# Determination of Relative Densities and Water Absorption of Coarse Aggregates

Topics: Density, Mass, Sieve Pages: 5 (936 words) Published: November 23, 2011
Experiment Title : Determination of relative densities and water absorption of coarse aggregates.

Objective : To determine the relative densities and water absorption of a coarse aggregate. Description of Sample : The sample used was naturally occuring riverside aggregate and was left to soak for 24 hours prior to the experiment. Apparatus Required A pycnometer – a pycnometer is a litre glass jar which has a conical screw on it's lid, and a small aperature at the apex of the conical lid. The use of a pycnometer allows the same volume to be measured repeatedly. ● An electronic mass balance ● A water bottle ● A pan ● An oven ●

Procedure
This experiment was carried out under conditions of constant temperature. ●

The masses of an empty clean and dry pycnometer and pan were measured. ●

The pycnometer was carefully filled with water until an upward meniscus is formed in the aperture. Surplus water was then removed to produce a downward meniscus. ●

Then the mass of the water filled pycnometer was measured using the electronic mass balance. This value was then recorded. ●

The sample of gravel was then added to the pycnometer until it took up roughly 60% of the pyncometer. The remaining 40% being occupied by water. ●

The outside of the pycnometer was then dried thoroughly using tissue paper and then weighed using the balance. The mass was then recorded. ●

The aggregate gravel was then removed, dried and placed in the pan. The mass of this pan containig the gravel was then found and recorded. ●

Lastly the gravel was oven dried for a set period of time (1 week) and it's mass was then recorded. ●

Results
A = Mass of saturated surface dry sample = 0.766 kg B = Mass of pycnometer & sample & water = 1.9 kg C = Mass of pycnometer & water = 1.498 kg D = Mass of oven dry sample = 0.75 kg

Calculations
Relative density of oven dried sample = =
0.75 0.766−(1.9−1.498) D A−( B−C)

=

375 182

= 2.06

Relative density of saturated surface dry sample = A−(B−C) = 0.766 0.766−(1.9−1.498)

A

=

383 182 D

= 2.10

Apparent relative density = D−( B−C) =
0.75 0.75−(1.9−1.498)

=

125 58

= 2.16

Water Absorption = 100 ( A−D)
D

=

100 (0.766−0.75) 0.75

=

32 15

= 2.13%

Inaccuracies would arise if the apparatus used was not clean and dry. ●

If the pycnometer was not properly dried of any spillage water, the recorded masses would be inaccurate. ●

The lost and/or gain of some of the aggregate sample would again lead to inaccuracies in the measuring of the masses. ●

Mass plays a vital role in this experiment so the most sensitive electronic mass balance available shoud be used. ●

Experiment Title : Determination of surface index of sand.

Objective : To determine the surface index of a sample of sand. Description of Sample : The sample used was dry white – grey sand. Sand Type : Eglinton FS 1 Sand Manufacturer : Omya UK Manufacturer's Description : Specially graded dried white sand. Apparatus Required An electronic mass balance A mechanical sieve shaker ● A pan ● A graded sieve stack with varying sieve mesh sizes. ● ●

A mechanical sieve shaker imparts a vertical and lateral motion to the sieve, causing the particles to bounce and turn so as to present different orientations to the sieving surface.

Procedure
Clean all sieves and measure their individual masses using an electronic balance. ●

Arrange the sieves according to their size, placing the sieves with the largest gratings at the top, and place them on the mechanical sieve shaker. Add 2 Kg of sand to the sieves and place the lid on. ●

Turn on the mechanical sieve shaker and allow it to shake the sieves for 3 minutes.Turn off the shaker and allow the sand to settle for 1 minute. ●

Remove the lid and using the balance record the new masses for each individual sieve. ●

Results

Sieve Mesh Size 4.75 mm 2.36 mm 1.18 mm 0.6 mm 0.212 mm 0.15 mm

Initial Mass 1.380 kg 1.250 kg...