concretedesignlab-specificgravitytest-01

Mechanics of Materials Laboratory Notes

Civil Engineering Technology (CET) 3135

Aggregate Specific Gravity Test

Prepared by

Edward P. Steinhauser, PE

Civil Engineering Technology

September 2014

Mechanics of Materials Laboratory Notes Metropolitan State University of Denver Aggregate Specific Gravity Test Page 2 of 9 Department of Engineering Technology

INTRODUCTION

The Specific Gravity of aggregate is defined as the ratio of mass of a volume of material at a

stated temperature to the mass of the same volume of distilled water at a stated temperature

(ASTM C 125). The specific gravity generally is reported as the specific gravity at a

temperature of 20o Celsius (oC). The specific gravity can also be determined by dividing the

density of the aggregate solids (agg) (not including voids) by the density of water (w). The density of the aggregate used in the specific gravity test is the actual material density of the

aggregate without the voids. The volume of the aggregate is determined using Archimedes

principal which states that a body submerged in water will displace a volume of water equal to

the volume of the submerged mass (Serway and Beichner, 2000).

The specific gravity of the aggregate is used determine the specific volume of the coarse

aggregate and fine aggregate and to determine the approximate entrapped air content in the

concrete mix, calculations which is included in the American Concrete Institute (ACI) Standard

211 Recommended Practice for Selecting Proportions for Normal and Heavyweight Concrete. Due to the variability of aggregate strength, water absorption, and frictional properties; the material properties of different types of cement; and the type and quality of water

used; final production concrete mix designs, at times, need to be adjusted.

For the Aggregate Specific Gravity test, a 500 milliliter (mL) glass Erlenmeyer Flask (clean and

dry) will be placed on a precision scale to determine the mass in grams. The Erlenmeyer Flask

will then be filled with distilled water to the 500 mL mark (making certain that the bottom of the

meniscus is at the 500 mL mark). A vacuum pump will be used to apply a vacuum of no more

than 5 inches of mercury (Hg) (a negative pressure reading) to the distilled water in the flask to

remove entrapped air. After vacuuming, the water level will be checked to determine that it is at

500 mL mark. Any water clinging to the neck of the flask above the 500 mL mark should be

removed with a dry paper towel. The flask and the 500 mL of distilled/de-aired water will be

placed on a precision scale to determine the mass in grams. The flask will be emptied and the

flask will be filled with approximately 100 grams (+5 grams) of coarse aggregate (the actual

mass of coarse aggregate should be determined using a precision scale). The flask, with the

coarse aggregate, will be filled to the 500 mL mark with distilled water. A vacuum pump will be

used to apply a vacuum of no more than 5 inches of mercury (Hg) to the distilled water and

coarse aggregate in the flask to remove entrapped air. After vacuuming, the water level will be

checked to determine that it is at 500 mL mark. Any water clinging to the neck of the flask

above the 500 mL mark should be removed with a dry paper towel. The coarse aggregate should

be fully saturated prior to the mass determination. The flask, the coarse aggregate and the 500

mL of distilled/de-aired water will be placed on a precision scale to determine the mass in grams.

Once the masses of the flask; the flask and 500 mL of deaired and distilled water; the flask,

coarse aggregate, and 500 mL of de-aired and distilled water are determined, the specific gravity

equation is used to determine the specific gravity. The same procedure above will be used to

determine the specific gravity of the fine aggregate.


Specific Gravity of Aggregate: For the Aggregate Specific Gravity test, a 500 milliliter (mL)

glass Erlenmeyer Flask will be placed on a precision scale to determine the mass (Mfl). The flask

will then be filled with distilled water to the 500 mL mark, and the water will be de-aired using a

vacuum pump. The flask and the 500 mL of distilled/de-aired water will be placed on a

precision scale to determine the mass in grams (Mfl+w). The flask will be filled with distilled

water and 100 grams of coarse aggregate (Magg) to the 500 mL mark, and the water will be de-

aired using a vacuum pump. The flask, the coarse aggregate and the 500 mL of distilled/de-aired

water will be placed on a precision scale to determine the mass in grams (Mfl+w+agg). Once the

masses of the flask; the flask and 500 mL distilled/de-aired water; the flask, coarse aggregate,

and 500 mL distilled/de-aired water are determined, the specific gravity equation will be used to

determine the specific gravity (SG). The same procedure above will be used to determine the

specific gravity of the fine aggregate.

The specific gravity is determined by dividing the density of the aggregate solids (agg) (not including voids) by the density of water (w). This specific gravity equation is as follows.

=

It should be noted that the density of any material () is equal to the mass of the material (M) per unit volume (V) of the same material. The density equation is as follows.

