ChipSealSpecification.pdf

Section 409. — ASPHALT SURFACE TREATMENT

Description

409.01 This work consists of constructing a single or multiple asphalt surface treatment with aggregate or precoated aggregate. This work also includes constructing an asphalt fog seal without aggregate.

Surface treatment aggregate designation is designated as shown in Tables 409-1, 409-2, and 409-3.

Asphalt is designated as shown in AASHTO M 20 or M 226 for asphalt binder and AASHTO M 140 or M 208 for emulsified asphalt.

Material

409.02 Conform to the following Subsections:

Aggregate 703.10 Asphalt binder 702.01 Blotter 703.13 Emulsified asphalt 702.03

Construction Requirements

409.03 Composition. Submit the following information and samples for approval at least 21 days before placement:

(a) Aggregate samples. 80 pounds from each stockpile produced and the gradation range represented by each.

(b) Aggregate gradation target values. The proposed percentage of each stockpile to be used and the proposed target value for each sieve size.

(c) Asphalt samples. Two 1-quart samples of asphalt binder or emulsified asphalt from the same source and of the type to be used for the surface treatment.

(d) Asphalt temperature. Apply asphalt at temperatures according to Table 702-1.

(e) Spread rates. The proposed spread rate for the aggregate and asphalt material.

409.04 Equipment. Furnish equipment as follows:

(a) Asphalt distributor.

(1) Capable of heating asphalt evenly;

(2) Adjustable full circulation spray bar to 15-foot width;

(3) Positive controls including tachometer, pressure gauge, volume measuring device, or calibrated tank to uniformly deposit asphalt over the full width within 0.02 gallons per square yard of the required rate; and

(4) Thermometer for measuring the asphalt temperature in the tank.

(b) Rotary power broom.

(1) Self-propelled; and

(2) Capable of controlling the vertical broom pressure.

(c) Pneumatic-tire rollers. Furnish a minimum of two pneumatic-tire rollers both with the following capabilities:

(1) Self-propelled;

(2) Minimum compacting width – 5 feet; and

(3) Gross weight adjustable within the range of 200 to 360 pounds per inch of compaction width.

(d) Aggregate spreader.

(1) Self-propelled;

(2) Minimum of 4 pneumatic tires on 2 axles; and

(3) Positive controls to uniformly deposit the aggregate over the full width of asphalt within 10 percent by mass of the required rates.

(e) Other equipment. Other equipment of proven performance may be used in addition to or in lieu of the specified equipment when approved by the CO. Provide two-way communication between the asphalt distributor and the aggregate spreader if the roadway alignment does not permit visual contact.

409.05 Surface Preparation. On existing asphalt surfaces, ensure that the surface is dry. Immediately before placing the layer, remove loose dirt and other objectionable material from the surface by approved methods. Fog seal patches using a slow setting emulsion diluted with an equal part water. Apply the diluted emulsion at a rate of 0.17 gallons per square yard.

On existing aggregate surfaces, prime the surface according to Section 411. Allow the primed surface to cure at least 5 days for cutback asphalt or 24 hours for asphalt emulsions. Ensure that the primed surface is dry for surface treatments using asphalt binder or slightly damp for surface treatments using emulsified asphalt.

409.06 Weather Limitations. Apply surface treatments with aggregate only when ambient air and surface temperatures are above 60 °F and rising, when the weather is not foggy or rainy, and when rain is not anticipated for at least 24 hours after application.

Apply fog seals only when the ambient air and surface temperatures are above 50 °F and rising, when the weather is not foggy or rainy, and when rain is not anticipated for at least 24 hours after application.

Complete all surface treatment applications 2 hours before sunset.

409.07 Production Start-up Procedures for Surface Treatments. At least 10 days before the start of constructing all surface treatments containing aggregate, arrange for a pre-surface treatment conference. Coordinate attendance with the CO and any applicable subcontractors. Be prepared to discuss or submit the following:

(a) Proposed schedule of operations.

(b) List of all equipment and personnel to be used in the production and construction of the work.

(c) Proposed traffic control plan.

(d) Discuss Section 153, minimum frequency schedule for process control sampling and testing (to be performed by the Contractor).

(e) Discuss Subsections 409.07, 409.08, and 409.09.

(f) Discuss spill prevention and safety contingency plan.

Provide 7 days advance notice before constructing all asphalt surface treatments containing aggregate. Also use these start-up procedures when resuming production after termination due to nonconforming work.

On the first day of placement of each surface treatment layer, or whenever there is a change in the surface texture or aggregate gradation, construct a 500-foot control strip that is one-lane wide.

Construct the control strip using material, lay-down, and compaction procedures intended for the remainder of the surface treatment. Cease production after construction of the control strip until the material and the control strip are evaluated and accepted.

Acceptable control strips may remain in place and will be accepted as a part of the completed surface treatment.

Repeat the control strip process until an acceptable control strip is produced.

