: Guidelines for Testing of Hardened concrete
by core testing.
Sampling : Ref. IS : 1199 –
1959 R.A. 2004.
The hardened concrete shall be minimum 14 days
old before the specimen removed.
ii) Specimen that show abnormal defects or that
have been damaged in removal shall not be used.
iii) Core drill shall be used for securing cylindrical
iv) Dia of core shall be at least 10 cm for determination
of pavement thickness.
v) Dia of core shall be at least 300% more than
nominal size of aggregate and in no case be less
than twice the nominal size of aggregate. The
height (length) shall be twice of dia of core.
Core dia shall be taken to nearest mm, two at
middle and two at quarter points of depth. Take
average of six readings
TESTING : Refer clause 4 of IS
: 516 – 1959 RA 2004.
Core of which , before capping, has a height of
less that 95% of dia, or after capping, a height
less than its dia shall not be used for testing.
ii) Capping shall be done where plane is not within
0.05 mm, with suitable material with a compressive
strength not less than that of the core.
iii) Testing shall be done in compressive testing
machine of class 1 or 2 and compressive strength
shall be arrived as per the graph given herein
below based on the height and diameter ratio of
Limitation : Refer clause 17.4.1
of IS 456 – 2000
The core taken shall be representative of the
hardened concrete work and in no case shall be
less that three core specimen for each sample.
: Refer clause 17.4.3 of IS : 456-2000
The concrete is acceptable if the average equivalent
cube strength of the cores is equal to at least
85% of the grade of tested concrete for corresponding
average and no individual strength shall be less
: Refer clause 17.8 of IS : 456 –
Non-destructive tests provide alternatives to
core tests for estimating the strength of concrete
in a structure.
tests: Non-destructive tests are used to obtain
estimation of the properties of concrete in the
structure. The methods adopted includes following.
PULSE VELOCITY (UPV) :Refer IS : 13311(part
1)1992 RA 2004
The estimated strength may vary from the actual
strength by + 20 percent.
HAMMER : Refer IS : 13311 Part 2 : 1992
The probable accuracy of prediction of concrete
strength in a structure is + 25 percent. If the
relationship between rebound index and compressive
strength can be checked on various specimens the
accuracy of result will be greatly increased.