DHARM704 GEOTECHNICAL ENGINEERINGcalcium chloride may render a soil more suitable for stabilisation with cement in spite of the
presence of organic matter.
Cement content
The normal range of cement content used is 5 to 15% by weight of the dry soil, finer soils
requiring greater quantity of cement. The more the cement content, the greater is the strength
of the resulting soil-cement. A compressive strength of 2000 to 3000 kN/m^2 as obtained from a
test on a cylinder of soil-cement after 7 days of during must be satisfactory. High early strength
cement yields better results than ordinary cement.
Compaction
Adequate compaction is essential. Optimum moisture is to be used in the process as there is no
problem of stability as for concrete.
Mixing
Uniform mixing will lead to strong soil-cement. The efficiency of mixing depends upon the
type of plant used. Mixing should not be done after hydration has begun.
Admixtures
Addition of about 0.5 to 1.0% of certain chemicals such as lime or calcium chloride to soil-
cement has been found to accelerate the set and to improve the properties of the final products
(Lambe, Michaels and Moh, 1959).
Designing and testing soil-cement
Soil-cement mix design consists of selecting the amount of cement, the amount of water and
the compaction density to be achieved in the field. The thickness of the stabilised soil and also
the placement conditions are to be decided upon. The thickness of a soil-cement base is to be
taken equal to that required for a granular base for a good subgrade, and as equal to 75% of
that required for a granular base for a poor subgrade. Usually 15 to 20 cm thickness is ad-
equate for a soil-cement base.
The procedures adopted for design are:
(i) Complete method, using moisture-density, freeze-thaw, and wet-dry tests;
(ii) Short-cut method for sandy soils, using moisture-density and strength tests in con-
junction with the charts prepared by the Portland Association; and
(iii) Rapid method, using moisture-density tests and visual inspection.Field construction of soil-cement
The steps in the construction of soil-cement are:
(i) Pulverization of soil
(ii) Adding water and cement
(iii) Mixing
(iv) Spreading and compaction
(v) Finishing and curing
In advanced countries most of the operations are mechanised. The method may be mixed-
in-place, travelling plant, or stationary plant type.