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Publication Number: FHWA-HRT-10-049
Date: August 2010

LTPP Specific Pavement Studies (SPS) Materials Action Plan Final Report

Chapter 2. MAP Development

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2.1 Materials testing Needs Analysis

The numbers of required, available, and missing tests presented in this report are based on database queries. It is not always possible to accurately determine from the database if a test is required or possible to run on a layer. For example, the open graded drainage layers on SPS-1 and -2 projects are represented as treated base layers in the database because construction specifications required that they be treated with 2 percent asphalt to add stability during construction. Although they are a treated base layer, it is not possible to extract an intact core of this material because of lack of cohesion.

Thus, the amount of missing tests is a planning number that was expected to be overstated so that resources estimates would be conservative. Because the LTPP database changes as new information is acquired, the basis for the number of required tests can change due to the identification of new material layers in the pavement structure each time a needs assessment is performed.

2.2 Status of SPS Materials Data (2004)

The status of the missing SPS materials data in April 2002 and in April 2004, after 2 years of effort, is summarized in table 1.

Table 1. Status of SPS materials test data, 2002-2004.

 

April 2002

April 2004

Change

Required Tests

35,467

34,529

-938

Available Tests

18,299

22,359

+4,060

Missing Tests

17,168

12,170

-4,998

Percent Missing Tests

49%

35%

14%

Detailed information on these counts is contained in the

As table 1 and the appendices indicate, the efforts undertaken by the LTPP program between 2002 and 2004 resulted in a significant reduction in missing SPS materials test data. The number of missing tests was reduced by 4,998 as a result of the addition of 4,060 new data sets and adjustments to the number of required tests. About one third of the materials tests were still missing in 2004-an improvement but still a significant problem.

2.3 Modifications to MS&T Plan Requirements

The FHWA took into consideration recommendations from the Materials ETG and LTPP contractors to establish the following priority material test requirements for the MAP:

The following tests were not included as part of the action plan:[1]

Some of these tests were still performed as part of other test protocols, ancillary to other tests, or based on agency participation. For example, classification of unbound soils and base materials (tests SS04 and UG08) are included in this list because they are not tests per se but computations based on other test results.

In general, the Materials ETG's rationale for recommending tests not be included in the plan was usually that the tests were somewhat outmoded and were not likely to provide valuable information in the future.

One or more layers/materials on the following SPS projects were not included as part of the 2004 MAP because they had already been removed or because the project site was out of study and not considered for further testing:

Material layers from these sites were not included in the assessment of data needs.

Another assessment of data gaps and needs was performed in 2004 using the new MAP priority test guidelines and the contents of the May 2004 national upload of the LTPP database. Table 2 contains counts by test type and type of material to satisfy the priority test requirements developed for the MAP. Based on the layer structure contained in the database at this time, approximately 12,650 tests were identified as necessary to fill material data gaps. Differences between data needs in table 2 and those reported in table 1 are due to changes in pavement structure data in the database and the more explicit test section-based requirements for the MAP.

Table 2. Required tests by test type to fill data gaps.

Test Description Material Layer
AC PCC Unbound TB-AC TB-PCC TB Totals
AC01 Core Examination and Thickness 1,167     590     1,757
AC02 Bulk Specific Gravity 1,744     652     2,396
AC03 Maximum Specific Gravity 292     110     402
AC04 Asphalt Content (Extraction) 284     47     331
AC07 Tensile Strength/Res. Modulus/Creep 357     118     475
AE03 Specific Gravity 16 °C (60.8 °F) 319     109     428
AE05 Viscosity 60 °C (140 °F), 135 °C (275 °F) 321     109     430
AG01 Coarse Aggregate Specific Gravity 346     110     456
AG02 Fine Aggregate Specific Gravity 348     116     464
AG04 Extracted Aggregate Gradation 289     50     339
AG05 NAA Test-Fine Aggregate Particle Shape 488     137     625
 Subtotal: 8,103
PC01 Compressive Strength   31     48   79
PC02 Split Tensile Strength   29     90   119
PC03 Coefficient of Thermal Expansion   88     93   181
PC04 Static Modulus of Elasticity   50     92   142
PC06 Core Examination and Thickness   334     511   845
PC08 28 Day Air Content   121     93   214
 Subtotal: 1,580
SS01/UG02 Sieve Analysis     316     12 328
SS02/UG03 Hydrometer     244     0 244
SS03/UG04 Atterberg Limits     300     12 312
SS07/UG07 Resilient Modulus     523     12 535
 Subtotal: 1,419
TB01 Type and Class. of Materials and Treatment       911 612 28 1,551
 Subtotal: 1,551
 Totals 5,955 653 1,383 3,059 1,539 64 12,653

AC = Asphalt concrete
PCC = Portland cement concrete
TB-AC = Asphalt concrete treated base
TB-PCC = Portland cement concrete treated base
TB = Treated base

2.4 NEW AND Aging Tests

While addressing the need to resolve material data gaps based on previous criteria, new and aging tests were added to improve materials structure information with little added cost. Aging tests are repeats of previous tests to capture material property aging effects.

New tests included the following:

Aging tests were only to be performed on HMA or PCC layers, not on material from unbound base, subbase, or subgrade layers nor on treated bases or subbases. They included the following:

Table 3 outlines the 2004 sampling requirements for the new and aging tests by type of SPS experiment.

Table 3. Sampling requirements for new and aging tests.

Experiment/ Project Cores Per Project Number of Projectsa Total Cores
12-inch Cores 4-inch Cores 12-inch Cores 4-inch Cores
SPS-1 3 12 16 48 192
SPS-2 6 18 13 78 234
SPS-5 6 24 17 102 408
SPS-6 3 12 13 39 156
SPS-8 Flex 3 12 15b 45 180
SPS-8 Rigid 3 9 8b 24 72
Totals 82 336 1,242

a Does not include projects eliminated from the action plan. b There are 19 SPS-8 projects; 4 of them have both AC and PCC test sections.

Bulk samples of the unbound base, subbase, and subgrade materials to run the specific gravity test were designated to be obtained from the 12-inch core locations identified in table 3. Where the proper drill rig to cut 12-inch holes was not available, a saw-cut opening was requested to access the underlying unbound materials.


[1] The first two letters of the test designation indicate the material type. AC: asphalt concrete, AE: extracted asphalt cement, PC: portland cement concrete, SS: subgrade soil, TB: treated base, UG: unbound granular base.

 

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