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5 and frequent turning, stopping, and starting. Although chip emulsions are used. Therefore, construction aggregates should seals can be constructed in such environments with success, be moistened by spraying water on the stockpile and mixing the time required for emulsions to gain sufficient strength to with a front-end loader before chip-seal operations begin. resist the turning, acceleration, and deceleration of vehicles in large volumes is often long enough to preclude their use. Toughness and Durability Aggregates must have enough strength to resist crushing 2.5 Materials during construction and trafficking. Breakdown of the aggre- 2.5.1 Aggregate Chips gate during construction and trafficking could lead to inunda- tion and flushing if the coarse particles are reduced to fine Aggregate properties, including size, shape, and gradation; particles. cleanliness; moisture content; toughness and durability; and porosity influence chip-seal performance. Porosity Size, Shape, and Gradation Porous aggregates will absorb more asphalt than nonporous aggregates. Therefore, the amount of asphalt absorbed must Aggregates that interlock after construction rolling and be accounted for during the design stage. early trafficking provide higher stability under loads. This interlocked aggregate surface is more resistant to displace- ment and thus has a lower potential for dislodgement of chips 2.5.2 Asphalt Emulsion and vehicle damage and flushing. The performance of a chip seal is largely dependent on the Larger aggregates require higher emulsion application rates in order to provide an equivalent embedment percentage to asphalt emulsion. Performance is related to the adhesive abil- smaller aggregates. This higher application rate allows slightly ity of the binder for the aggregate chips and the underlying more tolerance during construction with respect to depth of pavement, the durability and flexibility of the binder, and the chip embedment in the binder. Also, the higher binder appli- ability of the binder to maintain these properties over a wide cation provides greater sealing ability. range of environmental conditions and snowplow action. Aggregates retained between two adjacent sieve sizes provide the best interlock, followed by aggregates that occupy the space Emulsion Type between three adjacent sieve sizes; these are often described as one- and two-sized aggregate chips, respectively. The perfor- Emulsified asphalts should be rapid setting types. Although mance of the one- and two-sized chips is related to the manner rapid setting emulsions allow faster removal of traffic control, by which the chips are embedded in the emulsion. If well- they can set too quickly in very hot weather or even form a graded aggregates are used, the fine aggregate often enters the skin on the surface after application, creating a barrier to chip emulsion before the coarse aggregate, causing the coarse aggre- embedment. Medium setting emulsions require more time gate to have less binder available for adhesion and resulting in to set, requiring traffic control to remain in place longer and loss of the coarse fraction, vehicle damage, and flushing. increasing the possibility for vehicle damage. However, while rapid setting emulsions are the most desirable as a chip-seal binder, medium setting emulsions have been used success- Cleanliness fully on low volume roads when strict traffic control is main- Emulsified asphalts can be produced with the ability to coat tained. Medium setting emulsions have also been successful aggregate chips containing small quantities of minus no. 200 when chips are more uniformly graded or contain higher aggregate. The maximum amount of this fine aggregate is quantities of minus no. 200 particles. dependent on the emulsion. For example, medium setting emulsions can tolerate a higher percentage than most rapid Emulsion Class setting emulsions; this is often related to the demulsibility of the emulsion. The higher the demulsibility, the less minus Emulsions are classified based on the particle charge of the no. 200 can be tolerated before setting occurs and there is loss asphalt droplets within the water phase of the suspension. of adhesion to the coarse chips. Anionic emulsions have a negative charge and cationic emul- sions a positive charge. There are also a limited number of emulsions classified as nonionic with no appreciable charge. Moisture Content These emulsions can be considered interchangeable as both Aggregates in the saturated surface dry condition provide classifications should provide equal performance with respect better resistance to sweeping than dry aggregates when asphalt to adhesion to aggregate chips. Research has shown no