LIME STABILISATION OF SOIL SUBGRADES

CONTENTS

Caution !
Specifications, Reports, Advice Notes
Links

CAUTION !

Lime stabilisation is a very useful, cost effective and environmentally friendly form of creating a capping layer from suitable in-situ  soils.
In some situations lime stabilization is even being considered for sub-base / roadbase layers, although this is more likely to be the first part of a two part process using ordinary portland cement, ground blast furnace cement, pulverised fuel ash, or some other hydraulic binding agent. 
The processes that combine lime with other hydraulic binders can also be used to stabilise other suitable, and inert, reclaimed materials to produce load bearing lower layers of a road pavement.

BUT, with all these processes it is essential you have the correct type/classification of cohesive soil as a naturally occurring subgrade for the process to work.

You will need SERIOUS technical and laboratory support in assessing the suitability of the subgrade.

Sulphate content of the soil, or more importantly the lack of sulphates, is critical.

If there is free sulphate in the lime treated subgrade it will combine with the calcium in the lime to form calcium sulphate, i.e. GYPSUM.

In forming gypsum it takes in water of crystalisation, (quite a lot of water), and creates considerable expansion / "heave".

The more available sulphate the more "heave".

This was a major problem with the road pavement on one section of the M4 shortly after construction, the section failed badly due to this problem, and had to be replaced.
More recently large sections of the A10 Wadesmill Bypass failed and had to be reconstructed because of significant amounts of heave in the lime stabilised layer.

This problem is now well documented and relevant information on lime stabilisation is not too hard to find.

Other types of chemical reaction are possible which will subsequently cause problems in the road pavement over time, I am not sufficiently knowledgeable to discuss these situations.

As I have already said you need serious technical advice on this type of work as this layer forms the foundation of your expensive subsequent layers of pavement. If the lower levels of the road pavement fail, in whatever manner, the cost of repair or replacement is going to be extremely high and disruptive.

SPECIFICATIONS, REPORTS, ADVICE NOTES

TRL - Soil stabilisation with cement or lime   
This "state of the art review" is a collection of TRL reports relating to the subject of soil stabilization. 

BS 1924 : Stabilised materials for civil engineering purposes

Part 1 : General requirements, sampling, sample preparation, and tests on materials before stabilisation
Part 2 : Methods of test for cement stabilised and lime stabilised material

TRL Report 424 : Detailed chemical analysis of lime stabilised materials

TRL Contractor Report 151 : Stabilised capping layers using either lime, or cement, or lime and cement
This report describes the results of an investigation of the properties, performance and specification of soils stabilised with lime and/or cement for the construction of capping layers 
This report is quite comprehensive in discussing all aspects of using lime or cement, or a combination of both as a means of stabilising in-situ material to replace an imported granular capping layer. 
It incorporates current specifications for use in Britain as well as describing specifications used in the U.S.A.. 

TRL Report 505 : Swell test requirements for lime stabilised materials 
This report describes the investigation of a number of soil types that were stabilised with quicklime, and subject to a testing methodology aimed at providing data to assess the applicability of the swell test as an indicator to the suitability and acceptability of materials for lime stabilisation.

DOT Advice Note HA 74/00 : Treatment of fill and capping materials using either lime or cement or both
to be found in :-
The Design Manual for Roads and Bridges : Volume 4 - Geotechnics and Drainage : Section 1 - Earthworks,

LINKS
I always try to refer to other sites when possible in compiling my site, these may include commercial sites that include worthwhile information on the particular subject, this reference does not constitute a recommendation, but they will be useful sites to visit to increase your knowledge.

For further information on lime stabilisation, press --------> HERE 
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and ---------------------------------------------------------------------------------> HERE  
and ---------------------------------------------------------------------------------> HERE 

These particular links will help those unfamiliar with lime/soil stabilisation, some include a range of appropriate images, they were gleaned form the web using Google, and the key words "lime stabilisation" and "soil stabilisation".

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