CBR PLUS soil stabilization can be applied to various kinds of roads, namely:

• Virgin Soil Roads - these are new roads to be constructed over virgin territory
• Existing Soil Roads - these are existing soil or unpaved roads which need to be re-habilitated or upgraded
• New Multi-layered Roads - multi-layered gravel roads which carry heavy traffic
• Existing Multi-layered Roads - rehabilitation or upgrading
• Temporary roads such as haul roads and detours
• Parking lots
• Airstrip Runways.

Step 1 Soil Analysis and anticipated Traffic Loading

The local soil from the proposed project has to classified in terms of either AASHTO or the Unified Classification System. This is done by means of sieve analysis and the Atterberg Limits test.

The proposed traffic loading for the road has to be determined.

CBR PLUS will further analyze the soil for reactivity with the CBR PLUS product, to ensure compatibility and determine the correct application or dosage rate for the particular soil to be treated.

All soils are different and react differently with the CBR PLUS. This test ensures the optimum application rate for each soil type and also ensures highest performance possible.

Step 2 Design the Road

The information from Step 1 is used to design the proposed road and the appropriate construction method is prescribed. This would include the construction sequence, number of layers required in the road, equipment to be used, additional material such as clay or gravel that has to be added to modify the soil and post construction monitoring and treatment.

All recommendations are based on road layers 150 mm or 6 inches thick.

Step 3 Equipment Required:

For most methods of construction, the machinery equipment required is listed as follows:

Table 4.1 List of Machinery needed for Construction

Assuming that the specified layer (15 cm) material is either in place on the road (therefore requiring ripping or scarifying for mixing to take place) or sufficient material brought from borrow pits and dumped alongside road edge for 15 cm layer to be cut in from dumped piles by grader when mixing.

Average daily production is about 300 to 750 meter length x 7-9 meter width x 15 cm thickness or about 1.2 km - 1.5 km / week. (i.e., 2,000 - 5,000m2 / day or 10,000 - 25,000 m2/week).

Step 4 Construction Procedure

1. Clearing the road of any vegetation and organic topsoil to ensure construction is possible within the boundaries.

2. Sides have to be excavated for new roads and cleared for existing roads.

3. Shape the road to ensure at least 4-6% side slope for drainage.

4. Layer thickness must be in multiples of 15cm, and where more than one layer is to be treated, windrow the top layer to expose the lower layer.

5. Imported material, where recommended, must be placed and spread.

6. The layer material must be scarified with a grader to loosen and break down lumps or clods as much as possible. Where necessary a rotorvator or disc harrow must be used to help loosen and break down lumps.

7. Determine the required quantity of CBR PLUS needed to treat the area of road open and also determine the quantity of water required to raise the moisture content of the soil to 1% above OMC.

8. Equally distribute the quantity of CBR PLUS into the water tankers before the mixture is sprayed evenly over the open area. The CBR PLUS is fully soluble in water and must be added to tanker only after (not before) the tanker has the full or required quantity of water in it.

9. Mixing of the water and CBR PLUS in the tanker can be facilitated by circulating the water with the pump, or where no pump is fitted, to drive the tanker backwards and forwards over a short distance.

10. The diluted mixture is sprayed onto the layer while being processed by grader, disc harrow, or rotorvator until the layer of soil has been well mixed.

11. After re-shaping the road, compaction can begin with a roller. Where heavy clays are present, compaction must be by pad foot and in layers of 5-7cm, from the bottom up.

12. Final shaping with the grader is followed by final rolling, usually with a peumatic roller.

Step 5 Opening to Traffic

During construction and immediately after final compaction, the roadway can be opened to traffic. Any deformation should be corrected by grading and compaction before the material dries out fully.

Step 6 Curing

After the stabilized layer has been compacted to the required density and brought to the required lines and grades in accordance with the typical cross section, the completed section should be cured. This curing is accomplished by the daily application of water with the water tanker, depending upon the climate and the depth of treatment, usually for seven to ten days after completion date.

During this period traffic may use the stabilized road.

Please note that during this period small quantities of CBR PLUS remain on the surface which may create a slippery face in some instances during rainfall and depending upon the type of soil stabilized. This slipperiness is normal and usually disappears after the curing period or a few rainstorms.

Step 7 Maintenance

One of the major advantages of CBR PLUS over other soil stabilizers is the fact that CBR PLUS can be repaired.

CBR PLUS is not cementitious. Normal wear of the gravel road surface i.e., gravel loss, rutting and dust can be expected. To repair the road to its original state, wet the road surface thoroughly and follow normal grader blade maintenance procedures. Provided no untreated material is brought into the road from the sides during grading, the traffic will re-compact the road again without re-treatment with CBR PLUS.

If untreated material from the road side is brought onto the road during maintenance grading, the surface should be treated with a very small dosage of CBR PLUS.

Step 8 Surfacing

If surfacing of the treated road surface is required, the field moisture content of the stabilized layer must be allowed to stabilize between 50 to 60 % of optimum moisture content. Depending on the soil type, climate and temperature (including rainfall during this curing period), this may take between 6 to 12 weeks or longer.

Step 9 Life span of CBR PLUS Stabilized Layer

The change in the treated clay is permanent and will not reverse itself due to leaching. In theory therefore, the CBR PLUS treated road should last forever if the construction procedure and instructions are followed properly, but in reality special variability of subsoil and drainage is expected. Normal wear and tear prevails and the roads built with CBR PLUS stabilized soil will require some maintenance.

The resultant road should however present a significantly improved rideability, particularly in wet weather, and substantial reductions in maintenance.

There are some CBR PLUS stabilized roads in existence, which have been used continuously for over twenty years.