How to define Soil Stabilisation?

“Soil stabilisation” is achieved if an in-situ Soil has been rendered usable for risk free application in any earthwork. However, we have to distinguish between “soil improvement” (a not very significant increase in quality, particularly of the workability of a soil) and the real “soil stabilisation” (an actual change of the soil properties to a considerable degree). 

How to achieve Soil Stabilisation?

In the past 50 years many attempts at improving the behaviour of soils have been undertaken with the aim to avoid the substitution of conventional construction material for unsuitable in-situ soil, i.e. soil of lower quality. The products chosen for this purpose can be divided into the following groups:

– Products gluing together the soil particles, such as binding agents, and

– Products gluing at a change of the chemical composition of the soil, thus reacting with the soil, and improving its properties.

Some products out of these two groups show both effects, e.g. hydraulic binders.

What all these products have in common is the fact that they can be used only under certain conditions, i.e. with certain soil types and certain granulations of the soil. They often fail to yield satisfactory results because soils rarely have a homogeneous composition, and this makes it impossible to anticipate the effect.

Are these products still on the market?

Cement and lime are in use for soil improvement, mainly as curing aid, as well as for soil stabilisation.

The great bulk of these products, however – approx. 200 are known to us – disappeared as fast as they turned up.

A number of them had not been developed for soil stabilisation anyway but were mere industrial waste products to be ‘buried’ on such sites of application.

Some others were limited in their effectiveness to certain soil types only and of insignificant or short term effect, and thus of little or no value. 

What are the advantages of the CONSOLID System?
This System, comprising the combinations CONSOLID 444/CONSERVEX and CONSOLID 444 / SOLIDRY, was developed and devised specifically for the purpose of soil stabilisation, avoiding the paths other products (binders and chemical reactants) had gone and which had prevented a success.

Any cohesive soil has a tendency to petrify again; all it needs to achieve this goal is a very, very long time span and very high pressure. It is possible, however, to accelerate this procedure by catalytic processes. If the soil can be activated by catalysts or pseudo-catalysts and influenced in complex processes in its undesired behaviour, a considerable improvement can be achieved with nearly all kinds of soil and with the same quantities of additives. 

This is what the CONSOLID System does: The use of CONSOLID 444 results in an irreversible agglomeration of the fine particles and in this way a reduction of the active soil surface. The adhering water film is destroyed to a high extent, thus activating the inherent binding power of the soil. The water content in the soil, especially its capillary saturation, is highly diminished and slowed down. An additional treatment of the soil with CONSERVEX or SOLIDRY enables a ‘tailored’ degree of stabilisation in accordance with the requirements of each particular construction site. 

What soil consistency is required?
Here the normal standards for earth constructions apply: soil should always be worked with at its Proctor optimum or slightly above, but never at too low a moisture content. The CON-SOLID System frees the bound water, which easies the compaction process enormously, especially with gravel and rock-containing material that can be wedged.

The treated soil loses its ability to take up water to a high extent. This results in a constantly increasing compaction by the traffic, even if the initial compaction has taken place at too high moisture content.

This continuous compacting effect can no longer be disturbed by the destructive impact of swelling soil when taking up water, the density increases constantly and the effect of the CONSOLID System remains a permanent one.

What types of soil can be treated?
Principally all types of cohesive or semi-cohesive soils can be influenced to the required ex-tent.

The degree of stabilisation is determined by the requirements of the construction. Supposition: the soil must be mechanically mixable.

Very heavy sticky clays (such as some organic clays, e.g. black cotton soil) may cause problems and have to be adapted by adding sandy material.

Is there an optimal soil composition existing for CONSOLID?
Normal physical conditions may be taken into account: the better the granular composition, i.e. the sieve curve, the higher the mechanical stability of the soil.

An unfavourable granulation or an overrate of a certain fraction can be improved by mixing4n other soil available nearly in order to reach the starting point for a high mechanical stability, because the better the starting point with regard to the bearing capacity, the greater the effect of the treatment with the CONSOLID additives.

Are any temporal limitations to be considered
None – provided the soil in question is workable.

If rainfall is expected, the work can be interrupted at any time and continued at the same stage after an improvement of the weather occurs. CONSERVEX or SOLIDRY can be incorporated immediately after CONSOLID 444. 

How to apply the CONSOLID products?
CONSOLID 444 and CONSERVEX are liquid products, which have to be diluted with water to obtain the working solutions. This is done on the construction site, taking into account the actual moisture content of the soil. I.e., is the soil moist, less water has to be added; is it dry, more water is necessary. Yet the quantities of additives determined in the laboratory always remain the same. 

If SOLIDRY is used in addition with CONSOLID 444, this product is applied in dry state and mixed into the soil. This is an advantage particularly on sites where due to an already high moisture content in the soil the addition of aqueous solutions might cause problems in terms of compaction.

Does the CONSOLID System reduce the permeability of soil?
Yes – on the one hand by better compactibility of the soil and on the other by rendering the soil water-resistant up to any required extent, even to full impermeability. 
How to calculate the quantities of CONSOLID additives?
Has the specific weight of the soil and its moisture content to be considered? 

No; products used in soil stabilisation should not be delicate or problematic in their application. Natural soils keep changing in their granulation, and a correspondingly changing application rate of the additives on the site would hardly be possible. We recommend working with the following values: 

1 m3 of soil 2000kg (2 tons) 

1 m2, 25 cm deep; therefore 500 kg 

1 m2, 10 cm deep; therefore 200 kg 

As standard quantities of the additives, empirical tests have revealed the following amounts for the overwhelming majority of existing soils: 

for CONSOLID 444: 0.2 litre per m2 

for CONSERVEX: 0.5 to 1% of soil weight = 1 to 2 litres per m2 

for SOLIDRY: l to 2% of soil weight= 2 to 4 kg per m2. 

CONSOLID 444 and CONSERVEX are diluted on the construction site with as much water as the soil will accept for optimal compaction. 



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Environmental engineering for soil stabilisation