Compaction Test

STUDENT CODE OF ETHIC(SCE)

DEPARTMENT OF CIVIL ENGINEERING

CENTER OF DIPLOMA STUDY

I, hereby confess that I have prepared this report on my own effort. I also admit not to receive or give any help during the preparation of this report and pledge

that everything mentioned in the report is true.

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INTRODUCTION

Compaction of crushed aggregate/soil is a mechanical process by which the

crushed aggregate/soil are placed closely by reducing the air voids. This is turn

reduces the air voids and increased density but may also increase shear strength.

The degree of compaction is measured in terms of the dry density of the crushed

aggregate/soil. Increase in dry density of crushed aggregate/soil due to

compaction mainly depends the moisture content and the compaction effort. It is

found that with the increase moisture content at a given amount of compaction to

density of crushed aggregate/soil first increased and then decreases. There exists a

moisture content which is called optimum content OMC at which the crushed

aggregate/soil has maximum dry density.

OBJECTIVE

To determine the optimum moisture content (OMC) and maximum dry density of the

given crushed aggregate/soil sample using modified proctore compaction test.

APPARATUS

Crushed aggregate/soil

Cylinder

Scoop

Mould

Base plate

Compactor

PROCEDURE

1. Prepared all the apparatus that needed in this experiment as above.

2. Weight 6000g of aggregate/soil as a sample that was prepared by lab instructor.

3. Thoroughly mixed the selected representative sample with 1% amount sample equal

to 60ml of water dampen.

4. Form a specimen by compacted the prepared crushed aggregate/soil in the mold in

five approximate layers to give a total compacted depth of about 127mm each layer

being compacted 56 uniformly distributed blows.

Collar

Space disk with ‘T’ handle

Tray

5. Remove the extension collar, carefully trim the compacted crushed aggregate/soil

using straight Edge.

6. Weight the mold and wet soil.

7. Removed the material from the mold and take a representative sample (not less than

100g) to determine the moisture content.

8. Repeated the procedure from step 3 to 7 for four or five more samples with increased

moisture content (until 5% or 6% above the expected OMC).

9. Put all the 5 containers that have several sample into oven for the drying work.

10. Take the reading of weight of all samples that have been burn for the moisture

content.

CALCULATION

Dry density (ɣd)

Weight of empty mould = W1 (gm)

Weight of mould + wet sample = W2 (gm)

Volume of mould = V

Wet density ɣ = W 2−W 1

V( gc m3 )

Dry density ɣd = ɣ

1+ɷ

Water content

Weight of empty container = A

Weight of container + wet crushed aggregate = B

Weight of container + dry crushed aggregate = C

Water content ɷ = B−CC−A

x100

Plot the dry density (ɣd) Vs (w%) water content. Obtained the maximum dry density and

OMC from the plotted curve.

RESULTS AND ANALYSIS

Water Content % 2 4 6 8

Weight of empty mould = W1 (gm) 16600 16600 16600 16600

Weight of mould + wet sample = W2 (gm)

21150 21500 21300 21200

Volume of mould = V (cm³) 3230 3230 3230 3230


V( gc m3 )

1.41 1.52 1.46 1.42

Dry density ɣd = ɣ1+ɷ

1.21 1.01 0.97 1.18

Weight of empty container = A 0.10 0.10 0.05 0.05

Weight of container + wet crushed aggregate = B

0.45 0.25 0.20 0.35

Wt. of can + dry crushed aggregate = C 0.40 0.20 0.15 0.30


0.17 0.5 0.5 0.2

Example calculation for specimen 1% water content:

Volume of mould, V = πr2h = π (7.6)2 (17.8)

= 3230cm3


V

= 21150−166003230

= 1.41gcm3


= 0.45−0.400.40−0.10

= 0.17

Dry density ɣd = ɣ1+ɷ

= 1.411+0.17

= 1.21gcm3

DISCUSSION

From the experiment we had carried out, there are some errors had been found that

occurred during the experiment by our group, which are:

1. Parallax and zero errors.

When we measured the volume of water by measuring cylinder in this experiment,

our eyes are not perpendicular to the reading on the measuring cylinder. It will

cause the accuracy of water content. Other than that, the water in the measuring

cylinder should be fully transferred to avoid low accuracy of result. To overcome

these problems, we must ensure that our eyes are perpendicular to the reading and

make sure the water is fully transferred. Thus, the result will be more accurate.

2. Random error.

When we operated the metal rammer freefall for compaction on soil in the mould,

we may accidentally freefall the rammer before we had pulled it until it maximum

height. Actually, this will affect the force of compaction on the soil that will cause

the lower accuracy of result. We can increase the accuracy by repeat the

experiment and take the average result. On the other hands, we may also ensure we

had pulled the metal rammer until design height before freefall for compaction.

3. Systematic error.

When we weighted the container and the soil, the balance may not show the

exactly reading. There may be some residue left on the balance and some air

resistances affect the balance reading. Hence, the result of the weighting will be

affected. We can increase the accuracy of the experiment by repeating the

experiment and carry the weighting process in an enclosed room without air

resistance.

Documents

Compaction Test