Compressive Strength of Cement is the capacity of taking compressive loads of cement.
It is determined by compressive strength test on mortar cubes compacted by means of a standard vibration machine. Standard sand (IS:650) is used for the preparation of cement mortar. The specimen is in the form of cubes 70.6mm*70.6mm*70.6mm.
APPRATUS:-
1. Cube Mould of size 70.6mmX70.6mmX70.6mm (As per IS:10080)
2. Vibration Machine (As per IS: 10080)
3. Compression Testing Machine
4. Measuring Cylinder
5. Balance
PROCEDURE:-
1. Environmental condition for cement testing should be of temperature 27± 2⁰ C.
2. Take 200 g of cement and 600 g of standard sand and mix them dry thoroughly.
3. Add (P/4+3)X8 [ P is % of water required for preparing paste of standard consistency] to the dry mix of cement and sand and for a time of 3 to 4 minutes mix them properly si that they form a mix of uniform colour. If the mix is not homogeneous after 4 minutes reject the mix and do the procedure again.
4. Clean the cube moulds of cement thoroughly and place them the vibrating machine. It should be hold properly in position by clamps provided on the machine..
5. Fill the mould with entire quantity of mortar using a suitable hopper attached to the top of the mould for facility of filling and vibrate it for 2 minutes at a specified speed of 12000±400 per minute to achieve full compaction.
6. Remove the mould from the machine and keep it in a place with temp of 27±20C and relative humidity of 90% for 24 hours.
7. After 24 hrs remove the cube from the mould and immediately submerge in fresh clean water in temperature controlled cube curing tank where its temp. is kept in 27±20C. They should be submerged in waster till testing.
8. Prepare at least 9 cubes in the manner explained .
9. Place the test cube on the platform of a compressive testing machine so that the cubes central line and central line of platform coincides. No packing materials to be used between the cubes and loading plates.
10. At the rate of 35 N/mm2/minute apply the load steadily and uniformly.
11. 3 Cubes to be tested on completion of 3,7 and 28 days of testing and to be reported as shown below.
CALCULATIONS:-
Compressive Strength = P/A
[ P=Maximum load applied to the cube. (N)
A=Cross sectional area (Calculated from the mean dimensions) (mm2) ]
- Compressive strength is reported to the nearest 0.5 N/mm2
- Specimens that are manifestly faulty, or that give strengths differing by more than 10% from the average value of all the test specimen should not be considered.
- Test three cubes for compressive strength for each period of curing.
REPORTING OF RESULTS:-
Test result of Cement Cube Testing is reported as following..
