Page 132 - RoadCem Manual - PCT BV

• Reduced sensitivity to moisture changes.
• Improved workability.
• Increased durability.
• Reduced maintenance.
• Reduced environmental impact.
As indicated in Figure 5.28 the choice of chemical stabiliser will depend on the material to be stabilised and the position in the road pavement it is to occupy. However, our experience has shown that only RoadCem options offers consistant and continous benefits and advantages.
These stabilisers are generally applied at relatively low dosages, typically between 3 and 6 per cent by mass. However, if problems are to be avoided, they must be subjected to careful and well-controlled processing and construction.
Specifications for chemically treated materials vary in different parts of the world and for different road authorities.
With the exception of RoadCem based stabilization potential problems and pitfalls with these type of materials includes:
• Propensity to crack particularly with cement treatment (cement only).
• Degradation of cementing action due to carbonation.
• Requirements for greater level of skill and control during construction.
EFFECTS OF CARBONATION
Lime- and, to a lesser degree, cement-stabilized soils can lose strength through carbonation. This effect is particularly evident in lime-stabilized fine-grained and relatively weak soils (especially calcretes). For base course materials, prolonged exposure of these lime or cement stabilized soils to the air before sealing can also result in a weak upper layer being produced prior to surfacing. Subsequent crushing of the aggregate as well as poor bonding between surface and the base can occur, leading to pavement failure. Measures that ameliorate the effects of carbonation during the stabilization process includes:
• Immediate covering with the next layer of material.
• Immediate application of a bitumen prime coat.
• Full moist curing (with no drying of the surface).
• Construction of layer with a sacrificial thickness to be bladed off.
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