Long-Life Flexible Pavement: Myth, Reality, and the Way Forward

Long-life flexible pavements with more than 40 years of life expectancy are often found to be the most economical solution for heavily trafficked roads. Based on long-life flexible pavement design, construction, and maintenance practices in Hong Kong, this paper discusses four issues related to long-life flexible pavements: the cost and benefit, distresses, binder aging, and maintenance strategies. The studies found that long-life pavements are the most economical and environmentally friendly option for moderately and heavily trafficked roads. Long-life pavement cannot be realized by simply increasing asphalt concrete thickness; instead, attentions also need to be paid to construction details. A major distress mode is interfacial deterioration caused by inadequate bonding and high air voids content at the interface. In contrary to long-held belief that asphalt binder in deep pavement layer does not age, recent studies found binder throughout the long-life pavement structure is severely aged after long-time field service. Current practices and field experiments indicate that certain maintenance measures such as crack sealing are not necessary for long-life pavements in certain climate regions. Therefore, long-life pavement demands less maintenance treatments. The findings are expected to contribute to better practices in long-life flexible pavement design, construction, and maintenance.