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Publication Number: FHWA-RD-07-052
Date: September 2007

Long Term Pavement Performance Project Laboratory Materials Testing and Handling Guide

Protocol P52
Test Method for Classification and Descriptionof Subgrade Soils (SS04)

This LTPP Protocol covers the procedures for classification and description of subgrade soils. The test shall be carried out in accordance with ASTM D2488-00 and AASHTO M145-87I as modified by the following. The sections of the reference standards included in this protocol without modifications shall be strictly followed. All other sections of this protocol shall be followed as herein written.

Classification and description using Protocol P52 shall be carried out on the bulk samples of the subgrade layer after; (1) assigning the appropriate layer number, (2) determining the natural moisture content in accordance with Protocol P49, (3) performing gradation tests in accordance with Protocol P51, and (4) carrying out the Atterberg Limits tests in accordance with Protocol P43.

The observations made during the bulk sample handling in the laboratory and test sample preparation, and the results of the gradation and Atterberg Limits tests (Protocols P51 and P43) shall be used in determining the classification in accordance with this protocol (P52). The test results shall be reported separately for the test samples obtained from each designated sampling area.

The locations and sample numbers for P52 testing are as shown on the laboratory testing plans developed for each project.

When bulk samples of the subgrade layer are retrieved from BA1, BA2, BA3... type 12-inch (305-mm) diameter boreholes, these bulk samples are combined and prepared in accordance with AASHTO T87-86. Because the bulk samples are combined, the Location Number of the sample should have an asterisk placed as the third digit. Similarly, the LTPP Sample Number should have an asterisk placed as the third and fourth digits.

The following definitions will be used throughout this protocol.

  1. 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 subgrade layer may not conform to the above definition. Subgrade soils are prepared and compacted before the placement of subbase and/or base layers. For the LTPP material sampling and testing program, the subgrade layer is considered to be representative of the subgrade soils within 12 inches (305 mm) below the top of the subgrade, unless otherwise indicated on field exploration logs (bore hole logs and/or test pit logs).
  2. Bulk Sample: That part of the pavement material that is removed from an unbound layer from the borehole(s) and the test pit at the designated locations. The bulk sample of each layer is shipped in one or more bag(s) to the participating laboratory. The material from one layer should never be mixed with the material from another layer-even if there is less than the desired amount to perform the specified test.
  3. Test Sample: That part of the bulk sample of an unbound layer which is prepared and used for the specified test. The quantity of the test sample may be the same, but will usually be less than the bulk sample size.

1. SCOPE

1.1 This protocol covers ASTM D2488-00, visual-manual procedures for the classification and description of subgrade soils, and for assigning material codes according to the LTPP terminology for pavement materials and soils as described in Table 4.26 of Chapter 4 of the LTPP Laboratory Material Testing Guide.

1.2 This protocol also requires the use of AASHTO classification (AASHTO M145-87I standard) and the respective material codes according to the LTPP terminology for pavement materials and soils as described in Table 4.26 of Chapter 4 of the LTPP Laboratory Material Testing Guide.

1.3 Standard values shall be inch-pound units.

2. APPLICABLE DOCUMENTS

2.1 ASTM Standards: As listed in ASTM D2488-00.

2.2 AASHTO Standards:
AASHTO M145-87I The Classification of Soils and Soil-Aggregate Mixtures for Highway Construction Purposes.
AASHTO T87-86 Dry Preparation of Disturbed Soil and Soil Aggregate Samples for Test.

2.3 LTPP Protocols:
P51 Sieve Analysis of Subgrade Soils.
P42 Hydrometer Analysis.
P43 Determination of Atterberg Limits of Unbound Granular Base and Subbase Materials and Subgrade Soils.
P46 Resilient Modulus of Unbound Granular Base/Subbase Materials and Subgrade Soils.

2.4 Other LTPP Documents: LTPP Laboratory Material Testing Guide.

3. DEFINITIONS

As listed in Section 3 of ASTM D2488-00.

4. SUMMARY OF METHOD

4.1 As described in Section 4.1 of ASTM D2488-00. This method yields standardized criteria and procedures for describing and identifying soils based on a visual examination and simple manual tests.

4.2 As described in Section 4.2 of ASTM D2488-00. The soil is classified using Table 4.26 of the LTPP Laboratory Material Testing Guide based on ASTM D2488-00 using visual-manual procedures only.

4.3 Material classification designations and codes are used to report the classification and description.

5. SIGNIFICANCE AND USE

5.1 As described in Section 5 of ASTM D2488-00 for subgrade soils.

5.2 This protocol is also used to assign "Mr Material Type" (Type 1 or Type 2) for the resilient modulus testing (Protocol P46).

6. APPARATUS

As required in Section 6 of ASTM D2488-00.

7. REAGENTS

As listed in Section 7 of ASTM D2488-00.

8. SAFETY PRECAUTIONS

As required in Section 8 of ASTM D2488-00.

9. SAMPLING

9.1 The bulk sample shall be considered to be representative of the subgrade layer from which it was obtained from the field. If the bulk sample is contained in more than one bag then these bulk samples shall be combined as described in Protocol P51 and considered as the test sample for this protocol.

9.2 If the test sample being examined is smaller than the minimum recommended amount listed in Section 9.3 of ASTM D2488-00, the report shall include an appropriate comment.

10. DESCRIPTIVE INFORMATION AND CLASSIFICATION FOR TEST SAMPLES

10.1 Use Sections 10 to 15 of ASTM D2488-00 for the descriptive/visual-manual classification information to be assigned to the test samples. In addition, the descriptions and visual-manual classification shall be reported by using the material codes provided in Table 4.26 of Chapter 4 of the LTPP Laboratory Material Testing Guide.