=

Since the aggregate is irregularly shaped, and is difficult to measure volume with a ruler or

calipers, the volume of the aggregate is determined using Archimedes principal which states that

a body submerged in water will displace a volume of water (Vdw) equal to the volume of the

submerged mass (in our case the volume of aggregate, Vagg).

The first step is to consider the mass of the flask, coarse aggregate and water (Mfl+w+agg). This

mass is equal to the mass of the flask and water (Mfl+w) minus the mass of displaced water (Mdw)

plus the mass of aggregate (Magg) which yields the following equation.

++ = + +

Using algebra and solving the above equation for mass of displaced water (Mdw), the following

equation is obtained:

= + ++ +

Next, the volume of aggregate (Vagg) is determined and is equal to the volume of displaced water

(Vdw) using Archimedes principal. By using algebra and rearranging the above density equation,

the volume of aggregate (Vagg) is also equal to the mass of displace water (Mdw) divided by the

density of water (w). This equation is shown below.


= =

The density of the aggregate (agg) is equal to the mass of the aggregate (Magg) per unit volume of the same aggregate (Vagg). Further, substituting the volume of aggregate (Vagg) equation into

the density equation, the density equation reduces as follows.

=

=

(

)=

Substituting the mass of displaced water (Mdw) equation into the above equation, the density of

aggregate (agg) equation reduces to the following equation.

=

=

+ ++ +

Substituting the density of aggregate (agg) equation into the specific gravity (SG) equation, the following equation is obtained.

=

= (

) (

+ ++ + )

The above specific gravity (SG) further reduces to the following equation.

=

+ ++ +

The above specific gravity (SG) equation is used to calculate the specific gravity for both fine

and coarse aggregate. The specific gravity of both the fine and coarse aggregate should be

compared to reference values of specific gravity for both fine and coarse aggregate as well as the

percentage error between the experimentally determined value and the reference value.

LIST OF EQUIPMENT

Several pieces of equipment will be necessary to perform the Aggregate Specific Gravity test. A

30 minute setup up time is recommended in advance of the start of the test. The list of

equipment for this test is as follows:

1. Precision Balance with 0.01 gram readability (note: the laboratory balance has

a maximum capacity of 3000 grams do not exceed the maximum capacity).

2. One (1) 500 milliliter (mL), Erlenmeyer flask

3. One (1) 500 mL, glass beaker


4. Horsepower vacuum pump with pressure gauge

5. Vacuum hose

6. Ziploc bag with vacuum bag connector and valve attachment

7. Stirring rod

8. Distilled water

TEST PROCEDURES

Several procedural steps are necessary for the Aggregate Specific Gravity test. The test

procedures follow in similar manner with American Society for Testing and Materials (ASTM)

C 127 Standard Test Methods for Specific Gravity and Absorption of Coarse Aggregate, and

ASTM C 128 Standard Test Methods for Specific Gravity and Absorption of Fine

Aggregate. The test procedures are listed below.

1. Clean and dry the 500 milliliter (mL) glass Erlenmeyer flask and 500 mL

beaker if necessary.

2. Place 500 mL glass flask on the precision scale to determine the mass in

grams.

3. Place 500 mL glass beaker on the precision scale to determine the mass in

grams.

4. Fill the flask with distilled water to the 500 mL mark. Make certain that the

bottom of the meniscus is at the 500 mL mark.

5. Place 500 mL flask with distilled water in the Ziploc bag with vacuum bag

connector and valve attachment. Close bag to create vacuum seal. Do not tip

flask and do not cause distilled water to spill.

6. Attach one end of the vacuum hose to vacuum bag connector and valve

attachment on the Ziploc bag, and the second end of the vacuum hose to the

vacuum pump.

7. Turn vacuum pump on (plug vacuum pump into electrical outlet) and apply a

vacuum of no more than 5 inches of mercury (Hg) (a negative pressure

reading) to remove entrapped air from the distilled water in the flask. Vacuum

for approximately 2 minutes. Do not vacuum water out of flask and do not

agitate water!

8. After vacuuming, check the water level to determine that the water level is at

the 500 mL mark. If water level is low, fill flask to the 500 mL mark (bottom

of meniscus should be at 500 mL mark). Any water clinging to the neck of

the flask above the 500 mL mark should be removed with a dry paper towel.

9. Place the flask and the 500 mL of distilled/de-aired water on the precision

scale to determine the mass in grams.

10. Empty the flask of the distilled/de-aired water and dry the flask.


11. Fill the beaker with approximately 100 grams (+5 grams) of coarse aggregate.

12. Carefully pour the 100 grams of coarse aggregate into the flask and determine

the mass of coarse aggregate using the precision scale.

