Process Specifications
Description
This work shall consist of rehabilitating an asphalt pavement by heating, scarifying, reshaping, rejuvenating and compacting the existing pavement.
Procedure
The entire surface to be rehabilitated shall be cleaned of water, earth and foreign material. All base failures shall be repaired in accordance with local specifications and paid for separately. Rehabilitation work shall be performed only when the air temperature in the shade is at least 45º F. and the forecast is for rising temperatures.
Utilizing a one-pass continuous process, the surface of the existing pavement shall be heated, rejuvenated and scarified to a one inch nominal depth (Note 1) with the surface temperature of the old pavement not to exceed 375º F. Heat shall be applied under an enclosed or shielded hood and shall extend at least four inches beyond the width of scarification on both sides. Scarifying shall be accomplished with pressure scarifiers. The heating-scarifying operation shall not exceed 30 feet per minute. When a repaving pass is being made adjacent to a previously placed mat, the longitudinal repaving seam shall extend at least two inches into the previously placed mat.
Note One
The depth of scarification will be determined by scraping out and weighing the heated and scarified material from a one square foot area. This weight shall be 75% of the theoretical weight of one square foot by 1 inch of compacted bituminous surface course. Total equipment length of the pre-heater and heater-scarifier shall not exceed 115 feet.
Immediately before the scarifying operation, an approved asphalt modifier shall be applied at the approximate rate of 0.10 gallon per square yard. The engineer may waive or adjust the requirement for the asphalt modifier if the existing pavement condition warrants this action. The surface shall then be leveled, by distributing the heated, scarified and treated (HST) material over the width being processed, so as to produce a uniform cross section. The minimum temperature of the HST material after leveling shall be 175º F. The (HST) material shall be compacted before the temperature of the mix drops below 150º F.
Compaction shall be accomplished with an 8 to 10-ton steel wheel roller in static mode. The roller shall be equipped with an adequate scraping or cleaning device on each wheel to prevent the accumulation of material on the wheels. When used for the compaction of bituminous mixtures, the roller shall be equipped with a water system which will keep all wheels uniformly wet to prevent material pickup when required.
Method of Measurement
The heat-scarifying process will be measured in place and the area computed in square yards. The asphalt modifier will be measured in gallons. If provided as a payment item, the preparation of the base will be measured in square yards.
Basis of Payment
This work will be paid for at the contract unit price per square yard for HEATER-SCARIFYING, and per gallon for ASPHALT MODIFIER. If provided as a pay item, the preparation of the base (exclusive of additional material required) will be paid for at the contract unit price per square yard for PREPARATION OF BASE.
