Page 127 - RoadCem Manual - PCT BV

Thus, it is pore water pressure or suction of the water in the pavement, rather than the amount of water, that affects pavement behaviour. Two soils of different textures may have similar strength, and stiffnesses, even though their moisture contents may be quite different.
RoadCem/Cement modified materials effectively eliminate the negative term in the equation for shear strength making shear strength significantly higher under critical environmental conditions.The RoadCem approach especially becomes beneficial when problem soils and materials are in question.
Problem soils and materials are those materials which by virtue of their unfavourable properties would normally require special treatment before acceptance in the pavement structure or for a sub base. This category of soils and materials includes:
• Low-strength soils.
• Expansive clays (“black cotton” soil).
• Collapsible sands.
• Dispersive soils.
• Organic soils.
• Saline soils or presence of saline water.
• Weathered materials.
The characteristics, investigation, testing and design counter-measures to deal with problem soils are well covered in the literature and are not dealt with in depth in this manual.
In dealing with such materials, a careful balance has to be struck between the cost of RoadCem and Cement treatment. The benefits to be derived from avoiding the import of other suitable material and the costs of environmental damage needs to be taking into account.
Low-strength soils
Soils with a soaked CBR of less than 3 per cent (< 2 per cent in dry climates) are described as Low- strength soils.
TRADITIONAL
Typical traditional treatment measures for such soils include:
• Removal and replacement with suitable material.
• Chemical or mechanical stabilization.
• Elevation of the vertical alignment to increase soil cover and thereby redefine the design depth within the pavement structure.
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