COMPRESSIVE STRENGTH TEST FOR CONCRETE
Aim: To establish Compressive strength of concrete sample for acceptance
1.Compressive Testing machine having adequate capacity.
- Remove the cubes required for testing from curing tank wipe clean of water and air dry them to surface dryness.
- Stack cubes in sequence as per mix, dates, locations etc.
- Record the actual surface area ( Sq cm)of the cube which will be in contact with Platen of CTM ( A in cm2 or mm2 ).
- Weigh the cubes and record the weights in the register ing.
- Place the cube on platen centrally keeping toweled side in front.
- Position the top platen on cube surface. See that there is no gap left between cube top and platen.
- Load the CTM at desired speed without any shocks.( Pointer and needle shall move together)
- When crushing takes place in the specimen, needle will start falling back but pointer will remain at maximum reading.
- Record the reading shown by pointer viewing perpendicular to the face of dial.(Load applied in kN or tone- W)
- Relieve the load from CTM. Remove the cube. Clean the platens.
- Check the features of cube failure. Good failure is that cube mass retained shall have concavity on sides. If failures are occurring consistently by crack developing only on one side it means cubes are eccentrically loaded. If cracks are always developed centrally means point load is getting applied due to Convexity of platens. Remedial measures are required to be taken for this.
- Compressive Stress ( c ) in N / mm2 or Kg / cm2 as below :
- c = Wx1000 /A in N/mm2 or Kg /cm2
- Average of the set of Three or more cubes to be recorded (c’ ).
- When three or more cubes from single batch/lot is tested, max variation is allowed +/- 15%. If any cube is showing more variation, result of that cube is discarded and average of two or more is to be taken.
- Record is generated as per the sample format given in chronological order.
Format to be Used: To be recorded in Cube Register.
|COMPRESSIVE STRENGTH OF CONCRETE CUBES|
|Date of Casting||Date of Testing|
|Grade of Concrete||Age of Cubes||7 Days||28 Days|
|Structure / Location||Size of Cube||150x150x150 mm|
|Pour Card No.|
|S.No||7 Days||28 Days||Remarks|
|Cube ID Mark||Wt. of Cube
|Comp. Load (KN)||Comp. Strength (N/mm2)||Average Comp. Strength (N/mm2)||Cube ID Mark||Wt. of Cube (g)||Comp. Load (KN)||Comp. Strength (N/mm2)||Average Comp. Strength (N/mm2)|
|Remarks ( If Any) –|