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priming Road Construction

Dust Laying using Bitumen Emulsions

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.

Life Expectancy

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.

You have sound knowledge about  Dust Laying using bitumen emulsions  and you have an another ideas, comments, usage of various techniques by your experience.Please leave a comment what all about it.

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priming Road Construction

Dust Laying Using Bitumen Emulsions

We already discussed concerning the dust laying under bitumen emulsions. But, i figured to go over at length here “how are we able to apply” that Dust laying can be utilized on unsealed granular pavements to minimize dust nuisance, in addition to decrease maintenance costs and lack of  pavement material.

The work tip describes using  bitumen emulsion.   Dust  laying using bitumen emulsion is usually only applicable to low  traffic roads  (under about 100 v/l/d), hard standing areas, haul roads and temporary pavements on construction sites.

Bitumen Emulsions

Types Used for Dust Laying

The best option emulsion grade for dust laying is usually anionic slow setting (ASS) although cationic slow setting (CSS) could also be used.

Dilution

The emulsion is diluted with water just before use.  Dilution rates change from 4:1 water:emulsion to 12:1 water:emulsion, based on surface condition and application rate. A wetting agent or surfactant might be put into assist dilution and surface penetration.  The wetting agent should be suitable for the kind of  emulsion used.  Advice on compatible wetting agents and recommended dosage rates is obtainable from bitumen emulsion suppliers.

Compatibility from the water should be checked before diluting emulsion. When diluting emulsions, it is important to add water towards the emulsion, not emulsion to water to prevent premature breaking of emulsion. Only sufficient diluted emulsion for immediate use ought to be produced previously, as stored diluted emulsions are usually unstable.

Application Rates

An average application rate for diluted emulsion is all about 1.0 L/m2 of total liquid. If surface run-off occurs, the speed of application ought to be reduced. Lower application rates and better concentrations of emulsion are utilized on  hard surfaces . Higher application rates and much more diluted mixtures are utilized on softer and much more  permeable surfaces .

I am expecting write some more tips on dust laying  by using   bitumen emulsions  are in next post. You can Visit here.

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priming Road Construction

Types of Bitumen Surface in Road

Types of bitumen surface will  depend on various type of designed where applicable. Bitumen surface in road consists of a thin (often less than 7 mm) coating of sprayed bitumen (the binder) into which is embedded a covering layer of aggregate. The bitumen surfacing will normally overlay a compacted gravel or crushed rock base which has been primed with a  cutback bitumen , although occasionally pavements may be  bitumen surfaced  without the prior applications of a primer.

The function of the cover aggregate is to resist abrasion and to transmit the wheel loads directly to the underlying pavement. The  bitumen binder  serves to hold the aggregate in position and prevents it being dislodged by the traffic.

The essential requirements of a bitumen surface are :-

• The surfacing should be hard wearing, skid resistant and smooth running.

• The surfacing should protect the underlying pavement from loss of moisture and unraveling under traffic loads.

• The surfacing should provide a high degree of waterproofing to protect the pavement from the effects of climatic changes.

Types of Bitumen Surface

The various types of bitumen surface work include :-

(1) Priming.

This consists of spraying a primer onto the compacted gravel or crushed rock base. The primer is normally bitumen which has been made more fluid called cut-back bitumen by the addition of kerosene (cutter) so that most of it will soaking. Priming is carried out to prepare the surface for the subsequent seal coat and to assist in waterproofing the pavement.

(2) Primer Seal.

This is a heavier primer which is covered with sand or fine aggregate (up to 7 mm maximum size). The sand provides a wearing surface which can carry traffic for a limited period of time (e.g. up to six months).

(3) Seal Coats.

The most common seal coat consists of a single application of bitumen (binder) which is sprayed onto the primed pavement followed by an application of aggregate which is rolled with rubber tyred rollers to embed the stone in the bitumen. The aggregate particles are all about the same size so that all the stone will protrude approximately the same amount above the surface of the bitumen.

This treatment is also used for resurfacing existing bitumen surfaced roads.Other forms of seal coats include :-

• A single application of bitumen followed by an application of coarse aggregate (e.g. 20 mm or 16 mm) followed then by an application of fine aggregate (10 mm or 7 mm).

• Two or more successive application of bitumen and aggregate in which the rates of application of the bitumen and size of the aggregate are successively reduces.

(4) Special Treatments.

Common special treatments are :-

(a) Dust Laying – the application of low viscosity (fluid) slow curing cut-back bitumen, or a diluted  bitumen emulsion  to a dusty road surface.

(b) Surface Enrichment – the light application of bituminous material, such as cut- back bitumen or diluted  bitumen emulsion  to increase the binder content. If the bitumen surface treatment is very light it is sometimes referred to as a “fog Coat”.

(c) Penetration Macadam – a course of rolled crushed aggregate grouted with bitumen.

(d) Slurry Sealing. – the application of a mixture of bitumen emulsion, water and fine aggregate to an aged and cracked road surface by a spreading box.

Slurry sealing is not strictly a sprayed treatment but is included in this course for convenience.

To achieve a satisfactory bitumen surfacing, all phase of the work, from the preparation of the pavement, through the application of primer, binder and cover aggregate, and the subsequent compaction of the aggregate by rolling, must be carefully designed and supervised.