f'cr = f'c + 1.34S
f'cr = f'c + 2.33S - 3.45 500
Where S = standard deviation
Where a concrete production facility does not have test records meeting the
requirements above but does have a record based on 15 to 29 consecutive
tests, a standard deviation shall be established as the product of the
calculated standard deviation and a modification factor from the following
table:
MODIFICATION FACTOR
FOR STANDARD DEVIATION
NUMBER OF TESTS*
Use tabulation in paragraph
less than 15
DETERMINING REQUIRED AVERAGE STRENGTH
15
1.16
20
1.08
25
1.03
30 or more
1.00
*Interpolate for intermediate numbers of tests.
2.2.6.2
Average Compressive Strength without Previous Test Records
When a concrete production facility does not have sufficient field strength
test records for calculation of the standard deviation, the required
average strength fcr shall be determined as follows:
If the specified compressive strength f'c is less than 20.7 MPa 3,000 psi,
f'cr = f'c + 6.89 1,000
If the specified compressive strength f'c is 20.7 to 34.5 MPa 3,000 to
5,000 psi,
f'cr = f'c + 8.27 1,200
If the specified compressive strength f'c is over 34.5 MPa 5,000 psi,
f'cr = f'c + 9.65 1,400
PART 3
EXECUTION
3.1
EQUIPMENT
3.1.1
Capacity
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NOTE: Refer to the appropriate DM for the capacity.
Guidance is also found in EM 1110-2-2000.
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The batching, mixing, conveying, and placing equipment shall have a
capacity of at least [_____] cubic meters yards per hour.
SECTION 03301A
Page 28
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