MATERIALS DIVISION

MEMORANDUM

GENERAL SUBJECT: Frequency of Density Testing

NUMBER: MD 288-07

SPECIFIC SUBJECT: Materials Manual of Instructions: Section 314 Density Control and Section 317 Minimum Acceptance Sampling Requirements

DATE: April 10, 2007

DIRECTED TO: District Construction Engineers

SIGNATURE: Andrew Mergenmeier, PE

Signature on original copy of memorandum

It has been a shared view of the Materials Division and the District Materials Engineers that there has not been adequate density testing of our roadway embankments, thus reducing the quality of these structures. The following revisions to the Materials Manual of Instructions are an attempt to improve the quality control of these structures. The original testing frequency was developed at a time when density tests were conducted by labor intensive volumetric methods. With today’s technology to conduct these tests (i.e. nuclear density gauges), more density tests can be conducted with less time and labor than earlier methods. The Scheduling and Contract Division and District Construction Engineers support the revisions.

Revise paragraph 1 of Section 314 Road Sampling, Testing, and Inspection

The following section contains instructions for the density and depth control of compacted embankments and finished subgrades (density), cement or lime stabilized subgrade, consisting of material in-place or imported material other than aggregate base, subbase, or select material, treated or untreated aggregate base, subbase, and select material, and aggregate shoulder materials. The following section contains instructions for the density and depth control of compacted materials. This includes the following: embankment material; finished subgrade (prior to paving); cement and lime stabilized subgrade (consisting of material in-place or imported material other than aggregate

base, subbase or select material); stabilized or untreated aggregate base, subbase or select material; aggregate shoulder material.

Revise paragraph 3 of Section 314.01 (a)

The density of soil is defined as the weight per unit volume (lbs. per cu. ft.) (kg per cu. m.) in a oven-dry condition. of the soil (and water) per unit volume (lbs. per cu. ft.) (kg per cu. m). The dry density of a soil is defined as the weight of just the soil per unit volume (lbs. per cu. ft.) (kg per cu. m). The moisture content of a soil is the ratio of the weight of water in a soil mass versus the weight of the dry soil in that same volume, expressed as a percentage. The optimum moisture content is the moisture content at which maximum density can be achieved by a standard compaction effort. The maximum theoretical density is that density where the most soil can be compacted into a unit volume by a standard compaction effort that achieves a minimum volume of voids, and those voids are filled with water, (no air is present). The maximum theoretical density of a soil can be determined using VTM-1. The maximum theoretical density may also be determined using the One-Point Proctor Method VTM-12. The percent compaction is the ratio of the in-place density versus the maximum theoretical density expressed as a percentage.

Delete Paragraph 4 of Section 314.01(a)

Optimum moisture is that moisture content of a soil at which maximum density can be obtained under the standard compaction procedure.

Delete all of Paragraph 5 except the last sentence of Section 314.01(a)

The percentage compaction is the ratio of the dry weight of the soil (density), as placed by mechanical means, to the maximum dry weight (density) of the same soil compacted in the Laboratory under a standard procedure (AASHTO T99, Method A), or as modified. This ratio may also be determined using the One-Point Proctor Method, VTM-12, in lieu of AASHTO T99. However, i In case of determining field density by the nuclear method, the percentage compaction is determined in a somewhat different manner, as outlined in Sec. 314.01(c)(1) herein.

Revise Paragraph 7 of Section 314.01(a)

In addition to information available on soil survey reports, it may be necessary to submit representative samples of the soil to be compacted to the District Laboratory, unless the One-Point Proctor Method is used for this determination in the field. Samples submitted to the District Laboratory should be from 30 to 50 lbs. (15 to 25 kg), or one full bag. If C.B.R. tests are to be performed, 2 full sample bags are required (four full sample bags if resilient modulus testing is required). The following information shall supplement that normally given on Form TL-11 which accompanies the sample:

Delete Subsection (3) Rubber Balloon Method of Section 314.01 (c)

(3) Rubber Balloon Method When specified, field density tests by the Rubber Balloon Method will be conducted in accordance with AASHTO T205. Percentage compaction will be determined by comparing the field density obtained with the Laboratory, AASHTO T99 (VTM-1), or the One-Point Proctor, VTM-12, density.

Renumber subsection (4) Other Methods to subsection (3) in Section 314.01 (c)

(3)(4) Other Methods Other methods may occasionally be adopted for use in determining field density. The procedures outlined in pertinent instructions will be followed.

