Chip Seal Best Practices (2005) / Chapter Skim
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Pages 12-18
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From page 12... ...
CHIP SEAL DESIGN METHODS Chip seal design methods largely fall into two fundamental categories: empirical design based on past experience and design based on some form of engineering algorithm. A large body of research is available on formal chip seal design practices.
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From page 13... ...
Table 1 shows the percentage of North American respondents using the various design methods. Past Experience in Empirical Methods The very early practitioners of surface treatments or seal coats appear to have used a purely empirical approach to surface condition of existing pavement, traffic volume, and actual type of chip seal being used.
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From page 14... ...
These characteristics basically involve the following stages of design: • Evaluate surface texture; • Evaluate traffic conditions: volume, speed, percentage of trucks, etc.; • Evaluate climatic and seasonal characteristics; • Evaluate and select type of chip seal; • Evaluate aggregate selection; • Determine binder application rate; and • Determine how many hours per day are available for construction operations. Evaluate Surface Texture Surface texture refers to the surface properties of the pavement surface (Sprayed Sealing Guide 2004)
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From page 15... ...
Critical differences based on the construction sequence, number of courses sealed, and variations in aggregate nominal size generally distinguish between the different types of chip seals. The basic divergence with double chip seal design is that the total design binder application rates are less than for a conventional single-course chip seal (McLeod 1969)
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From page 16... ...
Double chip seals have less noise from traffic, provide additional waterproofing, and are a more robust seal in comparison with a single chip seal (Sprayed Sealing Guide 2004)
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From page 17... ...
The geotextile is carefully rolled over a tack coat, followed by a single chip seal being placed on top, as shown in Figure 17. Evaluate Aggregate Selection The selection of the specific aggregate essentially establishes the thickness of the chip seal, because this type of surface 18 treatment is intended to be literally one stone thick.
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From page 18... ...
After all, the primary purpose of a chip seal is to prevent water intrusion into the underlying pavement structure, and the asphalt layer formed by the binder is the mechanism that performs this vital function. The previously explained design methods are all based on the assumption that single-course chip seal design requires the use of uniformly graded aggregate spread one stone thick in a uniform manner.
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