Attachment_01_Hot_Mix_Asphalt_Model.pdf

Performance Work Statement

Purpose and Scope The Airfields and Pavements Branch (APB) has been tasked by the U.S. Air Force to evaluate non-traditional asphalt pavement test sections. As part of this research full-scale accelerated pavement testing on representative pavement structures will be conducted. These pavement structures require a surface layer of hot mix asphalt (HMA).

Work Listed below are specific items that will be provided by the APB and items that are to be provided by the contractor.

Work Items Provided by the APB:

1. All subgrade, base preparation and paving surface preparation.

2. Quality control operations:

a. Random sampling and testing will be conducted by the Contracting Engineer at ERDC.

b. Random samples may be taken at the plant, for specimen compaction, and tested for laboratory air voids and TSR. A portion of the same sample may be tested for theoretical maximum density (TMD), aggregate gradation, and asphalt content. Randomly selected cores shall be taken from the finished pavement mat and the longitudinal joint, and tested for density. Random sampling shall be in accordance with procedures contained in ASTM D 3665.

The test results must demonstrate an in-place density of 92-96% of TMD. If test results fail to meet the required density, the test section shall be removed and replaced at no cost to the Government.

c. Determination of final compacted asphalt layer thickness will be performed using rod & level and total station elevation measurement techniques.

Work Items and Materials Provided by the Contractor:

The Contractor shall provide a hot-mix asphalt surface course, complete and in-place, meeting the following requirements:

AGGREGATES

Coarse aggregate (defined as material retained on the No. 4 sieve (4.75 mm) shall consist of sound, tough durable particles free from material films that would prevent thorough coating and bonding with the asphalt material and free from organic matter and other deleterious substances.

Provide coarse aggregate meeting the following requirements:

a. The percentage of loss shall not be greater than 40 percent after 500 revolutions when tested in accordance with ASTM C131.

b. The magnesium sulfate soundness loss shall not exceed 18 percent after 5 five cycles when tested in accordance with ASTM C88.

c. Coarse aggregate shall consist of at least 75 percent by weight of coarse aggregate containing at least two mechanically fractured faces when tested in accordance with

ASTM D5821.

d. Coarse aggregate shall be generally cubical in shape and contain not greater than 20 percent flat and elongate particles at a 3:1 ratio when tested in accordance with ASTM D4791.

e. Clay lumps and friable particles shall not exceed 0.3 percent by weight when tested in accordance with ASTM C142.

Fine aggregate (defined as material passing the No. 4 sieve (4.75 mm) and retained on the No.

200 sieve (0.075 mm)) shall consist of clean, sound, tough durable particles free from clay, silt, or any objectionable material. Provide fine aggregate meeting the following requirements:

a. Quantity of natural sand added to the aggregate blend shall not exceed 15 percent by weight of total aggregate.

b. Individual fine aggregate sources shall have a sand equivalent value greater than 45 when tested in accordance with ASTM D2419.

c. The fine aggregate portion of the blended aggregate shall have a uncompacted void content (fine aggregate angularity) greater than 45.0 percent when tested in accordance with ASTM T304 Method A.

d. Clay lumps and friable particles shall not exceed 0.3 percent by weight when tested in accordance with ASTM C142.

Mineral filler (defined as material passing the No. 200 sieve (0.075 mm)) shall consist of a non-plastic material meeting the requirements of ASTM D242.

Provide a combined aggregate gradation that conforms to the design master range specified in Table 1, when tested in accordance with ASTM C136 and ASTM C117. The gradation shall be uniform from coarse to fine and not vary from the low limit on one sieve to the high limit on the adjacent sieve or vice versa.

Reclaimed asphalt pavement (RAP) shall not be allowed for the project.

Table 1. Combined Aggregate Gradation Master Range

Sieve Size Percent Passing By Mass

1.0 in. (12.5 mm) 100 3/8 in. (9.5 mm) 90-100 No. 4 (4.75 mm) 58-78 No. 8 (2.36 mm) 40-60 No. 16 (1.18 mm) 28-48 No. 30 (0.600 mm) 18-38 No. 50 (0.300 mm) 11-27 No. 100 (0.150 mm) 6-18 No. 200 (0.075 mm) 3-6

ASPHALT BINDER

Asphalt binder shall conform to AASHTO M320 Performance Grade (PG) 67-22. The Government Engineer may sample and test the binder at the mix production plant at any time before or during mix production.

MIX DESIGN

The mixture proportions shall be designed using a Superpave gyratory compactor set at 75 gyrations. The mixture properties shall meet the criteria shown in Table 2. The proposed mix design shall be submitted to the Government Engineer at least 14 days prior to construction of the test section. No mixture shall be placed prior to Government approval.

Table 2. Superpave Gyratory Compaction Criteria

Property Value Air voids (%) 4

VMA (%) 15

Dust/Binder Ratio 0.8-1.2 TSR (minimum %) 75

CONSTRUCTION

The Contractor shall provide the necessary equipment to spread, finish and compact the hot mix asphalt test section. Production and placement equipment shall be in good working order and meet the applicable requirements of Section 401 of the latest edition of the Mississippi Department of Transportation Standard Specifications for Road and Bridge Construction.

