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Analysis of Bitumen Draindown Characteristics of Sisal-plastic Modified Open Graded Asphalt

T. Mungathia
Z. A. Gariy
T. Nyomboi


A study was done to determine the feasibility of improving bitumen retention of open graded asphalt (OGA) concrete through the use of sisal fiber and a blend of high-density polyethylene (HDPE) and low-density polyethylene (LDPE) type of waste plastics. Open graded asphalt concrete is made of gap graded aggregate whose sizes range from 6mm to 12mm. The main objective of this research was to determine how sisal fibre can be used to reduce bitumen draindown and effectively utilize waste plastics in construction of flexible pavement to improve strength and performance capabilities. 5mm long sisal fibre of varying proportion percentage ranging from 0.1%, 0.2%, 0.3% and 0.4% were used in preparation of the samples. Further 2-3mm shredded waste plastic was varied from 0%, 1%, 3%, 5% and 7% in another set of asphalt concrete samples. The optimum percentage quantities of sisal fibre and waste plastics obtained at optimum Marshall stability were used in the determination of bitumen draindown. Aggregates were mixed with 5% waste plastics and heated at 170oC until waste plastics coated the aggregates. Thereafter, 0.3% sisal fibre treated with sodium hydroxide (NaOH) was mixed with hot bitumen and coated hot aggregates at 170°C. The resultant mix was analyzed for bitumen retention properties to assess its suitability for road construction. The draindown was found to be 0% for Sisal-Plastic modified samples as compared to 6.5% for control mix. The adoption of the findings of this study will lead to improved road pavement strengths that can bear increasing traffic loads without rutting or cracking. Utilization of waste plastic will help to improve the environment through friendly disposal of waste plastics.

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eISSN: 1561-7645