Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 222222
Loughborough University

Centre for Innovative and Collaborative Construction Engineering

2015


Dr Paul Beetham

Thesis

Enhancing the understanding of lime stabilisation processes

Project Title

Enhancing the understanding of lime/cement stabilisation reactions

Company

Opus / Independent Stabilisation Company (ISC)

Supervisors

Academic:
Professor Neil Dixon
Dr Paul Fleming

Industrial:
Mr C Notman
Mr J Bateman

Director of Research:
Professor Stephen Ison

Research Period

2010 - 2014

 

Enhancing the understanding of lime/cement stabilisation reactions

Context and Background

The stabilisation of earthworks materials, with the addition of quick lime has been a common UK industry practice for over 20 years.  The addition of quick lime is considered to have several benefits for many cohesive soils:

  • Reduction of moisture content;
  • Immediate changes in the soils physical and chemical properties, leading to a reduction in  plasticity and increased workability.
  • Long term stabilisation reactions, similar in nature to pozzolanic cement reactions.

Some project experiences have not realised the typical benefits described above. These cases resulted in vastly different physical behaviour, such as heaving, loss of all shear strength, and/or dessication of the modified fill.  Research understanding to date has attributed some of this unusual behaviour to reactions with high sulphur clays and the resultant formation of expansive minerals, such as ettringite[i]

Industry observations consider that high sulphur and expansive processes do not always appear to be the main causality of the unusual behaviour, indeed some high sulphur clays have been stabilised without resultant heave effects. In some cases, it is suspected that mineralogical modifications may result in the long term de-stabilisation of the fill, as opposed to stabilisation.

Currently the industry avoids the stabilisation of high sulphur fills from certain geological formations, e.g. Oxford and London Clays. With increasing taxation on the landfill of earthworks materials, the desire to maximise the scope for stabilisation is becoming of substantial commercial benefit.   Linked into this is the requirement to enhance the understanding of modification reactions and potentially permit use of materials previously considered high risk.

Aims and Objectives

The general scope of the project is to enhance the understanding of clay/binder modification reactions by improving knowledge and understanding. At project conception, the following are considered key work areas:

  • Investigate mineralogical changes during stabilisation of fills from UK geological formations.
  • Proposal/development of test procedures to identify unusual modification behaviour.
  • Investigate Links between routine classification tests ( Liquid index, Activity Index etc.), the anticipated modification behaviour and resultant strength/stiffness properties[ii];

Method and Current Status

At project conception, the following are considered key work areas:  Investigate mineralogical changes during stabilisation of fills from UK geological formations.  Proposal/development of test procedures to identify unusual modification behaviour.  Investigate Links between routine classification tests (Liquid index, Activity Index etc.), the anticipated modification behaviour and resultant strength/stiffness properties.

Benefits and Expected Outcomes

Currently the industry avoids the stabilisation of high sulphur fills from certain geological formations, e.g. Oxford and London Clays. With increasing taxation on the landfill of earthworks materials, the desire to maximise the scope for stabilisation is becoming of substantial commercial benefit. Linked into this is the requirement to enhance the understanding of modification reactions and potentially permit use of materials previously considered high risk.



[i] Professor D N Little & Dr B Herbert presented (Tremti Sept 2005)  “Ettringite formation in Lime-treated Soils: Establishing Thermodynamic Foundations for Engineering Practice”, which inferred a link between ettringite with sulphides and mineralogy.   This paper along with Rogers & Glendining’s paper “Modification of Clay soils using Lime” presented at the 1996 Thomas Telford lectures @ Loughborough university, lead to some interesting questions, relating to High Plastic Limit changes, possibly leaving the soil in a dessicated moisture condition (i.e. High negative liquidity Index).

[ii] It would be of major benefit to produce a simpler and more cost effective means of testing for potential swelling issues e.g. with use of classification tests, before and after stabilisation.

 

Beetham, P., Dijkstra, T., Dixon, N..  Nucleation in Lime Stabilised Soils. In Proc of IS-GI Brussels 31 May & 1 June 2012. Vol II, pp269-280

 

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Loughborough University
Leicestershire
LE11 3TU

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