Application Tests for Chip Seal and Microsurfacing

Microsurfacing Jones et al. [24, 25] analyzed the performance of seven polymer-modified asphalt emulsions for microsurfacing application. The objective of their studies was to examine effects of different polymers on microsurfacing performance. The same asphalt, surfactant and aggregates were used to eliminate all other variables 

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]. 

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