Standard Test Method for The Determination of Bulk Density

PURPOSE:

To find out the Bulk Density of aggregate (i.e. unit weight and voids in aggregate).

STANDARD: 
ASTM C-29

APPARATUS:

•  Weighing Balance
•  Temping Rod
•  Measuring Cylinder
•  Shovel or stool

SCOPE AND SIGNIFICANCE:

This method is used to determine the bulk density of given specimen during the concrete mix design when the aggregate is to be batched by volume or by weight. Then it is necessary to know the mass of the aggregate that will fill the container of unit volume.

If we know the bulk density of aggregate material than we can easily calculate the mass required to fill a unit volume container.

Bulk Density also indicates the %age of voids present in the aggregate material.

This %age of voids effects the grading of the aggregate which is important in higher strength concrete.

*We will get %age voids by comparing loose state and compacted state.

RELATED THEORY:

Bulk Density:

It is the mass of the unit volume of bulk aggregate material.

The term volume includes the volume of the individual particle and the volume of the voids between the particles.

Bulk density is used in weight and volume batching both.

Absolute Density:

It is the mass per unit volume of individual particles only.

Voids:

It is a space between the individual particles and in a unit volume of the aggregate mass and is not occupied by the solid mineral matters.

*Voids within the particles are not included in the voids for the determination of bulk density by this method

Facts about Bulk Density:

Bulk Density depends upon how densely the aggregate is packed.

It also depends upon the size, distribution and shape of the particles.

If particles are of the same size then it can be packed to a limited extent but when the smaller particles are added, the voids get filled with them and thus the bulk density increases.

For a coarse aggregate a higher bulk density means that there are few voids which are to be filled by the fine aggregate and cement thus the bulk density also depend upon  the degree of packed.

PROCEDURE:

1.     Weigh the empty cylinder
2.     Calculate the volume of the empty cylinder.
3.        Take the weight of cylinder with aggregate.

*The Procedure will be same for fine and coarse aggregate.

OBSERVATIONS AND CALCULATIONS:

Table of observations for Bulk Density

Sample State	Sample Type	Wt. of container	Volume of  container	Wt. of container + wt. of agg.	Wt. of aggregate	Bulk density
		(Kg)	(m3)	(Kg)	(Kg)	(kg/m3)
LOOSE	Fine	5.7	.0035	10.60	4.9	1400
	Coarse	7.45	.0053	15.3	7.85	1481
COMPACTED	Fine	5.7	.0035	11.15	5.45	1557
	Coarse	7.45	.0053	16.20	8.75	1651

    Increase in Bulk Density (Fine aggregate) =    11.21 %

    Increase in Bulk Density (Coarse aggregate) =  11.48 %

COMMENTS:

The bulk density is more in compacted state as compared to the loose which shows that the bulk density greatly depends on the degree of compaction or how densely it is packed.            Usually increase in bulk density  should be above 15% for coarse aggregate and should be below 15% for fine aggregate, But in our results it is 11.20% for fine aggregate and 11.48% for coarse aggregate. This deficiency is may be due to not following precautions.