Job No. 5

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Plain & Reinforced Concrete-I Lab Manual

Job No. 5:

Standard Test Method for the Determination of Relative Density (i.e. Specific Gravity) And

Water Absorption of the Coarse Aggregates.

Code: ASTM C127-04

Scope & Significance:

In this test method we determine the relative density (i.e. Specific Gravity) and the water

absorption of the coarse aggregates. The information obtained from specific gravity is helpful in

the following ways:

The knowledge of the specific gravity is important for the concrete technologist to determinethe properties of concrete made from such aggregates.

It is used for the calculation of the volume occupied by the aggregates in various mixtures. The pores at the surface of the particles affect the bond between the aggregate and the cement

paste and thus influence the concrete strength.

Normally it is assumed that at the time of setting of concrete, the aggregate is in the saturatedand surface dry condition, If the aggregate is to be batched in the dry condition, then it is

assumed that sufficient amount of water will be absorbed from the mix to bring the aggregate

in the saturated condition. If an additional amount of water is not added as a cover for the

absorbed water, the loss of workability is resulted.

Water absorption is a measure of porosity of aggregates. Higher water absorption means more pores hence aggregates will be consider as weak. Water absorption value ranges from 0.1% - 2% for aggregates which are used in road

surfaces.

Aggregates with water absorption up to 4% are acceptable in base course.Limitation:

The limitation of the test is that, it cannot be used for the light weight aggregates.

4.1Related Theory:Aggregates:

Aggregates may be classified as:

Coarse Aggregates

Fine Aggregates

Coarse Aggregates:

Any material which is retained on BS sieve #4 (ASTM sieve 4.75mm) is known as coarse

aggregate.

Fine Aggregates:

Any material which is passing BS sieve #4 (ASTM sieve 4.75mm) is known as fine

aggregate.

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Types of Crush Available In Pakistan:

1. Sargodha Crush:Sargodha crush possess the following properties:

Greenish in color High strength Usually elongated particle.

2. Marghalla Crush:Marghalla crush possess the following Properties:

Grayish in color Low in strength.

3. SakhiSarwar Crush:SakhiSarwar crush possess the following:

Whitish in color.Absorption:

It is the increase in the mass of the aggregate due to the penetration of water into the

pores of the particles during a prescribed period of time.

The term absorption does not include the amount of water adhering to the surface of the

particles. Water absorption is expressed as percentage of the dry mass.

SaturatedSurface Dry (S.S.D.) Condition:

It is the condition related with the aggregate particles in which the permeable pores of the

aggregate particles are filled with water but without free water on the surface of the particles.

Oven Dry Density:

It is the mass of the oven dried aggregate per unit volume of the aggregate particles.

The term volume includes the volume of the permeable and the impermeable pores and does not

include the volume of the voids between the particles.

Saturated Surface Dry (S.S.D) Density:

It is the mass of the saturated surface dry aggregate per unit volume of the aggregate

particles.

The term volume includes the volume of the permeable and the impermeable pores which

are filled with water and does not include the volume of the voids between the particles.

Apparent Density:It is the mass per unit volume of the impermeable portion of the aggregate particles.

OR

It is the mass per unit volume of the solid portion of the particles excluding the voids.

Specific Gravity / Relative Density:

It is the ratio of the density of the aggregate material to the density of the gas free

distilled water at a standard temperature (i.e. 4 C).

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The relative density is a dimensionless quantity and is expressed as oven dried, saturated

surface dry and apparent.

Oven Dried Specific Gravity:

It is the ratio of the oven dried density of the aggregate to the density of the gas free


Saturated Surface Dry Specific Gravity:

It is the ratio of the saturated surface dry density of the aggregate to the density of the gas

free distilled water at a standard temperature (i.e. 4 C).

Apparent Specific Gravity:

It is the ratio of the apparent density of the aggregate to the density of the gas free


4.2Apparatus: Balance Sample container Water tank Sieves Oven

4.3Procedure:The sample of the aggregate is immersed in water for 24hrs to essentially fill all the

pores.Remove the test sample from the water and roll it in a large absorbent cloth until all

visible films of water are removed.Wipe the larger particles individually. A moving stream ofair is permitted to assist in the drying operation. Take care to avoid evaporation of water

from aggregate pores during the surface-drying operation. Determine the mass of the test

sample in the saturated surface-dry condition. Record this and all subsequent masses to thenearest 0.5 g or 0.05 % of the sample mass, whichever is greater.

In order to calculate the volume of the aggregate, immediately place the saturated-

surface-dry test sample in the sample container and determine its apparent mass in water at23 2C. Take care to remove all entrapped air before determining its mass by shaking the

container while immersed. The difference between the mass in air and the mass when the

sample is immersed in water equals the mass of water displaced by the sample. This mass of

water equals the volume of water displaced because:

water = mwater /Vwatermwater= Vwaterwater= 1gm/cm

3

Vwater= Vaggregate

Dry the test sample in the oven to constant mass at a temperature of 110 C, cool in air at

room temperature 1 to 3h, or until the aggregate has cooled to a temperature that iscomfortable to handle (approximately 50 C), and determine the mass in order to calculate

the oven dried specific gravity of the specimen.

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4.4Calculations:Coarse Aggregate

Weight of Oven Dry Sample in Air (gms) = A =

Weight of Saturated Surface Dry Sample in Air (gms) = B =Weight of Saturated Sample in Water (gms) = C =

Bulk Specific Gravity (Oven Dry) = A/(B-C)

Bulk Specific Gravity (SSD) = B/(B-C)

Apparent Specific Gravity = A/(A-C)

Water Absorption (%) = (B-A)*100/B

4.4Observations & Calculations:Calculation of Specific Gravity:(for fine aggregates)

Sr.

No.Type ofCrush

Weight of Agg.

(Wagg.)

Volume of

Water

Volume of

Water + Agg.

Volume of

Aggregate

(Vagg.)

Specific

Gravity

=

gm mL mL gm -

1 Lawrance-pur

sand

500 500 680 180 2.78

2 Lawrance-pur

sand

500 500 680 180 2.78

3 Lawrance-pur

sand

500 500 680 180 2.78

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Calculation of Specific Gravity:(for coarse aggregates)

Sr.

No.

Type of

Crush

Weight of Agg.

(Wagg.)

Volume of

Water

Volume of

Water + Agg.

Volume of

Aggregate

(Vagg.)

Specific

Gravity

=

gm mL mL gm -

Calculation of Water Absorption:

Sr.

No.

Type of

Crush

SSD Weight OD Weight

Wt. of

Absorbed

Water

Water Absorption

=

Gm gm gm -

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