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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 P42
Test Method for Hydrometer Analysisof Subgrade Soils (SS02)

This LTPP protocol covers the determination of the particle size analysis of subgrade soils by the hydrometer analysis. This protocol is based on the test standard AASHTO T88-00 (Particle Size Analysis of Soils). The test shall be carried out in accordance with this standard (AASHTO T88-00), 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.

Determination of particle size analysis using Protocol P42 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 for the subgrade layer, (3) performing the gradation test (Protocol P51) and (4) determining the Atterberg Limits (Protocol P43). The test sample for the hydrometer analysis (Protocol P42) shall be prepared at the same time as the test samples for gradation (Protocol P51) and Atterberg Limits (Protocol P43) are prepared.

The locations and sample numbers for P42 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 and reduced to a representative test size in accordance with AASHTO T248-83. Because the bulk samples are combined from several locations, 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:

a) 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. However, 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 SPS 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).

b) 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.

c) 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 describes the quantitative determination of the particle size distribution of material finer than a No. 200 (0.075-mm) sieve by hydrometer analysis according to AASHTO T88-86, and as described in this protocol.

1.2 As stated in Section 1.2 of AASHTO T88-86.

2. APPLICABLE DOCUMENTS

2.1 AASHTO standards:

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

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

2.2 LTPP Protocols:

P51 Sieve Analysis of Subgrade Soils.

P43 Determination of Atterberg Limits.

P52 Classification and Description of Subgrade Soils.

P49 Determination of Natural Moisture Content.

3. APPARATUS

The apparatus for the hydrometer analysis shall be the same as required in Section 2.1 of AASHTO T88-00.

4. DISPERSING AGENT

As required in Section 3.1 of AASHTO T88-00.

5. GENERAL REQUIREMENTS FOR WEIGHING

As stated in Section 4.1 of AASHTO T88-00.

6. TEST SAMPLES

6.1 Assign the appropriate layer number to the bulk sample of the subgrade soil that is being tested. The bulk samples are handled in the laboratory as described in Section 6.1 of Protocol P51. The following sections of this protocol refer to the combined bulk sample from one sampling area only.

6.2 A representative portion of the bulk sample for the particle size analysis shall be prepared according to the procedure described in Sections 4.1, 4.2 and 4.2.1 of AASHTO T87-86, for Dry Preparation of Disturbed Soil and Soil Aggregate Samples for Test.

6.3 The required weight of the test sample shall be selected from Section 5.1.2 of AASHTO T88-00 based on the classification of the subgrade soil as determined from Protocol P52.

6.4 A test sample shall be taken from the portion passing the No. 10 (2.00-mm) sieve. The test sample shall be weighed. The approximate weight of the test sample shall conform to the weight requirement described in Section 5.1.2 of AASHTO T88-00.

6.5 The portion of the test sample retained on the No. 10 sieve (2.00-mm) shall be discarded and the procedure described in Section 6 of AASHTO T88-00 shall not be used.

6.6 The test sample (passing the No. 10 [2.00-mm] sieve) selected in Sections 6.3 and 6.4 of this protocol shall be processed by the method described in Section 5.2 of AASHTO T87-86. Samples for hygroscopic moisture and hydrometer analysis shall be weighed immediately.

7. HYDROMETER AND SIEVE ANALYSIS OF FRACTION PASSING THE NO. 10 (2.00-mm) SIEVE

7.1 Determination of Composite Correction for hydrometer readings shall be carried out as described in Sections 7.1 to 7.3 of AASHTO T88-00.

7.2 Determination of hygroscopic moisture shall be made as described in Section 8.1 of AASHTO T88-00.

7.3 Dispersion of soil sample shall be done as required in Sections 9 or 10 of AASHTO T88-00.

7.4 Perform the hydrometer test according to Section 11 of AASHTO T88-00. The last required reading for the hydrometer test will occur at 1440 minutes (24 hours). No further readings need be obtained. If during this time frame, the percent smaller than 0.001 mm (0.04 mils) cannot be obtained, do not record an entry for the percent smaller than 0.001 mm (0.04 mils) on Form T42. Leave the data field for percent smaller than 0.001 mm (0.04 mils) blank and record a code "48" in the comments data entry field of the data sheet. The definition of code "48" is given in Section 9.4 of this protocol.