10.2 Use the AASHTO classification system (AASHTO M145-87I) for assigning the AASHTO classification using material codes provided in Table 4.27 of Chapter 4 of the LTPP Laboratory Material Testing Guide.

10.3 The material shall also be assigned Mr Material Type "1" or "2" for use in the resilient modulus testing (Protocol P46). According to Protocol P46, all unbound granular base and subbase materials and subgrade soils are categorized as Type 1 or Type 2 according to the following rules:

  1. All unbound granular base and subbase materials are categorized as "Type 1" materials.
  2. All unbound subgrade soils which meet the criteria of 70 percent maximum passing the No. 10 (2.00-mm) sieve and 20 percent maximum passing the No. 200 (0.075-mm) sieve are also categorized as "Type 1" materials.
  3. All unbound subgrade soils not meeting the criteria given in (b) above are categorized as "Type 2" materials.
  4. All thin-walled tube samples of the subgrade soils are also categorized as "Type 2" materials.

11. REPORT

The following information is to be recorded on Form T52.

11.1 Sample Identification shall include: Laboratory Identification Code, Region, State, State Code, SHRP ID, Layer Number, Field Set Number, Sample Area Number, Sample Location Number, LTPP Sample Number.

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

11.3 Test Results

Report the following:

11.3.1 Visual-Manual Description based on ASTM D2488-00

  1. Range of particle size (as described in Section 10.10 of ASTM D2488-00).
  2. Maximum particle size (as described in Section 10.11 of ASTM D2488-00).
  3. Color description (as required in Section 10.3 of ASTM D2488-00).
  4. Material Codes for other properties according to Table 4.27 of the LTPP Laboratory Material Testing Guide. Up to 10 four-digit codes are allowed.

11.3.2 Visual-manual classification using a three-digit code from Table 4.27 of Chapter 4 of the LTPP Laboratory Material Testing Guide as required in Sections 14 and 15 of ASTM D2488-00.

11.3.3 AASHTO Classification Code using a three-digit code according to Table 4.28 of Chapter 4 of the LTPP Laboratory Material Testing Guide.

11.3.4 "Mr Material Type" based on the guidelines provided in Section 10.3 of this protocol. The subgrade bulk sample can be assigned either "1" or "2" for Mr Material Type designation depending on the criteria (a) and (b) stated in Section 10.3 of this protocol. However, the subgrade bulk sample shall be assigned Mr Material Type "2" if a thin-walled tube sample of the subgrade was retrieved from the same area.

11.4 Comments shall include LTPP standard comment code(s), as shown in Section 4.3 of this Guide and any other note as needed. Use codes 61 to 65 as given below for additional comments.

Code Comment
61 Insufficient size of the test sample because the quantity of the bulk sample was significantly less than that required for the tests.
62 Presence of roots and other organic material in the bulk sample retrieved from the field.
63 Presence of mica in the bulk sample retrieved from the field.
64 The bulk sample contained cobbles or large size aggregates (stone fragments passing the 12-in. [305-mm] sieve and retained on the 3-in. [76-mm] size sieve).
65 The test sample included shale chunks, claystone, mudstone, siltstone, and sandstone which convert into soils after field and/or laboratory processing (crushing, slacking, etc.).

12.5 Use Form T52 (Test Sheet T52) to report the above information (Items 11.1 to 11.4).

LTPP LABORATORY MATERIAL HANDLING AND TESTING
LABORATORY MATERIAL TEST DATA
CLASSIFICATION AND DESCRIPTION
LAB DATA SHEET T52

SUBGRADE SOILS
LTPP TEST DESIGNATION SS04/LTPP PROTOCOL P52

LABORATORY PERFORMING TEST:______________________________________________________________

LABORATORY IDENTIFICATION CODE:__ __ __ __

REGION _________________ STATE ___________________ STATE CODE __ __

EXPERIMENT NO _____ SHRP ID __ __ __ __

SAMPLED BY: ______________________________________________ FIELD SET NO. __

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

1. LAYER NUMBER (FROM LAB SHEET L04) __
2. SAMPLING AREA NO. (SA-) __ __ __ __
3. LABORATORY TEST NUMBER __ __
4. LOCATION NUMBER (Enter an asterisk as the third digit) __ __ __ __ __ __
5. LTPP SAMPLE NUMBER (Enter an asterisk as third and fourth digit) __ __ __ __ __ __ __ __
6. VISUAL-MANUAL DESCRIPTION (Section 11.3.1 of Protocol P52)
      (a) RANGE OF PARTICLE SIZE ________________________ _______________________
      (b) MAXIMUM PARTICLE SIZE ________________________ _______________________
      (c) COLOR DESCRIPTION ________________________ _______________________
      (d) CODES - OTHER PROPERTIES (Table 4.27 of LTPP Lab Guide) __ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __
7. VISUAL-MANUAL CLASSIFICATION (Section 11.3.2 of Protocol P52) __ __ __ __ __ __
8. AASHTO CLASSIFICATION CODE (Section 11.3.3 of Protocol P52) __ __ __ __ __ __
9. Mr MATERIAL TYPE (Section 11.3.4 of Protocol P52) ___ ___
10. COMMENTS (Section 11.4 of Protocol P52)
      (a) CODE __ __ __ __ __ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __ __ __ __ __
      (b) NOTE ________________________ ______________________
11. TEST DATE __ __-__ __-__ __ __ __ __ __-__ __-__ __ __ __

NOTE: 1. RESULTS OF TEST SHEETS T51 AND T43 ARE USED FOR CLASSIFICATION AND DESCRIPTION ON TEST SHEET T52.

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

 

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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.
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