Skip to contentUnited States Department of Transportation - Federal Highway Administration FHWA Home
Research Home   |   Pavements Home
Report
This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-RD-07-052
Date: September 2007

Long Term Pavement Performance Project Laboratory Materials Testing and Handling Guide

Protocol P02
Test Method for Visual Examination and Thicknessof Asphaltic Concrete Cores (AC01)

This LTPP protocol covers visual examination, determination of thickness (measurement of length) of asphaltic (bituminous) concrete cores, and layer identification and determination of layer thickness within an AC core. This test shall be the first test to be performed on AC cores from a LTPP pavement section.

The test shall be carried out in accordance with the following procedures, on every AC core retrieved from the C-type and A1, A2, locations from a pavement section. The following definitions will be used throughout this protocol.

a) Core: An intact cylindrical specimen of the pavement material that is removed from the pavement by drilling at the designated location. A core can consist of, or include, one, two or more different layers.

b) Layer: That part of the pavement produced with similar material and placed with similar equipment and techniques. The material within a particular layer is assumed to be homogeneous. The layer thickness can be equal to or less than the core thickness or length.

c) Test Specimen: That part of the layer which is used for the specified test. The thickness of the test specimen can be equal to or less than the layer thickness.

In this protocol the use of the term core implies the entire length of the core.

1. SCOPE

1.1 This method covers the visual examination of the entire AC core and the measurement of the length of the entire AC core in the laboratory.

1.2 This method also covers the identification and determination of thickness of the individual layers within the AC core.

2. APPLICABLE DOCUMENT

2.1 AASHTO T148-86, Measuring Length of Drilled Concrete Cores.

3. APPARATUS

3.1 The apparatus shall be a calipering device that will measure length of axial elements of the core.

3.2 The apparatus shall be so designed that the core will be held with its axis in a vertical position by three symmetrically placed supports bearing against the lower end. These supports shall be short posts or stubs of hardened steel, and the ends that bear against the surface of the core shall be rounded to a radius of not less than ¼ in. (6.4 mm) and not more than ½ in. (12.7 mm).

3.3 The apparatus shall provide for the accommodation of cores of different nominal lengths over a range of at least 1 to 10 in. (25 to 250 mm).

3.4 The calipering apparatus shall be so designed that it will be possible to make a length measurement at the center of the upper end of the core and at three additional points spaced at equal intervals along the circumference of a circle of measurement whose center point coincides with the center of the core and whose radius is approximately one-half of the radius of the core.

3.5 The measuring rod or other device that makes contact with the end surface of the core for measurement shall be rounded to a radius of ? in. (3.2 mm). The scale on which the length readings are made shall be marked with clear, definite, accurately spaced graduations. The spacing of the graduations shall be 0.1 in. (2.54 mm) or a decimal part thereof.

3.6 The apparatus shall be stable and sufficiently rigid to maintain its shape and alignment without distortion or deflection of more than 0.01 in. (0.25 mm) during all normal and measuring operations.

4. CORE PREPARATION

4.1 If the AC pavement surface is bonded with a treated base or subbase layer and/or PCC layer (as shipped to the laboratory) then the AC core shall be carefully removed by sawing. It is important that layer thickness of each bonded layer shall be measured prior to sawing, and recorded on Form T01A, T31, T66 as appropriate.

4.2 The core shall be free of any condition not typical of the pavement surface. If a core is found damaged or shows abnormal defects then it shall not be used for length measurement and its condition shall be recorded during the visual examination described in Section 6.

4.3 If a core drilled from a pavement placed on an aggregate base course or subbase course includes particles of the aggregate bonded to the bottom surface of the core, then the bonded particles shall be removed by wedging, or by chisel and hammer, applied so as to expose the lower surface of the AC core. If during the removal of the bonded aggregate the AC is broken so that the instructions of Section 5.4 can not be followed, the core shall not be used for length measurement and its condition shall be recorded during the visual examination described in Section 6.

4.4 Care shall be exercised in preserving the marked arrow, if present, on the top surface of the core. The arrow indicates the direction of traffic on the pavement.

