Suitability of Nuclear Densometer Testing on Glass Cullet ... · inch minus in size and was supplied by Stoneway Concrete Company. According to the contractor’s site superintendent,

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Suitability of Nuclear Densometer Testing on Glass Cullet Aggregate

FINAL REPORT

Prepared for

Recycling Technology Assistance Partnership (ReTAP)

A program of the Clean Washington Center,

a division of the Department of Community, Trade & Economic Development

2001 Sixth Avenue, Suite 2700

Seattle, Washington 98121

December 7, 1994

Prepared by

Dames & Moore

500 Market Place Tower

2025 First Avenue

Seattle, Washington 98 12 1

n i s recycled paper is recyclable

Copyright 01 994 by Clean Washington Center

Report No. GL-94-2

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c DAMES & MOORE 500 hlARKi.T PLACE TOWER. 2 0 3 FIRST AVENUE. SEATTLE. WASI-:!'.C~TOT 9$:?!

(206) 728-0744 FAX. (206) 727-3350

December 7, 1994

Mr. Skip Koch Clean Washington Center Department of Trade and Economic Development 2001 6th Avenue, Suite 2700 Seattle, Washington 98 121

Letter Report Geotechnicd Study Suitability of Nuclear Densimeter Testing on Glass Cullet Aggregate for The Clean Washington Center Dames & Moore Job No. 258S4-002-016

Dear Mr. Koch:

We are pleased to

Ms. Joan Wright and have

herein our letter report of a geotechnical study regard suitability of measuring ices were authorized by cullet aggregate using

ided in accordance with our proposal dated

1.0 BACKGROUND

The suitability of glass cullet as a construction aggregate was studied by the Clean Washington Center and Dames & Moore in 1993. The cullet was evaluated in terms of its engineering performance, environmental impact, cost comparability with natural aggregate, and safety in handling. The study concludes that cullet, as an aggregate is strong, clean, safe, and economical. Dames & Moore produced a total of five reports for the study:

Program Design, March 1993 0 Task 2: Environ ility Evaluation, June 1993

Task 3: Equipment Evaluation, June 1993 Task 4: Engineering suitability Evaluation, June 1993

0 Task 5: Evaluation of Cullet As A Construction Aggregate, June 1993.

During the course of the engineering suitability evaluation, a series of nuclear densometer tests were conducted to study the feasibility of using the densometer for density and moisture measurements on the cullet samples. The tests were conducted in our Seattle soil laboratory. Details of the test procedures and test results can be found in the Task 4 report referenced above.

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Department of Trade and Economic Development December 7, 1994 Page 2

The laboratory data indicated that the test results were inconclusive regarding the possible use of the nuclear densometer for the density and moisture measurements of the cullet sample. As a result, Dames & Moore recommended a further study using a field test program in which the moisture and density of the cullet fill material be tested by the nuclear densometer, as well as a parallel test using the sand replacement (sand cone) method.

2.0 SCOPE OF SERVICES

The scope of our c evaluation of the tes

1.

involved performance of in-situ tests on a cullet fill material and services included the following:

Performance of 1 (one) nuclear densometer test on the soil subgrade at a location adjacent to the fill area. The contractor compacted the subgrade prior to our test and the compactive effort was approximately the same as that used in the placement of the cullet fill.

2. Performance of a total of 12 nuclear densometer tests on the last lift of the cullet fill. The tests were conducted at four test locations. At each location four measurements were obtained with a

ned with a 6-inchdepth mode, tions were spaced at least 5 feet.

re content tests using the s at the same location.

The in-situ density and moisture content tests were c cted in accordance with the following test S:

a. Densometer - ASTM D2922-91, and ASTM D5195-91.

Each test consisted of 4 measurements, with the radioactive source of the gage pointing at the same location but the base of the gage rotated 90 degrees after each measurement.

b. Sand cone - ASTM D1556-90

Test using both the standard cone with a diameter of 6.5 inches and a larger sand cone

3. Evaluation and comparison of the test results. Development of any correlations between the test methods.

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4. Preparation of a written draft report outlining the procedure used, the results of the tests, and evaluation of the suitability of using the nuclear densometer for the density and moisture measurements of compacted crushed cullet aggregate.

