We already discussed about the what is the dust laying , types of bitumen emulsions used, how to diluted and the application rates etc in the previous post. It is recommended to get complete idea go over here. And we are going to discuss here, what are operations of dust laying and special conditions, Life of the road that can expect after dust laying using bitumen emulsions and the various other techniques of dust laying by soil stabilizing techniques.
Operations of Dust Laying
It is preferable to shape, if necessary, and lightly sweep the surface to remove excessive dust and loose material. A preliminary dampening may assist in obtaining a uniform distribution. Excessive dust will reduce effectiveness and require more applications. Spraying is generally carried out with a bitumen sprayer. Diluted anionic emulsions may be applied with a standard water cart, preferably one with a pressure spray bar. Unbroken anionic emulsions can generally be completely removed by flushing with clean water to leave little, if any, bituminous residues.
Cationic emulsions should only be used in a conventional bitumen sprayer, as they leave a coating of bitumen on any surface, including metal, with which they come into contact.
Bituminous residues can be difficult to remove from equipment that is not designed for spraying of bituminous materials. Traffic should be kept off the surface until the emulsion is fully broken and the surface is dry. This is generally a minimum of 2 to 3 hours.
The initial emulsion dust laying treatment is usually followed up with a second application after 2 to 3 days. A further treatment may be applied after 3 to 4 weeks.
Effective service life can vary from several weeks to six months or more, depending on: the number of applications, weather,? traffic conditions, and nature of pavement material.
Service life can be extended by repeated applications. The time interval between subsequent applications generally increases
Dust Laying Using Soil Stabilization Techniques
Greater effectiveness of bitumen emulsion as a dust laying procedure for unsealed granular pavements may be achieved using stabilization techniques. Again, slow setting grades of emulsion (ASS or CSS) are used, but without dilution. Emulsion is applied by spray bar to a scarified surface and then mixed in by a stabilizing machine or grader, prior to compaction of the surface layer.
Typical application rates vary from 1% to 3% of residual binder by mass of the soil being treated. Lower application rates are used with well-graded granular materials.
Higher rates are required for sandy materials. Stabilization using bitumen emulsion is not suitable for fine-grained soils and materials of high plasticity. Efficiency of distribution of the emulsion through the soil is influenced by moisture content. A moist soil facilitates mixing and even distribution. Dry soil causes premature breaking of the emulsion and poor distribution. Excessive moisture makes the soil unstable and prevents proper compaction.
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