Section 408 — Ultrathin Bonded Wearing Course

Description

408.01This work consists of placing an ultrathin bonded wearing course (UTBWC).

Material

408.02Conform to the following Subsections: Antistrip additive 702.05 Asphalt binder 702.01 Polymer- modified emulsified asphalt membrane 702.02(e) Ultrathin bonded wearing aggregate 703.18

Construction Requirements

408.03Composition of Mix (Job -Mix Formula). Provide mixes of aggregate, asphalt binder, and antistrip additive that meet the aggregate gradation shown in Table 703 -10 and design parameters shown in Table 408-1 at the proposed optimum binder content (OBC). Include additional design trial points that bracket the OBC with at least one point at 0.4 percent above and below the OBC. Test draindown and determine film thickness on these trial points. Do not propose an OBC less the 5.0 percent by total weig ht of mix. Table 408-1 Ultrathin Bonded Wearing Course Requirements Design Parameters Test Method Requirement Film thickness, µm Asphalt Institute MS -2 Table 8.1(1) 12.0 minimum Drain down, % AASH TO T 305(2) 0.10 maximum Moisture susceptibility AASHTO T 283(3) 0.70 minimum

(1)Film thickness is calculated based on effective asphalt content and determined as follows: 𝑃𝑃𝑇𝑇=�𝑃𝑃𝑏𝑏𝑀𝑀 𝑈𝑈𝑆𝑆×𝐺𝐺𝑏𝑏×1000�×106 where: FT = Film Thickness in µm Pbe = Effective asphalt content by total weight of mix according to Asphalt Institute, MS-2 Asphalt Mix Design Methods , 7th edition S A = E s t i m a t e d s u r f a c e a r e a o f t h e a g g r e g a t e b l e n d i n m2/kg according to MS -2 Asphalt Mix Design Methods, 7th edition, Table 8.1 Gb = Specific gravity of asphalt binder

(2)Combine aggregate and asphalt binder at supplier’s recommended mixing temperature. Return to the basket any coated aggregate that falls through the wire basket during loading and do not consid er it as draindown.

(3)Make 4 -inch diameter specimens with a compacted height of 2.5±0.05 inches. Compact specimens using methods according to AASHTO T 283. Use mixture and compaction temperatures recommended by the binder supplier.

(a)Recycled asphalt pavement use. Do not use RAP in the JMF.

(b)Submittals. Submit JMF at least 21 days before the control strip. Include the location of commercial mixing plants to be used and a separate JMF for each plant. Include a signed statement prepared by the tes ting laboratory that certifies the proposed JMF meets the requirements of the contract and can be placed in the field during production to meet contract requirements. For each JMF, submit the following:

(1)Aggregate .

(a)Designate target values within the gradation band specified for the aggregate grading shown in Table 703-10 ;

(b)Percent passing each sieve size for the aggregate blend;

(c)Source and percentage of each aggregate stockpile to be used;

(d)Average gradation of each aggregate stockpi le from process control tests; and

(e)Results of aggregate quality tests. Include Los Angeles abrasion, sodium sulfate soundness, fractured faces, flat and elongated particles, sand equivalent, and specific gravity results from tests performed within 1 year o f aggregate use.

(2)Asphalt binder.

(a)Target asphalt binder content by total weight of mixture;

(b)Recent test results from the supplier for the asphalt binder including a temperature -viscosity curve; and

(c)Laboratory mixing temperature range and laboratory compaction temperature range for the performance grade asphalt to be used in the mix.

(3)Antistrip additives. If part of the JMF:

(a)Name of product;

(b)Manufacturer; and

(c)Dosage rate.

(c)Changes and resubmissions. If a JMF is rejected or a material source is changed, submit a new JMF for approval. Allow 14 days for approval. Do not start mix production until the JMF is approved.

408.04Mixing Plant. Conform to Subsection 401.04.

408.05Equipment.