Preparation of a final report incorporating Clean Washington Center’s comments to the draft report. The final report will be submitted to the Center in camera-ready form and in an ASCII file for IBM compatible computers.

5.

3.0 FIELD AND LABORATORY TESTING

LD TESTING

The field testing was conducted at the new ECO Center in Issaquah, Washington. The construction of the center utilized about 1,000 tons of cullet to raise the floor subgrade about 2.5 feet. At the time of our field test, building frames have not been erected. The cullet has been placed between foundation stem walls. The cullet was about 314- inch minus in size and was supplied by Stoneway Concrete Company. According to the contractor’s site superintendent, Mr. Ross Duncan, the cullet was placed in 8-inch lifts and compacted with several passes of both Bomag BW-60 and BW-118-AD vibratory compactors. The former weighs about 1,800 pounds and the latter weighs about 5,500 pounds.

Density testing was conducted at four locations in the building’s slab area. The tests were conducted at the top of the fill. The test locations were spaced at least 5 feet and were at least 10 feet from walls. The results are presented in Section 4.0 of this report. The following paragraphs describe the test procedures used at each test location:

1. Nuclear densometer tests were performed using three test modes: 1) backscatter mode, 2) 6-inch mode, and 3) 12-inch mode. For each test mode, a total of four measurements were obtained with the radioactive source of the gage pointing at the same location but the base of the gage rotated 90 degrees between measurements. Due to the levelness of the test surface, the tests were conducted with the gage base in direct contact with the cullet.

2. After the nuclear densometer tests, a sand cone test was conducted at the same location. A 6.5- inch-diameter sand cone was used at Test Locations 1,2 and 3. A 12-inch-diameter sand cone was used at test Location 4.

At Test Locations 3 and 4, an attempt was made to reduce the disturbance effect of the sand cone test method by freezing the cullet using dry ice. Dry ice was placed on the test surface for about two hours and was removed prior to testing. The removal of the dry ice induced an uneven test

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surface at Test Location 4. Therefore, at this location, a leveling course of fine sand about 1/4 inch in thickness was placed on the surface prior to the nuclear densometer test.

During the sand cone tests conducted at Locations 3 and 4, we found that the dry ice only froze the top two to three inches of the material.

3.2 LABORATORY TESTING

Cullet samples collected in-situ were transported to our Seattle laboratory for further testing. The tests included four moisture content determinations and one Standard Proctor Compaction test. The former was conducted according to ASTM D2216 test method, and the latter was conducted according to ASTM D698 test method.

4.0 TEST RESULTS

uclear densometer test conducted on the subgrade soil indicated a wet density of 118.3 pounds per cubic feet percent, and a dry density of 95.6 pcf.

The compaction test results for the cullet are shown on Plate 1 which is included at the end of this report. The results indicate a maximum dry density of 11 1 pcf and an optimum moisture content of 1.8 percent. According to the site superintendent, the project specification requires that the cullet fill material be compacted to at least 95

t o f t h . um dry density based on the Standard Proctor test.

The sand cone and nuclear densometer test results obtained at Test Locations 1 through 4 are summarized in Tables 1 through 4, respectively. These tables are also included at the end of the report. Three groups of data, namely, wet density, moisture content, and dry density are presented in each table. The results of the sand cone test method and the nuclear densometer test method are listed in the same column for easy comparison. As previously mentioned, the nuclear densometer tests consist of three test modes. For each test mode, a total of four measurements were obtained. The average value of the four measurements is provided. Also provided for each test mode are the standard deviation of the four measurements and the difference of the average value &om the sand cone result.

The percent compaction values that are listed for the sand cone and for each mode of the nuclear densometer test represent the ratio between the dry density obtained from the in-situ density tests and the maximum dry density obtained from the Standard Proctor compaction test. As indicated previously, for the project site where the in-situ

ucted, the required minimum level or degree of compaction is 95 percent.

