**TEST PROCEDURES FOR CLEAN COARSE AGGREGATE AND FINE AGGREGATE**

Perform all aggregate sampling and testing in accordance with current specifications and procedures referenced in the
*NCDOT Standard Specifications for Roads and Structures, Aggregate Sampling (Roadway)* and procedures outlined in this manual.

**Aggregate for Concrete **

Hydraulic cement concrete is a mixture of cement and water paste in which aggregate particles are embedded. Aggregate is granular material such as sand, gravel, crushed stone, and blast-furnace slag that usually occupies about 75 percent of the concrete’s volume. Besides reducing volume changes due to drying shrinkage of the cement-water paste, aggregates are economical filler that reduces the cost of concrete. Aggregate properties significantly affect the workability of plastic concrete and also affect the durability, strength, thermal properties, and unit weight of hardened concrete.

**Aggregate for Asphalt Mixes **

Most of the material in an asphalt concrete mixture is aggregates. The aggregates contribute strength and stability to the completed pavement system. All of the particles needed in the aggregate that will meet specifications and do the job usually cannot be found in a single material; therefore, it becomes necessary to blend different sizes and materials in the proper quantities to produce the desired gradation.

In order to accomplish this blending process correctly, it becomes extremely important that the materials to be blended be properly sampled and the gradation or sieve size be accurately determined.

**
1. TEST PROCEDURES - CLEAN COARSE AGGREGATE**** **

The sample is obtained from a stockpile, conveyor belt, or any other location approved by the Department according to established procedures and taken to the laboratory. When sampling Clean Coarse Aggregate, follow the sampling procedures listed in

Exhibit C.

Each sample should be clearly identified by a properly filled out Sample Identification Card, (

Exhibit D).

If the sample is to be split with half to be made available to the Department use the procedures for splitting a sample (using a splitter) listed in

Exhibit D.

The split half of the Quality Control (QC) Sample, when approved by the Department on a site-by-site basis, may be force dried as long as care and judgment are taken to avoid overheating. When rapid drying a sample, follow procedures listed in

Exhibit E.

Coarse aggregate will be tested for gradation in accordance with AASHTO T 27 procedures and the wash test will be performed in accordance with AASHTO T 11.

**Washed Gradation Procedures - Clean Coarse Aggregate (AASHTO T 11) **

**Test Procedures: **

1. Once the sample is dried to a constant mass it is allowed to cool to the touch prior to proceeding with any testing procedures.

2. Split sample until a workable size of 1,000 to 2,000 grams is obtained. Follow procedures for splitting a sample described in Exhibit D.

3. Weigh and record weight of sample (Total dry Wt.).

4. Place sample in a container and cover with water to assure a thorough separation of material finer than the No. 200 sieve form the coarser particles.

5. Using a large spoon vigorously agitate contents within the container.

6. Immediately pour the wash water over a nest of sieves that are arranged with the coarser sieve on top.

7. Care should be used to avoid pouring the coarse particles out of the container.

8. Add water as previously described and repeat the procedures.

9. Repeat this process until the wash water is clear.

10. All material retained on the nested sieves shall be returned to the washed sample.

11. The washed aggregate shall be dried to a constant mass at a temperature of 110° C (+/- 5° C) [230° F (+/- 9° F) If using the Rapid Dry method follow the procedures in

Exhibit E.

12. Weigh and record weight of the sample (Wt. after washing).

13. Calculate the percent passing the No. 200 sieve.

**Calculation (formula):**

**Example: **

Assumption - a washed gradation test is performed on a sample of 57M material

Total dry Wt. = 1,520 grams

Wt. after washing = 1,515 grams

Percent Passing No. 200 Sieve = **0.3 % Passing**

**Sieve Analysis Procedures - Clean Coarse Aggregate (AASHTO T 27) **

**Test Procedures: **

1. Once the sample is dried to a constant mass it is allowed to cool to the touch prior to

proceeding with any testing procedures.

2.When testing material which 100% passes the 3/4 sieve, split the sample into a workable size of 10 to 15 pounds. Follow procedures for splitting a sample described in Exhibit D.

3. Based on the Specifications for the material being tested, the proper sieves are selected.

Additional sieve(s) may be added as needed to determine Fineness Modulus or to prevent

sieve overloading.