(a)Pavers. Use pavers that are designed and built for applying the UTBWC. Provide a paver with the following:

(1)Self-propelled integrated distributor -paver with a receiving hopper, feed conveyor, insulated emulsion storage tank, spray bar, variable -width heated vibratory tamper bar screed, electronic device to determine rate of emulsion application, and variable width adjustment.

(2)Capable of applying polymer -modified emulsified asphalt membrane using a metered mechanical pressure spray bar at a temperature from 120 to 180 ºF. Capable of continuously monitoring the rate of spray and providing a uniform rate across the width of the paver.

(3)Capable of applying the UTBWC mix within 5 seconds of applying the polymer -modified emulsion.

(4)Capable of spreading and finishing the UTBWC mix to the required cross -section, grade, and at least 12 inches more than the required width and producing a uniformly finished surface without segregation, tearing, shoving, gouging, and other blemishes. (5) Equipped with automatic screed controls with sensors that can sense grade from an outside reference line, sensing the transverse slope of the screed, and providing the automatic signals that operate the screed to maintain grade and transverse slope.

(6)Heated, vibratory, full- width feed auger screed extension.

(7)Operable at forward speeds consistent with satisfactory mix lay down.

(b)MTV. Conform to Subsection 401.05(b).

408.06Surface Preparation. Thoroughly clean the existing surface of all loose material, dirt, and other deleterious substances by approved methods. Remove pavement markings. If needed, use pressurized water and vacuum systems to ensure a clean surface. Protect stone masonry, manhole covers, drains, grates, catch basins, other utility structures, curb and gutter, sidewalks, and walls with plastic or building felt. Clearly mark protected and covered features that will be re -exposed. Do not start placement of the UTBWC until patching according to Section 418 and crack filling according to Section 414 has been completed.

408.07Weather Limitations. Place the UTBWC on a dry, unfrozen surface when the ambient air temperature in the shade is above 50 ºF and rising and the pavement surface temperature is above 50 ºF. Do not place UTBWC when te mperatures below 32 °F are anticipated within 36 hours after application.

408.08Preparing and Mixing Material. Conform to Subsections 401.08, 401.09, and 401.10.

408.09Hauling. Conform to Subsection 401.11.

408.10Production Start- Up Procedures.

(a)Preparatory phase meeting. Conduct a pre -paving preparatory phase meeting according to Subsection 153.06(a) at least 3 days before the start of paving operations . Be prepared to discuss and provide the following:

(1)Proposed schedule of paving operations; 390 (2)List of all equipment (compaction, laydown, haul), and personnel used in the production and construction of the work; (3)Proposed traffic control plan for paving operations including provisions for pavement drop- offs and moving operations;(4)Procedures for constructing the control strip including placing, rolling, finishing, and roughness procedures;(5)AASHTO T 308 asphalt binder and aggregate correction factors on Form FHWA 1640, Worksheet for Ignition Furnace Binder Correction Factor for each JMF; (6)Proposed polymer- modified emulsified asphalt membrane application rate; and (7)Proposed placement sequence and joint locations. (b)Control strip. Provide at least 7 days’ notice before starting production of an asphalt concrete mix.Produce and place approximately 200 tons of mix to construct a control strip, one -lane wide, and at the des ignated lift thickness on the first day of production. Construct the control strip on the project at an approved location. Construct the control strip using mix production, lay- down, and compaction procedures intended for the entire mix. Construct a control strip for each equipment combination and each plant from which production is intended. Stop production after construction of the control strip until the asphalt concrete mix and the control strip are evaluated and accepted. Review the conditions of the existing pavement and propose a polymer -modified emulsified asphalt membrane application rate for approval 7 days before completing the control strip. It is estimated that the target application rate will be from 0.15 to 0.20 gallons per square yard. Evaluate and determine the application rate during the control strip. In coordination with the CO, adjust the application rate based on existing conditions and recommendations from the supplier. Take and test at least three control strip UTBWC mix samples and evaluate according to Subsection 408.15 and Table 408-2. Repeat the control strip process until an acceptable control strip is produced. Conform to Subsection 106.01 for the disposition of material in rejected control strips. Accepted control strips may remain in place and will be accepted and measured as a part of the completed pavement. After a control strip is accepted, full production may start. Use start -up procedures if resuming production after a termination of production due to unsatisfactory quality.

