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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 P55
Test Method for Moisture-Density Relationsof Subgrade Soils (SS05)

This LTPP Protocol covers the determination of the moisture-density relations of subgrade soils. This protocol is based on AASHTO T 99-86 ("The Moisture-Density Relations of Soils Using a 5.5-lb [2.5 kg] Rammer and a 12-in. [305-mm] Drop"). The test shall be carried out in accordance with this standard (AASHTO T99-86), as modified herein. Those sections of the AASHTO standard included in this protocol by reference and without modification shall be strictly followed. All other sections of this protocol shall be followed as herein written.

The determination of the moisture-density relations using Protocol P55 shall be performed on the bulk samples of the subgrade layer, after; (1) assigning the appropriate layer number, (2) determining the natural moisture content (Protocol P49) from jar samples of the subgrade layer, (3) performing the sieve analysis test (Protocol P51), (4) determining the Atterberg Limits (Protocol P43), and (5) completing the classification and description test (Protocol P52). The results of the moisture-density test (Protocol P55) will be recorded in the PPDB and are also used to ascertain molding water content and density values. These parameters will be later used to reconstitute test specimens from the bulk samples of the subgrade layer for the resilient modulus testing (Protocol P46).

The test shall be performed on a representative test sample obtained from the bulk samples of subgrade soils. The test results shall be reported separately for the test samples obtained from each designated sampling area.

The locations and sample numbers for P55 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, prepared and reduced to a representative test size in accordance with AASHTO T87-86 and 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 materials 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

1.1 This method of test covers the determination of the relationship between the moisture content and density of subgrade soils when compacted in a 6-inch (152-mm) diameter mold with a 5.5-lb (2.5-kg) rammer dropped from a height of 12 in. (305 mm). Two alternate procedures are provided as follows:

Method B - A 6-in. (152-mm) diameter mold: soil material passing a No. 4 (4.75-mm) sieve.
Method D - A 6-in. (152-mm) diameter mold: soil material passing a ¾-in. (19-mm) sieve.

1.2 Select method "B" or "D" as appropriate based on the results of the sieve analysis (Protocol P51).

1.3 As stated in Section 1.3 of AASHTO T99-86.

2. APPLICABLE DOCUMENTS

2.1 ASTM Standards
ASTM D653 Terms and Symbols Relating to Soil and Rock.

2.2 AASHTO Standards
AASHTO T99-86 The Moisture-Density Relation of Soils Using a 5.5-lb [2.5-kg] Rammer and a 12-in. [305-mm] Drop.

AASHTO R-11 Recommended Practice for Indicating Which Places of Figures Are To Be Considered Significant in Specified Limiting Values.

AASHTO T19-88I Unit Weight and Voids in Aggregate.

AASHTO M231-87I Weighing Devices Used in the Testing of Materials.

AASHTO M92-85 Wire-Cloth Sieves for Testing Purposes.

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

AASHTO T248-83 Reducing Field Samples of Aggregates to Testing Size.

2.3 LTPP Protocols

P51 Sieve Analysis of Subgrade Soils.

P52 Classification and Description of subgrade soils.

P49 Determination of Natural Moisture Content.

P44 Moisture-Density Relations of Unbound Granular Base/Subbase Materials.

P46 Resilient Modulus of Unbound Granular Base and Subbase Materials and Subgrade Soils.

3. APPARATUS

The apparatus for moisture-density relations testing shall conform to the requirements of Section 2 of AASHTO T99-86 with the following exceptions:

3.1 Molds - As required in Section 2.1, 2.1.2 and 2.1.3 of AASHTO T99-86. Delete Section 2.1.1 and Note 1 of AASHTO T99-86.

LTPP PROTOCOL P55 - METHOD "A"

Note – 4-inch (102-mm) molds will not be used in this test, therefore Method A of AASHTO T99-86 will not be used as is. However, Method A is not deleted from this protocol as part of the procedure contained in Method A (Sections 3 and 4) of AASHTO T99-86 is used in Method B.

