastructural projects but also in high rise structures, nuclear reactor, defense structure etc. Now-a-days fibers are the most used materials to improve the ductile property of concrete. The properties of carbon fibers, such as high stiffness, high tensile strength, low weight, high chemical resistance, high temperature tolerance and low thermal expansion makes them one of the most promising fiber materials to be used in the Fiber Reinforced concrete (FRC). Use of polypropylene fibers reduces cracks during plastic and hardened state particularly when it is use in structural elements such as beam, column, slabs etc. which improves the quality of concrete constructions. Hence, addition of carbon fibers and polypropylene fiber to HPC increases toughness, energy absorption capacity of High Performance Fiber Reinforced Concrete (HPFRC). The present experimental investigation has been focused to develop a comprehensive understanding of test slab specimen under impact loading. HPC of M60 grade of concrete integrated with carbon fibers and polypropylene fibers. Series of twelve slab test specimens having three each of M60 grade Slabs of (600x600mm) with varying thickness of 60, 50 and 40 mm with and without carbon fibres (0.5% by volume),polypropylene fibres (900 gm/m3), and combination of both. Impact tests on the slab test specimens were carried out on a low velocity repeated impact test machine using instrumented drop weight hammer of 10.2 kg attached with Load Cell and was designed, fabricated and installed at Civil Engineering Department, UVCE, Bangalore University, Bengaluru - 56. Accelerometer, LVDT’s was used to record the Time-histories and Load, Deflection, and Acceleration. The experimental result shows a significant increase in the energy absorption, peak loads same number of impact blows for the carbon and polypropylene fibre reinforced concrete test slab specimen.