Cement mortar cube casting by vibration machine is required to find out the compressive strength of cement. We described full procedure of cement mortar cube casting by vibration machine as per IS code 4031.
What is cement mortar cube?
To find compressive strength for any type of cement, we cast 9 mortar cubes with the cement mortar which prepared by mixing a certain proportion of cement, water and graded sand in a procedure and circumstances. we are describing below.
Why Cement mortar cube required?
1. To ensure the compressive strength of cement
2. For concrete trial mixes
Apparatus and Tools required for Cement mortar cube casting
1. One non-porous plate for mixing cement and graded sand.
2. Two numbers of trowel.
3. Stopwatch for mixing in a time limit.
4. Weighing balance with accuracy 1 gram.
5. Standard sand, zone I, zone II and zone III confirming to IS 650-1991.
Let’s see what inside the IS 650
Nothing but just the particle size of standard sand which is
zone-I passed through 2.0 mm and retained on 1.0 mm
zone-II passed through 1.0 mm and retained on 0.5 mm
zone-III passed through 0.5 mm and retained on 90 micron,
6. Cement mortar cube Vibration machine confirming to IS 10080-1982
This IS codes 10080 – 1982 showing the manufacturing details of the vibration machine and its speed. So only the thing we have to remind that it’s speed, which shall be 12000 +/-400 rpm ( round per minute ).
7. Poking rod for poking in the mortar while vibration in vibration machine.
8. Cube moulds 9 numbers with base plates ( size described below )
9. Graduated glass for measure water, with capacity 150 to 200 ml, permissible variation shall be ± 1 ml and graduation lines of the cylinder shall be in circles and numbered.
10. Tray for weighing cement and standard sand
11. Hand gloves for safety
CEMENT MORTAR CUBE MOULD SIZE
The size of mortar cube mould is 70.6 mm * 70.6 mm*70.6 mm.
CEMENT MORTAR CUBE CASTING IS CODE
IS Code for cement mortar cube is IS 4031 part 6.
Precautions before proceeding Cement mortar cube casting
1. Non-porous plate and trowels shall be clean before starting mixing cement mortar, we should not use trowels and non-porous plate in wet condition, this moisture may affect on compressive strength of cement.
2. The temperature of the room where cement mortar mixing and cement mortar cube casting is going to be done shall be 27 +/- 2 degree Centigrade, means between 25 to 29.
3. Like temperature, Humidity is also an important factor for cement mortar cube test, humidity shall be 65 +/- 5 percent means between 60 to 70.
4. Water temperature for mixing in cement mortar shall be maintained between 25 to 29 centigrade.
5. For each cement mortar cube mould, separate weight of materials and mixing shall be done.
Procedure of Cement Mortar Cube Casting
1. For each cube 800 gram cement and standard sand required in which cement 200 gram and standard sand zone-I 200 gram, zone-II 200 gram, zone-III 200 gram.
cement – 200 gram and standard sand – 600 gram.
so “cement mortar ratio” is 1:3.
2. Water content shall be calculated as we are showing here
The formula for water content = (P/4+3)*8, where p is standard consistency of cement
if standard consistency of cement is 28 percent then
(28/4 +3)*8 = 80 gram
3. Mix cement and standard sand in dry condition first, at least one minute.
4. Cement mortar mixing time is 3 to 5 minutes, it will start when you adding water in cement and finish when put the mix in vibration machine.( important )
5. Start the stopwatch and add water in cement simultaneously.
6. Mix properly by using both trowels, it’s very important.
7. A de-shuttering agent like lubricant oil or grease shall be applied inside the cement mortar cube moulds.
8. Empty mould with base plate shall be fixed and tighten in vibration machine before mixing mortar.
Start Vibration Machine
9. After proper mixing, the cement mortar shall be placed in empty cement mortar mould fixed in vibration machine within the time limit.
10. Be ensure about the run time for vibration machine 2 minute means 120 seconds in vibration machine digital scale before start the machine.
11.After start vibration machine, temping shall be done 20 times in 8 seconds in cement mortar cube.
12. After vibration 120 seconds, cement mortar cube shall be removed from vibration machine and kept on firm ground or platform.
13.Where cement mortar cube shall be placed for 24 hours after casting temperature 25 to 29 centigrade and humidity at least 90 percent shall be maintained.
14. After 24 hours, de-mould all 9 cement mortar cubes and put in the water tank.
15. Compressive strength test shall be done as follows:
03 cubes for 03 days, 03 cubes or 07 days and 03 cubes for 28 days.
CEMENT MORTAR CUBE FORMULA OF COMPRESSIVE STRENGTH
Compressive Strength = Applied Load / Surface area = 283 KN / 70.6*70.6 mm2 (load assumed)
= 283*1000 N / 4984.36 mm2 = 56.78 N/mm2
or Shortcut Compressive strength formula = Load / 4.984 ( for only mortar cube compressive strength).
so Compressive strength of cement mortar = 283 / 4.984 = 56.78 N/mm2 or MPa.
COMPRESSIVE STRENGTH OF CEMENT MORTAR LIMIT
Minumum limit for OPC53
compressive strength of cement required for ordinary portland cement in 3 days – 27 N/mm2 or MPa,
7 days – 37 N/mm2 or MPa
28 days – 53 N/mm2 or MPa