POLYTECHNIC UNIVERSITY OF THE PHILIPPINESCOLLEGE OF ENGINEERING

DEPARTMENT OF CIVIL ENGINEERING

Experiment No. 2.5:COARSE AND FINE AGGREGATES

OBJECTIVE

At the end of the experiment, the student should be able

1. to perform unit weight test of aggregate

2. to determine the unit weight of aggregates which will be used in the design mix

proportion of portland cement concrete

APPARATUS

1. balance (accuracy is 0.1% of test load)

2. tamping rod

3. measure

4. straight edge

5. shovel

6. scoop

DISCUSSION

The unit weight of a material can be defined as the weight of a given volume of

graded aggregate. It effectively measures the volume that the graded aggregate will

occupy in concrete and includes both the solid aggregate particles and the voids between

them.

The unit weighs of fine and coarse aggregates within the ASTM grading limits are

generally in the range of 1450 – 1750 kilograms per cubic meter of fine and coarse

aggregates show that unit weight is maximum if fine is 35 to 40 % by weight of the total

aggregates. This is so because such blends will a produce a minimum percentage of

voids.

The unit weight values are used in designing concrete mixtures. Voids in between

aggregate particles which will be filled by the mortar can also be calculated.

The unit weight of aggregates are affect by 1) degree of compaction – the greater

the compaction, the higher is the unit of weight; 2) grading – properly graded aggregates

has less amount of voids hence higher unit weight; 3) shape of particles – rounded

particles will produce less voids than angular particles.

CALIBRATION OF MEASURE

1. Weigh the measure. (Wm)

2. Fill the measure to the brim.

3. Cover it with a piece of glass plate in such a way as to eliminate bubbles and

excess water.

4. Weigh the water and measure. (Ww)

5. Take the temperature of the water and determine its unit weight (qw) from table 3,

interpolating if necessary.

6. Calculate the volume of the measure. (V)

PROCEDURE

Rodding Procedure

This is applicable to aggregates having a maximum size of 40mm or less.

1. Fill the measure one-third full.

2. Tamp the layer of aggregate 25 times with a rod.

3. Fill the measure two-thirds full, and do step 2.

4. Fill the measure to overflowing and again do step 2.

5. Level the surface of aggregates.

a) For fine aggregate, use a straight edge.

b) For coarse aggregate use your fingers or a straight edge such that any

slight projections of the larger particles balance the voids in the

surface below the top of the measure.

6. Weigh the measure and the aggregate. (Wl)

7. Determine the compact unit weight of the aggregate by rodding.

CALCULATION

Where:

V = Volume of the measure (m3)

Ww = Weight of the measure and water (kg)

Wm = Weight of the measure (kg)

qw = Unit weight of water (kg/m3)

Where:

qi = Unit weight of the aggregate.

W = Weight of the aggregate and measure

Where:

e = percentage of voids (%)

Dd = Bulk specific gravity (dry basis) pf aggregate as

determined in accordance with the previous test method

IRTC PCC 14 TEST FOR UNIT WEIGHT OF

COARSE AGGREGATES

DATA SHEET

Test Performed by: _________________________ Date Tested: _________________

Room Temperature: __________________ C Weather: ____________________

Water Temperature: __________________ C

Sample Identification ____________________________________________________

____________________________________________________

TEST NO. 1 2 3

1. Volume of Container, cu. M.

2. Weight of Container, kg

3. Wt of Container + Wt of Gravel, kg

4. Wt of Gravel = [3] – [2], kg

5. Unit Weight = [4]/[1], kg/cu. m

6. Average Unit Weight, kg/cu. m.

COMPUTATIONS / REMARKS