Concrete Cube Casting Procedure and frequency | Sampling of Concrete

Concrete Cube Casting Procedure and frequency is required to achieve Compressive strength result of concrete, Sampling of concrete and Concrete cube casting shall be done as per IS Code. So we described here how to sampling of concrete and concrete cube casting procedure and frequency as per IS Code.
 

What is concrete cube ?

Concrete cubes are the representative of those concrete structure for which we are casting cubes. We conduct compressive strength test on these concrete cubes and we get compressive strength value what required for a related concrete structure.
 

Why Concrete Cube Casting required?

As we described, concrete cubes represent the compressive strength of related structure from which we have taken a concrete sample and cast cubes. So that we cast concrete cubes.

Sampling of Concrete procedure IS Codes

IS Code 1199 for concrete sampling.
 

Concrete Cube Casting Procedure IS Codes

IS Code 516 for Concrete Cube Casting.
Concrete Cube Casting Procedure and frequency

Concrete sampling procedure for cube casting

Sampling of concrete for any grade shall be truly representative of the same mix. Concrete sample shall not be less than 0.02 cubic meter in volume. Concrete mix sampling shall be done from various points in the batch.
 

There are two ways of concrete sampling

 
1. Concrete Sampling from transit mixture
Take minimum three concrete sample while discharging, about the time one quarter, one half and three quarter. We should not take concrete sample from first batch while discharging. We should take concrete mix sample on a non absorbent tray.
2. Sampling of concrete at the time of placing
We should take concrete sample while placing and collect from at least five well distributed positions by avoiding segregation. We should not take sample from edge.
 

Concrete Cube Casting Apparatus and Tools Required

1. Concrete cube moulds of size ( 150 mm * 150 mm * 150 mm )
2. Temping rod ( length – 600 mm, dia – 16 mm )
3. Trowel or scoop
4. Non absorbent tray ( capacity minimum 0.02 cubic meter of concrete )
 

Precautions Before Concrete Cubes Casting

1. Use only clean concrete cube moulds otherwise clean it before use.
2. Ensure that all cube mould’s screw are properly tight.
3. Apply de-shuttering oil / agent in inner surface of cube moulds.
 
 

Concrete Cube Casting Procedure

1. Take concrete sample as we described before.
2. Mix concrete sample to avoid any segregation.
3. Concrete cube shall be casted in three approximately equal layers.
4. Start pouring concrete mix in three cube moulds up to 50 to 60 mm height for first layer.
5. Start temping minimum 35 times maximum 50 times by temping rod in uniform manner over the cross section of the mould.
6. Then pour second layer approximately 50 mm and temp between 35 to 50.
7. While temping, temping rod should not insert previous layer.
8. Same procedure shall be repeated for third layer.
9. Now top surface of concrete shall be finished with trowel or English trowel.
Concrete Cube Casting Procedure and frequency, sampling of concrete
10. If any trace or gap formed by temping rod, struct on the side of cube moulds to avoid surface voids too.
11. Place a glass plate or metal plate on the top of concrete cubes to stop moisture evaporation.
12. If you are using vibration table for cube compaction, the time for vibration should not more than one minute for each layer.
13. After casting, concrete cubes shall be placed on vibration free place or firm ground.
14. Temperature and Humidity shall be maintained where concrete cubes are placed after casting,
temperature 27 +/- 2 degree centigrade, related humidity 90 percent.
15. After 24 hours, de-mould cubes, marking shall be done and shift the concrete cubes in cube storage tank .
16. The temperature of cube storage tank water shall be 27 +/-2 degree centigrade.
 

Concrete Cube Sampling Frequency

Minimum 03 concrete cube shall be casted for each transit mixer or as per concrete structure quantity.
 

Concrete Cube Casting Frequency as per IS Code

Quantity of Concrete (cum)Number of cube required for 28 days
1 – 53
6 – 156
16 – 309
31 – 5012
51 – 10015
101 – 15018
151 – 20021
for each 50 cum increment, o3 concrete cube shall be increased.
1 Sample = 03 cubes, This concrete cube frequency for only 28 day compressive strength.
If 03 days or 07 days compressive strength required, additional concrete cubes shall be cast as per engineer’s instructions.
 
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