Asphalt Emulsion Tests

Polymer Honeycomb Stmcture in Cured Asphalt Emulsion 

Modified asphalt emulsion with latex is not just an emulsion of polymer-modified asphalt, but rather an emulsion containing dispersed latex particles in the aqueous 

Latex Modified Emulsion Cured Asphalt Emulsion 

Right Latex particles transform to a continuous polymer film surrounding asphalt particles, which cures to form the honeycomb structure. 

Scanning electron microscope observation of the microsurfacing pavement confirmed the presence of the polymer honeycomb structure [22]. Here, a sample of the freshly applied pavement sample was treated with OSO4 and the asphalt was extracted with MEK (methyl ethyl ketone) solvent The treatment with OSO4 makes the SBR polymer insoluble to the organic solvent and also improves the contrast for the scanning electron microscope, SEM, observation. 

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EmulsffiedAsphalts (ASTMD244). This standard covers a variety of tests for the composition, handling, nature and classification, storage, use, and specifying of asphalt emulsions used primarily for paving purposes. 

Muncy, H.W. (Ed.) Asphalt Emulsions, ASTM Publ. STP 1079, American Society for Testing and Materials Philadelphia, PA, 1990. 

The authors concluded that SBR latex continues to perform well in virtually all the laboratory tests to which it has been subjected. They also recognized that the materials which were received as latices, tended on average to outperform the soHd polymers. These conclusions, especially LWT results, can now be understood in the Hght of the formation of the polymer honeycomb structure providing excellent rutting resistance of the asphalt emulsion residue. This is demonstrated in Figs 12-13 to 12-16]. 

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. 

An example of the test results is shown in Eig. 12-19, which demonstrates early cohesion development with the latex modified asphalt emulsion [28]. Marchal et al. [27] report that the maximum chip retention does not exceed 80 % even with a fully cured asphalt emulsion, and approximately 50 % chip retention is considered to be strong enough to be open to traffic. Use of a specially designed brash appears to reduce a problem of chip build-up around the steam-hose [29]. 

E. Comet, Esso Abrasion Cohesion Test, A Description of the Cohesive Breaking of Emulsions for Chip Seals, Proc. Int. Symp. Asphalt Emulsion Technology, 1999, pp. 346 355. 

J. L Marchal, P. Julien, N. Boussad, Bitumen Emulsion Testing Towards a Better Understanding of Emulsion Behavior, ASTM Symp. Asphalt Emulsion, 1990. 

Various types of sulfur-asphalt pavement field test sections have been placed in the U.S., Canada, and Europe. Shell Canada Ltd. has conducted field trials in Canada (1,18,19,20). Gulf Oil Canada has also placed test sections of sulfur-asphalt pavement in which the sulfur and asphalt cement were incorporated into the mixture as an emulsion (4). Societe Nationale des Petroles D Aquitaine (SNPA) placed field test sections in France using the emulsion process (5). 

Figure 4.14 Apparatus for distillation test of bitumen emulsions. (Reprinted from ASTM D 6997, Standard test method for distillation of emulsified asphalt. West Conshohocken, Pennsylvania, US ASTM International, 2012. With permission [ ASTM International].)...

The stage where the compatibility of the bituminous emulsion with the selected aggregate is examined is necessary since there are a variety of aggregates to be used for a given bitumen emulsion. The properties of the cold asphalt are directly related to the capability of the bitumen emulsion to coat the aggregate particles with bitumen. This is determined by executing the coating test. 

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