e.
Using the average strength for each w/c at each age, plot all
results from each of the three mixtures on separate graphs for w/c
versus:
3-day flexural strength
7-day flexural strength
14-day flexural strength
[28-day flexural strength]
[90-day flexural strength]
3-day compressive strength
7-day compressive strength
14-day compressive strength
[28-day compressive strength]
[90-day compressive strength]
f.
From these graphs select a w/c that will produce a mixture giving
a [28] [90]-day flexural strength equal to the required strength
determined in accordance with paragraph "Average CQC Flexural
Strength Required for Mixtures".
g.
Using the above selected w/c, select from the graphs the expected
3, 7, 14, [28] [90]-day flexural strengths and the expected 3, 7,
14, [28] [90]-day compressive strengths for the mixture.
h.
From the above expected strengths for the selected mixture
determine the following Correlation Ratios:
(1) Ratio of the 14-day compressive strength of the selected
mixture to the [28] [90]-day flexural strength of the mixture (for
acceptance).
(2) Ratio of the 7-day compressive strength of the selected
mixture to the [28] [90]-day flexural strength of the mixture (for
CQC control).
i.
If there is a change in materials, additional mixture design
studies shall be made using the new materials and new Correlation
Ratios shall be determined.
j.
No concrete pavement shall be placed until the Contracting Officer
has approved the Contractor's mixture proportions.
2.11.3
Contractor Quality Control for Average Flexural Strength
**************************************************************************
NOTE: The first option at the end of this paragraph
is for "Cylinders/Beams" and the second option is
for "Beams".
**************************************************************************
The Contractor's day to day production shall be controlled (CQC) in
accordance with the criteria herein, in the following subparagraphs, and in
paragraph: Concrete Strength Testing for CQC. This is entirely different
from the acceptance requirements of paragraph: Concrete Strength for Final
Acceptance, and it is mandatory that both sets of requirements must be met.
In order to ensure meeting the strength requirements specified in
paragraph: SPECIFIED CONCRETE STRENGTH AND OTHER PROPERTIES, during
production, the mixture proportions selected during mixture proportioning
studies and used during construction shall produce a required average CQC
SECTION 02753
Page 50
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