194 SECTION 420
420.01 Description
This work consists of an application of bitumen followed by an application of cover coat material on a prepared surface.
420.02 Equipment
Equipment Section Self-Propelled Pneumatic -Tired Rollers 151.01 A.3 Aggregate Trucks 152.01 C Bituminous Tank Truck 152.01 E Bituminous Equipment 154 Liquid Bitumen Distributors 154.02 B Aggregate Spreader 154.02 C Use a broom with a positive means of controlling the vertical pressure on the broom head.
420.03 Materials
Item Section Aggregate 816 Bitumen 818.02 E
420.04 Construction Requirements
A.General. Begin seal work after May 15 and on or before September 1. Allow material to cure as shown in Table 420-01 before applying seal coat materials. Table 420 -01 Curing Period Material Type Curing Period Prime Coat 4 days Asphalt Cement Pavements 7 days Emulsion Pavements 15 days Schedule the work so that the last bitumen application of the day is sufficiently cured to allow installation of the short-term pavement marking before sunset.
B.Preparation of Surface.
1.General. Prepare the surface by removing loose dirt and deleterious material . 195 2. Spotting Tabs. Before applying bitumen, install spotting tabs every 200 feet along the centerline and at the beginning and end of the no-passing zones. After installation of permanent pavement markings, remove spotting tabs by cutting the tabs flush with the roadway surface.
C.Application of Bitumen. The Engineer will direct the application rate of bitumen. Apply bitumen with a liquid bitumen distributor in a uniform and continuous spread. Correct skipped areas and deficiencies. Apply bitumen to a dry surface with a minimum pavement surface temperature of 60°F. Protect the surface of structures and other roadway appurtenances against tracking and splatter ing. If applying bitumen in multiple passes, overlap the bitumen along adjoining edges of the passes. Maintain traffic without pickup or tracking of bitumen. Promptly shut off the bitumen spray at the end of the application to prevent lapping at transverse junctions. Before continuing the application, spread building paper or metal sheets to cover the previously treated surface a sufficient distance back from the joint to allow the sprayers to operate at the established application rate upon reac hing the untreated surface.
D.Cover Coat Material Application. The Engineer will direct the application rates of the cover coat material. Flush the cover coat material with clear water and ensure it is well drained before applying it to the roadway. Within one minute following the application of the bitumen, spread the cover coat material uniformly over the bituminous material with an aggregate spreader. Apply cover material by hand to areas that are inaccessible to the aggregate spreader. Cover deficient areas with additional cover coat material or blotter material as directed by the Engineer. Use a self-propelled pneumatic -tired roller immediately behind the spreader and continue for a minimum of four complete passes. Ensure the roller speed does not exceed 7 MPH on the initial pass. Sweep loose cover coat material from the roadway after the material has set and within 24 hours of application. Do not dislodge embedded aggregate. Use a vacuum or pickup sweeper to remove excess material accumulated in curb and gutter sections. 196 E. Blotter Material Application. Apply blotter material in the quantity and manner directed by the Engineer if necessary to correct bleeding. Apply the blotter material with a mechanical spreader.
F.Traffic Control. Furnish flagging and pilot cars as specified in Section 704, “Temporary Traffic Control” . Include the cost of flagging and pilot cars in the price bid for other items. On two-lane, two-way traffi c highways place flaggers and signs at each end of the seal operation and at major intersections within the seal operation area. On divided highways, place flaggers and signs at major intersections within the seal operation area. Keep the following signs covered until the seal operation is within 3 miles of the nearest sign: − No Centerline Stripe; − Do Not Pass; − Fresh Oil Loose Rock; and − Speed Limit.
G.Maintenance. Maintain the seal coat during the seal coat operation and continue maintenance for 5 calendar days after completion of the seal coat operation. Maintenance of the seal coat may include additional: − application of bitumen; − application of cover coat material; − rolling; and − sweeping. Do not place loose cover coat material from the shoulder onto the new sealed surface. Perform a final sweeping at the end of the maintenance period. Remove excess material from roadway and shoulders.
H.Acceptance.
1.Bitumen. Obtain samples of this material under the observation of the Engineer. The Engineer will take immediate possession of the samples .
2.Cover Coat Material. The Engineer will collect and test three samples for each lot of material. A lot is defined as 1,200 tons. If the final lot is less than 600 tons, the Engineer will include it in the previous lot. If the final lot is 600 tons or greater, the Engineer will sample it as a separate lot. If the average of the three samples does not meet the gradation specified, the Engineer will either reduce the contract unit price, as specified in Payment” , or reject the material. Do not incorporate additional material if two consecutive lots deviate from the gradation. Restart placement operations after taking corrective actions and passing a gradation test.
3.Blotter Material. The Engineer will collect and test one sample of blotter material for every 5 roadway miles, or fraction thereof. Samples will be collected from material stockpiled on the project or delivered to the project.
420.05 Method of Measurement
The Engineer will measure, completed and in place as specified in Section 109.01, “Measurement of Quantities”.
420.06 Basis of Payment
A.General. Pay Item Pay Unit __Liquid Asphalt Gallon __Emulsified Asphalt Gallon Cover Coat Material Class__ Ton or Square Yard Blotter Material Ton Such payment is full compensation for furnishing all materials, equipment, labor, and incidentals to complete the work as specified.
B.Spotting Tabs. Include the cost of the spotting tabs in the price bid for “Cover Coat Material Class__.”
C.Contract Price Reductions.
1.General. The Engineer will determine contract price adjustments by multiplying the applicable adjustment factor by the contract unit price for the aggregate and the amount of material in the lot represented by the test. If contract price adjustments ar e warranted in more than one category, a contract price reduction will be applied for each area of deficiency.
2.Aggregate Gradation All Sieves Except No. 200 Sieve. Price Adjustment Factor (except No. 200) = 5 × Sum of deviation from range limits on all sieves If the aggregate fails to meet the specified gradation on one or more sieves, the Engineer will reduce the contract price by the sum of the deductions.
3.Aggregate Gradation No. 200 Sieve. Price Adjustment Factor (No. 200) = 10 × Deviation from range limit Section 421 198 SECTION 421 MICRO SURFACING
421.01 Description
This work consists of applying a thin overlay material composed of modified emulsified asphalt, aggregate, water, and additives over a prepared surface.
421.02 Equipment
Equipment Section Aggregate Trucks 152.01 C Bituminous Tank Trucks 152.01 E Micro Surfacing and Slurry Seal Equipment 154.02 D Calibrate each mixing unit in the presence of the Engineer before starting work. Perform calibration according to ISSA -MA 1. Include the individual calibration of each material at various settings in the documentation.
421.03 Materials
Item Section Water 812 Aggregate for Micro Surfacing 816.04 Bituminous Material for Micro Surfacing 818.03 Obtain samples of the bitumen under the observation of the Engineer. The Engineer will take immediate possession of the samples.
A.Aggregates. Screen the stockpile before delivery to the paving machine to prevent having oversize material in the mix.
B.Mineral Fillers. Use mineral filler to improve mixture consistency and to adjust mixture breaking and curing properties. Use material that meets the requirements of ASTM D 242. Use levels o f mineral filler between 0.0 and 3.0 percent. Submit a certificate of compliance for the m ineral filler.
C.Field Control Additives. Use additives to accelerate or retard the break/set of the micro surfacing. Submit a certificate of compliance stating that the liquid field control additive is compatible with the mix design.
421.04 Construction Requirements
A.Mix Design. Submit a mix design prepared by a qualified testing laboratory. Submit the certified test reports with the mix design. Use the same materials in th e mix design as on the project.
Source: North Dakota Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 229–232 of 550.