4. The sieves are placed into the mechanical shaker with the smallest opening on bottom and largest opening on top.

5. Weigh and record the weight of the sample.

6. Place the sample in the mechanical shaker and agitate for 10 minutes.

7. Carefully remove each sieve, weigh and record the retained material (cumulatively) using the following steps:

a. Remove the top sieve weigh and record material retained

b. Remove the next sieve from the shaker and add the retained material to the material from the first sieve.

c. Record cumulative weight from both sieves

d. Remove the next sieve from the shaker and add the retained material to the material from the two previous sieves.

e. Record cumulative weight from all three sieves

f. Repeat this process for each of the remaining sieves to the catch pan.

8. Calculate the cumulative percent retained for each sieve

9. Calculate the percent passing for each sieve.

**Example of Calculating Percent Passing: **

Assume a sieve analysis is performed on the 57M sample that was previously tested to determine the percent passing the No. 200 sieve (using the wash gradation test). Based on the test results, 0.3 percent passed the No. 200 sieve. The total weight of the (dry) sample used for the sieve analysis is
**34.1 lbs.**

Step 1 - Determine Cumulative Percent Retained for each sieve:

Example of 1” Sieve

Step 2 - Determine Percent Passing for each sieve:

**Sieve Analysis – Clean Coarse Aggregate Work Problem 1**

** **

Check the following sieve analysis of a sample to determine if it meets the minimum

specification requirements for a # 67 stone. This sample was taken at a Ready Mix Concrete Plant. Circle any sieves, if any, which exceed the minimum specifications.

Does this sample meet the minimum Specifications for # 67 stone? ________________

Note: The ½“ sieve is not a standard size for # 67 stone. The information is needed for use in design and control of plant mix asphalt.

**Sieve Analysis - Clean Coarse Aggregate Work Problem 2 **

Check the following sieve analysis of a sample to determine if it meets the minimum

specification requirements for a # 57 stone. This sample was taken at the quarry during

production. Circle any sieves, if any, which exceed the minimum specifications.

Does this sample meet the minimum Specifications for # 57 stone? ________________

**TEST PROCEDURES - FINE AGGREGATE**

The sample is obtained from a stockpile, conveyor belt, or any other location approved by the Department according to established procedures and taken to the laboratory. When sampling Fine Aggregate, follow the sampling procedures listed in

Exhibit D.

Each sample should be clearly identified by a properly filled out Sample Identification Card,

If the sample is to be split with half to be made available to the Department use the procedures for splitting a sample (using a splitter) listed in

Exhibit D.

The split half of the Quality Control (QC) Sample, when approved by the Department on a site-by-sitebasis, may be force dried as long as care and judgment are taken to avoid overheating. When rapid drying a sample, follow procedures listed in

Exhibit E.

Fine Aggregate will be tested for gradation in accordance with AASHTO T 27 procedures and the wash test will be performed in accordance with AASHTO T 11.

**Washed Gradation Procedures - Fine Aggregate (AASHTO T 11) **

**Test Procedures:**

1. Once the sample is dried to a constant mass it is allowed to cool to the touch prior to proceeding with any testing procedures.

2. Split sample until a workable size of 400 to 600 grams is obtained (Note: this sample size deviates from standard AASHTO procedures). Follow procedures for splitting a sample described in

Exhibit D.

3. Weigh and record weight of sample (Total dry Wt.).

4. Place sample in a container and cover with water to assure a thorough separation of material finer than the No. 200 sieve form the coarser particles.

5. Using a large spoon vigorously agitate contents within the container.

6. Immediately pour the wash water over a nest of sieves that are arranged with the coarser sieve on top.

7. Care should be used to avoid pouring the coarse particles out of the container.

8. Add water as previously described and repeat the procedures.

9. Repeat this process until the wash water is clear.

10. All material retained on the nested sieves shall be returned to the washed sample.

11. The washed aggregate shall be dried to a constant mass at a temperature of 110° C (+/- 5° C) [230° F (+/- 9° F) If using the Rapid Dry method follow the procedures in Exhibit D. If using the Rapid Dry method follow the procedures in Exhibit D.

12. Weigh and record weight of the sample (Wt. after washing).

13. Calculate the percent passing the No. 200 sieve.

**Calculation (formula):**

**Example: **

Assumption - a washed gradation test is performed on a sample of 2S sand

Total dry Wt. = 514 grams

Wt. after washing = 504.9 grams

**Sieve Analysis Procedures - Fine Aggregate (AASHTO T 27) **

**Test Procedures: **

1. Once the sample is dried to a constant mass it is allowed to cool to the touch prior to proceeding with any testing procedures.

