Abstract
Calcium alginate capsules within asphalt concrete can gradually release interior asphalt rejuvenator under cyclic loading to repair micro cracks and rejuvenate aged asphalt in-situ. However, asphalt pavement will become aged due to environmental and traffic factors during the service period. In view of this, this paper investigated the effect of ageing on the healing properties of asphalt concrete containing calcium alginate/attapulgite composite capsules under cyclic loading. The capsules were fabricated using the orifice-bath method and the morphological structure, mechanical strength, thermal stability, oil release ratios and healing levels of capsules in fresh, short-term ageing and long-term ageing asphalt concrete were explored. The results indicated that the different ageing treatments would not damage the multi-chamber structure nor decrease the mechanical strength of capsules but would induce the capsules release oil prematurely. The premature oil released from capsules in turn can offset the ageing effect owing to ageing treatment. The short-term ageing and long-term ageing plain asphalt mixtures gained strength recovery ratios of 39.3% and 34.2% after 64,000 cycles of compression loading, while the strength recovery ratios of short-term ageing and long-term ageing asphalt mixtures containing capsules were 63.5% and 54.8%, respectively.
Highlights
Asphalt mixture has been the principal surface paving material on highway due to its outstanding performance
The capsules in asphalt mixtures after shortterm ageing treatment and compaction still kept complete shape, which implied that the capsules withstand the thermal and mechanical conditions in short-term ageing asphalt concrete
The capsules within asphalt concrete after long-term ageing treatment still deformed slightly and kept intact, which implied that the capsules presented good shape stability after the treatment (85 ◦C, 5 days)
Summary
Asphalt mixture has been the principal surface paving material on highway due to its outstanding performance. To maintain asphalt pavements in optimum condition during their lifespan, external maintenance is usually conducted on pavement by the road agencies The existing maintenance measures focusing on repairing the cracks are all passive methods since they were taken only after macro cracks occur on the road surface. These measures consume masses of natural resources and result in heavy ecological pollution such as greenhouse gas emissions [5,6] and volatile organic compounds emissions [7]. Intelligent and clean maintenance technologies are highly desirable for asphalt highways
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