408.11Placing and Finishing. Do not use mixes produced from different plants unless the mixes are produced according to the same JMF, use material from the same sources, and are approved. Apply the polymer -modified emulsified asphalt membrane at the rate approved in the control strip according to Subsection 407.08 and this Section. Apply the target application rate within a tolerance of ±0.02 gallons per square yard. Do not allow wheels or other parts of the paving machine to come in contact with the polymer -modified emulsion membrane before the UTBWC mix is applie d. Use a metered mechanical pressure spray bar at a temperature of 140 to 180 °F. Continuously monitor the rate of spray and provide a uniform application across the entire pavement width. Confirm the application rate of the polymer- modified emulsified asp halt membrane at least every 4 hours of production time by dividing the volume of polymer -modified emulsified asphalt membrane used by the area of paving for that timeframe. Place the UTBWC mix at the temperature recommended in the JMF. Measure temperature of the mix in the hauling vehicle immediately before dumping into the MTV or measure it in the windrow immediately before pickup. Place the UTBWC mix with a paver conforming to Subsection 408.05. Control horizontal alignme nt using a reference line. Automatically control the grade and slope from reference lines, a ski and slope control device, or dual skis. Use skis having a minimum length of 20 feet. Place the UTBWC to the thickness shown in the plans. Measure thickness wit h a depth probe transversely across the mat in wheel paths and near centerline at least once every 500 feet. Submit certified weight tickets for the materials supplied. Place the UTBWC mix as continuously as possible. Do not overlap or hot lap the asphalt. Pave through lanes after paving adjacent shoulders, tapers, driveways, road connections, turn pockets, and transitions. For UTBWC mix placed on the areas adjacent to through lanes, cut the hot asphalt as necessary to form neat, straight, vertical joints a long the lane lines. If polymer- modified emulsion membrane is spilled into the hopper of the paver, remove and dispose of the contaminated material according to Subsections 203.05 and 203.07. In areas where mechanical spreading and finishing are impractical, place and finish the mix with alternate equipment to produce a uniform surface closely matching the surface obtained when using a mechanical paver. Use an MTV on mainline construction if placing UTBWC mix. Suspend paving if the MTV malfunctions during paving operations. Do not resume mix placement until the MTV is operational. 408.12 Rolling. Provide at least two steel double drum asphalt rollers with a weight of at least 11 tons. Provide well maintained rollers with functioning water system and scrapers to prevent adhesion of the fresh mix onto the roller drums. A release agent (added to the water system) may be required to prevent adhesion of the fresh mix to the roller drums. Do not use diesel fuel as a release agent. Operate rollers according to the manufacturer’ s recommendations. Immediately after placing the UTBWC mix, make at least two passes with a double drum asphalt roller operated in the static mode. Complete compaction before the UTBWC mix temperature falls below 185 ºF. Do not allow the roller to remain stationary on the freshly placed UTBWC mix. Do not cause cracking, shoving, or undue displacement.

408.13Joints, Trimming Edges, and Cleanup. Use butt joints for longitudinal and transverse joints. At connections to existing pavements and previously placed lifts, make the transverse joints vertical to the depth of the new pavement. Form transverse joints by cutting back the previous run to expose the full-depth course. Dispose of material trimmed from the edges and any other discarded asphalt mix according to Subsection 203.07. Protect the completed UTBWC from traffic until it has sufficiently hardened to resist abrasion, shoving, pickup, and raveling.

