Page 129 - RoadCem Manual - PCT BV

TRADITIONAL
Traditional methods of dealing with collapsible soils includes the following:
• Excavation of material to a specified depth below ground level and replacement in thin lifts (typically 200 mm).
• Ripping of the road bed, inundation with water and compaction with heavy vibrating rollers.
• Use of high energy impact compaction at In-situ moisture content
• Chemical treatment
ROADCEM
RoadCen treatment falls in the fourth category and makes the use of these materials for pavement structure viable and justified. The mechanism of action is the overall reduction in effective loading thus preventing settlement.
The above measures are all relatively expensive to undertake and a careful balance should be struck between the costs and benefits of their application.
Dispersive soils
These soils, some of which are clayey gravels, are easily eroded in the presence of water - a property that makes them problematic when they occur in cut slopes and in drainage channels. They have almost no resistance to erosion, are susceptible to pipe developments in earthworks, crack easily and have low shear strength. Their identification involves the use of a combination of indicator tests, observations of erosion patterns, soil colour, terrain features and vegetation.
TRADITIONAL
The following measures are typically employed where dispersive soils are encountered:
• Erosion protection in cut slopes and drainage channels.
• Modification with 2% to 3 % lime or alternative chemical treatment. ROADCEM
RoadCem/Cement treatment falls in the second category and makes the use of these materials for pavement structure viable and justified. The mechanism of action is through stabilization and erosion control.
Saline soils or presence of saline water
The presence of soluble salts in pavement materials or subgrades can cause damage to the bituminous or other surfacing of roads. This problem occurs mostly in the semi-arid regions where the dry climate, combined with presence of saline materials (often calcrete or minewaste) and/or saline ground or surface water, create conditions that are conducive to the occurrence of salt damage. Such damage occurs when the dissolved salts migrate to the road surface, mainly due to evaporation. At he surface tehy become supersaturated and then crystallize with associated volume change. This creates pressures which can lift and physically degrade the surfacing and break the adhesion with the underlying pavement layer.
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