Performance of double layer porous asphalt incorporating coconut shell and coconut fibre

Abstract

The extensive use of coarse aggregate in construction has caused the reduction in the availability of the material. Thus, new sources of aggregates from environmental waste have been considered as coarse aggregate is one of the main components in highway industry. The abundance of coconut shells (CS) as waste material, which has contributed to environmental issues, has placed CS as a choice to replace coarse aggregate. This research focuses the partial replacement of CS in coarse aggregates and coconut fibres (CF) as additives in double layer porous asphalts (DLPA). CS and CF were soaked in 5wt% of Sodium Hydroxide (NaOH) solution before prior to mix in the asphalt mixture. CS has been used to substitute 0%, 5%, 10% and 15% of 5 mm of coarse aggregate, while 0%, 0.3% and 0.5% of CF were added into the asphalt mixtures respectively. The physical and chemical properties of CS were determined by various tests, namely FESEM, EdX, Aggregate Impact Value, Los Angeles Abrasion Value, and Specific Gravity and Water Absorption test. The asphalt mixtures were prepared using the Marshall Method and underwent the Cantabro and binder drain-down tests to determine optimum binder content for different replacement percentages of CS. The samples then underwent several tests such as the Marshall Stability, Resilient Modulus, Rutting Resistance test, Aging, Permeability and Sound Absorption tests to investigate the engineering properties. From the investigations, DLPA with 10% of CS replacement and 0.3% of CF additives showed improvement in the Resilient Modulus and Marshall Stability test by 55.9% and 8.54% respectively. On the other hand, 15% of CS replacement and 0.5% of CF additives showed the improvement in the Permeability test and Sound Absorption test by 10% and 5.6% respectively. The 10% of CS replacement without CF additives produced better results for the Aging Resilient Modulus test, which showed improvement 35.6%. These three mixture designs which showed better results in the properties tests went through Asphalt Pavement Analyzer together with the control sample. The results showed that the best mixture design in this study is obtained from mix design of 10% of CS replacement and 0.3% of CF additives. This concludes that CS is an alternative choice to partially replaced aggegrate, while CF is a good choice as additive in asphalt pavement.