for Highway Construction Page 235 of 715 SECTION 406 – ROAD MIX PAVEMENT
406.01 Description.
Construct 1 or more courses of road mix pavement on a prepared base or road surface.
406.02 Materials.
Provide asphalt of the type and grade specified. Provide asphalt and anti -stripping additive as specified in 702 , if required. The Engineer will accept the asphalt at the point of delivery. Provide aggregate as specified in 703 . The Engineer will accept the aggregate at the point of delivery from Contractor -provided sourc es or the crushing plant from designated sources.
406.03 Construction Requirements.
A.Season and Moisture Limitations. Do not apply asphalt if sur face or weather conditions prevent proper construction. Do not construct road mix pavement before May 15 or after September 15.
B.Equipment. Provide scarifying, mixing, spreading, finishing, and compacting equipment, an asphalt distributor, and equipment for heating the asphalt. Ensure the distributor is designed, equipped, maintained, and operated so asphalt can be applied uniformly on variable widths of surface at readily determined and controlled rates with un iform pressure. Provide distributor equipment that includes a tachometer, pressure gauges, accurate volume measuring devices or a calibrated tank, and a thermometer for measuring temperatures of tank contents . Equip distributors with a power unit for the pump and full -circulation, vertically adjustable spray bars. Use compaction equipment and/or rolling methods to produce the required compaction without damaging the work.
C.Preparation of Roadbed. Uniformly compact the roadbed surface. Keep the prepared base in good condition before placing the bituminous surface course. Leave the prime coat undisturbed for at least 24 hours. Spread bl otter as specified in 402 in an approved quantity to absorb the excess asphalt , if the asphalt does not penetrate and the roadway must be used by traffic. Allow the tack coat to dry until i t is tacky enough to receive the road mix material.
D.Placing Aggregate . Uniformly spread aggregate on the road by the use of spreader boxes or other approved mechanical spreading devices. for Highway Construction Page 236 of 715 E. Application of Asphalt . Uniformly distribute the asphalt in successive applications, in quantities and at intervals, as approved. Ensure the mixing equipment follows immediately behind the distributor after each asphalt application to partially mix the aggregate and the asphalt and ensure the asphalt application temperature is as specified.
F.Mixing . Windrow the enti re mass of asphalt and aggregate on the road surface after the last asphalt application and partial mixing , and then mix until aggregate particles are coated with asphalt, the whole mas s has a uniform color, and the mixture is without fat or lean spots, balls, or uncoated particles. Avoid cutting into the underlying course or contaminating the mixture with earth or other extraneous matter during the mixing operati ons. The Engineer may require confining the mixing process to part of the width or area of the roadway to allow traffic to pass. Add aggregate or asphalt as required and remix if the mixture shows an excess, a defici ency, or uneven distribution of asphalt. If the mixture contains excessive amounts of moisture or volatile matter, blade, aerate, or otherwise manipulate the mixture until the moisture and volatile contents are satisfactory. Do not spread the mix if the surface to be covered is in unsatisfactory condition. Blade loose material into a windrow at the end of each day’s work or when the work is interrupted by weather or other conditions, whether mixing is completed or not, and keep in a windrow until o perations are resumed.
G.Spreading, Compacting, and Finishing. Spread the material by a patrol or a mechanical spreader as approved. Avoid cutting into the underlying base if spreading from the windrow. Roll the surface after the mater ial is spread. Use compaction equipment and/or rolling methods to produce the required compaction without damaging the work. Perform initial rolling with a pneumatic -tire roller and final ro lling with a 3 -wheel or tandem -type steel -wheel roller. Roll parallel to the road centerline starting at the outer edges of the road, overlapping the shoulders and progress toward the center, overlapping on successive passes by at least ½ the width of the roller, except on superelevated curves where rolling progresses from the lower to the upper edge. End each pass at least 3 feet in advance or to the rear of the end of the preceding pass. Blade the surface during compaction to fill ruts and remove incipien t corrugations or other irregularities as necessary. Continue rolling until the surfacing is a uniform texture and meets the compaction specified.
H.Surfacing Approaches . Construct road mix pave ment on approaches as specified or as directed.
I.Surface Smoothness . The Engineer will test the completed surface in accordance with Idaho IT 87. Ensure the surface does not vary more than ¼ inch from a 10- foot s traightedge.
J.Aggregate for Road Mix Pavement in Stockpile . Provide aggregate material in stockpiles at approved locations. Prepare the stockpile site by clearing and smoothing as directed. Construct stockpiles that are neat and regular in form and occupy as small an area as possible. Construct by first distributing the material to be for Highway Construction Page 237 of 715 stockpiled over the entire base and building upward in successive layers at least 3 feet in depth. Do not end- dump or convey materials over the sides of the pile.
406.04 Method of Measurement.
The Engineer will measure acceptable work as follows:
1.Aggregate and asphalt for road mix pavement by the ton.
2.Anti-stripping additive by the percentage of additive per ton of asphalt .
3.Approaches by the each paved regardless of size.
4.Aggregate for road mix pavement in stockpile by the ton or cubic yard.
406.05 Basis of Payment .
The Department will pay for accepted quantities at the contract unit prices as follows: Pay Item Pay Unit Aggregate for Road Mix Pavement ......................................................... Ton Approaches ............................................................................................ Each Aggregate for Road Mix Pavem ent in Stockpile ..................................... Ton or CY Aggregate for Road Mix Pavement , Load, Haul, and Place .................... Ton Emulsified Asphalt for Road Mix Pavement ............................................ Ton Percent Anti -Stripping Additive for Road Mix Pavement ......................... TOA for Highway Construction Page 238 of 715 SECTION 407 – SCRUB COAT
407.01 Description.
Construct a scrub coat on the road surface.
407.02 Materials.
Provide asphalt of the type and grade specified. Provide asphalt and anti -stripping additive as specified in 702, if required. The Engineer will determine acceptability of the asphalt at the point of delivery. Provide aggregate for scrub coat as specified in 703.04. The Contractor does not need to use multiple stockpiles. The E ngineer will determine acceptability of the aggregate from the Contractor -provided sources at the point of delivery and at the crushing plant from designated sources.
407.03 Construction Requirements.
A.General. Do not place scrub coat materia l on wet or frozen surfaces. Ensure the ambient and surface temperature is 60°F and rising. Clean the surface by brooming or other approved methods.
B.Mixing . Mix the plant mix sc rub coat as specified in 405.03. Mix the road mix scrub coat as specified in 406.03. Produce mixtures at the lowest temperature that will produce a uniform workable mixture not exceeding 165°F.
C.Equipment. Use compac tion equipment and/or rolling methods to produce the required compaction without damaging the work.
D.Spreading, Compacting, and Finishing. Apply the tack coat as specified in 401, before applying the scrub coat . Sufficiently aerate the scrub coat material before spreading. Spread and tight blade from shoulder to shoulder or as directed. Fill depressions, irregularities, and cracks and smooth to create a uniform surface. Roll with pneumatic -tire roller s concurrently with the spreading. Finish roll with a steel -wheel roller.
407.04 Method of Measurement.
The Engineer will measure acceptably c ompleted work as follows:
1.Scrub coat , asphalt , and anti -stripping additive by the ton, if required. The Engineer will not accept batch weights as a method of measurement. A deduction w ill not be made for the weight of the asphalt or other addit ives in the mixtures.
2.Anti-stripping additive by the percentage of additive per ton of asphalt .
407.05 Basis of Payment .
The Department will pay for accepted quantities at the contract unit prices as follows:
Source: Idaho Standard Specifications for Highway Construction, 2023 Edition. Pages 271–273 of 768.