2. Based on the Specifications for the material being tested, the proper sieves are selected.

Additional sieve(s) may be added as needed to determine Fineness Modulus or to prevent

sieve overloading.

3. The sieves are placed into the mechanical vibrator with the smallest opening on bottom and largest opening on top.

4. Weigh and record the weight of the sample.

5. Place the sample in the mechanical shaker and agitate for 10 minutes.

6. Carefully weigh and record the retained material on each sieve (cumulatively) using the

following steps:

a. Carefully remove the nest of sieves from the shaker.

b. Remove the top sieve weigh and record material retained

c. Remove the next sieve and add the retained material to the material from the first

d. Record cumulative weight from both sieves

e. Remove the next sieve and add the retained material to the material from the two

f. Record cumulative weight from all three sieves

g. Repeat this process for each of the remaining sieves to the catch pan.

7. Verify mass of sample prior to sieving is within 0.3% of sample mass originally placed on

nest of sieves

8. Calculate the cumulative percent retained for each sieve.

9. Calculate the percent passing for each sieve.

**Example of Calculating Percent Passing: **

Assume a sieve analysis is performed on the 2S sand sample that was previously tested to

determine the percent passing the No. 200 sieve (using the wash gradation test). Based on the test results, 1.8 percent passed the No. 200 sieve. The total weight of the (dry) sample used for the sieve analysis is
**514.0 grams**.

Step 1 - Determine Cumulative Percent Retained for each sieve:

Step 2 - Determine the Percent Passing for each sieve:

**Sieve Analysis - Fine Aggregate Work Problem 1 **

Determine if the following sieve analysis of a sample meets the minimum specification

requirements for a 2MS sand. This sample was taken at the job site prior to use. Circle sieves, if any, which exceed the minimum specifications.

Total weight of sample (oven-dried) =
**547.9 grams**

Weight of sample after washing #200 =
**506.5 grams**

Does this sample meet the minimum Specifications for 2 MS sand? ________________

**
3. FINENESS MODULUS (F.M.)**

Fineness Modulus is defined by the American Concrete Institute (ACI) as “*an empirical factor obtained by adding the total percentages (by weight) of an aggregate sample retained on each of a specified series of sieves, and dividing the sum by 100*”. Fineness Modulus (F.M.) is defined mathematically as the sum of the cumulative percentage retained on the standard sieves divided by 100. The Standard Size Sieves are 6”, 3”, 1 ½”, ¾”, 3/8”, No. 4, No. 8, No. 16, No 30, No. 50, and No. 100. It is an index to the fineness or coarseness of the aggregate. The F.M. is an index of the fineness of the aggregate and should not be less than 2.3 or more than 3.1, nor vary by more than 0.20 from batch to batch.

(**Note:** When testing the gradation, the No. 200 sieve is used as required in the Specification.

However, it is
**not** used in calculating the F.M. Do
**not** include material retained in the Pan when calculating the F.M.)

Fineness Modulus Example

Total weight of the sample (oven-dried before washing) =
**514.8 grams**

Oven dry weight (after washing #200) =
**504.0 grams**

Step 1 - Determine Cumulative Percent Retained for each sieve:

Step 2 – Determine the Fineness Modulus Index

The Fineness Modulus (F.M.) is defined mathematically as the sum of the cumulative

percentages retained on standard sieves divided by 100.

**Fineness Modulus Work Problem 1 **

Complete the following sieve analysis to determine if this sample of 2S material for use in

concrete meets minimum Specifications. This sample was taken at the job site prior to use.

Calculate the Fineness Modulus (F.M.) of this material.

Total weight of sample (oven-dried) =
**573.0 grams **

Weight of sample (after washing #200) =
**557.4 grams**

Determine the F.M. Index = _____________________________________________________

Based on the F.M. Index, this material is rated as a ___________ Sand.

A. Coarse

B. Medium

C. Fine

**AGGREGATE QC PROCESS- FLOW CHART**

**CLEAN COARSE AGGREGATE AND FINE AGGREGATE QA PROCESS – FLOWCHART**

The following flowchart summarizes the QA procedures for sampling and testing clean coarse and fine aggregate.