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5.0 DISCUSSION AND CONCLUSIONS

5.1 DISCUSSION

An examination of the test results reveals the followings:

1.

2.

The subgrade material, on which the cullet fill was placed, is a medium firm silty soil. The nuclear densometer test results indicate a dry density of 95.6 pcf and moisture content of 23.7 percent. Based on these values and based on our observation of the subgrade material, we believe that the cullet fill material was placed on a fum base which would allow the compactive effort be transmitted to the cullet fill material. Since there were no density tests conducted at each lift during the build-up of the fill area, the effect of the subgrade to the nuclear densometer tests performed at the top lift of the fill is unknown. However, based on the 2.5 feet thickness of the fill, we believe that the subgrade effect is negligible.

When comparing the sand cone and nuclear densometer test results, we found that the nuclear densometer test method generally yield. lower density values than the sand cone method. The differences are 4.3 percent to 11.7 percent for the backscatter mode, 1.2 percent to 7.2 percent for the 6-inch mode, and 0.5 percent to 5.6 percent for the 12-inch mode. The only exception to this are the dry density results obtained at Test Location 3. With &inch and 12-inch test modes at Location 3, the nuclear densometer test method yields slightly higher density values than the sand cone method. The difference in this case is 0.6 percent to 1.8 percent.

The comparison also shows that the difference resulted from the two test methods is the highest for the backscatter mode. The difference reduces about 100 percent when the 6-inch and 12-inch modes are used.

The reasons that the nuclear densometer measures lower density values than the sand cone method are unclear. One possible source of error that may cause the difference is the disturbance effect inherent in the sand cone method. The disturbance of the side walls of the test hole may cause the side walls to deform, resulting in a smaller hole/volume and thus greater density. The use of the larger sand cone and freezing technique at Test Location 4 were to reduce the effect and tendency of disturbance. Unfortunately, based on the field observation, the dry ice did not effectively freeze the test material and the disturbance of the side walls was observed.

During the course of this study we consulted with the gage manufacturer regarding the use of nuclear densometer for density measurement on cullet. The manufacturer’s engineering personnel believe that the measurement made on cullet should have an accuracy no different than

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measurements made on natural materials such as clay, sand and gravel. The in-depth search for the factors causing the difference between the nuclear densometer and sand cone test methods is beyond the scope of this study.

One possible cause of the low density values obtained from the backscatter mode is the possible non-uniform distribution of the particles in the top lift of the fill. We surmise that the vibratory action of the compaction equipment caused the finer particles to migrate toward the bottom of the lift. This uneven distribution of particle size resulted in a larger void space in the upper portion of the lift. Consequently, the backscatter mode, which measures the density at the surface, produced lower density values than the 6-inch and 12-inch modes as expected.

The sand cone test results indicate that the in-place dry densities of the cillet range from 106.9 pcf to 115.2 pcf and the moisture contents range from 2.3 percent to 4.8 percent. Based on the maximum dry density of 11 1 pcf obtained from the Standard Proctor compaction test, these in- place dry densities indicate that the cullet fill was compacted to compaction levels range from 96.3

rcent to 103.8 percent. It is our opinion that these compaction levels are reasonable for the light and medium-weight compaction equipment used.

on the maximum dry density obtained from the Standard Proctor compaction test, the backscatter mode test results indicate that the cullet was compacted to compaction levels ranging from 91.5 percent to 99.0 percent. The results from the 6-inch mode indicate 96.8 percent to 102.2 percent compaction, and the results from the 12-inch mode indicate 98.0 percent to 101.5 percent compaction.

These results appear to indicate that the level or degree of compaction increases as the depth of the test mode increases. We believe that this trending is normal and we expect similar trending for a poorly graded, coarse natural aggregate. Also, in terms of percent compaction, the data indicate a highest degree of variation for the backscatter mode and the lowest degree of variation for the 12-inch mode.

ter test method always yields lower moisture content values than the sand e method. The differences in t e m of percentage range from 29.2 percent to 50.0 percent, but

the differences in terms of absolute value range from 1.1 percent to 1.8 percent. This difference in absolute value is small.

