The effect of coarse aggregate structure on the performance of porous asphalt mixture

• Main Author: Lin, Zonglin
• Other Authors: Wong Yiik Diew
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering::Civil engineering::Transportation
• Online Access: http://hdl.handle.net/10356/61581
• Institution: Nanyang Technological University

The objective of this project is to investigate the feasibility of altering the gradation of granite aggregates, with coarse aggregates as the main constituent, into pathway design. The pathway is to be designed for pedestrians and cyclists. Three mixes, each involving a different type of gradation, were designed according to LTA’s specification for porous asphaltic mixes. Pen 60/70 was the bitumen used as the binder initially which was later replaced with PG67 bitumen after conducting the Cantabro test which yielded undesirable results. In addition, hydrated lime which was initially used as the filler was also replaced with granite with sizes less than 0.075mm. The binder content varied among the 3 gradations. Small cylindrical specimens were fabricated and compacted by gyratory compactor. Water permeability test was conducted on the small cylindrical specimens to assess their porosity and the amount and connectivity of the voids. As porous asphalt mixture (PAM) constitutes mainly of coarse aggregate, all the 3 gradations exhibited relatively good permeability during the water permeability test. The purpose of these performance tests is so that the permeability aspect and the strength and durability aspects can have a balance without overly compromising on any particular aspect. The overall investigation reveals that there are notable changes by altering the gradation of granite aggregate into PAM. Gradation 1 was made the control in this study as the percentages of fines aggregates and coarse aggregates were in between the other 2 gradations. Overall, results showed that it is feasible to use coarse aggregates as the main constituent of pavement design given under the condition that a strong binder is used. PG 67 contained rubber additives which provided stronger adhesion to compensate for the lower strength of PAM compared to dense asphalt mixture or the traditional Portland cement concrete used in pavement. More in depth studies and research are recommended to further improve on the durability and aesthetic aspect.