**Example of QC Sampling **

Scenario: Beginning the second week of January Hard Rock Quarry begins shipping 57M for the first time this calendar year. This material is being shipped to a local concrete producer, asphalt producer, and Department maintenance facility. Based on production and amount of material ordered this material will be shipped for approximately the next 3 weeks. The following tables summarize the tonnage shipped each day along with number of samples and sample numbering.

During Week 1 of this scenario 5,345 tons of 57M was shipped. Based on the minimum

sampling frequency of one sample per 2,000 tons, 2.67 samples are required. In order to prevent a possible shortage of samples we
**strongly** recommend “closing out” each week. Therefore, for this example, 3 samples are obtained and tested.

During Week 2 of this scenario 14,825 tons of material was shipped. Based on the minimum sampling frequency of one sample per 2,000 tons, 7.41 samples are required. In order to prevent a possible shortage of samples we
**strongly** recommend “closing out” each week. Therefore, for this example, 8 samples are obtained and tested.

During Week 3 of this scenario 240 tons of material was shipped for the week. Though less than 2,000 tons of material was shipped this week a minimum of one sample is required if any material is shipped. QC-12 obtained on Friday was required due to visit by a Department representative.

**
TEST PROCEDURES FOR AGGREGATE BASE PRODUCTS**

**1. Types of Aggregate Base Products**

**Aggregate Base Course (ABC)** consists of a well-graded blend of fine and coarse aggregate particles. When ABC is placed meeting the required specifications and compacted to the minimum density requirements, it functions as an excellent foundation for the pavement structure. The major structural function of an aggregate layer serving as a pavement base course or sub-base is to distribute the stresses applied to the pavement surface from traffic loading.

Aggregate Base Course can provide sufficient strength and rutting resistance to maximize

bearing capacity and reduce rutting failure within the pavement layers. A quality ABC layer can also provide additional benefits such as, controlling pumping, reducing frost action, improving drainage of surface or subsurface water, controlling volume change in the subgrade when expansive soils are present, and minimizing the lateral movement of the flexible pavement system.

**Cement Treated Base Course (CTBC)** is an aggregate base material with the addition of

cement and is generally used on highways with high traffic volumes. CTBC offers the same

benefits as ABC; however, the addition of cement provides a higher strength or bearing capacity.

**Aggregate Base Course (Modified) (ABC-M)** is an aggregate base type product with a different gradation specification when compared to ABC. ABC-M is generally used for maintenance stabilization.

**Stabilizer Aggregate (SA)** is an aggregate base type product with a different specification

requirement when compared to ABC. SA is generally used on construction projects for subgrade stabilization.

**2. Types of ABC **

**Type A ABC – Production Pile**. Type A ABC is ABC from a production pile. A production

pile can have new material added while existing material is being shipped to a customer.

Procedures for accepting material, taking roadway assurance check samples, correcting material, applying penalties, and rejecting material are provided in Exhibit I.

**Type B ABC – Approved Stockpile**. Type B ABC is ABC that is used to build an Approved

Stockpile. An Approved Stockpile differs from a production pile in that specific procedures

must be followed as it is constructed. Additional information regarding Approved Stockpiles is provided in Exhibits I and J.

When sampling aggregate base material, the sample is obtained from a stockpile, conveyor belt, or any other location approved by the Department according to established procedures and taken to the laboratory. When sampling aggregate base material, follow the sampling procedures listed in

Exhibit C.

Each sample should be clearly identified by a properly filled out Sample Identification Card, see

Exhibit D.

Use the procedures for splitting a sample (using a splitter) listed in

Exhibit D.

The Quality Control (QC) Sample, when approved by the Department on a site-by-site basis, may be force dried as long as care and judgment are taken to avoid overheating. When rapid drying a sample, follow procedures listed in

Exhibit E. If the quarry is required by the Department to test for Plasticity Index (P.I.) then the sample must be dried at a temperature not exceeding Each sample should be clearly identified by a properly filled out Sample Identification Card, see

Exhibit D.

Use the procedures for splitting a sample (using a splitter) listed in

Exhibit D.

The Quality Control (QC) Sample, when approved by the Department on a site-by-site basis, may be force dried as long as care and judgment are taken to avoid overheating. When rapid drying a sample, follow procedures listed in

Exhibit E. If the quarry is required by the Department to test for Plasticity Index (P.I.) then the sample must be dried at a temperature not exceeding 60° C or 140° F.

