Behaviour of Fibre-Reinforced Rubcrete Beams Subjected to Impact Loading

Impact resistance of a material is of utmost significance in many essential structural applications. But, concrete is weak in withstanding impact/collision/blast loads. Addition of crumb rubber as a replacement of mineral aggregates has yielded a material which has high impact resistance and is termed as rubcrete. It has been observed that 0–20% replacement of fine aggregates with crumb rubber produces rubcrete with high energy absorption capacity. But, rubcrete is usually associated with a reduction in strength. Pretreatment of crumb rubber particles and grading them in the same proportion as that of the fine aggregates will help to mitigate the reduction in strength. Addition of steel and polypropylene fibres aids in maintaining the strength characteristics of rubcrete and facilitates control in the generation and propagation of cracks. Improved energy absorption characteristics were observed for steel and polypropylene fibre contents up to 1% and 0.3%, respectively. In order to determine the optimum proportions of crumb rubber, steel fibres and polypropylene fibres, the energy absorption capacity of prisms of size 100 × 100 × 500 mm was evaluated. Results show that 15% of crumb rubber, 0.75% of steel fibres and 0.2% of polypropylene fibres were the ideal proportions of crumb rubber, steel fibres and polypropylene fibres, respectively, to attain maximum energy absorption/cost ratio. This paper presents the results of numerical and experimental studies conducted on the impact behaviour of M 40 and M 60 grade ordinary concretes, rubcrete and fibre-reinforced rubcrete beams of dimensions 100 × 150 × 1200 mm. Durability studies were also carried out on fibre-reinforced rubcrete mixes to ascertain their behaviour in extreme environments. From the durability studies, it was noticed that when exposed to severe environments, fibre-reinforced rubcrete specimen had comparable properties with that of ordinary concrete.