Stone mastic asphalt (SMA) use in Toronto since 1994 has proven most favourable, with demonstrated enhanced durability, friction, deformation resistance and fatigue endurance, compared to conventional surface course mixes. Additionally, for composite pavements (asphalt concrete over concrete base slabs), the SMA has mitigated the early asphalt concrete reflective cracking problem associated with the concrete base. For composite pavements, falling weight deflectometer (FWD) testing is completed to determine the need to repair rocking or cracked slabs. Following milling of the old cracked asphalt concrete, and slab repair, a lift of heavy duty binder course hot-mix asphalt is placed, followed by the SMA surface course. Pavement performance monitoring has shown that the reflective cracking previously experienced has been mitigated by the SMA. For instance, the Lake Shore Boulevard 1995 SMA under heavy traffic, including Indy car racing, is in excellent condition and virtually crack free. This is similar to the Georgia experience with SMA use in the Atlanta area, for instance, for composite pavement rehabilitation. It appears that another plus can be added to the life-cycle performance and cost effectiveness of SMA use - mitigation of reflective cracking due to its excellent flexibility and fatigue endurance with the rich mastic component. The performance evaluation of a number of SMA projects since 1990, including life-cycle cost analyses, is also given. (Author/publisher)
Samenvatting