**3. Test Procedures – Aggregate Base Products **

**Sieve Analysis Procedures – Aggregate Base Products (AASHTO T 27) **

**Test Procedures: **

1. Once the sample is dried to a constant mass it is allowed to cool to the touch prior to proceeding with any testing procedures.

2. The 1 ½”, 1”, ¾”, ½”, 3/8”, #4 and #10 sieves are placed in the mechanical shaker with the smallest openings on bottom and largest openings on top. A pan is placed in the shaker to catch the -#10 material. The ¾” and 3/8” sieves are not necessary to determine gradation but are inserted to prevent overloading other screens.

3. Weigh and record the weight of the sample.

4. Place the sample in the mechanical shaker and agitate for 10 minutes.

5. Carefully remove each sieve, weigh and record the retained material using the following

steps:

a. Weigh and record material retained on the 1 ½” sieve

b. Add retained material from the 1” sieve to the 1 ½” material.

c. Weigh and record the cumulative weight of material retained on 1” sieve

d. Add retained material from the ¾” sieve to the 1 ½” and 1” material.

e. Add retained material from the ½” sieve to the 1 ½”, 1”, and ¾” material

f. Weigh and record as the cumulative weight of material retained on the ½” sieve

g. Add retained material from the 3/8” sieve to the 1 ½”, 1”, ¾”, and ½” material.

h. Add retained material from the #4 sieve to the 1 ½”, 1”, ¾”, ½”, and 3/8” material

i. Weigh and record the cumulative weight of material retained on the #4 sieve.

j. Add retained material from the #10 sieve to the 1 ½”, 1”, ¾”, ½”, 3/8”, and #4 material

k. Weigh and record the cumulative weigh of material retained on the #10 sieve.

l. The - #10 material in the shaker pan is reduced by splitting to a sample size of

approximately 800-1200 grams and placed in a sample can. This sample of - #10 material is used to determine the percent passing the #40 and #200 sieves and, if required, the Liquid Limit (L.L.) and Plasticity Index (P.I.).

6. Split sample until a minimum of 300 grams is obtained. The remaining - #10 material is set aside for determining Liquid Limit and Plasticity Index if required.

7. Weigh and record weight of sample (Total Dry wt., pre-washing).

8. Place sample in container and cover with water.

9. Using a large spoon vigorously agitate contents within the container to assure a thorough separation of material finer than the #200 sieve from the coarser particles.

10. Immediately pour the wash over a nest of sieves that are arranged with the coarser sieve on top (ex. #8 - #16 plus the #200 sieves).

11. Care should be used to avoid pouring the coarse particles out of the container.

12. Add water as previously described and repeat steps from 9 - 11.

13. Repeat this process until the wash water is clear.

14. All material retained on the nested sieves shall be returned to the container.

15. The washed aggregate shall be dried to a constant mass at a temperature of 110°C(+/-5°C[230°F(+/-9°)]). If using the Rapid Dry method follow procedures in Exhibit D.

16. Once the sample is dried it must be allowed to cool to the touch prior to performing any additional tests.

17. Weigh and record weight of the sample (Total Dry Wt.., after washing). Calculate the percent passing the #200 sieve.

18. Place sample in a mechanical shaker with a nest of sieves, including a catch pan, and cover plate. The sieve sizes are as follows: #30, #40, #100, and #200 (place sieves with the largest openings on top and the smallest on bottom). The #30 and #100 are included to prevent overloading the sieves.

19. The sample is screened for 10 minutes in the mechanical shaker.

20. Add the material retained on the #30 sieve to the material retained on the #40 sieve.

21. Weigh and record the material retaibned on the #40 sieve.

22. Add the material retained on the #100 sieve to the material retained on the #40 sieve.

23. Add the material retained on the #200 sieve to the #40 and #100 material.

24. Weigh and record the cumulative material from the #40, #100, and #200 sieve to determine the cumulative weight retained on the #200 sieve.

25. Verify mass of sample after sieving is within 0.3% of mass placed on nest of sieves.

26. Calculate the cumulative percent retained on each sieve to the #10 sieve.

27. Calculate the percent passing each sieve down to the #10 sieve.

28. Calculate the cumulative percent retained on the #40 and #200 sieve (- #10 material or Soil Mortar).

29. Calculate the percent passing on the #40 and #200 sieves.

30. Complete the gradation results with the percent passing for each sieve (top to bottom).

31. When reporting the #200, use the percent passing the #200 sieve by wash.

Example of Calculating Percent Passing:

Assume this sieve analysis is performed on ABC. The total weight of the (dry) sample used forthe sieve analysis is **41.4 lbs**.

