How does it work?

The Stabilizing Process for Anionic Soils

CBR PLUS was developed to enhance the expulsion of adsorbed water in clay particles, to achieve maximum density, with less mechanical effort and to prevent the re-adsorption of water. This results in a permanently stabilized construction material.

Most clay minerals are made up of stacks of silica and alumina sheets. The arrangement of these sheets result in different clay minerals such as kaolinite, montmorillonite and illite.

Simply stated, these clay minerals inherently have a predominantly negative electrical or anionic charge. This causes the clay minerals to have a strong attraction for any cations that are present. The negative clay minerals attract cations like iron filings to a magnet and will react with water when present. (The electrostatic forces are greater in close proximity to the clay molecule or particle, resulting in very strong bonds). Normal temperatures and compaction pressures will not remove them. This layer of water is known as the electrostatic diffused double layer or adsorbed water.

Further away from the clay particle, the water molecules are no longer in an attracted or orientated state. This water is known as pore water or absorbed water.

Certain clays, like montmorillonite, have spaces between the plates or layers, that can absorb water causing them to expand. These are known as expansive or swelling clays and are the cause of many failures in foundations or road layers.

The obvious solution is to reduce the adsorbed layer of water surrounding the soil particle. If powerful positive molecules (such as the 4+ charge in CBR PLUS) can be

supplied, the negative charge of the clay minerals can be satisfied or balanced out. At the same time any weaker cations, such as water can easily be disassociated and replaced, and/or occupation of the vacant ionic sites on the clay surface can take place.

Large cations such as sodium, calcium and water cannot easily fit into these sites and are easily disassociated or replaced. Small cations, on the other hand, fit firmly into

these vacated sites, balancing the clayÕs negative charge with positive ions that cannot be removed. The clay is now relatively inert to water and the soil mass is permanently stabilized.

This is precisely what CBR PLUS does.

OK, but what about?

…costs?

A. Application of CBR PLUS modifies the compactability of locally available soils for road construction. The cost of CBR PLUS is usually significantly less than the cost of hauling gravel to modify the local soils.

… prep time?

A. There is a distinct improvement in the workablilty of the soil after applying CBR PLUS. This saves time when grading and placing the soil. During the compaction stage, the number of passes required with the various compactors is reduced — often up to 50%.

… wet conditions?

A. The treated soil or road surface becomes hydrophobic or water repellent. The soil does not deteriorate in wet conditions, resulting in improved trafficability.

… dust?

A. Dust diminishes by up to 90% depending on soil type. This reduces the need for frequent grading and other maintenance, resulting in cost savings and safer driving conditions.

…application to an existing road?

A. CBR PLUS can be applied to an existing road surface to prevent rutting, gravel loss and provide dust control without rebuilding the road. The correct amount of CBR PLUS is applied with a water tanker in three or four applications. It penetrates the soil and reacts sufficiently to correct these problems.

…the need to repeat the treatment?

A. The reaction of CBR PLUS with the clay particles in the soil is permanent. Some existing roads have been in use for over 20 years and have shown little or no deterioration over this period. If re-treatment is required at all, it would only be if additional material is imported.

… regrading or repairing a treated road?

A. To repair damage in a road that was previously treated with CBR PLUS, merely wet the surface, regrade and ensure that the material pushed to the side is replaced onto the road. Provided no new untreated material is placed onto the road, the soil will recompact as if freshly treated. The repaired surface can be compacted by machine or by traffic forces.