Physical dimensions for the HMA test section are 25-ft.-wide by 300-ft.-long and is located under shelter in the ERDC Hangar 2 Pavement Test Facility. The HMA will be placed on top of a surface (prepared by ERDC) consisting of a 12-in.-thick base course over a 36-in.-thick prepared subgrade. The HMA shall be placed in two 12.5-ft.-wide paving lanes. Final compacted minimum HMA thickness shall vary from 1 in. to 3 in. as shown in Figure 1.

At least 7 days prior to HMA placement, the Contractor shall submit, in writing, a paving plan to provide proposed placement sequencing.

FIGURE 1. Plan view of test section layout.

It is the intent of these specifications that the final compacted HMA thickness be no less than that shown in Figure 1. Surface elevations of the final compacted HMA will be measured by ERDC using rod and level and total station measurement techniques along the centerline of each completed lane at approximately 12 in. intervals. If it is found that the HMA thickness is less than that shown in Figure 1, the test item shall be removed and replaced at no cost to the Government.

If it is found that HMA thickness exceeds those shown in Figure 1 by 0.25 in., the section shall be diamond ground.

It is highly recommended that the Contractor exceed the thickness requirements presented in Figure 1.

Mat density shall be 92 to 96 percent of theoretical maximum density and will be measured based on the average of three cores randomly obtained by ERDC from each HMA thickness section (e.g. 3 cores will obtained from 1-in.-thick HMA, 3 cores will be obtained from 2-in.-thick HMA, 3 cores will be obtained from 3-in.-thick HMA). If test results fail to meet the required density, the test section shall be removed and replaced at no cost to the Government.

Longitudinal joint density will not be required or tested.

A tack coat shall be used to bond the asphalt layers, where applicable. Tack coat shall be a cationic slow set emulsion (CSS-1) applied at a rate of 0.03 gal/sy. Other products and/or application rates must be approved by the Government Engineer.

DIAMOND GRINDING

Areas exceeding the design thickness by 0.25 in. shall be diamond ground. The grinding equipment shall be a power driven, self-propelled machine that is specifically designed to smooth and texture pavement surfaces with diamond blades. The effective wheel base of the machine shall not be less than 12.0 ft. It shall have a set of pivoting tandem bogey wheels at the front of the machine and the rear wheels shall be arranged to travel in the track of the fresh cut pavement. The center of the grinding head shall be no further than 3.0 ft. forward from the center of the back wheels. The equipment shall be of a size that will cut or plane at least 2.0-ft.-wide. The equipment shall be capable of grinding the surface without causing spalls.

Where grinding is required, it will be performed across the entire 12.5 ft. lane width.

The grinding operation shall proceed in a manner that produces a uniform finish surface. The Contractor shall establish positive means for removal of grinding residue. Grinding water and residue shall not be permitted to flow across adjacent test areas. The Contractor shall have sufficient collector and/or discharge hose to ensure a majority of grinding residue is discharged outside the Hangar 2 test facility.

The grinding process shall produce a pavement surface that is smooth and uniform in appearance with a longitudinal line type texture. The line type texture shall contain parallel longitudinal corrugations that present a narrow ridge corduroy type appearance. The peaks of the ridges shall not be more than 1/16 in. higher than the bottoms of the grooves.

The use of an asphalt milling machine as an alternative to diamond grinding equipment shall not be permitted.

Security Requirements

1. All contractor employees, to include subcontractor employees, requiring access to Army installations, facilities and controlled access areas shall complete AT Level I awareness training within 30 calendar days after contract start date or effective date of incorporation of this requirement into the contract, whichever is applicable. The contractor shall submit certificates of completion for each affected contractor employee and subcontractor employee, to the COR or to the contracting officer, if a COR is not assigned, within 5 calendar days after completion of training by all employees and subcontractor personnel. AT Level I awareness training is available at the following website: https://atlevel1.dtic.mil/at

2. All contractor and all associated sub‐contractors employees shall comply with applicable installation, facility and area commander installation/facility access and local security policies and procedures (provided by government representative). The contractor shall also provide all information required for background checks to meet installation access requirements to be accomplished by installation Provost Marshal Office, Director of Emergency Services or Security Office. Contractor workforce must comply with all personal identity verification requirements as directed by DOD, HQDA and/or local policy. In addition to the changes otherwise authorized by the changes clause of this contract, should the Force Protection Condition (FPCON) at any individual facility or installation change, the Government may require changes in contractor security matters or processes.

Delivery Required Start Date: Two weeks after contract is awarded Required Completion Date: One week after first day on government site Total Project Time: Three weeks from date of award

Safety

It is the responsibility of the contractor to ensure worker safety by informing the workers of any potential hazardous practices. Occupational Safety and Health Administration (OSHA) guidelines must be followed at all times for hazardous practices for handling and placing concrete. Workers are required to be informed of all hazardous materials and practices that may involve exposure to toxic materials in the workplace. Material Safety Data Sheets (MSDS) must be available to all workers at the work site.