Step 1 - Determine Cumulative Percent Retained for each sieve:

Example of 1" Sieve Cumulative Percent Retained

Assume this sieve analysis for the - #10 (Soil Mortar) material began with a dry weight of 320.0 grams

Step 2 - Determine Cumulative Percent Retained for the #40 and #200 sieves (- #10 material or Soil Mortar):

Example of #40 Sieve (Soil Mortar):

Step 3 - Determine Percent Passing for each sieve:

*Percent Passing = 100 - Cumulative Percent Retained*

Example of 1” Sieve

Example of #40 Sieve (Soil Mortar):

Step 4 – Determine Percent Passing for each sieve (total sample):

Percent Passing Total Sample (#40) = Percent Passing #10 x Percent Passing #40 x 100

Example: % Passing #40 (total) = 0.30 x 0.52 x 100 = 15.6 or 16 % Passing

Percent Passing Total Sample (#200) = Percent Passing #10 x Percent Passing #200 x 100

**Sieve Analysis – ABC Work Problem 1**

Assume the following results represent sample QC-20. Determine the percent passing for each sieve (including Soil Mortar). The total weight of the sample is 82.3 lbs and a 100.0 gram sample was used to test the soil mortar (#40 and #200 sieves).

**Sieve Analysis – ABC Work Problem 2 **

Assume the following results represent sample QC-21. Determine the percent passing for each sieve (including Soil Mortar). The total weight of the sample is 81.1 lbs and a 105.0 gram sample was used to test the soil mortar (#40 and #200 sieves).

**Gradation Specifications – ABC Work Problem 1**

Using the results from Work Problems 1 and 2 (QC-20 & QC-21), determine if any of the two sampling lot exceeds Specifications for Gradation. Place a single asterisk if a Gradation

Specification. The Specifications are provided and are also listed in Table I-2 Exhibit I.

(*) - Gradation Specification exceeded

**Atterberg Limit (Liquid Limit and Plasticity Index) Procedures **

If the quarry has been identified by the Department as having potential problems with Liquid

Limit (LL) or Plasticity Index (PI), the Atterberg Limits must be determined for each 6,000 tons of material shipped. The Liquid Limit is defined as the moisture content at which a soil passes from a plastic state to a liquid state and is determined by AASHTO T 89. The Plastic Limit is defined as the moisture content at which a soil passes from a semisolid state to a plastic state and is determined by AASHTO T 90. The Plasticity Index (PI) is the numerical difference between the Liquid Limit and Plastic Limit (P.I. = L.L. – P.L.).

**Obtaining - #40 Material **

To determine the Atterberg Limits, use the remaining - #10 material that was set aside while

performing the sieve analysis (Step 5 k). Since the Liquid Limit and Plasticity Index are determined on the - #40 material, the sample must be separated into two parts. This can be accomplished by sieving the material over a #40 sieve and a catch pan. The fraction retained on the #40 sieve shall be ground in a mortar with a rubber-covered pestle or suitable mechanical device in such a manner as to break up the aggregation of material particles without fracturing the individual grains. If the sample contains brittle fragments such as flakes of mica, fragment of sea shell, etc., the grinding operation shall be done carefully and with just enough pressure to free the fragments from adhering to particles of finer material. After grinding the sample, it is to be re-sieved over the #40. The grinding and sieving process are repeated until the following conditions are met:

• Repeated grinding only produces a small amount of - #40 material

• Rubbing the + #40 material between the thumb and forefinger indicates the material is clean

Once clean, the remaining + #40 material is discarded. The - #40 material (in catch pan) is

thoroughly mixed and placed into a sample can. This sample will be used to determine the

Liquid Limit and Plasticity Index and should be clearly identified.

**Inspection and adjustment of Atterberg (or Liquid Limit) Device **

The Atterberg Device shall be inspected to determine that it is in good working order, that the pin connecting the cup is not worn sufficiently to permit side play; that the screws connecting the cup to the hanger arm are tight; and that a groove has not been worn in the cup through long usage. The grooving tool shall be inspected to determine that the critical dimensions are as shown in Figure1.