LTPP PROTOCOL P55 - METHOD "B"

4. SAMPLE

4.1 Prepare the subgrade soil sample in accordance with Sections 4.1 and 7 of AASHTO T87-86 (Dry Preparation of Disturbed Soil and Soil Aggregate Samples for Test).

4.2 The weight of the test sample should approximately be 20 lb (9 kg). Check the gradation test results (Protocol P51) for percentage of coarse material passing the 1 ½-in. (38-mm) sieve and retained on the No. 4 (4.75-mm) sieve. If this percentage is up to 5% then Method B of Protocol P55 shall be used. Include this coarse fraction in the test sample for moisture-density test and record this deviation from the AASHTO T99-86 standard by using special comment code 74 (See Section 10.4 of Protocol P55) on Form T55.

4.3 If there is more than 5% coarse material passing the 1 ½-in. (38-mm) sieve and retained on the No. 4 (4.75-mm) sieve, then use Method D of Protocol P55 to perform the moisture-density test. Use special comment code 75 (See Section 10.4 of Protocol P55) to record this condition on Form T55.

4.4 Discard any coarse material larger than the 1 ½-in. (38-mm) sieve size and do not use this material for the moisture-density test. Use special comment code 76 (See Section 10.4 of Protocol P55) to record this condition on Form T55.

5. PROCEDURE

5.1 Follow the same procedure as described in Section 6 of Method B and Section 4 of Method A of AASHTO T99-86, as appropriate.

5.2 The point at which the wet unit mass either decreases or does not change should be achieved within 3 to 5 water addition increments for this test. If the optimum moisture cannot be found by the fifth increment, note this using a special comment code on Form T55.

LTPP PROTOCOL P55 - METHOD "C"

Note – 4-inch (102-mm) molds will not be used in this test, therefore Method C of AASHTO T99-86 will not be used as is. However, Method C is not deleted from this protocol as part of the procedure contained in Method C (Sections 7 and 8) of AASHTO T99-86 is used in Method D.

LTPP PROTOCOL P55 - METHOD "D"

6. SAMPLE

6.1 Prepare the subgrade soil sample in accordance with Sections 4.1 and 7 of AASHTO T87-86 (Dry Preparation of Disturbed Soil and Soil Aggregate Samples for Test).

6.2 The weight of the sample should approximately be 30 lbs (14 kg). Check the gradation test results (Protocol P51) for percentage of coarse material passing the 1 ½-in. (38-mm) sieve and retained on the ¾-in. (19-mm) sieve. If this percentage is up to 5% then Method D of Protocol P55 shall be used. Include this coarse fraction in the test sample for the moisture-density test. Record this deviation from the AASHTO T99-86 standard by using special comment code 77 (See Section 10.4 of Protocol P55) on Form T55.

6.3 If there is more than 5% coarse material passing the 1 ½-in. (38-mm) sieve and retained on the ¾-in. (19-mm) sieve, then the test sample for the moisture-density testing shall be sieved using a ¾-in. (19-mm) sieve to separate the coarse fraction retained on the ¾-in. (19-mm) sieve. Discard this coarse fraction from the test sample for the moisture-density. Use special comment code 78 (See Section 10.4 of Protocol P55) to record this condition on Form T55.

6.4 Discard any coarse material larger than the 1 ½-in. (38-mm) sieve and do not use this material for moisture-density test. Use special comment code 76 (See Section 10.4 of Protocol P55) to record this condition on Form T55.

7. PROCEDURE

7.1 Same as described in Section 10.1 of Method D and Section 8 of Method C of AASHTO T99-86.

7.2 The point at which the wet unit mass either decreases or does not change should be achieved within 3 to 5 water addition increments for this test. If the optimum moisture content cannot be found by the fifth increment, note this using a special comment code on Form T55.

8. CALCULATIONS

8.1 As required in Section 11.1 of AASHTO T99-86.

9. MOISTURE - DENSITY RELATIONSHIP

9.1 Same as described in Section 12.1 of AASHTO T99-86 except: Delete "or kilograms per cubic meter".

9.2 Optimum Moisture Content - As required in Section 12.2 of AASHTO T99-86 except: Delete "or kilograms per cubic meter".