The nuclear densometer is designed in such way that the moisture content measurement is independent to the depth of the test mode, and the measurement always occurs at the surface. As mentioned previously, the vibratory action of the compaction equipment would cause the finer

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particles to accumulate toward the bottom of the lift. When combining the non-uniformity in particle size and the free-draining property of the cullet, we believe that the top portion of the lift would retain less moisture. Since the nuclear densometer always measures the moisture content at the top portion of the lift, and the sand cone method include material at depths, the former method generated lower moisture content than the latter.

In general, the wet density values have the similar trending as the dry density values. The results indicate that the nuclear densometer test method yields lower wet density values than the sand cone method. The differences range from 5.6 percent to 11.7 percent for the backscatter mode, 0.9 percent to 7.2 percent for the 6-inch mode, and -0.3 percent to 5.6 percent for the 12-incb mode.

The dry density values from the nuclear densometer testing are the result of an internal calculation using the measured wet density and moisture content. Assuming that the moisture content measurement is in error due to the previously mentioned non-uniformity, the dry density values can be corrected using the moisture content measured using the sand cone method. When this correction is made, the results indicate a maximum reduction of about 1.5 percent in the dry density and the percent compaction values. Note that for densometer tests with 6-inch or 12-inch modes the corrected percent compaction is still above the required 95 percent after correction.

The standard deviation the four measurements of the nuci 3.0 at Test Location 1, 1.0 to 2.7 at Test Location 2, 1.7 at Test Location 4. These values indicate relatively small dispersion of the test data.

5.

d e n s o m a tests range from 2.3 to 2 at Test Location 3, and 0.9 to 1.2

6.

5.2 CONCILJSIONS

Based on the test data and above discussion we conclude that nuclear densometer testing can be used for in-situ testing of cullet fill material. No correction to the nuclear densometer test results is required. The test should be conducted with the radioactive source extended to about the full depth of the compacted lift.

The density test results from the nuclear densometer and sand cone methods are relatively close. The former tends to generate lower density values than the latter. When used for quality control purpose, this tendency will allow the densometer to error on the conservative side.

The densometer may only be able to measure the moisture content of the cullet in the upper portion of a lift. This is likely due to the tendency of uneven particle distribution and lower moisture retention capacity in the upper portion. However, because the cullet material is in general a freedraining material, the difference in the moisture content in the upper and lower portion of a lift is small. The nuclear densometer test data have indicated that even when a higher moisture content obtained from the sand cone result is applied, the densometer test results will still

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yield compaction levels that are satisfactory for structural fill. Based on this evaluation, we conclude that moisture correction is not required.

Only one measurement is necessary at each test location. Rotating the densometer to obtain an average value of four measurements tends to improve the accuracy but may not have much effect on the compaction level. However, whenever a failed test occurs, an average value from four measurements can be considered for confmation purpose.

The test frequency should be similar to that used for regular fill control, that is, one test per lift per about 2,500 s q u m feet of fill area.

6.0 CLOSURE

It has been a pleasure to provide our services in th is matter. If you have any questions, please feel free to call.

very truly yours,

DAMES & MOORE, LNC.

C.J. Shin, Ph.D., P.E. Project Engineer

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COMPACTION TEST

MOISTURE CONTENT (“A)

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SYMBOL SAMPLE DEPTH DESCRIPTION TEST OPTIMUM MAX.DRY LOCATION (ft) METHOD MOISTURE(%) DENSITY(pcf)

1.8 111 0 Teststrip 0 3 4 inch minus wllet ASTM 0698

REMARKS :

1 0-3 1 -1 994

JOB NO. 25854-002-01 6

Densify Testing on Culler DAMES & MOORE Plate 1

Dames 8t Moore

TABLE 1 Sand Cone and Nuclear Densometer Test Results at Test Location 1

Wet Moisture Dry Density Content Density

'ercent Compac Juclear lensometer

I I"." pano Lone on ( % I 102.1 3ackscatter Mode 111.0 1.5 109.4

110.3 1.7 108.5 105.8 1.6 104.1 109.5 1.5 107.9

4verage 109.2 1.6 107.5 Standard Deviation 2.3 3ifference from sand cone result ( % I 5.8 30.4 5.1 ?ercent Compaction (%I 96.8

