Inspection
Immediately after stripping the formwork, all concrete shall
be carefully inspected and any defective work or small defects either removed
or made good before concrete has thoroughly hardened. In case of doubt
regarding the grade of concrete used, either due to poor workmanship or based
on results of cube strength tests, compressive strength tests of concrete on
the basis of 16.3 and / or load test may be carried out.
Core Test
The points from which cores are to be taken and the number of
cores required shall be at the discretion of the engineer-in-charge and shall
be representative of the whole of concrete concerned. In no case, however,
shall fewer than three cores be tested.
Concrete in the member represented by a core test shall be
considered acceptable if the average equivalent cube strength of the cores is
equal at least 85 percent of the cube strength of the grade of concrete
specified for the corresponding age and no individual core has a strength less
than 75 percent.
In case the core test results do not satisfy the requirements
or where such tests have not been done, load test may be resorted to.
Load Tests on Parts of
Structures
Load tests should be carried out as soon as possible after
expiry of 28 days from the time of placing of concrete. The structure should be
subjected to a load equal to full dead load of the structure plus 1.25 times
the imposed load for a period of 24 hours and then the imposed load shall be
removed. The deflection due to imposed load only shall be recorded. If within
24 hours of removal of the imposed load, the structure does not recover at
least 75 percent of the deflection under superimposed load, the test may be
repeated after a lapse of 72 hours. If the recovery is less than 80 percent,
the structure shall be deemed to be unacceptable. If the maximum deflection in
mm, shown
during 24 hours under load is less than 40 l2 / D, where l
is the effective span in m and D, the overall depth of the section in mm, it is
not necessary for the recovery to be measured and the recovery provisions will
not apply. Other non-destructive test methods may be adopted, in which case the
acceptance criteria shall be agreed upon between the engineer-in-charge and the
contractor and the tests shall be done under expert guidance.
