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Many methods for prevention of reflective cracking by use of sheets, grids or stress absorbing membranes have been applied for the existing concrete slab pavements or asphalt pavements with severe cracks. Stone Mastic Asphalt (SMA) with high performance asphalt is developed for prevention of reflective cracking. The asphalt is 177 in penetration and 84 degree Celsius in softening point (TR&B). It is modified asphalt with a high-content SBS and a small amount of newly developed additive. The m-value by BBR test of the asphalt is twice that of conventional SBS-modified asphalt. The SMA with the developed asphalt is high
in stress absorbing capacity and flexibility as well as in rutting resistance. The number of load cycles to rupture by flexural fatigue test of the SMA with this asphalt is over 200 times as great as that of the SMA with a
conventional modified asphalt. Two test pavement sections were built in August 2003 on a national highway in Niigata Prefecture. The objective of the test was to observe asphalt overlays on concrete slab pavements. The thickness of concrete pavement was designed for 1,000 heavy vehicles per day. One of the test sections consisted of a 6-cm thick SMA
and the other consisted of a 3-cm thick dense graded asphalt concrete plus a 3-cm thick stress absorbing membrane interlayer (SAMI) on the concrete slab. Four years after overlaying, an inspection of reflective cracking was performed. The percentage of reflective cracking was 0.1% in the SMA section and 10.2% in the SAMI section. From these observations, it could be concluded that the SMA with the developed high performance Asphalt might be useful for overlays to prevent reflective cracking on concrete pavements.

Institute of Research and Development, Taisei Rotec Corporation, Tokyo, Japan
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