The aggregate used should be about one-half the diameter of that used in the first application. Reduce the amount of bituminous material by one-third or one-half of the first layer. Sweep away loose aggregate so that subsequent layers will bond together. Lay this layer the same as a single surface treatment. Use the following guidelines for a multiple surface treatment: Although multiple surface treatments are usually more than 1 inch thick, they are still considered surface treatments because each layer is usually less than 1 inch thick and the total surface treatment does not add appreciably to the load-carrying capacity of the base. Use smaller particles of aggregate and less bituminous material for each successive layer. This type of treatment involves two or more successive layers of single surface treatments. When a tougher, more resistant surface is desired than that obtained with a single surface treatment, use a multiple surface treatment. For information on subgrade, subbase, and base preparation, seeĤ-35. On the contrary, if the base dries out completely, cracks may develop and a heavy rain could cause swelling and density loss. In general, the lowest acceptable moisture content for the upper portion of the base course before priming should not exceed one-half of the optimum moisture content. Heavy rains may strip a properly primed base to some extent, but the tendency will not be so great as on an improperly cured base. Rain also tends to strip the prime from a base that was too wet when primed. Moisture tends to come out, especially in hot weather, and strip the prime from the base during construction. If the base is too wet, it will not take the prime properly.Ĥ-10. Completely cover the base with the minimum amount of water and let it dry or nearly dry before applying the prime coat. If sprinkling is necessary, however, apply water lightly at a rate of about 0.2 to 0.3 gallon per square yard, depending on the condition of the base, the temperature, and the humidity. The base can be sprinkled with water, although it is not preferred.
If the base is not broomed, apply a prime coat and lightly roll it with a pneumatic roller.Ĥ-9. Broom the surface of the base if it contains an appreciable amount of loose material (fine or coarse) or if it is excessively dusty.
#Road mix base free
Ensure that the base is well-graded, shaped to the desired cross section, compacted to a specified density, well-drained, clean, and free of excessive moisture but not completely dry. Time limitations may prevent the use of ramps in the TO therefore, aggregate may be deposited at ground level directly from the trucks.Ĥ-8.
To minimize segregation, place a truck ramp at one end of the pile so that trucks can back up the ramp and dump aggregate over the top area of the stockpile or use a clamshell bucket without teeth to build up the stockpile. Deposit aggregate in layers that are about 3 feet thick.
The larger particles may fall down the slope, and the smaller particles will be left near the top of the stockpile. Aggregate may separate if it is dumped into piles with long, sloping sides. Maintain separate stockpiles for each aggregate. Large stockpiles are usually rectangular with a flat top to ease computation of volumes and built-in layers, to retain uniformity of gradation, and to avoid segregation.Ĥ-4. (Īddresses the issue of processing aggregate from pits and quarries.) Aggregate is usually stockpiled at the pit and construction site to prevent shortages during an operation. Aggregate is transported in trucks from the pit where it is produced and screened to a convenient location near the construction site.