5. PROCEDURE FOR THICKNESS (LENGTH) MEASUREMENT

5.1 Before any measurements of the core length are made, the apparatus shall be calibrated with suitable gauges so that errors caused by mechanical imperfections in the apparatus are known. When these errors exceed 0.01 in. (0.25 mm), suitable corrections shall be applied to the core length measurements.

5.2 The core shall be placed in the measuring apparatus with the smooth end of the core, that is, the end that represents the upper surface of the pavement placed in the down position so as to bear against the three hardened-steel supports. The core shall be placed on the supports so that the central measuring position of the measuring apparatus is directly over the mid-point of the upper end of the core.

5.3 Four measurements of the length shall be made on each core, one at the central position and one each at three additional positions spaced at equal intervals along the circumference of the circle of measurement described in Section 3.4. Each of these measurements shall be read to the nearest 0.1 in. (2.5 mm) either directly or by estimation.

5.4 If, in the course of the measuring operation, it is discovered that at one or more of the measurement points the surface of the core is not representative of the general plane of the core because of a small projection or depression, the core shall be rotated slightly about its axis and a complete set of four measurements made with the core in the new position.

5.5 The individual measurements shall be recorded to the nearest 0.1 in. (2.5 mm) and the average of four measurements, expressed to the nearest 0.1 in. (2.5 mm), shall be reported as the average thickness of the core.

5.6 Identification and Determination of Thickness of Individual Layers within an AC core: Determination of the appropriate layer number and layer thickness of individual layers of a pavement structure is vital to LTPP and a critical element for the entire LTPP program. The procedure described in Appendix B to Protocol P01 shall be followed for identification and determination of thickness of individual layers within an AC core.

6. PROCEDURE FOR VISUAL EXAMINATION

6.1 Cores are to be visually examined for general condition, distresses and defects such as cracks, voids, layer separation, aggregate distribution, bleeding, general type and shape of aggregate such as rounded gravel, angular crushed stone, etc. and indication of stripping. The field logs describing the cores should also be reviewed prior to the visual examination in order to be aware of and confirm or reject any notations made in the field.

6.2 The bottom surface of the core shall also be examined and any condition affecting the length measurements, such as uneven surface due to removal of underlying bonded aggregates from the aggregate base or subbase course (as described in Section 4.3), shall be recorded.

6.3 Results of visual examination shall be based on LTPP standard codes, as described in Appendix A to LTPP Protocol P01.

7. REPORT

The following information is to be recorded on Form T01A:

7.1 Sample identification about the entire core shall include: Laboratory Identification Code, State Code, SHRP ID Field Layer Number, Field Set Number, Sample Location Number, LTPP Sample Number.

7.2 Test identification shall include: Laboratory Test Number, Test Date, LTPP Test Designation, LTPP Protocol Number.

7.3 Test Results:

  1. Average Thickness of Core (L) to the nearest 0.1 inch.
  2. Comments based on Visual Examination. Use standard visual examination result codes listed in Appendix A to LTPP Protocol P01 and a note, if needed, not exceeding 25 characters.

7.4 Comments shall include: LTPP standard comment code(s), as shown in Section 4.3 of the LTPP Laboratory Material Testing Guide, and any other note as needed.

7.5 Use Form T01A (Test Sheet T01A) to report the above information (Items 7.1 to 7.4).

7.6 Use Form T01B (Test Sheet T01B) to report the layer number and layer thickness of individual layers within AC core as determined using the procedure of Appendix B to LTPP Protocol P01.

APPENDIX A
CODES FOR VISUAL EXAMINATION OF ASPHALTIC CONCRETE CORES

This attachment to LTPP Protocol P01 describes a series of two-digit codes for reporting the results of visual examination of AC cores.

