Effect of the grain size of recycled rubber on the behaviour of an asphalt mix

The elimination of a large quantity of waste such as plastic, bottles, tyres, etc., that are generated in large quantities and produce an environmental impact and risk in the areas where they are produced and stored. The current study aims to use recycled rubber grain (GCR), originating from discarded tyres, in the manufacture of asphalt concrete. Seven mixtures were designed using the Marshall methodology, one mixture without the addition of the rubber grain, which will be the control mixture for comparison, and six mixtures with the addition of 1% of rubber grain of varying sizes, which oscillate between that passing through a sieve of 2.36 mm (No. 8) and that retained on a sieve of 0.075 mm (No. 200). Once the respective working formulas had been determined, performance tests were carried out such as: susceptibility to humidity damage, plastic deformation resistance, resilient modulus, fatigue resistance and skid resistance or each of the mixtures. The results show that the incorporation of rubber grain in some cases produces a slight decrease in the optimum content of asphalt cement, increase in Marshall stability, an improvement in plastic deformation, an increase in resistance, a longer fatigue life in comparison with a conventional mixture. The results of the laboratory tests indicate that in using recycled rubber grain, it is possible to obtain asphalt concretes with improved required technical characteristics whilst constructing a surface which is environmentally friendly