chapter 3 rigid pavement - DOT On-Line Publications - Department ...

FHWA TECHNICAL ADVISORY T 5080.17
July 14,. 1994
Additional information on acceptance procedures is
provided in the Technical Advisory on Acceptance
of Materials T 5080.11.
d. It is recommended that compressive strength be
accepted using statistical criteria (based on
average strength and standard deviation) to ensure
that the strength, f',, at 28 days, is equal or
exceeded by the average of any set of three
consecutive strength tests. No individual test
(average of two cylinders) can be more than 3.5
MPa below the specified strength. There are two
strengths to be considered. One is the minimum
specified strength (f',) which is a function of
the structural requirements. The second is the
average strength for mix design (f':,). The flo
must be higher than f', to ensure that the
concrete will exceed the minimum specified
strength. The following recommendations for f',,
are from AC1 318.
(1) Unknown Standard Deviation
Specified compressive
strength, MPa
f'c
Less than 20MPa
20MPa to 35MPa
Over 35MPa
(2) Known-Standard Deviation
Required average
compressive.
strength, MPa
f ' :r
f'c
+ 6.9
f'; + 8.3
f'; + 9.6
For greater than 30 test results (one test
result is the average of two cylinder breaks)
f’c, is the greater of the two values from
the following equations.
MPa
f',, = f', + 1.4s
f',, = f', + 2.4s - 3.5
S = Standard deviation
3.1022