testing for sg and wa of coarse aggregate

8/13/2019 Testing for SG and WA of Coarse Aggregate

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I. Objective of the experiment:In this experiment we want to find the specific gravity and water absorption of coarse

aggregates, which has been place in water for 24h and after it has been dry up in the

oven. For this experiment, we based on the ASTM C127 standard method and carries

out three different separate tests for more accurate result. This experiment will also

helped us to determine and discuss about the different values due to the errors and

some other factors that has been affected during the process.

II. Introduction Specific Gravity is the characteristic that mostly used for calculation for

volume occupied by the aggregate in various mixtures that contain aggregate

such as Portland cement concrete, bituminous concrete, and other mixtures that

are proportioned or analyzed on an absolute volume basis.

Water Absorption values are widely for calculation of the proportional differentmass of an aggregate as the water is absorbed in the pore spaces within the

constituent particles, compared with dry condition, when it is deemed that the

aggregate has been in contact with water long enough to satisfy most of the

absorption potential.

These two values are very important to engineers when building structures highhumidity atmosphere and the place where there are a huge different in humidity

daily or monthly. It helps engineer to determine the correct amount of the

coarse aggregate during the mixture process so that they can get the better

quality for their concrete. Moreover, before the structures have been finished,

these values must be taken into account for calculate the total weight and

expansion of the structures when there are different in humidity in the

atmosphere.


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III. Materials and Toolsa. Sample:

Coarse Aggregate: it must be place in the tap water for at least 24h tomake sure that all of its pores have been filled with water. 3.5kg of

fine aggregate (weight before place in the tap water) is needed to carry

out 3 separate tests.

b. Apparatus:1) Balance with 0.1g precise that also can weight sample in the water2) Metal pans3) Drying oven4) High Water Absorption Towels5) Backet with holes


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IV. Procedures:1. Use the metal shovel to take out the wet coarse aggregate out of the container and

place those aggregate on the towel.

2. Then roll aggregate on that towel so that water on its surface will absorb by thetowel to dry the surface of the wet coarse aggregate to get saturated-surface-dry

aggregate (SSD)

3. Then use your hand to touch and determine if it is already has the dry surface, ifnot yet, continue step 2.

4. Use the balance to weight SSD sample in a basket about 1000g in the air and markas B.

5. After place attach that basket with the balance and place it into the water bath.Wait until there will be no more bubble coming up. Shake it gently to speed up the

process. Then wait until the number on the balance is constant. Record that

number as C1.

6. Remove the basket from the water bath then place that sample in a metal platethen put it in the oven dry.

7. Take that same empty basket and attach it to the balance then measure its weightand mark as C2

8. Subtract C2 from C1 to get the weight of coarse aggregate in the water and markas C.

9. Set the oven dry for constant temperature of 115oC and wait 24H to get the oven-dry aggregate

10. Use balance to weight the oven-dry aggregate and mark as A

! Repeat this process for 3 times


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V. DataA: Oven-dry weight

B: Weight of coarse aggregate in air

C:Weight of coarse aggregate in the water

S:Weight of saturated surface dry aggregate

1stExperiment

A1 197.3g

B1 1060.4g

C1 667.5

2nd Experiment

A2 193.6g

B2 1241.6g

C2 780g

3rd

Experiment

A3 196.2g

B3 1000.2g

C3 630.0g


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VI. CalculationSpecific Gravity of Saturated Surface Dry Fine Aggregate

SG(SSD) =S

B -C Specific Gravity of Oven Dry Fine Aggregate

SG(OD)=A

B -C

Water Absorption of Fine Aggregate

WA (%) =B - A

A!100

First Experiment

200.8( )

342.8 200.8 4652.5809

.8SG SSD = =

+ !

197.3( )

342.8 200.8 465.82.5359SG OD = =

+ !

200.8 197.3(%) 100 1.77%

197.3WA

! = " =

Second Experiment

200.2( ) 2.5932

345.3 200.2 468.3SG SSD = =

+ !

193.6( )

345.3 200.2 468.32.5077SG OD = =

+ !

200.2 193.6(%) 100 3.41%

193.6WA

! = " =

Third Experiment

201.4( ) 2.6430

353.8 201.4 479.0SG SSD = =

+ !

196.2( )

353.8 201.4 479.02.5748SG OD = =

+ !

201.4 196.2(%) 100 2.65%

196.2WA

! = " =


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Average Result:

2.5809

2.5359 2.507

2.5932 2.6430( ) 2.6057

3

( ) 2.53943

1.77 3.41 2.6

7 2.57

5(%)

48

2.61%3

avg

avg

avg

SG SSD

SG OD

WA

+

+ +

+= =

= =

+ + = =

Standard Deviation:

( )

( )

(%)

SG SSD

SG OD

WA

!

!

!

= 0.0268

= 0.0275

= 0.6701

The table shows the overall summary of the result:

1st

Experiment

2nd

Experiment

3rd

Experiment

Average Standard

Deviation

SG (SSD) 2.5809 2.5932 2.6430 2.6057 0.0268

SG (OD) 2.5359 2.5077 2.5748 2.5394 0.0275

WA (%) 1.77% 3.41% 2.65% 2.61% 0.6701


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VII. ConclusionAccording to the result from our experiments,

The average of Specific Gravity of Saturated Surface Dry Fine Aggregate is 2.6057.

The average of Specific Gravity of Oven Dry Fine Aggregate is 2.5394.

The water absorption rate of the fine aggregate is 1.77%, 3.41%, 2.65%

Discussion:

Although the result of SG of SSD and OD for each experiments are close to each

others, but there are a huge different in result of Water Absorption and has the

standard deviation up to 0.67. So the overall result of this experiment should not be

trusted or used this result for practical purpose. The experiment went wrong might be

due to:

The sample fine aggregate that we used as the sample is not pure fine aggregate,but there are some dust (diameter < 75m) that mixed with aggregate.

The sample was continuously lose during the process, which we cannot make surethat all of the sample will be transferred from one container to another container

and also amount of sample lose for each experiment is not the same.

Furthermore, at the stage of Saturated Surface Dry (SSD), the drying surface rateof the three samples are not the same.

On the other hand, there are also other factors that affect our experiments such aseye-level error during the volume of water in the volumetric flask.

The test is recommended for carry out the new experiment and might also have to

improve the efficiency but trying to minimize above factors that affect the result. Some

improvement methods are:

Wash the sample to remove all dust (diameter < 75m) before use. It can be usedthe sieving method with the sieve number 200.

Minimize the loss of the sample while trying to transfer from one container toanother container.

Use Pycnometer instead of volumetric flask as it can decrease the eye level errorand also decrease the rate of transferring the sample from volumetric flask to other

container.


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Make sure that there should not be a big different rate of SSD, by each time try tomeasure the amount of wet aggregate taken out and time to dry to be similar.

More importantly make sure the level of distribution of sample in the conical

mold process should be the same or similar. And do not place the sample without

any covering of cloth is it is not being used or pause in any cases.


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VIII. References1. Basic Construction Materials by Theodore Marotta, John C. Coffey, Cynthia

LaFleur-Brown, Christine LaPlante. 8th Ed. Pearson 2010.

2. ASTM C0128-04A Test Method for Density, Relative Density (Specific Gravity), andAbsorption of Fine Aggregate

3. FINE AGGREGATE DENSITY TESTING, WHATIS THE RIGHT WAY TO DOIT? By Chris Rogers and Tom Dziedziejko

testing for sg and wa of coarse aggregate

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