7.5 Sieve Analysis shall be conducted as described in Section 12.1 of AASHTO T88-00 except: Use the No. 40 (0.425-mm) and No. 200 (0.075-mm) sieves for the sieve analysis.

8. CALCULATIONS

8.1 Percentage of hygroscopic moisture shall be calculated as required in Sections 13.1 and 13.2 of AASHTO T88-00.

8.2 Coarse Material.

8.2.1 The portion of the test sample (retained on the No. 10 [2.00-mm] sieve), as determined in Section 6.5 of this protocol is assumed to be free of hygroscopic moisture. See Note 9 of AASHTO T88-00.

8.2.2 Correct the mass of the fraction passing the No. 10 (2.00-mm) sieve for hygroscopic moisture, determined in Section 8.1 of this protocol (Section 13 of AASHTO T88-00).

8.3 Percentage of Soil in Suspension

8.3.1 As required in Sections 15.1, 15.2, 15.2.1 of AASHTO T88-00.

8.3.2 Assume a specific gravity (G) value of 2.65 if a better estimate is not available for the specific classification of the soil type determined according to Protocol P52.

8.3.3 Convert the percentage of soil in suspension to percentage of the total sample (representative portion of the bulk sample), as determined in the sieve analysis test (Protocol P51, Form T51). This shall be accomplished by multiplying the percentage of originally dispersed soil remaining in suspension by the expression:

(Cumulative percent passing the No. 10 [2.00-mm] sieve)/100
where cumulative percentage passing the No. 10 (2.00-mm) sieve is taken from the sieve analysis test results on Form T51.

Example: 35% passing the No. 10 (2.00-mm) sieve was recorded from sieve analysis (Protocol P51) on Form T51.

The percentage of soil in suspension as determined in Section 8.3 of this protocol (Section 15.1 and 15.2 of AASHTO T88-00) should be corrected by multiplying it with 35/100 or 0.35.

8.4 Diameter of Soil Particles in Suspension - As described in Section 16 of AASHTO T88-00.

8.5 Fine sieve analysis.

8.5.1 Calculate percent particles larger than the No. 10 (2.00-mm) sieve by subtracting the percent passing the No. 10 (2.00-mm) sieve (from Form T51) from 100.

8.5.2 As described in Section 17.1 of AASHTO T88-86 using the sieves listed in Section 7.5 of Protocol P42.

8.5.3 The percent retained on each sieve (calculated in 8.5.2 of this protocol) shall be converted to the percentages of the total test sample by multiplying these values by the expression:

(Cumulative percent passing the No. 10 [2.00-mm] sieve)/100

8.6 Plotting - As described in Section 18.1 of AASHTO T88-00.

8.7 Precision - As described in Section 20 of AASHTO T88-00.

9. REPORT

The following information is to be recorded on Form T42.

9.1 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.

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

9.3 Test Results

Report the following:

9.3.1 The result from the accumulation curve (Section 19.1 of AASHTO T88-00) shall be reported as follows.

(a) Particles larger than 2 mm (No. 10 sieve)............................. percent

(b) Coarse sand, 2.0 to 0.42 mm (No. 10 to No. 40 sieve)........ percent

(c) Fine sand, 0.42 to 0.074 mm (No. 40 to No. 200 sieve)...... percent

(d) Silt, 0.074 to 0.002 mm (No. 200 sieve to 0.08 mils)........... percent

(e) Clay, smaller than 0.002 mm (0.08 mils to 0.04 mils)............ percent

(f) Colloids, smaller than 0.001 mm (0.04 mils).......................... percent

In these results: (a) shall be the same as calculated in Section 8.5.1 of this Protocol; (b) and (c) shall be the same as calculated according to Section 8.5.3 of this protocol; and (d), (e) and (f) shall be the same as obtained from the hydrometer analysis as calculated in Sections 8.3 and 8.4 of this protocol. Report (f) only if the percent smaller than 0.001 mm (0.04 mils) could be determined during the 1440 minute (24 hour) hydrometer analysis. If this item could not be determined in 1440 minutes (24 hours), do not record an entry for percent smaller than 0.001 mm (0.04 mils) on Form T42 and record a code "48" in the comments data entry field of Form T42. The definition of code "48" is given in Section 9.4 of this protocol.

