LOCATION:

Treatment Objectives:

• Increase the strength or bearing capacity of the base layer
• Save costs by milling the existing 200 mm asphalt layer into base - rather than removing it
• Avoid having to use gravel to modify base layer
• Reduce the weakening of base layer due to moisture - particularly in the spring thaw period
• Improve workability of clay base layer during construction, particularly compaction.

Construction Method:

The asphalt layer was milled into the base layer by milling with a CMI RT 500 road-milling machine to a depth of 30 to 36 cm. The CBR PLUS was then applied in a mixture of 250 : 1 parts water to CBR PLUS. The layer was then mixed well by milling it again with the RT500 resulting in a finely grained homogenous layer with very even particle distribution. Due to lack of space in the built up area it was not possible to windrow the material for compaction in lifts. As a result the full lift was compacted in one layer. Very thorough compaction was applied first with a 12 ton padfoot and thereafter with a 12 ton smooth drum roller. Finally after shaping, compaction was finished with a vibratory smooth drum roller.

The resultant compaction achieved was successful. DCP CBR values after one week were in excess of 100. Even with heavy gravel trucks traveling on the road, no deflection was observed and no rutting occurred. After four weeks the road was paved with a 75 mm hot asphalt layer.

Result :

The resultant road finished in a smooth surface with fine gravel making the surface. The result (before paving) is a dust free road that is completely trafficable in wet weather, without slipperiness or rutting. Construction costs were about one third of the alternative conventional construction methods.

During construction the soil was broken into small (8-12mm) particles, and as a result the CBR dosing was very effective and even throughout the layer. The soil was also easy to work with the grader. Compaction was quick and even, despite the fact that a 300 mm layer was compacted in one lift without any soft spots left behind.

Completed Street - Ready for Paving	3 Weeks after Construction - Very Hard Surface