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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 P51A
Test Method for Dry Sieve Analysisof Subgrade Soils (SS01)

This LTPP protocol covers the determination of the gradation of subgrade soils by dry sieve analysis. This protocol is based on test standard AASHTO T27-88I (Sieve Analysis of Fine and Coarse Aggregates) and is designated as LTPP Test SS01 for subgrade soils. The tests shall be carried out in accordance with AASHTO T27-88I), as modified herein. Those sections of the AASHTO standard included in this protocol by reference and without modifications shall be strictly followed. All other sections of this protocol shall be followed as herein written.

The purpose of LTPP P51A is to allow, at the Laboratory Manager's discretion, a dry sieving (in place of a wet and dry sieving-i.e., Protocol P51) procedure to be conducted on very "clean" subgrade soils. The general definition of "clean" for Protocol P51A is outlined below. Generally, Protocol P51A shall only be used on subgrade soils with estimated classifications of A-1, A-2 or A-3 by the AASHTO classification system and which meet certain specified conditions with respect to coatings on the coarse aggregate and clay lumps contained in the sample. The specific requirements are as follows:

WHEN TO USE PROTOCOL P51A
Protocol P51A is a dry sieving procedure for subgrade soils.
Two requirements must be met in order to used Protocol P51A:
Requirement 1 - less than twenty five percent of the surface area of the coarse grained soil fraction (i.e., + No. 4 [4.75-mm] material) is coated with soil fines (i.e., - No. 200 [0.075-mm] material).
Requirement 2 - a "significant" (i.e., as defined in the following table) amount of clay lumps or hard balls of fine materials are not present in the bulk sample of subgrade soil.
Both Requirement 1 and Requirement 2 must be met in order to use Protocol P51A. To determine if these requirements are met, the laboratory manager (or his/her designee) shall conduct a visual examination of the subgrade soil bulk sample. Approximately 22 lbs (10 kg) shall be split from the bulk sample.
Requirement 1

The coarse aggregate portion of this sample shall be examined to estimate the percent clay coating, if any. If twenty-five percent or less of the surface area is coated, then Requirement 1 is satisfied. If Requirement 1 is not satisfied, then the visual examination shall cease and a wet and dry sieving process shall be used (Protocol P51).

If Requirement 1 is met, then the sample shall be examined for clay lumps.
Requirement 2

If no clay lumps are apparent, then Requirement 2 is satisfied and dry sieving should be initiated in accordance with this protocol. However, if clay lumps are present then the size and number of the clay lumps in the sample should be estimated. The following table shall then be used to determine if Requirement 2 is met.

Note: The table below is based on a 22-lb (10-kg) sample. If the representative sample is smaller than 22 lbs (10 kg), appropriate reductions in the allowable number of clay lumps shown in this table shall be used.
APPROXIMATE CLAY LUMP SIZE ESTIMATED AASHTO CLASSIFICATION
A1, A2, A3 A4, A5, A6, A7 Use Protocol P51
¼ inch (6.3 mm) 70 clay lumps
? inch (9.5 mm) 20 clay lumps
½ inch (12.5 mm) 7 clay lumps
¾ inch (19.0 mm) 2 clay lumps
1 inch (25.0 mm) 1 clay lump
If clay lumps are present in sizes and amounts less than those shown in the above table for the appropriate estimated AASHTO classification, Requirement 2 is satisfied. If clay lumps are present in numbers greater than those specified above, the wet and dry sieving process (Protocol P51) shall be used.

If both or either Requirement 1 and Requirement 2 are violated , then Protocol P51 shall be used.

Determination of gradation using Protocol P51A shall be the first test to be performed on the bulk samples of the subgrade layer, after, (1) assigning the appropriate layer number and (2) determining the natural moisture content (Protocol P49) from jar samples for the subgrade layer, (3) estimating the AASHTO classification and (4) determining the applicability of Protocol P51 or P51A. In addition, the combined bulk sample of the subgrade shall be described during the bulk sample handling in the laboratory and test sample preparation for the gradation (P51A) and Atterberg Limits (Protocol P43) tests. These descriptions shall be later used for the classification and description of the sample (Protocol P52).

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, prepared in accordance with AASHTO T87-86 and reduced to a representative test size in accordance with AASHTO T248-83. 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.

1. SCOPE

This method covers the determination of the particle size distribution in the test sample of fine and coarse aggregates by dry sieving the test sample of the subgrade soil according to AASHTO T27-88I, and as described in this protocol.

2. APPLICABLE DOCUMENTS

2.1 AASHTO standards: As listed in Section 2.1 of AASHTO T27-88I.

AASHTO T87-86 Dry Preparation of Disturbed Soil and Soil Aggregate Samples for Test.

2.2 ASTM Standards: As listed in Section 2.2 of AASHTO T27-88I.

ASTM D2487-85 Classification of Soils for Engineering Purposes.

2.3 LTPP Protocols:
P43 Determination of Atterberg Limits.
P52 Classification and Description of Subgrade Soils.
P49 Determination of Natural Moisture Content.

3. SIGNIFICANCE AND USE

The gradation results obtained by following the test procedures of this protocol (P51A) and the Atterberg limits results (P43) shall be used for laboratory classification and description of subgrade soils (P52).

4. APPARATUS

As required in Section 5 of AASHTO T27-88I with the exception that the sieve sizes shall conform to Section 8.3.1 of Protocol P51A.

5. TEST SAMPLE

5.1 Assign the appropriate layer number to the bulk sample of the subgrade soil that is being tested. Weigh the total bulk sample received from the field for that layer. The bulk samples from the different sampling areas shall be weighed separately. The following sections of this protocol refer to the combined bulk sample from near one sampling area only. Combine the bulk samples if contained in more than one bag(s). Thoroughly mix the combined bulk sample and dry according to the procedure described in Section 4.1 of AASHTO T87-86.

