Optimum parafibre length according to mechanical properties in hot mix asphalt

Fibre is additive to hot mix asphalt that can improve fatigue life, rutting resistance, durability of asphalt concrete mixtures, creep compliance, tensile strength, dynamic modulus, elasticity, viscoelasticity, and reflective cracking. The fibres can be useful in controlling the cracks. Previous studies on various fibres have mostly focused on changing and optimising fibre percentage. No study has been conducted on appropriate fibre length in the mixture. Therefore, the effect of various fibre lengths on mixture properties needs to be clearly determined. The aim of this study was to evaluate the effect of various parafibre lengths on mechanical properties of hot mix asphalt through Marshall strength, indirect tensile strength, and resilient modulus tests. To achieve this, we added 0.5% fibre by weight of the asphalt mixture with lengths of 3, 6, 9, 12, 15, and 18 mm to hot mix asphalt samples and performed the above tests on the samples. The results showed that fibre improves hot mix asphalt mechanical properties; however, fibre percentage needs to be increased as the length increases, so that there are sufficient fibres present in the mixture to act against cracks. Accordingly, in all three tests, 12 mm fibres at 1% fibre content created the highest values. Therefore, the optimal fibre length was 12 mm, and for this length the most affected properties were resilient modulus, indirect tensile strength, and Marshall strength, respectively.