408.14Pavement Straightedge Measurement. Use a 10 -foot metal straightedge to measure at right angles and parallel to the centerline. Defective areas are surface deviations more than 0.25 inch, measured between any two contacts of the straightedge. Correct defective areas. Obtain approval for the proposed method of correction. 408.15 Acceptance. See Table 408-2 for sampling and testing requirements and the acceptance quality characteristic category. Antistrip additive s will be evaluated under Subsections 106.02 and 106.03. Asphalt binder and polymer- modified emulsified asphalt membrane s will be evaluated under Subsections 106.03 and 106.04. Construction of the UTBWC will be evaluated under Subsections 106.02 and 106.04. Aggregate gradation and aggregate properties will be evaluated under Subsect ions 106.03 and 106.04. Asphalt content will be evaluated under Subsection 106.04. The tolerance from the target for asphalt binder is ±0.5 percent. Asphalt pavement crack filling will be ev aluated under Section 418. Asphalt pavement patching will be evaluated under Section 414.

Measurement

408.16Measure the Section 408 pay items listed in the bid schedule according to Subsection 109.02 .

Payment

408.17The accepted quantities will be paid at the contract price per unit of measurement for the Section 408 pay items listed in the bid schedule. Payment will be full compensation for the work prescribed in this Section. See Subsection 109.05 . Table 408-2 Sampling, Testing, and Acceptance Requirements

Material

or Product Type of

Acceptance

(Subsection) Characteristic Category Test Method s

Specifications Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

Source

Aggregate

quality Measured & tested for conformance (106.04 & 105) Quality − Subsection

703.181 per type & source of material Source of materials Yes Before production −

Asphalt

binder Measured & tested for conformance (106.04 & 105) Quality − AASHTO M 320 1 per type & source of material Asphalt supplier or mixing plant Yes Before production −

Polymer -

modified emulsified asphalt membrane Measured & tested for conformance (106.04 & 105) Quality − Subsection 702.02(e) 1 per type & source of material Membrane supplier Yes Before production −

Mix Design

UTBWC

(mix design) Measured & tested for conformance (106.04 ) Gradation(2) − AASHTO T 11 & T 27 1 per each submitted mix design Stockpiles If requested 21 days before paving − Film thickness − See Table 408-1 " − " " − Draindown − AASHTO T 305(3) " − " " −

Moisture

susceptibility − AASHTO T 283(3) " − " " − Table 408- 2 (continued) Sampling, Testing, and Acceptance Requirements

Material

or Product Type of

Acceptance

(Subsection) Characteristic Category Test Method s

Specifications Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

Production Start -up (control strip)

UTBWC Measured &

tested for conformance (106.04 ) Gradation(2) − AASHTO T 30 3 minimum Truck or paver hopper Yes 24 hours −

Asphalt

content(1) − AASHTO T 308 " " " " −

Mix

temperature − − Each load & as directed Hauling vehicle before dumping or windrow before pickup − As directed − Table 408- 2 (continued) Sampling, Testing, and Acceptance Requirements

Material or

Product Type of

Acceptance

(Subsection) Characteristic Category Test Method s

Specifications Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

Production

UTBWC Measured &

tested for conformance (106.04 ) Gradation(2) − AASHTO T 30 1 per 300 tons Truck or paver hopper Yes 24 hours −

Asphalt

content(1) − AASHTO T 308 " " " " −

Mix

temperature − − Each load & as directed Hauling vehicle before dumping or windrow before pickup − Upon completion of measurement −

Polymer -

modified emulsion membrane " Quality − Subsection 702.02(e) 1 per 700 tons of mix Tanker or point of delivery Yes − −

Asphalt

binder " Quality − Subsection

702.011 per 700 tons of mix In line between tank & mixing plant Yes, tested by

Government Tested by

Government −

(1)Use AASHTO T 308, Method A. Calculate the asphalt binder content by weighing the sample before and after the burn using a calibrated external balance. Modify AASHTO T 308, parts 8.2 and 10.2 to allow the use of AASHTO T 255, Total Evaporable Moisture Content of Aggregate by Drying.

(2)Use only sieves indicated for the specified gradation.

(3)As modified by Table 408-1 .