9.3 Maximum Density - As required in Section 12.3 of AASHTO T99-86.

10. REPORT

The following information is to be recorded on Form T55.

10.1 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.

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

10.3 Test Results

Report the following:

10.3.1 The method used (Method B or Method D).

10.3.2 The optimum moisture content (OMC), as a percentage, to the nearest whole number.

10.3.3 The maximum density (MD),in lb/ft3 (pcf), to the nearest whole number.

10.3.4 Attach optimum moisture content curve plot, prepared in accordance with Section 12 of AASHTO T99-86, with Form T55.

10.4 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 associated with the moisture-density testing of bulk samples of the subgrade soils are given below.

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 matter 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.).
70 Test could not be completed within five water addition increments. Additional increments were made.
71 Degradation of the test sample was observed during the moisture-density test.
72 The quantity of the test sample was inadequate to complete the moisture-density test. Additional quantity was taken from other test samples or extra material to complete the moisture-density test.
73 Free water appeared at the bottom of the mold (i.e., seeped onto the place).
74 The gradation test results (Protocol P41 and Form T41 or Protocol P51 and Form T51, as appropriate) indicate up to 5% coarse material passing the 1 ½-in. (38-mm) sieve and retained on the No. 4 (4.75-mm) sieve. This coarse fraction was included in the test sample for the moisture-density test.
75 The coarse fraction passing the 1 ½ in. (38-mm) sieve and retained on the No. 4 (4.75-mm) sieve was more than 5%. Method D was used to perform the moisture-density test.
76 The test sample contained coarse material larger than the 1 ½ in. (38-mm) sieve. This coarse material was removed and not used for the moisture-density test.
77 The gradation test results (Protocol P41 and Form T41 or Protocol P51 and Form T51, as appropriate) indicate up to 5% coarse material passing the 1 ½-in. (38-mm) sieve and retained on the ¾-in. (19-mm) sieve. This coarse material was included in the test sample for the moisture-density test.
78 The coarse fraction passing the 1 ½-in. (38-mm) sieve and retained on the ¾-in. (19-mm) sieve was more than 5%. The test sample for the moisture-density testing was sieved using a ¾-in. (19-mm) sieve to separate the coarse fraction from the test sample. This coarse fraction was discarded from the test sample and not used in the moisture-density test.

The test sample was, therefore, not truly representative of the bulk sample.

83 Due to insufficient size of the bulk sample, the test sample for the moisture-density test (Protocol P44 or P55) was saved after the test and re-used for the resilient modulus test (Protocol P46).
84 Due to insufficient size of the bulk sample; the sample for the moisture-density testing was obtained from the gradation test sample. The gradation test (Protocol P41 or P51) was performed by dry sieving only.

10.5 If the type of face of the rammer is other than 2-in. (50.8-mm) circular face described herein, please describe the rammer that was used on Form T55.

10.6 Use Form T55 (Test Sheet T55) to report the above information (Items 10.1 to 10.5).

LTPP LABORATORY MATERIAL HANDLING AND TESTING
LABORATORY MATERIAL TEST DATA
MOISTURE-DENSITY RELATIONS

LAB DATA SHEET T55

SUBGRADE SOILS

LTPP TEST DESIGNATION SS05/LTPP PROTOCOL P55

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. TEST RESULTS (Section 10.3 of Protocol P55)
      (a) METHOD USED (B or D) ___ ___
      (b) OPTIMUM MOISTURE CONTENT (OMC), % __ __. __ __.
      (c) MAXIMUM DENSITY (MD), PCF __ __ __. __ __ __.
7. COMMENTS (Section 10.4 of Protocol P55)
      (a) CODE __ __ __ __ __ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __ __ __ __ __
      (b) NOTE _____________________ ____________________
_____________________ ____________________
8. TYPE OF RAMMER FACE (If other than that described in Section 10.5 of Protocol P55) _____________________ ____________________
9. TEST DATE __ __-__ __-__ __ __ __ __ __-__ __-__ __ __ __

NOTE: 1. INCLUDE THE OPTIMUM MOISTURE CONTENT CURVE WITH TEST SHEET T55 (SECTION 10.3.6 OF PROTOCOL P55).

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

 

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