The phenomenon that mixtures move to transverse direction is called rutting. Rutting are generated at wheel path of carriage-way in the cases of warmer climate areas, heavily trafficked roads, approaches to intersection, climbing lanes. Rutting are generated not only at the mixtures of surface course but also at the mixtures of binder course. Therefore, when milling and overlay is planned, it is necessary to investigate the extent of rutting influence prior to decide the depth of milling.

  The phenomenon that mixtures move to longitudinal direction is called corrugation (ripple shaped wrinkle of pavement surface). Corrugations are generated at curved section, sloped section and approaches to intersections. They are said to occur only at mixtures of surface course.

  The measure to prevent flows is to make the mixtures hard to move in hot summer season. Generally, it is done by the selection of aggregate gradation, maximum aggregate size, asphalt binder and or by their combination.

�@As the measure to cope with rutting varies depending on places, traffic conditions, it is usually reviewed case by case. The typically selected mixtures are dense graded asphalt concrete (maximum aggregate size 20mm) using modified asphalt, large stone asphalt concrete (maximum aggregate size:30 mm) and semi-flexible pavement. Hereunder are shown typical examples of application.

Places of application	Heavy vehicles traffic volume (veh/day/direction)	Surface course Dynamic stability*1 (wheel passes/mm)	Binder course Dynamic stability (wheel passes/mm)
rutting at ordinary road sections intersections	1,000 or more less than 2,000	W-Spax*2 (dense graded, maximum aggregate size:20 mm) Dynamic stability= nearly 1,500	---
	2,000 or more less than 5,000	W-Spax (dense graded, maximum aggregate size:20 mm) Dynamic stability= about 3,000	W-Spax (coarse graded) Dynamic stability= about 3,000
	5,000 or more	W-Spax (dense graded, mxumum aggregate size:20 mm) Dynamic stability= 3,000-5,000	Hi-Stac*3 (large stone, maximum aggregate size:30 mm) Dynamic stability= 6,000-10,000
rutting at bus stops and toll gates	Because of severe loading conditions including braking, two layers structure is adopted.	RP-Pavement*4	Semi-flexible pavement or W-Spax (coarse graded) Dynamic stability= about 3,000
At where above described measures are not sufficient	-	W-Epoc*5	W-Spax (coarse graded) DS= about 3,000
Corrugations at slopes, curved sections	In most of the cases, they occur only at surface course.	W-Spax (dense graded maximum aggregation size:20 mm) Dynamic stability= 1.500-3,000	---
*1 Dynamic Stability is measured by Wheel Tracking Test *2 W-spax is a brand name for a asphalt mixture using extra high viscosity asphalt. Because it is plant mix type, dynamic stability is adjustable by the amount modifier agent. *3 Hi-Stac is a brand name for a asphalt mixture with large stone aggregate of 30 mm or 40 mm. *4 RP-Pavement is a brand name for semi-flexible pavement *5 W-Epoc is a brand name of a special gap graded mixture using a combined binder of asphalt and epoxy resin.

  Besides above mentioned asphalt mixtures, we WatanabeSato are prepared to supply high quality rutting resistant asphalt concrete for special places such as bridges, namely W-Mastic type I, W-Mastic type II, FA-ToughCo, W-Epoc.