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 P56
Test Method for Densityof Subgrade Soils (SS08)

This protocol covers the test method for determining the in-place density of cohesive subgrade soils. This protocol is based upon the sample extrusion and preparation procedures described in AASHTO T208-90 (Unconfined Compressive Strength of Cohesive Soil). The test shall be performed in accordance with the following procedures on a representative subgrade sample from one of the thin-walled tube samples obtained at designated A-Type sampling locations.

1. SCOPE

1.1 This protocol covers the procedures for determining the in-place density and moisture content of cohesive subgrade soils. The test procedure utilizes subgrade samples which have been carefully extruded from thinwalled tubes, trimmed, and measured.

1.2 This test method is suitable only for non-organic soils which can retain a stable, undisturbed state when extruded and unconfined.

2. REFERENCED DOCUMENTS

2.1 AASHTO Documents:

AASHTO T208-90, Unconfined Compressive Strength of Cohesive Soil

2.2 LTPP Protocols

P49 Determination of Natural Moisture Content.

3. SIGNIFICANCE AND USE

This procedure is used to determine the density of the in-place subgrade soils.

4. APPARATUS

4.1 Sample Extruder - The sample extruder shall be capable of extruding the soil core from the sampling tube in the same direction of travel in which the sample entered the tube, at a uniform rate, and with negligible disturbance of the sample. Conditions at the time of sample removal may dictate the direction of removal, but the principal concern is to keep the degree of disturbance negligible.

4.2 Dial Comparator - The dial comparator, or other suitable device, shall be used to measure the physical dimensions of the extruded specimen to within 0.1% of the measured dimension.

Note 1 - Vernier calipers are not recommended for soft specimens, which will deform as the calipers are set on the specimen.

4.3 Balance - The balance used to weigh specimens shall determine the mass of the specimen to within 0.1% of its total mass.

4.4 Equipment - Equipment as specified in LTPP Protocol P49.

4.5 Miscellaneous Apparatus - Miscellaneous apparatus includes specimen trimming and carving tools and moisture content cans, as required.

5. PREPARATION OF TEST SPECIMENS

5.1 Specimen Size - The specimen height-to-diameter ratio shall be between 2 and 2.5.

5.2 Sample Extrusion - Handle the specimens carefully to prevent disturbance, changes in cross section, or loss of moisture content. If compression or any type of noticeable disturbance would be caused by the extrusion device, split the sample tube lengthwise or cut in small sections to facilitate removal of the specimen without disturbance. The tube specimens may be tested without trimming except for squaring off the ends. When trimming, remove any small pebbles or shells encountered. Carefully fill voids on the surface of the specimen with remolded soil obtained from the trimmings.

6. TEST PROCEDURE

6.1 Determine the mass, M1, of the moist specimen.

6.2 Determine the dimensions of the entire specimen. Determine the average height and diameter of the test specimen using the apparatus specified in 4.2. Take a minimum of three height measurements (120° apart), and at least three diameter measurements at the quarter points of the height. The dimensions shall be used to calculate the volume of the soil sample.

6.3 Determine the moisture content of the specimen in accordance with LTPP Protocol P49. The entire specimen, or a representative specimen sample, shall be used in determining the moisture content.

7. CALCULATIONS

7.1 If the entire specimen is used to determine the moisture content, the in-place dry density of the soil is expressed as the mass of the oven-dry soil divided by the total volume of soil, and is reported in pounds per cubic foot. The following equation may be used for the calculation of the density:

DD = (M2 / V) x 3.810

Where: M2 = oven-dry mass of the entire specimen, grams, and
V = volume of the specimen in cubic inches (to nearest 0.1 cubic inch).
(note: 3.810 is a factor transforming gm/in3 to pcf.)

7.2 If a representative specimen is used to determine the moisture content, calculate the oven-dry mass of the entire specimen, M2, in grams as follows:

M2 = [M1/ (100 + w)] x 100

Where: M1 = mass of entire moist specimen, g
w = moisture content of representative specimen, %, oven-dry mass basis

Then calculate the dry density, DD, of the entire specimen in pounds per cubic foot as follows:

DD = (M2 / V) x 3.810

Where: M2 = oven-dry mass of the entire specimen, grams, and
V = volume of the entire specimen in cubic inches (to nearest 0.1 cubic inch)
(note: 3.810 is a factor transforming gm/in3 to pcf.)

8. REPORT

Record the following on Form T56

8.1 Sample identification shall include: Laboratory Identification Code, Region, State, State Code, Experiment Number, SHRP ID, Field Set Number, Sampling Area Number, Layer Number, and Location Number.

8.2 Test identification shall include: LTPP Test Designation, LTPP Protocol Number, Laboratory Test Number and the Test Date.

8.3 Test Results

8.3.1 The height and diameter of the specimen, in inches, to two decimal places.

8.3.2 The mass of the moist specimen, in grams, to one decimal place.

8.3.3 The mass of the oven-dry specimen, in grams, to one decimal place.

8.3.4 The dry density of the specimen (DD), in lb/ft3 (pcf), to the nearest whole number.

8.3.5 The moisture content of the entire specimen, or representative specimen (w), as a percentage, to the nearest whole number.

8.4 Comments shall include LTPP standard comment code(s), as shown in Section 4.3 of this Guide and any other notes as required.

LTPP LABORATORY MATERIAL HANDLING AND TESTING
LABORATORY MATERIAL TEST DATA
DENSITY OF SUBGRADE SOIL

LAB DATA SHEET T56

SUBGRADE SOILS

LTPP TEST DESIGNATION SS08/LTPP PROTOCOL P56

LABORATORY PERFORMING TEST:____________________________________________________________

LABORATORY IDENTIFICATION CODE:__ __ __ __

REGION _________________ STATE ___________________ STATE CODE __ __

EXPERIMENT NO _____ SHRP ID __ __ __ __

SAMPLED BY: ______________________________________________ FIELD SET NO. __

DATE SAMPLED: __ __-__ __-__ __ __ __ SAMPLING AREA NO.: SA-______

1. LAYER NUMBER ______

2. LABORATORY TEST NUMBER __

3. LOCATION NUMBER __ __ __

4. LTPP SAMPLE NUMBER __ __ __ __

5. TEST RESULTS

  1. SPECIMEN HEIGHT, inches __ __.__ __
  2. SPECIMEN DIAMETER, inches __ __.__ __
  3. SPECIMEN MASS (moist), grams __ __ __ . __
  4. SPECIMEN MASS (oven-dry), grams __ __ __ __ . __
  5. MOISTURE CONTENT (w), % __ __.__
  6. DRY DENSITY (DD), pcf __ __ __.

7. COMMENTS

  1. CODE __ __ __ __ __ __
    __ __ __ __ __ __
  2. (b) NOTE _________________

8. TEST DATE __ __-__ __-__ __ __ __

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