Ground Improvement Techniques
AustStab Technical Note
No.1 May 2002
Lime stabilisation practice
1
Introduction
Lime stabilisation of materials is one of the oldest forms of stabilisation and sometimes the least understood.
The stabilisation of clay subgrades using quicklime has a long and successful history in many urban and rural regions of Australia, and is cost effective and a necessary requirement for Municipalities and State
Road Authorities seeking long-life roads to minimise future maintenance costs.
The possible applications of lime stabilisation are to: q q q increase subgrade stiffness (see Figure 1), reduce the PI of insitu pavement material, enhance volumetric stability for the top layer of select material, q modify subbase layers to improve stiffness of the pavement, and q produce a temporary construction platform for civil works. manufactured in Australia is processed through a fluid bed, rotary or vertical shaft kilns. Problems associated with transporting lime by sea over long distances limits the importation of this binder.
Table 1 The properties of lime used for soil stabilisation [Ref.1].
Composition
Form
Equiv.
Ca(OH)2
Bulk density
(t/m3)
Hydrated lime Ca(OH)2
Fine powder
1.00
Quicklime
0.45 to 0.56
0.9 to 1.3
CaO
Granular
1.32
Lime
Slurry
Ca(OH)2
Slurry
0.56 to
0.33
1.25
The manufacture of quicklime involves the heating of excavated limestone in a lime kiln to temperatures above 900°C resulting in carbon dioxide being driven off and calcium oxide being produced (see Figure 2).
The chemical equation is as follows:
CaCO3
The material type and condition of the existing pavement material will govern the application rate and construction practices. In order to understand the properties of lime and its reaction with soils, this construction tip aims to highlight: q q q q q q
2
the types of lime being used, the manufacture of lime, how does lime work with soil,
application
No.1 May 2002
Lime stabilisation practice
1
Introduction
Lime stabilisation of materials is one of the oldest forms of stabilisation and sometimes the least understood.
The stabilisation of clay subgrades using quicklime has a long and successful history in many urban and rural regions of Australia, and is cost effective and a necessary requirement for Municipalities and State
Road Authorities seeking long-life roads to minimise future maintenance costs.
The possible applications of lime stabilisation are to: q q q increase subgrade stiffness (see Figure 1), reduce the PI of insitu pavement material, enhance volumetric stability for the top layer of select material, q modify subbase layers to improve stiffness of the pavement, and q produce a temporary construction platform for civil works. manufactured in Australia is processed through a fluid bed, rotary or vertical shaft kilns. Problems associated with transporting lime by sea over long distances limits the importation of this binder.
Table 1 The properties of lime used for soil stabilisation [Ref.1].
Composition
Form
Equiv.
Ca(OH)2
Bulk density
(t/m3)
Hydrated lime Ca(OH)2
Fine powder
1.00
Quicklime
0.45 to 0.56
0.9 to 1.3
CaO
Granular
1.32
Lime
Slurry
Ca(OH)2
Slurry
0.56 to
0.33
1.25
The manufacture of quicklime involves the heating of excavated limestone in a lime kiln to temperatures above 900°C resulting in carbon dioxide being driven off and calcium oxide being produced (see Figure 2).
The chemical equation is as follows:
CaCO3
The material type and condition of the existing pavement material will govern the application rate and construction practices. In order to understand the properties of lime and its reaction with soils, this construction tip aims to highlight: q q q q q q
2
the types of lime being used, the manufacture of lime, how does lime work with soil,
application
References: Sydney, 1992. Zealand Report N0. 104, Wellington, NZ, 1998. Little, D Lime stabilization of bases and subbases Kendall Hunt Publishing Company, Iowa, USA, 1995. N0. 127, Wellington, NZ, 1998.