Revise paragraph 1 of subsection (1) Embankments and Finished Subgrades in Section 314.01 (d) Frequency of Field Density Tests

The minimum number of field density tests required will be one for each 10,000 cu. yds. (8,000 m3) or less of embankments, 2500 yd3 (1900 m3) or less of fill material placed, with the following additional requirements:

Revise paragraphs (a) and (b) and add new paragraph (c) of subsection (1) Embankments and Finished Subgrades in Section 314.01 (d) Frequency of Field Density Tests

(a) For fills from 500 to 2000 ft. (150 to 600 meters) in length, fill areas less than 500 ft. (150 m) in length, one density test will be required for each a minimum of 1 field density tests for every other 6-in. (150 mm) compacted layer within the top 5 ft. (1.5 m) of fill from the bottom to the top of fill starting with the second lift.

(b) For fills less than 500 to 2000 ft. (150 m) (150 to 600 meters) in length, one density test will be required for every four (4) - 6 in. (150 mm) layers from bottom to top of the fill a minimum of 2 field density tests for each 6-in. (150 mm) compacted layer within the top 5 ft. (1.5 m) of fill.

(c) For fills greater than 2000 ft. (600 m) in length, break into equal sections not to exceed 2000 ft. (600 m) and test each section in accordance with (b) above.

Revise the first paragraph under (b) in subsection (1) Embankments and Finished Subgrades in Section 314.01 (d) Frequency of Field Density Tests

The terms “embankment” and “fill” as used here used are intended to encompass the entire roadway in width, under construction between right-of-way lines, regardless of

whether the roadway is single or dual lane. For example, a dual lane fill would be considered as a single fill. However, each separate linear embankment or fill will be considered as a separate item and tested at the above specified rate, separately and independently of adjoining fills. Location of test run is to be staggered, so that the entire length, width, and depth of the fill is covered by tests, inclusive of slopes. The top, bottom, and middle of fills, and any necessary points in between, shall each be tested. When testing is not being conducted, the Inspector is to visually observe lifts being placed to ensure that proper placement and compaction procedures are being used followed.

Switch the order of the following two paragraphs in subsection (1) Embankments and Finished Subgrades in Section 314.01 (d) Frequency of Field Density Tests

In the finished subgrade in both cut and fill sections, a minimum of one test shall be made for each 1000 linear feet (300 m) of subgrade for each roadway (full width).

The amount of rock present in the embankment that will preclude conducting the density test should remain flexible, and should be at the discretion of the Project Inspector. However, it should be understood that if it is possible to conduct a test, then the test should be run. If a test can not be performed, location documentation of the rock layer shall be submitted in lieu of the test data on the appropriate density report.

Delete the 3rd paragraph of subsection (2) Cement or Lime Stabilized Subgrade in Section 314.01 (d) Frequency of Field Density Tests

The density recorded at each location will be considered as the density for the applied width of stabilization, and extending one-fourth (1/4) mile (0.5 km) longitudinally in each direction from the test location. If tests are made at closer intervals than that specified, the test data will apply to a point extending half-way between the test point and the next test point on either side.

Revise subsection (5) Backfill for Pipes and Box Culverts in Section 314.01 (d) Frequency of Field Density Tests

(5) Backfill for Pipes and Box Culverts

A minimum of one test every other compacted lift per lift on alternating sides of the Structure not to exceed for each 300 linear ft. (90 m) or portion thereof in Structure length. This test pattern will is to begin from the top of bedding material to 1 foot (0.3m) above the top of the structure. after the first 4-in. (100 mm) compacted layer above the structure’s bedding and will continue to 1 foot (0.3 m) above the top of the structure.

Revise subsection (8) Backfill for Minor Structures in section 314.01 (d) Frequency of Field Density Tests

(8) Backfill for Minor Structures Drop Inlets

To include Drop Inlets, Junction Boxes, Manholes etc. A minimum of one test per structure shall be performed. At the discretion of the engineer more tests may be necessary due to the dimensions or type of structure to be backfilled. A minimum of one test every other lift around the perimeter of the structure. The test pattern will begin after the first 4-in. (100 mm) compacted layer above the bedding and will continue to the top of the structure. Tests shall be staggered to assure consistent compactive effort has been achieved throughout.

Add new subsection (9) Backfill for Manholes in section 314.01 (d) Frequency of Field Density Tests

(9) Backfill for Manholes

Manholes shall have a minimum of one test (around the perimeter of the structure) every fourth compacted layer until the top five feet of the structure. The test pattern will begin after the first 4-in. (100 mm) compacted layer above the bedding and will continue to the top of the structure. In the top five feet one test every other lift around the perimeter of the structure.

Revise Section 317 paragraph one as follows:

Following is a condensed tabulation showing the minimum requirements for acceptance testing of soils and central-mixed aggregate. See also Secs. 205 and 206 for additional details governing minimum sampling and Independent Assurance sampling.

