MOISTURE SUSCEPTIBILITY CHARACTERISTICS OF SISAL-POLYETHENE MODIFIED OPEN GRADED ASPHALT CONCRETE
Keywords:Polyethene waste plastics, sisal fibre, open graded asphalt (OGA), sisalplastic modified open graded asphalt (SPMOGA), Marshall test, stability, flow, voids, drain down. Indirect tensile strength (ITS), tensile strength ratio (TSR)
The objective of the study was to evaluate if sisal fibre and polyethene waste plastics can be used in road construction of flexible pavement to improve strength and reduce moisture susceptibility. The indirect tensile strength test is used to determine the tensile properties of the Open Graded Asphalt (OGA) mixture which can be further related to the cracking properties of the pavement. The tensile strength ratio of bituminous mixtures is an indicator of their resistance to moisture susceptibility and a measure of water sensitivity. Clean polyethene waste plastics comprising of High-Density Polyethylene (HDPE) and Low-Density Polyethylene (LDPE) were shred into sizes 2-3mm using shredding machine. The open graded aggregates were heated and shredded plastics effectively coated over the aggregate by heating while mixing. Treated sisal fibres of 5mm length were mixed with hot bitumen. Sisal fibre was treated using 0.5N solution of sodium hydroxide solution (NaOH) at a temperature of 15-18°C, by immersing in a bucket of the solution for 12 hours, then removed and air-dried. Sisal fibre treated with 0.5N solution of sodium hydroxide makes sisal fibre become less porous with high density thus making more rigid asphalt concrete mix. The plastic-coated aggregate was mixed with mixture of sisal fibre and bitumen and the resultant mix was analyzed for tensile strength and moisture susceptibility to assess its suitability for road construction. It was observed that tensile strength of modified OGA increased from 0.44 MPA to 1.23MPa representing 180% increase for conditioned state samples when modified using 0.3% sisal fibre and 5% polyethene waste plastics by mass of dry aggregates. The tensile strength ratio of 99.9% of the Sisal-Plastic modified OGA indicated that the sample is highly impermeable to water as compared to sisal fibre modified or nonmodified control samples. In conclusion, the use of sisal fibre and polyethene waste plastics in the modification of asphalt concrete for road surfacing will strengthen the road pavements thereby increasing the road service life. Disposal of polyethene waste plastics by utilizing them in road construction will help improve the environment and further their successful application as construction materials in flexible pavement to improve road performance.