409.08 Asphalt Application. Calibrate the asphalt distributor spray bar height, nozzle angle, and pump pressure and check longitudinal and transverse spread rates weekly according to ASTM D 2995. If different asphalt distributors are used, calibrate each before use on the project. Ensure that the length of the spread is no more than can be covered with aggregate immediately after application.

Protect the surfaces of nearby objects to prevent spattering or marring. Spread building paper on the surface for a sufficient distance from the beginning and end of each application so the flow through the distributor nozzles may be started and stopped on the paper.

The CO will approve the exact application rate, temperature, and area to be treated before application and may make adjustments for variations in field conditions. Apply the asphalt uniformly with an asphalt distributor. Move distributor forward at the proper application speed at the time the spray bar is opened. Use care not to apply excess asphalt at the junction of spreads.

Correct skipped areas or deficiencies. Remove and dispose of paper or other material used.

409.09 Aggregate Application. When using asphalt binder, the aggregate surface should be dry. When using emulsified asphalt, the aggregate surface should be moist.

The CO will approve the exact application rate and area to be treated before application. Apply the aggregate uniformly with an aggregate spreader immediately after the asphalt is applied. Operate aggregate spreader so the asphalt is covered with the aggregate before wheels pass over it. During part-width construction, leave uncovered a strip of sprayed asphalt approximately 6 inches wide to permit an overlap of asphalt material.

Immediately correct excesses and deficiencies by brooming or by the addition or removal of aggregate until a uniform texture is achieved. Use hand methods in areas not accessible to power equipment.

When precoated aggregates are used, they may be mixed on the job or at a central mixing plant. Uniformly coat the aggregate with 1.0 to 2.0 percent residual asphalt, by weight of aggregate. Maintain the flow qualities of the precoated aggregate, so it is satisfactorily spread with an aggregate spreader.

Operate rollers at a maximum speed of 5 miles per hour. Do not permit the aggregate to be displaced by pickup or sticking of material to the tire surface. Sufficiently roll the surface to uniformly and thoroughly bond the aggregate over the full width. Complete rolling within 1 hour after the asphalt is applied to the surface.

409.10 Fog Seal. A fog seal consists of applying slow-setting emulsified asphalt diluted with water onto an existing asphalt surface. Apply the diluted emulsified asphalt according to Subsection 409.08 at a rate of 0.10 to 0.15 gallons per square yard depending on the condition of the existing surface. Allow the fog seal to penetrate undisturbed for at least 2 hours or until the emulsified asphalt breaks and is substantially absorbed into the existing surface. Then lightly cover remaining spots of excess asphalt with blotter according to Section 411 before opening the surface to traffic.

409.11 Single-Course Surface Treatment. A single-course surface treatment consists of applying asphalt material onto an existing surface immediately followed by a single, uniform application of aggregate. Apply the asphalt and aggregate according to Subsections 409.08 and 409.09 at the approximate rates shown in Table 409-1. Determine the exact rates based on approved control strips.

Use a pilot car according to Section 635 to limit traffic speeds. During the initial 45 minutes after completion of rolling, limit the traffic speeds to 10 miles per hour. Limit traffic speeds to 20 miles per hour for 24 hours.

Lightly broom the aggregate surface on the morning after construction. Maintain the surface for 4 days by distributing blotter according to Section 411 to absorb any free asphalt and by repairing areas deficient in aggregate. Sweep excess material from the surface using a rotary power broom when the temperature is less than 75 °F. Do not displace embedded material.

Table 409-1 Approximate Quantities of Material for

Single-Course Surface Treatment

D es ig na tio n

Nominal Maximum

Size of Aggregate

Aggregate Gradation (1)

Estimated Quantity of Aggregate (2) pounds/yd2

Estimated Quantity of Emulsified Asphalt (3) gallons/yd2

Estimated Quantity of Asphalt Binder (3) gallons/yd2

1A 3/4 inch B 40 – 49 0.33 – 0.46 0.22 – 0.31

1B 1/2 inch C 26 – 29 0.26 – 0.37 0.16 – 0.26

1C 3/8 inch D 20 – 26 0.16 – 0.29 0.11 – 0.20

1D No. 4 E 15 – 20 0.13 – 0.18 0.09 – 0.15

1E Sand F 9 – 15 0.09 – 0.15 0.07 – 0.13

(1) See Table 703-7 for aggregate gradations.

(2) Aggregate masses are for aggregates having a bulk specific gravity of 2.65, as determined by AASHTO T 84 and T 85. Make proportionate corrections when the aggregate furnished has a bulk specific gravity above 2.75 or below 2.55.

(3) Adjust the asphalt content for the condition of the road.