5.2 Obtain the representative test sample according to the procedure described in Section 6.2 of AASHTO T27-88I.

5.3 Use the natural moisture content determined from the jar samples of the subgrade soil earlier on Form T49 according to Protocol P49 for the respective bulk sample location(s) to estimate the weight of the test sample when dry.

5.4 The approximate weight of the test sample shall conform to the weight requirement described in Section 6.4 of AASHTO T27-88I for aggregates with nominal maximum size of 2 inches (51 mm) or less for the total bulk sample weighing 150 lbs (68 kg) or more. The approximate weight of the test sample shall not exceed 50 lbs (23 kg) for larger nominal maximum size aggregates. The approximate weight of the test sample shall not exceed 40 lbs (18 kg) if the total bulk sample weighs 100 lbs (45 kg) or more, but less than 150 lbs (68 kg).

Note: The nominal maximum aggregate size is defined as the smallest sieve size opening through which at least 95 percent of the aggregate passes. Delete Section 6.5 of AASHTO T27-88I.

5.5 Even if the weight of the test sample is less than the required minimum weight, the test shall be performed; however, this violation of the test standard AASHTO T27-88I shall be recorded as a standard comment code.

6. PROCEDURE

6.1 Dry the test sample to constant weight at a temperature of 110 ± 5°C (230 ± 9°F) and weigh to the nearest 0.1% of the weight of the sample.

6.2 Commence dry sieving by using the AASHTO T27-88I procedure in conformity with Sections 6.2 to 6.4 of this protocol.

6.3 Nest the sieves in order of decreasing size of opening from top to bottom and place the dried test sample on the top sieve. Agitate the sieves by hand or by mechanical apparatus for a sufficient period, established by trial or checked by measurement on the actual test sample, to meet the criterion for adequacy or sieving described in Section 7.4 of AASHTO T27-88I.

6.4 As required in Sections 7.3-7.7 of AASHTO T27-88I.

7. CALCULATION

Calculate percentages passing to the nearest 1% (for sieve sizes 3-in. [76-mm] to No. 80 [0.180-mm]), and to the nearest 0.1% for the No. 200 (0.075-mm) sieve on the basis of the total weight of the initial dry test sample.

8. REPORT

The following information is to be recorded on Form T51A.

8.1 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.

8.2 Test Identification shall include: LTPP Test Designation, LTPP Protocol Number, Laboratory Test Number, Test Date.

8.3 Test Results

Report the following:

Gradation results based on Section 7 of this protocol to the appropriate number of significant digits as follows:

Sieve Sizes Standard (mm) % Passing
3 in. (75.0) __ __ __.
2 in. (50.0) __ __ __.
1 ½ in. (37.5) __ __ __.
1 in. (25.0) __ __ __.
¾ in. (19.0) __ __ __.
½ in. (12.5) __ __ __.
3/8 in. (9.5) __ __ __.
#4 (4.75) __ __ __.
#10 (2.00) __ __ __.
#40 (0.425) __ __.
#80 (0.180) __ __.
#200 (0.075) __ __.__

8.4 Attach a cumulative particle size gradation curve such as shown in Figure 4 of ASTM D2487-85 with Form T51A.

8.5 Comments shall include LTPP standard comment code(s), as shown in Section 4.3 of this Guide and any other note as needed. Additional codes for special comments that may be associated with the testing of bulk samples are:

Code Comment
61 Insufficient size of 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-inch [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.).

In addition, record the weight of the test sample to the nearest 1 lb (0.5 kg) and the moisture content (Section 5.3 of Protocol P51A) to the nearest 1%.

8.6 Use Form T51A (Test Sheet T51A) to report the above information (Items 8.1 to 8.4).

LTPP LABORATORY MATERIAL HANDLING AND TESTING
LABORATORY MATERIAL TEST DATA
DRY SIEVE ANALYSIS OF SUBGRADE SOILS
LAB DATA SHEET T51A

SUBGRADE SOILS
LTPP TEST DESIGNATION SS01/LTPP PROTOCOL P51A

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) __ __ __ __ __ __ __ __
7. GRADATION (Section 8.3.1 of Protocol P51A) % PASSING SIEVE SIZE STANDARD (mm)
3 in. (75.0) __ __ __. __ __ __.
2 in. (50.0) __ __ __. __ __ __.
1 ½ in. (37.5) __ __ __. __ __ __.
1 in. (25.0) __ __ __. __ __ __.
¾ in. (19.0) __ __ __. __ __ __.
½ in. (12.5) __ __ __. __ __ __.
3/8 in. (9.5) __ __ __. __ __ __.
#4 (4.75) __ __ __. __ __ __.
#10 (2.00) __ __ __. __ __ __.
#40 (0.425) __ __. __ __.
#80 (0.180) __ __. __ __.
#200 (0.075) __ __.__ __ __.__
8. COMMENTS (Section 8.4 of Protocol P51A)
      (a) CODE __ __ __ __ __ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __ __ __ __ __
      (b) NOTE _________________ _________________
_________________ _________________
      (c) WEIGHT OF TEST SAMPLE __ __ __.__ lb. __ __ __.__ lb.
MOISTURE CONTENT __ __.% __ __.%
9. TEST DATE __ __-__ __-__ __ __ __ __ __-__ __-__ __ __ __

NOTE: 1. RESULTS OF TEST SHEETS T51A AND T43 ARE USED FOR CLASSIFICATION AND DESCRIPTION ON TEST SHEET T52.

2. ATTACH A CUMULATIVE PARTICLE SIZE GRADATION CURVE WITH FORM T51A (SECTION 8.3.2 OF PROTOCOL P51A).

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

 

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