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

The feasibility of the usage of porous asphalt mixture for light traffic road pavement, principally for pedestrians and bicycle cycling paths, was investigated in this project. The aim is to come up with a design that would be suited to be applied on pavements in Singapore and to evaluate how the performance of porous asphalt mixture (PAM) would vary with the different amount of coarse aggregate content. Three sets of experimental mixture made up of different gradations were tested and evaluated. They differed in the amount and percentage of coarse and fine aggregates. Bitumen PG76 was chosen to be used for the batching of all specimens in this study instead of the conventional PEN 60/70. A total of 60 small cylindrical specimens and 6 un-compacted specimens were mixed for performance testing. The performance tests carried out included: draindown test, permeability test, Cantabro test, Marshall stability test, dynamic creep test, indirect tensile test, theoretical maximal density test, aging test and moisture susceptibility test. The three gradations had varying coarse aggregate content with the percent passing for each sieve different. Gradation 1 had the greatest amount of coarse aggregate mass coming from sieve size 6.3mm - 9.5mm while Gradation 2 had the greatest amount of coarse aggregate coming from sieve size 4.75mm – 6.3mm. Lastly Gradation 3 had the greatest amount of coarse aggregate from sieve size 9.5mm – 13.2mm. The experimental results and discussion shown in this study will reflect how the three gradations perform. Permeability test results showed that all three gradations were highly porous with Gradation 2 having the highest voids content, thus the most permeable. However it is the weakest in terms of strength and resistance towards permanent deformations. It also had the worst results for dynamic creep and moisture susceptibility test. Gradation 1 had both high strength and resistance toward permanent deformations; however it is ranked last in terms of durability. Lastly, Gradation 3 had the best performance in dynamic creep and Marshall stability test, but it is the least porous. The overall investigation suggests that Gradation 3 is the best gradation amongst the three gradations. Thus, Gradation 3 will be recommended for implementation in real-life applications based on its properties tested in this study. Nevertheless more in-depth studies and researches are recommended.Bachelor of Engineering (Civil