By means of the gauge on the handle of the grooving tool, and the adjustment plat H Figure 1, the height to which the cup C is lifted shall be adjusted so that the point on the cup which comes in contact with the base is exactly 1 cm (0.3937 in.) above base. To adjust for the one centimeter lift, the strike point on the cup must be determined. To determine the strike point, place carbon paper between the cup and rubber base and turn the handle several times to get a carbon mark on the bottom of the cup. Place a piece of scotch tape across the middle of the carbon mark and slide the handle of the grooving tool until it touches the tape. The adjustment plate H shall then be secured by tightening the screws, I. With the gauge still in place, the adjustment shall be checked by revolving the crank rapidly several times. If the adjustment is correct, a slight ringing sound will be heard when the cam strikes the cam follower. If the cup is raised off the gauge or no sound is heard, further adjustment shall be made.

**Figure 1 – Atterberg Device**

Note: Plate “H” may be designed for using (1) one securing screw (I). An additional wear tolerance of 0.1 mm shall be allowed for dimension “b” for used grooving tools.

Feet for base shall be of resilient material.

(*) Nominal dimensions.

All tolerances specified are plus or minus (+/-) except as noted above.

**Liquid Limit Test Procedures (AASHTO T 89) **

No Liquid Limit results required if test cannot be performed (i.e. the material is non-plastic).

1. Verify the Atterberg Device is calibrated for a 1 centimeter drop of the brass cup.

2. Thoroughly mix and obtain 50 to 100 grams of the - #40 material and place it in an

evaporating dish.

3. Add water to the sample in the dish.

4. Mix the sample and water together with a spatula by stirring and kneading the sample.

5. If needed, continue adding water and mixing until the sample is near the Liquid Limit

(based on judgment and experience of person conducting test).

6. Using the spatula, place material in lower half of the brass cup using as few strokes as

possible (excess strokes will bring the water to the top of the sample).

7. Using the spatula strike off the sample to a depth of 1 centimeter in the cup.

8. Using the grooving tool, make a groove in the sample from the top to the bottom (verify

the sample and grooving tool blade are the same depth).

9. Attach the brass cup to the Atterberg Device.

10. Turn the crank 25 times at a rate of approximately 2 turns per second.

11. If the sample comes or flows together on the 25th blow between ¼” to ½” in the cup then

the material is considered to be at its liquid limit. If this does not occur on the 25th blow

then the sample will have to be dried or more water added to reach the liquid limit.

12. If repeating these steps to achieve the liquid limit, thoroughly clean and dry the grooving

tool and brass cup between each series.

13. If the requirements are met, use the spatula to obtain a slice of material which flowed

together by cutting at right angles to the groove from edge to edge (approximately 30

grams).

14. Place the sample into a moisture can or watch glass of known weight.

15. Weigh and record the weight of the sample.

16. Place the sample in an oven set at 110° C (+/- 5° C) [230° F (+/- 9° F)

for three hours or until dry.

17. Carefully (Caution: Hot) remove sample from oven.

18. Place glass on top of container to determine if moisture is forming on the glass. If

moisture forms, place sample back in oven. Repeat this process until sample is dry.

19. If dry, allow sample to cool to room temperature.

20. Weigh and record weight

21. Calculate percent of moisture and record

22. Discard material

**Plastic Limit Test Procedures (AASHTO T 90)**

Since the moisture content for the Liquid Limit is higher than the Plastic Limit this procedure

will dry the sample back to the moisture content at which the material remains plastic.

1. Take the remaining material in the brass cup (from Liquid Limit test) and form it into a

ball (approximately 15 grams).

2. Break the ball into 4 approximately equal ellipsoidal masses and place each on unglazed

paper.

3. Using your fingers, roll each ellipsoidal mass individually (on the paper) out into a 1/8”

diameter thread. Use only minimal pressure with your fingers and roll at an angle.

4. Repeat the rolling process on the paper until the material crumbles before reaching a 1/8”

diameter thread.

5. Once the first piece is rolled down collect and set it to the side. Repeat this procedure

with each of the remaining (3) pieces (Steps 3 and 4). Note: Use clean paper for each

mass “roll-down”.

6. Re-roll the total sample into one ball with your fingertips.

7. Place the sample into a moisture can or watch glass of known weight.

8. Weigh and record the weight of the sample.

9. Place the sample in an oven set at 110° C (+/- 5° C) [230° F (+/- 9° F) for three hours or

until dry.

