CHARACTERISTICS AND BEHAVIOR

The Chemical Characteristics and the Behavior of CBR PLUS
By Dr. G.h. Verdoorn

CBR PLUS was developed to assist the engineer in:
The retirement of the absorbed water to reach a Maximum density with smaller mechanical effort.

In order to prevent the re-absorption with the water, with which construction materials and soils are obtained, becomes permanently stabilized.

The compaction can be obtained easily and of an economic with the use of a variety of relatively cheap compaction components, such as caustic the diluted sulfuric acid or insipid form. The problems are that the material thus treated will not be stabilized permanently, and re-will absorb the water (after the first rains), in such a way that it will cause faults in the way.

CBR PLUS nevertheless, is a complex chemical formulation of which one of the active ingredients is the surfactant additive. The permanent action of this surfactant additive will depend on the presence of other active compounds that fortify the effect of the dispersion of the water in argillaceous materials, producing a permanent association between CBR PLUS and clay particles.

This formulation of active components causes that CBR PLUS is unique in their chemical constitution, its behavior and the final results, when is applied like a repellant to the water and a great aid in the compaction of the roads and highways.

The surfactant additive (fig 3) is surfactant (superficial active agent) and has the character due to the dual of its constitution and chemical behavior. The hydrophilic head is totally soluble in water and insoluble in most of reliable organic the non-polar solvents. This part of the molecule dissociates when the additive disperses in water and produces an ionic SO3 - which connects through the atom of sulfide to the call "tail" of the molecule.

Figure 3

This tail consists of an assembly of atoms of the coal and hydrogen and is totally insoluble in the water, for that reason it talks about it like the "hydrophobic tail". By nature is liofílic by miscible with the additive and solvents to the non-polar ones, due to his character of hydrocarbon.

In spite of the difference in the nature of the two parts of the molecule, it is soluble in water as well as in organic solvents. This dual behavior of the surfactant additive is used as means to disperse the water of argillaceous minerals.

The minerals of the clay consist of layers with a variety of ions freely associated in the surface. In a watery atmosphere, these ions move freely in the hydrosphere of particles of the clay and interchange positions at randomly.

Most of ions they are surrounded by a number of water molecules and therefore they reinforce the hydrophilic characteristic of the clay.

Great amounts of water and the mobility of cations and anions in a clay-water system produce an undesired plasticity; it is in the first place necessary to reduce the mobility of ions in the solution and secondly to release of the system as much water as it is possible. CBR PLUS provides a simple and economic chemical solution to this problem.

The treatment of the material with CBR PLUS provides to the required chemical agent, the reduction of the mobility of the ion and the repellency of argillaceous minerals to the water (fig 4).  

Figure 4

The hydrophilic head of the surfactant additive creates a chemical connection with the surface of clay particles, as much in the external and flat surfaces (fig 5). These connections can be of diverse nature:

1. Formation of direct chemical connection between anionic head SO3 of the additive and a cation of the metal in the surface. These connections are relatively strong. The inductive formation of the connection between an oxygen atom of group SO3 and a cation of the metal.

2.- The occupation of a vacant ionic space in the surface of the clay by the one of the surfactant additive.

3.- The hydrophilic head of the additive dissolves in a very thin waterproof cloak absorbed in the surface of the argillaceous mineral.

Figure 5

These interactions between the surfactant additive and argillaceous minerals have the following results:

1.- The cations that of another way would have been highly movable now are fixed to their positions and "practically sealed" by molecules of the surfactant additive. This also avoids that the ions form reliable complexes with water.

2.- Once the molecules of the additive have formed their associations (of any nature) with the particle of the clay, the hydrophobic tails move away of the flat surface to also form an repellent layer around the clay and in the surface of the interlayer.

3.- Naturally, the water would be repelled by the hydrophobic tails to such an extent that do not require any mechanical pressure virtually to release the water. In absence of the chemical agent, a mechanical pressure of up to 420 kg/cm2 removing the water would be required from the interlayer of the clay.

The compaction can now be reached with a minimum of mechanical effort and the particles of the clay are united in a very near association.

This gives rise to the natural cementation of the particles of the clay that, in the presence of the water (until thickness 2 000 Å around particles of the clay) would be impossible. The acquired natural densities, as well as the hydrophobic layers that surround particles by the clay, prevent the incorporation with small amounts of water in the system.

The final result of the CBR PLUS use could be summarized as: The compaction and the permanent stabilization are obtained with minimum mechanical effort, producing a base in which the particles are cemented simply by the direct bonding.

The existing capillaries in the compacted material have their covered internal walls with a hydrophobic layer and allow the free circulation of the water.

This means that the water could be in the way, without being absorbed by the treated material CBR PLUS. With the natural evaporation, this free water will be expelled without affecting the stability of the material.