Property of Self Compacting Concrete

Civil Concrete Engineering

Test conducted for determine property of material

Specific gravity of cement

The property specific gravity of cement is the ratio of the weight of a given Volume of substance to the weight of an equal volume of water. It is a mere number and it denotes how many times a substance is heavy as water Specific gravity of substance=wt density of a substance/wt density of water To find the specific gravity of cement, it is required to find the weight of a certain volume cement and the weight of an equal volume of water. As property  cement reacts with water its specific gravity is determined with reference to a non reactive liquid like kerosene Specific gravity of cement with respect to kerosene=wt of cement/wt of an equal volume of kerosene To find the specific gravity of kerosene with respect to water=wt of kerosene/wt of equal volume of water The specific gravity of cement is the calculation by multiplying specific gravity of cement with respect to kerosene with specific gravity of kerosene with respect to water

Procedure:

1. Clean dry and weigh specific gravity bottle
2. Take certain quantity of cement (about one fourth of the bottle)in the bottle and weigh(w2)
3. Pour kerosene over the cement to fill the bottle and find the total weight(w3)
4. Clean the bottle thoroughly with kerosene and fill the bottle with kerosene and weigh (w4)
5. Finally clean the bottle with water and weigh(w5)

Specific gravity of coarse aggregate 20 mm size

Apparatus and materials
1. Spring balance
2. Weight balance
3. Coarse aggregate of weight 2kg
4. Bucket
5. Water tank
6. Oven

Procedure
1. Aggregate property not less than 2 kg was taken. It was carefully washed to eliminate the finer particles and dust.
2. It was then positioned in a wire basket and deep in distilled water at a temperature between 22° to 32°C.
3. Immediately after absorption, the entrapped air was removed from the sample by lifting the basket it 25 mm above the base of the tank and allowing it to drop 25 times at the rate of about one drop per sec. During the operation, caution was taken that the basket and aggregate remain completely immersed in water.
4. They were kept in water for a period of 24 ± 1/2 hours afterwards.
5. The basket and aggregate were then jolted and weighed (weight A1) in water at a temperature 22° to 32° C.
6. The basket and the aggregate were then removed from water and allowed to drain for a few minutes and then the aggregate was taken out from the basket and placed on dry cloth and the surface was gently dried with the cloth. The aggregate was transferred to the second dry cloth and further dried.
7. The empty basket was again immersed in water, jolted 25 times and weighed in water (weight A2).
8. The aggregate was exposed to atmosphere away from direct sunlight for not less than
10 minutes until it appears completely surface dry. Then the aggregate were weighed in air (weight B).
9. Then the aggregate were kept in the oven at a temperature of 100 to 110°C and maintained at this temperature for 24 ± 1/2 hours. It was then cooled in the air-tight container, and weighed (weight C).
 A= the weight in gm of the saturated aggregate in water (A1 – A2),
 B = the weight in gm of the saturated surface-dry aggregate in air, and
 C = the weight in gm of oven-dried aggregate in air.

Specific gravity of fine aggregate
Apparatus and material
1. Pycnometer bottle
2. Balance of accuracy 0.001g
3. Vacuum source
4. Fine aggregate

Procedure
1. For fine aggregate property particle size less than 4.75 mm 500 gram of sample taken.
2. The pycnometer bottle should be well washed, cleaned, dried, and weighted accurately on sensitive balance.
3. It should than be filled with water to the top of the hole, so that surface of Water in the hole is flat.
4. The pycnometer than be dried on the outside & weighted accurately.
5. About 500 grams of the above sample was transferred to the pycnometer & weighted.

6. The pycnometer was filled with water and dry air entrapped in the aggregate was
topped with water to the level or the hole in the cone as before and the entire front removed from the surface.
7. The pycnometer was dried on the outside and weighed accurately.

Silt content of fine aggregate

In this test, we take sample of fine aggregate property which is passing through out 4.5mm sieve. Then after we take sample of NaCl about 10 gram and take 250 ml water and mix the NaCl and water and shake this sample about 60 second. Now in other beaker take about 50 ml of the mixture of water and NaCl and after fill 50 ml fine aggregate in this biker.
After again fill 50 ml mixture in this biker and shake this biker. Now this sample is put on table and stable for about some time and take reading of silt content.

Specific gravity of rice husk ash

Procedure
1. Clean dry and weigh specific gravity bottle
2. Take certain quantity of rice husk ash (about one fourth of the bottle)in the bottle andweigh(w2)
3. Pour kerosene over the rice husk ash to fill the bottle and find the total weight(w3)
4. Clean the bottle thoroughly with kerosene and fill the bottle with kerosene and weigh(w4)
5. Finally clean the bottle with water and weigh(w5)

Aggregate impact value test

 This test gives a relative measure of the resistance of an aggregate to sudden shock or impact, which in some aggregates differs from its resistance to a slow compressive load
 This test is done on aggregate size passing 12.5 mm I.S. sieve and retained on 10 mm I.S. sieve
Apparatus and materials

1. Aggregate impact value testing machine

2. Balance

3. I.S sieve 12.5mm, 10mm, 2.36mm

4. Oven dried aggregate
5. Tapping rod 10mm diameter, 230mm long

Procedure

  1. Take oven dry aggregate passing through 12.5 mm sieve and retained 10 mm sieve.
  2. Fill cylindrical measure of 7.5 cm diameter and 5 cm height in three equal layers. Each layer being tamed with 25 strokes by the tamping rod.
  3. Determine the net weight of aggregate in measure w1
  4. The whole simple is filled in cylindrical steel cup fixed on the base of the machine
  5. A hammer weighting about 14 kg is raise to a height of 380 mm above the upper surface of aggregate in the cup and allows falling on aggregate.
  6. Apply 15 such blows at an interval of not less than 1 second.
  7. Sieve crushed aggregate on I.S. sieve 2.36 mm. the fraction passing the sieve is weighed W2
  8. Aggregate impact value=(W2/W1)×100
  9. The aggregate impact value should not more than 45% for aggregate use for concrete and 30% for pavement surface.

Grading of coarse aggregate
Apparatus and materials
1. I.S. sieve of size 40mm, 20mm, 12.5mm, 10mm, 4.75mm, 2.36mm.
2. Coarse aggregate
3. Vibrator

Procedure

  1. 5 kg of coarse aggregates, arranged the set of IS sieves in order with the sieve size increasing to the top, and with pan at the bottom.
  2. Before the sieves analysis was performed the Aggregate sample has to be air dried in order to avoid lumps of fine particles and to prevent clogging of finer sieves
  3. Sieving could be done either manually or mechanically.
  4. In the manual operation the sieve was shaken giving movements in all possible directions to give chance to all particles for passing.
  5. Fineness modulus of coarse aggregate determined.
  6. Fineness modulus is defined as the sum of the cumulative % retained on the sieves of standard series divided by 100.
  7. The fineness modulus is an empirical factor and can be looked upon as the massed average size of a sieve on which the material is retained, the sieves being counted from the finest

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