Material Acceptance & Characterization

The materials selected for the construction of CC1 included:

 

• Subgrade,
• P-501 Portland cement concrete (PCC),
• P-154M subbase,
• P-209 base material;
• and P-306 cement stabilized base (econocrete). 

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As part of the CC1 construction, material characterization was performed on the different material layers.

Construction acceptance and material characterization tests were performed on subgrade, subbase, base and Portland cement concrete (PCC) materials.

 

A brief description of the construction acceptance and material characterization tests performed for each material is provided below.

 

For more information on the construction acceptance & material characterization for CC1 click on the links in the table below.  

 

Subgrade

A material known as County Sand and Stone Clay (CS&SC) purchased from County Sand & Stone Inc. in Norma, New Jersey was used for low strength subgrade with the target CBR of 4. A material called DuPont Clay sourced from Woodstown, New Jersey was used for medium strength subgrade with the target CBR of 8. For the high strength subgrade, the locally available sand was used with a target CBR of 20.

The specification for pavement and subgrade construction was modeled after the FAA specification contained in Advisory Circular 150/5370-10A.

 

QC for the subgrade:

 

• CBR (ASTM D4429),
• Moisture (ASTM D2216);
• and density (ASTM D2937).

 

Four groups of three or more CBR penetrations were performed on each subgrade lift. Lifts were typically 6 inches (15.2 cm) to 8 (20.3 cm) inches thick before proceeding to placement of the next lift. The locations of the CBR test groups were determined accordance to ASTM D3665. The table below contains the strengths and soil classification for each subgrade after construction.

 

 Initial CBR and Soil Classification for Each Subgrade

P-501 Portland Cement Concrete (PCC)

Plain (unreinforced) concrete slabs were constructed on a prepared base in accordance with Item P-501 in Advisory Circular 150/5370-10A.

 

Following the P-501 specification the minimum flexural strength was 600 psi (4.1 MPa). The mix design was developed to target a flexural strength of approximately 650 to 700 psi (4.5 to 4.8 MPa).

Several mix designs were produced to obtain the targeted flexural strength. The final mix design was based on a 50% sand and 50% No. 57 stone blend with a cement content of 500 lbs./cy (290 kg/cm). This resulted in a target strength of 740 psi. (5.1 MPa) at a water cement ratio of 0.47.

 

QC for the P-501 PCC:

 

• Slump,
• Air content;
• and compressive strength.

 

 

P-154 Subbase and P-209 Base Material

The base and subbase courses were composed of granular materials constructed on the finished, prepared subgrade following Advisory Circular 150/5370-10A, Items P-209 and Item P-154.

The P-209 base material used at the NAPTF were partial blend coarse Milestone Materials (obtained from Hanson Aggregates in Glen Mills, Pennsylvania, formally known as Milestone Materials) and fine Maryland Materials obtained from northeast Maryland. The P-154 subbase material was a uniformly graded, manufactured argillite screenings product called Grey Quarry Blend Fines. 

 

The tables below summarize the specified gradation requirements for P-154 and P-209 and the gradation used at the NAPTF.

 

For both P-154 and P-209, the material passing the No. 40 sieve was required to have a maximum liquid limit of 25 and maximum plasticity index of 6. 

 

For P-154, the actual liquid limit and plasticity index values were 16 and 3.1, respectively. Therefore, the requirements were met.

 

 P-154 Gradation Data and Requirements for Argillite Screenings Subbase

 

  P-209 Gradation Data and Requirements for Crushed Aggregate Base

QC for the subbase P-154 material:

 

• Gradations on bulk samples from the compacted lifts,
• Moisture and density measurements on the compacted lifts,
• Thickness measurements;
• and grade and surface condition.

 

The dry densities and moisture contents for P-209 base and P-154 subbase aggregates were determined using the modified Proctor test (AASHTO T180).

 

Resilient modulus tests were conducted following the SHRP Protocol P-46 testing procedure.

Current AASHTO test procedure did not exist at that time. AASHTO adopted SHRP P-46 as AASHTO T294 in 1994 but since withdrawn. The current standard for resilient modulus of soils is AASHTO T307 (20123).

 

 

P-306 Cement Stabilized Base (Econocrete)

Econocrete base for rigid pavements was mixed and placed following Item P-306, Econocrete Base, in AC 150/5370-10A. 

 

QC for the P-306 Econocrete base:

 

• Slump,
• Air content;
• and compressive strength.

 

A mix compromised of 50% sand and 50% stone with a cement content of 200 lbs./cy (115 kg/cm) was used. This resulted in an average 28-day compressive strength of approximately 600 psi (4.1 MPa).

 

Hot Mix Asphalt Materials

Hot Mix Asphalt (HMA) in CC1 was produced in accordance with Advisory Circular 150/5370-10A, Item P-401.

 

The same material was used for both HMA surface and HMA stabilized base layers. QC testing of the P-401 material during production was required to ensure that the final product met P-401 specifications. During production, aggregate gradation, binder content, mix temperature and mixture properties were monitored.

 

QC for the P-401 mix:

 

• Aggregate gradation,
• Mat and joint density,
• Asphalt content,
• Air voids;
• and stability.

 

The Marshall Test properties of the P-401 mixtures from the truck were measured during production using the Asphalt Institute MS-2 method.

 

The field densities of P-401 cores extracted from NAPTF flexible test items were measured using ASTM D2726 procedure.

 

Resilient modulus tests (ASTM D4123) and fatigue tests (AASHTO TP 8-94) were conducted at the University of Illinois Advanced Transportation Engineering Laboratory (ATREL) facility.

 

A total of seven cores were extracted from the NAPTF flexible test items for resilient modulus testing.

 

The average laboratory measured P-401 AC resilient modulus at 77°F (25°C) was 426 ksi (2940 MPa).

 

The primary acceptance test results for the HMA are summarized as follows:

 

• Average asphalt content = 5.4%
• Average compaction = 98% of 75 blow Marshall density
• Average plant air voids = 3.6%

 

 

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