Revise Section 317 Summary of Minimum Acceptance Sampling Requirements.

MATERIAL AND TEST

ROAD AND BRIDGE

SPECIFICATION REFERENCE

RATE OF SAMPLING LOCATION OF

SAMPLING REMARKS

1. Embankments

(a) Density, Any Method

303.10 303.01

One test per 10,000 cu.yd. (8000 m³) 2500 yd3

(1900 m3) or less plus: (a) for fills less than 500 ft. (150 m) one test per on every other (4) - 6 in. (150 mm) layers bottom to top of fill starting with the second lift; (b) for fills from 500 to 2000 ft. (150 to 600 m), one two test per 6 in. (150 mm) layer within top 5 ft. (1.5 m) of fill; (c) for fills greater the 2000 ft (600 m), break into equal segments not to exceed 2000 ft (600 m) and use same frequency for each section as for fills 500 to 2000 ft (150 to 600 m) in length.

Roadway When tests are not run due to gravel, rock, etc. give sta. and depth on report (at the same frequency) in lieu of test, with reason. For nuclear test, use Direct Transmission Method, VTM-10. See Note 4 for reports. If there is breakdown in nuclear testing equipment, continue density tests using other approved methods.

2. Finished Sub-grade (Both Cut and Fill Sections)-

(a) Density, Any Method

305.03. One test per 1000 linear. Ft. (300 m) Roadway of roadway (24 ft.)(7.3 m).

For nuclear test, use Direct Transmission Method, VTM-10. See Note 4 for reports. If there is breakdown in nuclear testing equipment, continue density tests using other approved methods.

MATERIAL AND TEST

ROAD AND BRIDGE

SPECIFICATION REFERENCE

RATE OF SAMPLING LOCATION

OF SAMPLING

REMARKS

4. Central-Mixed Aggregate (Treated or Un-treated) (a) Base, Subbase, and Select Material-(2) Grading and Atterberg Limits

209.02, 209.08, 208.02, 208.05.

Producer: Four (4) 30 to 40 lb. (15 to 20 kg) samples per 2000 ton (2000 metric ton) lot (4000 ton (4000 metric ton) lot may be used when normal production exceeds 2000 tons (2000 metric ton) per day ). Samples taken in stratified random manner.

From processing or mixing plant. Technician.

Same as Item 4(a)(1). Samples to be taken and tested by Producer's Certified Central-Mixed Aggregate Producer shall keep records of tests on Form TL-52A and maintain quality control charts and tests results will be reported on Form TL-52B.

MATERIAL AND TEST

ROAD AND BRIDGE

SPECIFICATION REFERENCE

RATE OF SAMPLING LOCATION

OF SAMPLING

REMARKS

5.Backfill for Pipes and Box Culverts

(a) Density, Any Method

302.07

303.04 Minimum one test every third layer at random intervals per lift on alternating sides of the structure for each 300 linear feet (90m) or portion thereof in structure length, starting after first 4-inch (100 mm) layer above bedding and continue to 1 ft. (0.3 m) above the top of the structure.

Roadway For nuclear test, use Direct Transmission Method, VTM-10. See Note 4 for reports.

6.Backfill for Abutments, Gravity and Cantilever Retaining Walls

302 Minimum of two tests every other lift up to 100 linear feet (30m).

Behind Retaining Wall

7.Mechanically stabilized Earth Walls (MSE)

302 Walls less than 100 linear feet (30m) shall have a minimum of one test every other lift. Walls more than 100 linear feet (30m) shall have a minimum of two tests every other lift not to exceed 200 linear feet (60m)

Zone of Select Fill for MSE Wall

8.Backfill for Drop Inlets

302

303.04

Minimum one test every other lift around the perimeter of each structure, after first 4- inch (100 mm) layer above bedding and continue to top of structure.

Roadway To include drop inlets, junction boxes, etc.

9. Backfill for Manholes 302.03 303.04

Minimum one test (around the perimeter of the structure) every fourth compacted layer until the top five feet of the structure, after 4- inch (100 mm) layer above bedding and continue to the top five feet. Top five feet shall have one test every other lift around the structure to the top of structure.

Roadway

cy: Chief Engineer State Construction Engineer Resident Administrators Area Construction Engineers District Materials Engineers American Concrete Paving Association NE Chapter, Southern Region Virginia Dept. of Minority Business Enterprise Virginia Ready-Mixed Concrete Association Federal Highway Administration Virginia Transportation Construction Alliance Precast Concrete Association of Virginia Old Dominion Highway Contractors Association Virginia Asphalt Association