Composite effects of filler on properties of asphalt concrete mixture and its bonding characteristics with asphalt

• Main Author: Zulkati, Anggraini.
• Other Authors: Sun Delai, Darren
• Format: Theses and Dissertations
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Civil engineering::Transportation
• Online Access: http://hdl.handle.net/10356/52722
• Institution: Nanyang Technological University

This research study systematically investigated the role of filler in the asphalt concrete mixture. The study hypothesised that the interdependent interactions of filler, asphalt and (coarser) aggregates shall determine the resultant performance of asphalt concrete mixture. A multi-interaction mechanism could be synergistically derived to understand the role of filler on performance of asphalt concrete mixture. The properties of three fillers: granite, hydrated lime and kaolin were characterised. Effect of type and content of filler on stiffening rate of the mastic was examined. For all fillers, a fairly similar stiffening effect was shown by the mastics at low content of filler. A more differentiated stiffening was observed at higher content of filler: kaolin had the highest stiffening effect, followed by hydrated lime and granite. The size and Rigden voids content of filler had the best agreement with the stiffening effect of the mastic. A series of experiment were conducted to evaluate the properties of three Singapore wearing course (W3B) mixtures each incorporating a different filler (granite, hydrated lime and kaolin). As compared with control W3B-granite mixture, favourable performance in terms of Marshall stability, resilient modulus, deformation resistance and stripping resistance was shown by W3B-hydrated lime mixture. Kaolin filler also provided a favourable enhancement to W3B-kaolin mixture in terms of stability and deformation resistance but with adverse effect in the stripping resistance. The findings from this study reveal that filler plays an important role in the asphalt concrete mixture. A multi-interaction mechanism which was synergistically derived from examining the underlying properties of filler and other constituent materials and describing possible interactions between them is presented. In essence, filler fills the voids created by larger aggregates, partly contributing to a desirable tight packing of aggregates. Filler affects the workability during mixing and compaction, and influences the optimum asphalt content. Filler also alters the properties of asphalt-filler mastic, stiffening the mastic and affecting the bonding characteristics of the mastic with the larger aggregates. The resultant properties of the mastic thus determine the overall performance of the mixture in terms of strength, stiffness and durability. In particular, effects of filler on the properties of mastic and asphalt concrete mixture are reliant on micro bonding between asphalt and filler. If the bonding is strong, the mastic shall provide favourable enhancement to the mixture. If the bonding is weak, the presence of filler may introduce a weak interface spot, possibly giving an adverse effect to the mixture. It is an academic contribution to present a scientific analysis of effects of filler in an asphalt concrete mixture, with elucidation on multi interaction mechanisms which explain how the presence of filler affects the overall performance of the mixture. The knowledge also synergistically supports the conventional empirical approach which merely relies on trial-error experiments, providing more fundamental thought to investigate the applications of unconventional materials such as industrial by-products in the road pavement, hence contributing to conservation of natural resource for sustainable development.