Table 409-2 Approximate Quantities of Material for

Double Course Surface Treatments

Designation (Thickness)

Nominal Maximum

Size of Aggregate

Aggregate Gradation(1)

Estimated Quantity of Aggregate(2) pounds/yd2

Estimated Quantity of Emulsified Asphalt (3) gallons/yd2

Estimated Quantity of

Asphalt Binder (3) gallons/yd2

2A (1/2 inch) 1st Application 3/8 inch D 26 – 35 0.16 – 0.26 0.09 – 0.18 2nd Application No. 4 E 9 – 15 0.26 – 0.33 0.15 – 0.24

2B (5/8 inch) 1st Application 1/2 inch C 29 – 40 0.26 – 0.33 0.15 – 0.24 2nd Application No. 4 E 14 – 20 0.33 – 0.42 0.20 – 0.27

2C (3/4 inch) 1st Application 3/4 inch B 40 – 49 0.29 – 0.42 0.18 – 0.27 2nd Application 3/8 inch D 20 – 26 0.42 – 0.49 0.27 – 0.35

(1) See Table 703-7 for aggregate gradations.

(2) Aggregate masses are for aggregates having a bulk specific gravity of 2.65, as determined by AASHTO T 84 and T 85. Make proportionate corrections when the aggregate furnished has a bulk specific gravity above 2.75 or below 2.55.

(3) Adjust the asphalt content of the first application for the condition of the road.

409.12 Double- and Triple-Course Surface Treatments. Double- and triple-course surface treatments consist of applying multiple layers of asphalt and aggregate. Apply each asphalt and aggregate layer according to Subsections

409.08 and 409.09 and at the approximate rates shown in Table 409-2 or 409-3. Determine the exact rates based on approved control strips.

Maintain the surface and limit traffic according to Subsection 409.11.

No wait is required between surface treatment applications when using an asphalt binder. Wait at least 24 hours between applications when using emulsified asphalt.

Table 409-3 Approximate Quantities of Material for

Triple Course Surface Treatments Designation (Thickness)

Nominal Maximum

Size of Aggregate

Aggregate Gradation(1)

Estimated Quantity of Aggregate(2) pounds/yd2

Estimated Quantity of Emulsified Asphalt (3) gallons/yd2

Estimated Quantity of Asphalt Binder(3) gallons/yd2

3A (1/2 inch) 1st Application 3/8 inch D 26 – 35 0.16 – 0.26 0.09 – 0.18 2nd Application No. 4 E 9 – 15 0.20 – 0.29 0.13 – 0.22 3rd Application Sand F 9 – 15 0.16 – 0.26 0.09 – 0.18

3B (5/8 inch) 1st Application 1/2 inch C 29 – 40 0.16 – 0.26 0.09 – 0.18 2nd Application 3/8 inch D 15 – 20 0.26 – 0.33 0.15 – 0.24 3rd Application No. 4 E 9 – 15 0.16 – 0.26 0.09 – 0.18

3C (3/4 inch) 1st Application 3/4 inch B 35 – 46 0.20 – 0.29 0.13 – 0.22 2nd Application 3/8 inch D 20 – 26 0.26 – 0.33 0.15 – 0.24 3rd Application No. 4 E 9 – 15 0.20 – 0.29 0.13 – 0.22

(1) See Table 703-7 for aggregate gradations.

(2) Aggregate masses are for aggregates having a bulk specific gravity of 2.65 as determined by AASHTO T 84 and T 85. Make proportionate corrections when the aggregate furnished has a bulk specific gravity above 2.75 or below 2.55.

(3) Adjust the asphalt content of the first application for the condition of the road.

409.13 Acceptance. See Table 409-4 for sampling and testing requirements.

Asphalt binder, and emulsified asphalt, will be evaluated under Subsections 106.04 and 702.09.

Aggregate gradation for asphalt surface treatment will be evaluated under Subsection 106.05.

The upper and lower specification limits are equal to the calculated mean of all test results plus or minus the allowable deviations shown in Table 703-7, except as follows:

(a) If the calculated mean value for any tested sieve exceeds the maximum gradation value shown in Table 703-7, the upper specification is equal to the maximum gradation value plus the allowable deviation, and the lower specification is equal to the maximum gradation value minus the allowable deviation.

(b) If the calculated mean value for any tested sieve is less than the minimum gradation value shown in Table 703- 7, the upper specification is equal to the minimum gradation value plus the allowable deviation, and the lower specification is equal to the minimum gradation value minus the allowable deviation.

Construction of asphalt surface treatment course will be evaluated under Subsections 106.02 and 106.04.

Prime coat and blotter will be evaluated under Section 411.

Measurement

409.14 Measure the Section 409 items listed in the bid schedule according to Subsection 109.02 and the following as applicable.

Measure surface treatment aggregate by the cubic yard in the hauling vehicle.

Measure prime coat and blotter under Section 411.

Payment

409.15 The accepted quantities will be paid at the contract price per unit of measurement for the Section 409 pay items listed in the bid schedule except the aggregate surface treatment contract unit bid price will be adjusted according to Subsection 106.05. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05.

Section 409. — ASPHALT SURFACE TREATMENT