STONE MASTIC ASPHALT TRIALS IN ONTARIO

Stone mastic asphalt (SMA) use in Europe (split mastic in Germany) and Japan, based on excellent frictional properties, plastic deformation resistance, fatigue endurance and durability, formed the basis for 1990 and 1991 technology transfer demonstration trials. The thrust of this SMA work has been to incorporate international experience using local aggregates, fillers, engineered asphalt cement and fibers. SMA is a gap- graded, dense, hot-mix asphalt with a large proportion of coarse aggregate (passing 2mm limited to about 20 percent, all crushed material) and a rich asphalt cement/filler mastic. The coarse aggregate forms a high stability structural matrix and the engineered asphalt cement, fine aggregate, filler and stabilization additive (typically fibre) form a mastic binding the structural matrix together. Plant and placement trials of two preliminary SMA design incorporating fly ash filler and fibre indicated no transportation, placement or compaction problems, but care must be taken to ensure proper mixing of any fibre added. From this demonstration work, SMA modified Marshall mix design procedures have been developed and four highway trial sections completed in 1991. Quality assurance testing indicated no significant problems in meeting SMA mix design requirements once production parameters were established. Monitoring and characterization of these SMA pavements are in progress with, for instance, very favourable rutting resistance and surface texture performance shown. For the covering abstract of this conference, see IRRD number 853909. (A)