*

5-inch Mode 116.2 1.5 114.5 112.5 1.5 110.8 110.2 1.7 108.4 111.6 1.3 110.2

Average 11 2.6 1.5 111.0

Difference from sand cone result (%) 2.8 34.8 2.0 Percent Compaction ( % I 100.0

Standard Deviation 2.6

12-inch Mode 115.8 1.5 114.1 11 5.4 1.5 113.7 111.9 1.8 109.9 114.5 1.4 112.9

Average 114.4 1.6 11 2.7 Standard Deviation 3.0 Difference from sand cone result (%I 1.3 30.4 0.5 Percent Compaction (%I 101.5

25854002 .XLS

Dames & Moore

Nuclear Densimeter


Backscatter 114.8 3.1 111.3 113.6 3.8 109.4 114.9 3.4 111.1 111.4 3.3 107.8

Average 113.6 3.4 109.9 Standard Deviation 1.6 Difference from sand cone result (%) 5.6 29.2 4.3 Percent Compaction (%) 99.0

ontent Density

6-inch 118.1 2.9 114.8 120.2 3.3 11 6.4

111.2 114.6 3.1 114.1 2.7 111.1

Average 116.8 3.0 113.4 Standard Deviation 2.7 Difference from sand cone result (%) 2.9 37.5 1.2 Percent Compaction ( % I 102.2

114.7 2.8 111.6 116.7 3.1 113.2 114.4 3.2 110.9 114.9 2.9 111.7

Standard Deviation

25854002. XLS

Dames & Moore

Uuclear lensimeter


Backscatter 101.7 2.2 99.5 103.5 1.8 101.7 103.6 2.3 101.3 106.3 2.5 103.7

Average 103.8 2.2 101.6 Standard Deviation 1.7 Difference from sand cone result ( % I 6.1 33.3 5.0 Percent Compaction ( % I 91.5

6-inch 109.1 1.9 112.2 1.5 107.4 1.9 109.3 2.3

107.1 110.5 105.4 106.8

Average 109.5 1.9 107.5 Standard Deviation 2.2 Difference from sand cone result ( % I ' 0.9 42.4 -0.6 Percent Compaction ( % I 96.8

12-inch 110.2 1.9 112.7 1.5 108.6 1.9 111.7 2.1

108.1 111.0 106.6 109.4

Average 110.8 1.9 108.8 Standard Deviation 1.9 Difference from sand cone result (%) -0.3 2.4 -1.8 Percent Compaction ( % I 98.0

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Dames & Moore


Wet Moisture Dry

(Pet) ( % I (Peg) Density Content Density

Sand Cone 118.9 3.2 115.2 Percent Compac Nuclear Densometer

ion (%) 103.8 Backscatter 106.4 2.0 104.3

104.9 2.0 102.8 103.9 1.9 102.0 104.8 1.5 103.3

Average 105.0 1.9 103.1 Standard Deviation 1 .o Difference from sand cone result (%) 11.7 40.6 10.5 Percent Compaction ( % I 92.9

5-inch 110.8 1.6 109.1 109.4 1.6 107.7 111.8 1.6 110.0 109.3 1.7 107.5

Prverage 110.3 1.6 108.6 Standard Deviation 1.2 3ifference from sand cone result (%) 7.2 50.0 5.7 'ercent Compaction ( % I 97.8

I2-inch 111.6 1.9 109.5 113.0 1.5 111.3 113.1 1.8 111.1 111.7 1.6 109.9

4verage 112.3 1.7 110.5 Standard Deviation . 0.9 Iifference from sand cone result (%) 5.6 46.9 4.1 'ercent Compaction (%) 99.5

25854002. XLS

Documents

Suitability of Nuclear Densometer Testing on Glass Cullet ... · inch minus in size and was supplied by Stoneway Concrete Company. According to the contractor’s site superintendent,