Code Description
01 Intact core; excellent condition; suitable for testing.
02 Hairline cracks on the surface of the core; suitable for testing.
03 Cracks and/or voids visible along the side of the core; core is suitable for testing.
04 Badly cracked or damaged core; unsuitable for testing except for maximum specific gravity (AC03) or asphalt content (AC04) tests.
05 Ridges on the sides of the core (identify by placing a straight edge along the side of the core when the distance between the straight edge and core face is 1/16 inch [1.6 mm] or greater); such a condition should be recorded if the core is used for any other test.
06 Very rough and uneven bottom surface of the core. Place the core on a level surface. Identify with this code when less than 75% of the surface area is in contact with a level surface when the core is perpendicular to the surface.
07 Core extremely damaged from sampling, shipping, or laboratory handling; unsuitable for testing. Core thickness was not measured.
08 Core was sawed in the laboratory to remove the core from the underlying bonded layer of base, subbase, or PCC
09 Core consisted of two or more AC layers. Core to be sawed in the laboratory and appropriate layer numbers to be assigned to each layer.
10 One or more AC layers have become separated due to sampling, shipping or laboratory handling; other layers, if present, to be sawed; and appropriate layer numbers to be assigned to each layer.
11 Segregation of coarse and fine aggregate is observed over 25% or more of the surface area of the core.
12 Voids in the matrix of the AC mixture are observed along the sides of the core.
13 Voids due to loss of coarse and fine aggregate are observed along the sides of the core.
14 Core is missing significant portions and can not be considered a coherent cylindrical core; unsuitable for testing.
15 Coarse aggregate along the face of the core contains 50% or more of crushed materials with fractured faces.
16 Coarse aggregate along the face of the core is a mixture of uncrushed gravel and crushed gravel or stone.
17 More than 10% of the surface area of the core contains soft and deleterious aggregate particles or clay balls. Soft is defined as those aggregates that can be easily scratched with a knife.
18 Slight stripping. Stripping is defined as the displacement of asphalt cement film from the surface of the aggregate. Slight stripping is identified when the asphalt cement film has been displaced from and/or discoloration is observed on less than 25% of the surface area of the aggregate(s), showing signs of stripping.
19 Severe stripping. A loss of coarse and fine aggregate has been noted over 25% or more of the core face and the asphalt film has been displaced from 25% or more of the surface area of the aggregate(s).
20 Slight bleeding. 5% or less of the asphalt matrix portion of the core is in a non-hardened condition and exhibits shiny and sticky surface.
21 Severe bleeding. More than 5% of the asphalt matrix portion of the core is in a non-hardened condition and exhibits shiny and sticky surface.
22 Skewed core. A core is considered skewed when either end of the core departs from perpendicularity to the axis by more than 0.5 degrees or ? inch in 12 inches (3 mm in 305 mm), as tested by placing the core on a level surface.
99 Other comment (describe in a note).

Any six codes from the above list can be used to report the results of the visual examination. A note may also be recorded (the note shall not be more than 25 characters long).

APPENDIX B
IDENTIFICATION AND DETERMINATION OF THICKNESS OF INDIVIDUAL LAYERS WITHIN AN ASPHALTIC CONCRETE CORE

This attachment to LTPP Protocol P01 covers the identification and determination of the thickness of individual layers within an AC core. The test shall be carried out on every AC core that has been tested by the Protocol P01 procedure for visual examination and determination of thickness of the entire AC core. Identifying layers, assigning appropriate layer numbers, and determining the layer thickness of individual layers within an AC Core are absolutely essential for proper test assignments and imperative in developing the materials portion of the PPDB. The assigned layer numbers shall be used for identifying and reporting all other AC and associated material tests.

1. SCOPE

1.1 This method covers the identification and determination of thickness of the individual layers within the AC core.

2. APPARATUS

2.1 A steel ruler marked with clear, definite, accurately spaced graduations. The spacing of the graduations shall be 0.1 in. (2.54 mm) or a decimal part thereof.

3. TEST PROCEDURE

3.1 Layer Identification - Individual layers within an AC core shall be identified by examining the entire core along its side. The interface of any two adjacent layers shall be marked by using chalk at four approximate equally spaced positions along the circumference of the core. The relevant inventory information on pavement layers and thickness should be reviewed prior to identifying the layers in the core. The LTPP Inventory Data Collection Guide codes for layer descriptions are shown in the following; however it is unlikely that all of the layers will be present in any one core.(19)

Overlay......................................01

Seal Coat.................................. 02

Original Surface Layer................ 03

AC Layer Below Surface............. 04

(Binder Course) Friction Course........................ 09

Surface Treatment................... 10

3.2 Layer Number Assignment - Proper assignment of layer number(s) within an AC core is vital to LTPP and a critical element prior to performing other laboratory tests. The following rules shall be used for assigning layer numbers to individual layers.

