Concrete cubes should be tested for compression in a machine of reliable type and of appropriate capacity suitable for the concrete grade. The permissible error shall be not greater than + 2% of the max. load.
The specimen after removing from the curing tank shall be allowed to dry for approx. 2 to 3 hours.
The cube shall be placed in the machine in such a manner that the load shall be applied to opposite sides of the cubes as cast that is, not to the top & bottom. The axis of specimen shall be carefully aligned with the center of thrust at the circular base plate.
The load shall be applied without shock & increased continuously at a rate approximately 140 kg / cm2 / minute. Until the resistance of the specimen to the increasing load breaks down & no greater load can be sustained.
The measured compressive strength of the specimen shall be calculated by dividing the max. load applied to the specimen during the test by the cross-sectional area.
The following information shall be included in the report on each test specimen:
Identification mark
Date of test.
Age of specimen.
Curing conditions, including date of manufacture of specimen in the field.
Weight of specimen.
Dimension of specimen.
Cross sectional area.
Maximum load.
Compressive strength.
Appearance of fractured faces of concrete and type of fracture, if these are unusual.
Acceptance Criteria: IS 456 clause 16.1 – Table 11
For concrete acceptance criteria i.e. Fck +3 N/mm2. i.e. for acceptance M30 should achieve 33 N/mm2 for average of 4 consecutive mean results. If not pls. obtain consultant approval for concrete acceptance
Cube Register shall be sent to structural consultant on monthly basis
Any concrete of a specified Grade shall meet the above requirements in 28 days.
Any concrete being supplied to our site, which does not achieve minimum characteristic strength at 28 days, shall be considered as failure and no other acceptance criteria shall be entertained.
The results to be shared with Structural consultant if consultant decides on concrete failure and instructs for core test, As per IS 456 clause 17.4 – core test to be done.
Considering the permissible tolerance Rebound hammer test may not be accepted.
For the Huge segregation, Honeycombs in vertical element to be analyzed with UST if found with varying very high at Top, Middle and bottom. Full depth core analysis may be recommended to analyses the Homogeneous concrete laying.
Core taken for analysis to be filed back with High strengths Micro concrete as per Bore packing method
If the results observed failure, then as per consultant instructions, with basis method and material approval from Structural consultant and QAQC the Strengthening process to be done.
Concrete Standard deviation report for each grade (Plant wise) and concrete cube register should sent on each month basis to structural consultant for approval and record purpose.
