flexural strength exceeding the specified strength, R, by the amount
indicated below. This required average CQC flexural strength, Ra, will be
used only for CQC operations as specified in paragraph: TESTING AND
INSPECTION FOR CONTRACTOR QUALITY CONTROL and as specified in the previous
paragraph. During production, the required Ra shall be adjusted , as
appropriate and as approved, based on the standard deviation of equivalent
[28] [90] average [28] [90]-day strengths being attained during paving.
a.
From Previous Test Records: Where a concrete production facility
has previous test records current to within 18 months, a standard
deviation shall be established in accordance with the applicable
provisions of ACI 214.3R. Test records from which a standard
deviation is calculated shall represent materials, quality control
procedures, and conditions similar to those expected, shall
represent concrete produced to meet a specified flexural strength
or strengths within 1 MPa 150 psi of the [28] [90]-day flexural
strength specified for the proposed work, and shall consist of at
least 30 consecutive tests. The Contractor shall perform
verification testing, as directed by the Contracting Officer, to
document the current strength. A strength test shall be the
average of the strengths of two specimens made from the same
sample of concrete and tested at [28] [90] days. Required average
CQC flexural strength, Ra, used as the basis for selection of
concrete proportions shall be the value from the equation that
follows, using the standard deviation as determined above:
Ra = R + 1.34S
Where: S
= standard deviation
R
= specified flexural strength
Ra = required average flexural strength
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
NUMBER OF TESTS
FOR STANDARD DEVIATION
15
1.16
20
1.08
25
1.03
30 or more
1.00
b.
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, Ra, shall be determined by adding 15 percent to the
specified flexural strength, R.
PART 3
EXECUTION
3.1
PREPARATION FOR PAVING
Before commencing paving, the following shall be performed. If used, forms
shall be in place, cleaned, coated, and adequately supported. Any
reinforcing steel needed shall be at the paving site. All transporting and
SECTION 02753
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