13. Fill the flask with the coarse aggregate to the 500 mL mark with distilled

water. Make certain that the bottom of the meniscus is at the 500 mL mark.

14. Place 500 mL flask with distilled water and coarse aggregate in the Ziploc bag

with vacuum bag connector and valve attachment. Close bag to create

vacuum seal. Do not tip flask and do not cause distilled water to spill.

15. Attach one end of the vacuum hose to vacuum bag connector and valve

attachment on the Ziploc bag, and the second end of the vacuum hose to the

vacuum pump.

16. Turn vacuum pump on (plug vacuum pump into electrical outlet) and apply a

vacuum of no more than 5 inches of mercury (Hg) (a negative pressure

reading) to remove entrapped air from the distilled water in the flask. Vacuum

for approximately 2 minutes. Do not vacuum water out of flask and do not

agitate water!

17. After vacuuming, check the water level to determine that the water level is at

the 500 mL mark. If water level is low, fill flask to the 500 mL mark (bottom

of meniscus should be at 500 mL mark). Any water clinging to the neck of

the flask above the 500 mL mark should be removed with a dry paper towel.

18. Place the flask with the coarse aggregate and the 500 mL of distilled/de-aired

water on the precision scale to determine the mass in grams.

19. Compute the Specific Gravity of the coarse aggregate

20. At the completion of the test, dispose of the coarse aggregate test as directed

by the laboratory coordinator.

21. Repeat the above procedures for the fine aggregate.

CALCULATIONS & RESULTS

A number of calculations should be performed for the Results section of this laboratory. The

calculations and results for this laboratory report should include:

1. A table should be generated that includes the following data: Aggregate Type; Mass of Aggregate (both fine and coarse aggregate); Mass of Flask; Mass of Flask and de-

aired/distilled water; Mass of Flask, de-aired/distilled water and Aggregate (both fine and

coarse aggregate); and the Specific Gravity of both Fine and Coarse Aggregate

2. The Specific Gravity of both the Fine and Coarse Aggregate should be compared to reference values for Fine and Coarse Aggregate. The reference from which the reference

values are determined should be cited. The percent error between the experimentally

determined value and the reference value should be computed.


LABORATORY REPORT

The laboratory report should be completed following the Mechanics of Materials Laboratory

Notes titled, Report Writing Guidelines and Grading Criteria. The report should include all of the items and sections listed in the Grading Criteria/Rubric on page 7 of 8 of the Report Writing

Guidelines and Grading Criteria notes. Sections of the report that are missing will not receive

credit. In addition, tables, figures and sample calculations listed above should be included in the

final report.

REFERENCES

American Society for Testing and Materials. 2000. Annual Book of ASTM Standards. Volume

04.02. ASTM C125 Standard Terminology Relating to Concrete and Concrete Aggregates. ASTM, West Conshohocken, PA.

Serway, R.A. and Beichner, R.J. (2000). Physics for Scientists and Engineers (5th Edition), Fort

Worth, TX: Saunders College Publishing.

American Concrete Institute. 2009. ACI 211.1-91 Recommended Practice for Selecting Proportions for Normal and Heavyweight Concrete. ACI, Farmington Hill, MI.


04.02. ASTM C127 Standard Specification for Specific Gravity and Absorption of Coarse Aggregates. ASTM, West Conshohocken, PA.


04.02. ASTM C128 Standard Specification for Specific Gravity and Absorption of Fine Aggregates. ASTM, West Conshohocken, PA.

www.matweb.com (2014). AISI 1045 Steel, cold drawn.


EXAMPLE RESULTS

Table 1 below includes the results of the specific gravity test of the 1045 Steel. The table below

includes the mass and volume of the flask; mass of flask and 500 mL of water; mass of the flask,

material and water; mass of the material; experimental specific gravity; reference value of

specific gravity; and the percentage error between the experimental and reference value of

specific gravity.

Description of Material: 1045 Steel

Flask Number: 6

Flask Volume, Vfl: 500 mL

Mass of Flask, Mfl: 282.41 grams

Mass of Flask, & de-aired/distilled water, Mfl+w: 799.34 grams

Mass of Flask, Material, & de-aired/distilled water, Mfl+w+agg: 833.52 grams

Mass of Material, Magg: 39.30 grams

Specific Gravity, SG: 7.68 unitless

Reference Value - Specific Gravity#, SG: 7.87 unitless

Percent Error: 2.5 percent

# - MatWeb, 2014

Table 1 Specific Gravity Test Results of 1045 Steel


SAMPLE CALCULATIONS

Specific Gravity of 1045 Steel:

=

+ ++ +

= 39.30

799.34 833.52 + 39.30 = 7.68

Percent Error:

= 100 (. .

. )

= 100 (7.87 7.68

7.68) = 2.5

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