LOCATION:

Treatment Objectives:

• Increase the strength or bearing capacity of the base layer
• Save costs by milling the existing 80 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 Bomag road milling machine to a depth of 15 cm. The CBR PLUS was then applied to 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 Bomag resulting in a finely grained homogenous layer with very even particle distribution. Using a grader, the top 75mm was windrowed and the lower layer was then compacted using a 10ton vibrating pad foot compactor. After this the top layer was placed from the windrows and again compacted by the pad foot roller and after shaping finished with a vibratory smooth drum roller.

Result :

The resultant road finished in a smooth surface with a fine gravel making up the surface. The gravel is held in place by the clay so that the result is dust free and completely trafficable in wet weather, without slipperiness or rutting ( Despite heavy truck loads) - to the extent that the client decided not to seal the surface.

During construction the soil was broken up into small (8-12mm) size particles, an as a result the CBR dosing was very effective and even throughout the layer and also the soil was easy to work with the grader . Compaction was quick and even, without any soft spots left behind.

Bomag Road Miller	Finished Surface After Final Compaction
Finished Road after 12 months	Surface after 12 months

CBR values taken with the dynamic cone penetrometer indicated that the in situ CBR values had increased from 26 to 167 over the twelve month period. This increase of 640 % show's the effects of the soil stabilization with CBR Plus.