Lime stabilisation: Developing methods

Student thesis: Master Thesis and HD Thesis

  • Michael Gärtner Nielsen
  • Brian Aagaard Christiansen
In many countries, lime-stabilisation is frequently used on the basis of existing methods. In Denmark, though, this is not the case. Lime-stabilisation is not widely used and there are no references to this method in the Danish road rules. This report aims to describe the theoretical, economic and practical aspects of lime stabilisation in road based constructions. The beneficial short term effects of stabilisation are examined by carrying out tests on three clay soils stabilised with quicklime. The goal is to uncover usable methods to determine the necessary percentage of lime to be applied in different clay types with different water percentages. A method for economic evaluation of lime-stabilised and unbound aggregate bases is converted from French methodology to Danish use. Lime-stabilisation occurs when quicklime or hydrated lime is added to clay soils and improves both the stiffness of the clay soils and their resistance to permanent deforma- tion. The exothermic formation of hydrated lime, from quicklime, significantly reduces the amount of water in the soil. There are two processes which improves the performance of clay soils. The first process is modification in which calcium ions are released from the hydrated lime and initiates several chemical reactions. These chemical reactions result in increased strength and a more granular structure of the clay soil. The second process is solidification in which the strength of the stabilised soil is increased over time due to an increased pH-value which causes the dissolution of silicon and aluminium from the edge of the clay plates. As a result, the compounds crystallize and thereby reduces plasticity and increases strength. The methodology of calculating durable subgrade layers in Denmark does not cover lime- stabilised soils. In this report such a method is described building on the existing methodology and programs. The mechanical experimentation uses the California Bearing Ratio (CBR) to uncover the increase in strength after stabilisation. Two different clay types are used in the tests and the tests are done with a lime percentage of 0-4 %. The results show an increase in strength shortly after stabilisation.
Publication date2009
Number of pages86
Publishing institutionAalborg Universitet
ID: 17689793