9.3.2 The results of the complete mechanical analysis furnished by the combined sieve (Protocol P51) and hydrometer analysis (Protocol P42) shall be reported as follows:

(a) Gradation results based on Sections 9.3.2 of Protocol P51 (Form T51) to the appropriate number of significant digits as follows:

Sieve SizesStandard (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) __ __.__

(b) Hydrometer analysis results:

Smaller Than Percent
0.02 mm (0.8 mils) __ __.__
0.002 mm (0.08 mils) __ __.__
0.001 mm (0.04 mils) __ __.__

9.3.3 Attach a cumulative particle size gradation curve such as shown in Figure 8 of AASHTO T88-86 with Form T42.

9.4 Comments shall include LTPP standard comment code(s), as shown in Section 4.3 of this Guide and any other note as needed. Record percentage of hygroscopic moisture content as calculated in Section 8.1 of this Protocol.

An additional code for a special comment associated with this protocol is given below.

Code Comment
48 Percent smaller than 0.001 mm (0.04 mils) could not be determined in 1440 minutes (24 hours).

9.5 Use Form T42 (Test Sheet T42) to report the above information (Items 9.1 to 9.4).

LTPP LABORATORY MATERIAL HANDLING AND TESTING
LABORATORY MATERIAL TEST DATA
HYDROMETER ANALYSIS
LAB DATA SHEET T42

SUBGRADE LAYER
LTPP TEST DESIGNATION SS02/LTPP PROTOCOL P42

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 the third and fourth digit) __ __ __ __ __ __ __ __
6. PARTICLE SIZE DISTRIBUTION (Section 9.3.1 of Protocol P42)
     (a) LARGER THAN 2 mm, % __ __ __. __ __ __.
     (b) COARSE SAND, 2 TO 0.42 mm, % __ __ __. __ __ __.
     (c) FINE SAND, 0.42 TO 0.074 mm, % __ __. __ __.
     (d) SILT, 0.074 TO 0.002 mm, % __ __.__ __ __.__
     (e) CLAY, SMALLER THAN 0.002 mm, % __ __.__ __ __.__
     (f) COLLOIDS, SMALLER THAN 0.001 mm, % __ __.__ __ __.__
7. GRADATION (Section 9.3.2 (a) of Protocol P42, Test Sheet T51; See Note 1) % PASSING SIEVE SIZES 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) __ __ __. __ __ __.
⅜ in. (9.5) __ __ __. __ __ __.
#4 (4.75) __ __ __. __ __ __.
#10 (2.00) __ __ __. __ __ __.
#40 (0.425) __ __. __ __.
#80 (0.180) __ __. __ __.
#200 (0.075) __ __.__ __ __.__
8. HYDROMETER ANALYSIS (Section 9.3.2 (b) of Protocol P42; See Note 2) % SMALLER THAN
0.02 mm __ __.__ __ __.__
0.002 mm __ __.__ __ __.__
0.001 mm __ __.__ __ __.__
9. COMMENTS (Section 9.4 of Protocol P42)
     (a) CODE __ __ __ __ __ __ __ __ __ __ __ __
__ __ __ __ __ __ __ __ __ __ __ __
     (b) NOTE ___________________ __________________
     (c) HYGROSCOPIC MOISTURE CONTENT __ __.% __ __.%
10. TEST DATE __ __-__ __-__ __ __ __ __ __-__ __-__ __ __ __

NOTE: 1. RESULTS OF TEST SHEET T51 ARE ALSO REPORTED ON TEST SHEET T42 (ITEM NO. 6 OF FORM T42).

2. ATTACH A CUMULATIVE PARTICLE SIZE GRADATION CURVE OF COMBINED SIEVE AND HYDROMETER ANALYSIS (SECTION 9.3.3 OF PROTOCOL P42).

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

 

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