Performance Evaluation of Cold Bituminous Mix Reinforced with Coir Fibre

Cold bituminous mix (CBM), which is a mixture of bitumen emulsion and aggregate that is mixed together at ambient temperature, has several advantages like energy savings, easiness in preparation, environmental benefits, and high production at low investment. But there are certain limitations of CBMs like inferior mechanical properties, high air voids, weak early life strength, long curing time and poor coating that hinder its extensive usage. The possibility of improving mechanical performance of CBMs by the addition of coir fibre is attempted in this study. The objectives of the study are to assess the improvement in performance of CBM due to addition of coir fibre and to identify the optimum length and optimum content of coir fibre for CBMs. Three coir fibre contents and three coir fibre lengths were used in this study. Performance evaluation of CBM modified with coir fibre was done through Retained Marshall Stability (RMS) test and Hamburg wheel tracking test. Coir fibre was added to the aggregates and mixed before the addition of pre-wetting water and emulsion, to achieve uniform distribution and to avoid balling of coir fibres. When coir fibre was added to the mix, Marshall Stability increased up to a certain level of coir fibre content depending on fibre length. Highest Marshall Stability value was obtained at 0.2% content (by weight of total mix) of coir fibre of 15 mm length. Resistance to moisture damage was assessed by RMS test. It was observed that the addition of coir fibre improved the RMS value. From the Hamburg wheel tracking test, it was observed that the addition of coir fibre improved rut resistance. For all fibre lengths, CBM with 0.2 % coir content showed the highest rut resistance, with 10 mm fibre length showed the best performance. Hence, coir fibre is recommended as a feasible additive for mechanical performance improvement of CBMs.