3.2.1 If the entire AC core retrieved from the pavement is intact and consists of only one layer (no layer interface observed and marked in Section 3.1 of Appendix B to Protocol P01) then this entire core is assigned the same layer number as the field layer number assigned to this layer on Field Operations Form 2 by the Drilling and Sampling Crew. Example: The following field layer numbers are assigned on Field Operations Form 2 to the materials samples retrieved from a pavement section included in a LTPP section.

Field Layer Number Material/Sample Type
4 AC Cores
3 Cement Treated Base (CTB) Cores
2 Unbound Subbase Samples
1 Subgrade Samples

If the AC core consists of only one layer, then its layer number should be 4 (same as the field layer number assigned in the field).

3.2.2 If two or more layers are identified in Section 3.1 of Appendix B to Protocol P01, then the layer numbers are assigned from the bottom layer to the top layer in the laboratory. The layer number of the bottom layer is required to be the same as the field layer number assigned to the entire AC core on Field Operations Information Form 2. The last layer number shall be assigned to the top layer of the AC core. For example, consider a pavement structure for which four layers were identified in the field (Field Operations Information Form 2), as in the example of Section 3.2.1 of Appendix B to Protocol P01. If four layers are identified by the laboratory within the AC core from this pavement, then the following layer numbers will be assigned to the individual layers.

Field Layer Number (for the entire AC Core) Layers Identified Within the AC Core Layer Number (from the bottom of the AC core)
4 Binder Course 4
  Original Surface Course 5
  Overlay 6
  Friction Course 7

(Note: The top of the friction course is the pavement surface in the above examples. This example is correct to the extent that there is no discrepancy in the other three layers below the AC layer.)

3.3 Determination of Layer Thickness - The thickness of the individual layers shall be determined to the nearest 0.1 inch (2.54 mm) by taking the average of four measurements at equal distances along the face of the core, on the positions marked for each layer identified in Section 3.1 of Appendix B to Protocol P01.

4. REPORT

The following information is to be recorded on Form T01B:

4.1 Sample identification shall include: Laboratory Identification Code, State Code, SHRP ID, Field Layer Number, Layer Number (as determined in Section 3.2 of Appendix B to Protocol P01), Field Set Number, Sample Location Number, LTPP Sample Number.

4.2 Test identification shall include: LTPP Test Designation, LTPP Protocol Number, Laboratory Test Number, Test Date.

4.3 Test Results:

  1. Layer Number
  2. Layer Description (use the codes shown in Section 3.1 of Appendix B to Protocol P01 for describing the individual layers within the AC Core).
  3. Layer Thickness for each layer within the AC Core, to the nearest 0.1 inches

4.4 Comments shall include: LTPP standard comment code(s), as shown in Section 4.3 of this Guide, and any other note as needed.

4.5 Use Form T01B (Test Sheet T01B) to report the above information (Items 4.1 to 4.4).

LTPP LABORATORY MATERIAL HANDLING AND TESTING
LABORATORY MATERIAL TEST DATA
AC CORE EXAMINATION AND THICKNESS
LAB DATA SHEET T01A

ASPHALT CONCRETE LAYER (ASPHALTIC CONCRETE PROPERTIES)
LTPP TEST DESIGNATION AC01/LTPP PROTOCOL P01

(This form is to be used to describe the entire AC core only)

(Treated base/subbase portions of the cores should be described on Form T31)

