particular specifications (road works) - CIDCO Maharashtra Ltd.

CIDCO OF MAHARASHTRA LTD
C.A.No.01/CIDCO/SE(KHR)/EE(KHR-I)/2010–11 Pg. No. 358
5.8.2.3 Test Specimen:
Three test specimens shall be made from each sample for testing at 28
days. Additional samples may be required for various purposes such as
to determine the strength of concrete at 7 days or at the time of striking
the formwork, or to determine the duration of curing, or to check the
testing error. Additional samples may also be required for testing
samples cured by accelerated methods as described in IS: 9103. The
specimen shall be tested as described in IS 5116.
5.8.2.4 Test results of sample:
The test results of the sample shall be the average of the strength of
three specimens. The individual variation should not be more than +
15 percent of the average. If more, he test results of the sample are
invalid.
5.8.2.5 Determination of Standard Deviation:
Where:
Concrete of each grade shall be analyzed separately to determine its
standard deviation.
The standard deviation of concrete of a given grade shall be calculated
using the following formula from the results of individual tests of
concrete of that grade obtained as specified in Table.
Estimated standard deviation = S =
ΣΔ 2
n - 1
Δ = Deviation of the individual test strength from the average
strength 'n' samples and
n = Number of samples test results.
When significant changes are made in the production of concrete
batches (for example changes in the material used, mix design,
equipment or technical control), the standard deviation value shall be
separately calculated for Such batches of concrete.