To determine Specific Gravity and Water Absorption of Coarse Aggregate.

To determine Specific Gravity and Water Absorption of Coarse Aggregate.

INTRODUCTION TO SPECIFIC GRAVITY:

The suitability of a building material especially the stones or the bricks for uses that are specially subjected to dampness is determined by the degree of heaviness concerning some standard material. This generally gives a relative idea of the amount of minerals compacted in unit mass. Also, it gives the relative heaviness of one stone or brick. For this purpose, the stones or bricks are tested for their specific gravity.

Apparatus Required:

• Balance, oven, net bucket, a tray-tight container large enough to take up the sample, filter paper, and funnel.

Materials Required:

• Coarse Aggregates from different sources.

THEORY:

Specific Gravity: Specific Gravity is defined as the ratio of the density of a solid (mass of solid) to the density of water at a specific temperature (generally at 4°C). It has a dimensionless unit. It determines how much a stone is heavier than water. Compact and heavier stones have higher specific gravity. It varies from 2.4 to 2.8. Stones with higher specific gravity should be selected for foundations and hydraulic structures.
Mathematically,

Sp. Gr.= (Density of a substance / Density of water)@specific temperature

Procedure:

• Take a sample of coarse aggregates of 3 kg.
• Take the water in a bowl and the whole sample dipped into water for about 24 hours.
• After 24 hours separate the coarse aggregates from the water and dry them with the help of a towel so that touching with hands should not leave any mark water.
• Then weigh that sample which is W1 then take the weight of the netted basket in water take that weight that is putting the sample in water that weight is W3.
• Now taking that material out of the basket it should be dried in the oven for about 24 hours.
• After 24 hours that material would be again checked with oven-dried weight W4.
• Now all these weights are as follows:

Observations:

1. Surface saturated dry = W1= _ g
2. Netted basket in water = W2 = g
3. Sample with a netted basket in water = W3 = g
4. Oven-dried weight = W4 = g

Now we have to determine the specific gravity, apparent specific gravity, and water absorption of coarse aggregates. All these requirements can be obtained with the help of the formula:

Calculations:

𝐴𝑝𝑝𝑎𝑟𝑒𝑛𝑡 𝑆𝑝𝑒𝑐𝑖𝑓𝑖𝑐 𝐺𝑟𝑎𝑣𝑖𝑡𝑦 =𝑊4 / 𝑊1 − (𝑊3 − 𝑊2)

Apparent Specific gravity =

𝑊𝑎𝑡𝑒𝑟 𝐴𝑏𝑠𝑜𝑟𝑝𝑡𝑖𝑜𝑛 = ( (𝑊1 − 𝑊4 )/ 𝑊4 )* 100

Water absorption = %

Results:

• The specific gravity of coarse aggregate is = _
  1. The apparent specific gravity of coarse aggregate =
  2. Water absorption of coarse aggregate is = %

Review Questions:

1. State the significance of this test.
2. Why saturated surface-dry condition of aggregate is required for the test?
3. What is the limit for the coarse aggregates to absorb the water?
4. Does the size of coarse aggregates affect its specific gravity and apparent specific gravity? Justify your answer.