LABORATORY PERFORMING TEST:_____________________________________________________________

LABORATORY IDENTIFICATION CODE: __ __ __ __

REGION _________________ STATE ___________________ STATE CODE __ __

EXPERIMENT NO _____

SAMPLED BY: ______________________________________________ FIELD SET NO. __

DATE SAMPLED: __ __-__ __-__ __ __ __

1. FIELD LAYER NUMBER (FROM FIELD OPERATIONS FORM 2) __

2. SHRP ID __ __ __ __ __ __ __ __ __ __ __ __
3. SAMPLING AREA NO. (SA-) __ __ __ __ __ __
4. LABORATORY TEST NO. __ __ __
5. LOCATION NUMBER __ __ __ __ __ __ __ __ __
6. SAMPLE NUMBER __ __ __ __ __ __ __ __ __ __ __ __
7. AVERAGE THICKNESS* (L) inches __ __ . __ __ __ . __ __ __ . __
8. VISUAL EXAMINATION      
      (a) CODE (Section 7.3(b), Protocol P01) ___ ___ ______ ___ ___ ___ ___ ______ ___ ___ ___ ___ ______ ___ ___
      (b) NOTE _____________________________________ _____________________________________ _____________________________________
9. COMMENTS      
(a) CODE (Section 7.4, Protocol P01) ___ ___ ______ ___ ___ ___ ___ ______ ___ ___ ___ ___ ______ ___ ___
(b) NOTE ________________________________ ________________________________ ________________________________
10. TEST DATE ___ - ___ - ____ ___ - ___ - ____ ___ - ___ - ____

____________________________________________________________

* Measure AC core thickness prior to sawing from other bonded layers.

GENERAL REMARKS:___________________________________________________________________________
SUBMITTED BY, DATECHECKED AND APPROVED, DATE
____________________________________________________________
LABORATORY CHIEF
Affiliation______________________
Affiliation______________________

LTPP LABORATORY MATERIAL HANDLING AND TESTING
LABORATORY MATERIAL TEST DATA
AC CORE EXAMINATION AND THICKNESS
LAB DATA SHEET T01B

ASPHALT CONCRETE LAYER (ASPHALTIC CONCRETE PROPERTIES)
LTPP TEST DESIGNATION AC01/LTPP PROTOCOL P01

(This form is to be used to report detailed information as described in Appendix B to Protocol P01)

LABORATORY PERFORMING TEST:______________________________________________________________

LABORATORY IDENTIFICATION CODE:__ __ __ __

REGION _________________ STATE ___________________ STATE CODE __ __

EXPERIMENT NO _____

SAMPLED BY: ______________________________________________ FIELD SET NO. __

DATE SAMPLED: __ __-__ __-__ __ __ __

1. (FIELD) LAYER NUMBER (FROM FORM T01A) __

2. SHRP ID __ __ __ __ __ __ __ __ __ __ __ __
3. SAMPLING AREA NO. (SA-) __ __ __ __ __ __
4. LABORATORY TEST NO. __ __ __
5. LOCATION NUMBER __ __ __ __ __ __ __ __ __
6. SAMPLE NUMBER __ __ __ __ __ __ __ __ __ __ __ __
7. LAYER INFORMATION
(Start layer number from the bottom layer within the AC Core) LAYER LAYER LAYER
NO. DESC. THICK (in) NO. DESC. THICK (in) NO. DESC. THICK (in)
___ __ __ __ __ . __ ___ __ __ __ __ . __ ___ __ __ __ __ . __
___ __ __ __ __ . __ ___ __ __ __ __ . __ ___ __ __ __ __ . __
___ __ __ __ __ . __ ___ __ __ __ __ . __ ___ __ __ __ __ . __
___ __ __ __ __ . __ ___ __ __ __ __ . __ ___ __ __ __ __ . __
___ __ __ __ __ . __ ___ __ __ __ __ . __ ___ __ __ __ __ . __

8. COMMENTS

      (a) CODE __ __ __ __ __ ____ __ __ __ __ __ __ __ __ __ __ ____ __ __ __ __ __ __ __ __ __ __ ____ __ __ __ __ __
      (b) NOTE ______________________________________ ______________________________________ ______________________________________
9. TEST DATE __ __ - __ __ - __ __ __ __ __ __ - __ __ - __ __ __ __ __ __ - __ __ - __ __ __ __

* Same layer number as entered in item 1 (Field layer number) if there is no other discrepancy in layers identified in the field and laboratory.

GENERAL REMARKS:___________________________________________________________________________
SUBMITTED BY, DATECHECKED AND APPROVED, DATE
____________________________________________________________
LABORATORY CHIEF
Affiliation______________________
Affiliation______________________

 

<< PreviousContentsNext >>

The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
FHWA
United States Department of Transportation - Federal Highway Administration