10. Carefully (Caution: Hot) remove sample from oven.

11. Place glass on top of container to determine if moisture is forming on the glass. If

moisture forms, place sample back in oven. Repeat this process until sample is dry.

12. If dry, allow sample to cool to room temperature.

13. Weigh and record weight.

14. Calculate percent of moisture and record.

15. Discard material.

**Formulas/Calculations - Liquid Limit, Plastic Limit, and Plasticity Index:**

*Plasticity Index (PI) = Liquid Limit – Plastic Limit*

**Example of Liquid Limit, Plastic Limit, and Plasticity Index **

Based on the results of this example a Liquid Limit (LL) of 24 and a Plasticity Index (PI) of 2

would be reported.

Once the calculations are completed determine if the results exceed any of the Specifications for Liquid Limit (LL) or Plasticity Index (PI) and record the results on the appropriate form.

Procedures for accepting material, taking roadway check samples, correcting material, applying penalties and rejecting aggregate base material are provided in

Exhibit I.

**AGGREGATE BASE COURSE PRODUCTS QA SPLIT SAMPLE PROCESS – FLOWCHART **

The following flowchart summarizes the QA Split sample procedures when sampling and testing an aggregate base type product. Refer to

Exhibit F for tolerances between QC and QA test results.

**SAMPLE SELECTION, NUMBERING AND IDENTIFICATION **

A verifiable random selection process must be used when sampling base course material. Randomly

selecting a sample location prevents biased sampling and a simple procedure using random

numbers can accomplish this task. An example of computer generated numbers may be as

follows:

**CALCULATING RANDOM LOCATION TYPE A AND TYPE B ABC **

**Type A ABC Random Numbers Calculation **

Each sampling lot is to be 2,000 tons.

The following example demonstrates how random numbers are used to determine the tonnage where each sample is to be taken for Type A ABC:

Step 2 - Calculate tonnage for the sample within the first 2,000 ton lot using a random number

from columns 1 and 2 above. In this example the number is 29. Place a decimal in front to get the random number of
**0.29** Multiply the random number by the tonnage as shown below:

2,000 tons x 0.29 =
**580 tons** (Pull the sample)

Step 3 – Strike a line through the random number 29 (do not use again). Go to the next random number (52) when calculating the tonnage for the next sampling lot.

This process would be repeated for each sample.

**Type B ABC Random Numbers Calculation **

The following example demonstrates how random numbers are used to determine the location in the stockpile where each sample is to be taken for Type B ABC:

Since the sample will be taken from a Type B ABC stockpile, the width and length of the pile

will be used to determine sampling locations. For this example the pile is 200 feet in length and 100 feet in width.

Step 2 - Calculate the random length for the sample using a random number from columns 3 and 4 above. In this example the number is 52. Place a decimal in front to get the random number of **0.52**. Multiply the random number by the length of the pile (refer to the calculations below). Determine a random width by using a random number from columns 1 and 2 above. In this

example the number is 41. Place a decimal in front to get the random number of
**0.41**. Multiply the random number by the width of the pile (refer to the calculations below).

200 feet x 0.52 =
**104 feet length**

100 feet x 0.41 =
**41 feet width**

Step 3 – Measuring the calculated distances from a fixed reference point on the pile location the point for the sample. Once a reference point is established it must remain the same until the pile is approved by the Geomaterials Engineer.

Step 4 – Strike a line through the random numbers 52 and 41 (do not use again). Use the next numbers in the sequence (67 and 27) when calculating the next sample location.

This process would be repeated for each layer of the stockpile until the pile is completed and

approved by the Geomaterials Engineer.

**Random selection and numbering ABC samples – Example **

Assume: A quarry has been awarded a contract to supply ABC for a construction project this year and begins shipping March 15. This is the first ABC shipped for the calendar year. Based on the number of trucks and location of the project the Contractor is projected to place approximately 2,000 to 3,000 tons per day. In addition to this project maintenance trucks of the Department are obtaining ABC. Based on calculations the tonnage a sample is to be taken and the sample number would be as follows:

Calculations: QC-1 = 2,000 tons x 0.58 = 1160 tons

QC-2 = 2,000 tons x 0.70 = 1400 tons + 2,000 tons = 3,400 tons (pull sample the following day)

VI. References

Standard Specifications for Transportation Materials and Methods of Sampling and Testing, American Association of State Highway and Transportation Officials