Road rehabilitation by COLD IN-PLACE RECYCLING of asphalt roads on clay.

Cold in place recycling or Full Depth Rehabilitation, is the most cost effective method available today for the rehabilitation of existing paved roads.

The top layer of asphalt or seal is milled with a Road Re-claimer or road milling machine to various depths (usually 15 to 30 cm.) depending on the thickness of the asphalt layer, so that the existing asphalt is broken down into small pieces. This milled asphalt is then mixed with the base material during this milling process.

Gravel (course grained materials) bases or sub bases are then stabilized by the injection of hot foamed asphalt during the milling process to compact and bind the gravel particles. This treatment binds the gravel particles together during their placement and also reduces the future effects of moisture in the treated layer.

This foamed asphalt process however cannot be used where the base contains fine-grained or clay soil with a plastic index higher than 6.

CLAYS, or fine-grained soils, can likewise be treated by injecting a CBR PLUS / Water mixture instead of the foamed asphalt into the milled layer during milling.

The effects of the CBR PLUS is to release the adsorbed or bound water from the clay particles and facilitate better compaction for higher resulting densities, while at the same time stabilizing the clay to reduce the effects that moisture will have on the treated layer.

It is no longer necessary to remove and replace the clay in the base with gravel or similar fine-grained material, since the treatment with CBR PLUS will strengthen the in situ clay material.

The milled asphalt layer is finely ground into a gravel-like material. During this milling process, the ground asphalt is mixed evenly into the base layer to mechanically strengthen the base material. At the same time the CBR PLUS/water mixture is sprayed into this finely ground soil/asphalt mixture to stabilize the clay. The milled asphalt, together with the effectively stabilized clay components in the modified soil mixture, provides a strong base layer that resists the effects of moisture.

COST SAVINGS

• Obviates the need to haul away existing old asphalt/base soil - Work is done in place.
• New gravel to replace the existing clay base is no longer required.
• Provides a simpler and more cost effective stabilization than lime or cement.
• Requires only one pass with the Road Re-claimer - The work is fast.
• Treated layer is resistant to the effects of moisture - Lasts longer.

Examples of highly successful projects of cold in-place recycling where the clay base was stabilized with CBR PLUS.

Residential Street - City of Edmonton - Alberta
200mm asphalt milled with 175mm heavy clay.
CBR PLUS stabilized the full layer.
80mm Asphalt layer was placed onto the treated layer.

Tera Parking Lot - Atlanta Georgia USA
100 mm Gravel milled with 100 mm clay base
CBR PLUS stabilized the full layer.
80 mm Asphalt layer was placed directly onto treated layer

Highway 19 - Saskatchewan Ministry of Highways
50mm Asphalt milled with 110mm heavy clay base
CBR PLUS stabilized layer. A 100 mm layer of gravel base was placed over the treated section and the surface was sealed.