Paving with Asphalt Emulsion

A latex modified asphalt emulsion can be prepared using several methods addition of the latex in the aqueous emulsifier solution, direct injection in the asphalt hne just ahead of the coUoid mill or post-addition to the pre-manufactured emulsion, as schematically shown in Fig. 12-9. Addition to the aqueous phase is the most commonly used method. The direct injection process often helps to produce an emulsion with a desired high viscosity for chip seal application (Sect. 12.3.1). This is due to the narrow particle size distribution of the asphalt emulsion produced with this process. 

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The typical cold paving method includes mixing aggregates with asphalt emulsion and thus it does not involve heating the components used to produce the asphalt-based formulation. Asphalt emulsions will be discussed in Sect. 12.3. 

In addition to the paving grades of emulsions, a variety of products are available that are suitable for industrial uses, for paper sidings, and for use in the roofing appHcation field. Asphalts emulsified with colloidal clays are especially suitable for outdoor appHcations because of their exceUent weathering properties. Some of these products have been adapted for use with roofing systems, either with bmsh or spray appHcation. 

Reduction in AC usage - Stable sulphur asphalt emulsions can be produced with up to 40%/wt. sulphur. Since binder volume is the critical factor in the paving mix, and since the relative density of the emulsion binder is greater than regular AC, the substitution of AC by sulphur is not a one-to-one relationship. With a 40 60 emulsion, AC usage is reduced by approximately 27%/wt. This can provide a significant cost saving as well as a lesser dependence on not-always reliable asphalt supplies. 

Asphalt emulsions are used in road paving for the production of a smooth, water-repellant surface. First, an asphalt O/W emulsion is formulated, which has sufficiently low viscosity to be easy to handle and apply, and which has sufficient stability to survive transportation, brief periods of storage, and the application process itself. The emulsion needs to be able to shear thin during application, and then break quickly when it contacts the aggregate. The asphalt emulsions are usually 40-70% bitumen and stabilized either by natural naphthenic surfactants released by treatment with alkali (for a somewhat similar situation involving bitumen processing see also [64]), or else by the addition of anionic or cationic surfactant [106]. Emulsified asphalt can be applied to gravel or rock even when wet [1,20,105,106]. 

Chip seal Loose chips from a freshly paved road are the major safety concern for chip seal operation, and several attempts were reported in the literature to develop a laboratory procedure to simulate the field experience. A modified fretting test (also know as the abrasion cohesion test Esso, ACTE) appears to be the most success-fid [26, 27]. In this test a known amount of CRS-2 asphalt emulsion and aggregates are spread on a roofing felt, and then rolled with a 301 rabber roller. The sample is subjected to the shearing action of a horizontal steam-hose, which is attached to a Hobart sun and planet mixer, and the percentage of retained chips is recorded as a function of curing time. 

The bituminous emulsion, preferably the cationic type, is produced from paving grade bitumen and should comply with the national specifications (CEN EN 13808 2013, ASTM D 2397 2012 or AASHTO M 208 2009, ASTM D 977 2012 or AASHTO M 140 2013, or Asphalt Institute 2008, for the European or US market). Useful information for selecting the appropriate bituminous emulsion can be found in an asphalt cold mix manual (Asphalt Institute MS-19 2008). 

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