The slump shall be determined in accordance with ASTM C 143/C 143M and
shall be within the range of 25 to 100 mm 1 to 4 inches. Where placement
by pump is approved, the slump shall not exceed 150 mm 6 inches. [Concrete
to be placed in [_____] may contain a chemical admixture for use in
producing flowing concrete in accordance with ASTM C 1017/C 1017M, and the
slump of the concrete shall not exceed 200 mm 8 inches].
2.2.5
Concrete Proportioning
Trial batches and testing requirements for various qualities of concrete
specified shall be the responsibility of the Contractor. Samples of
aggregates shall be obtained in accordance with the requirements of ASTM D
75. Samples of materials other than aggregate shall be representative of
those proposed for the project and shall be accompanied by the
manufacturer's test reports indicating compliance with applicable specified
requirements. Trial mixtures having proportions, consistencies, and air
content suitable for the work shall be made based on methodology described
in ACI 211.1, using at least three different water-cement ratios, which
will produce a range of strength encompassing those required for the work.
The maximum water-cement ratios required in paragraph MAXIMUM WATER-CEMENT
RATIO will be converted to a weight ratio of water to cement plus pozzolan
by mass, silica fume, or GGBF slag by mass equivalency as described in ACI
211.1. In the case where GGBF slag is used, the weight of the slag shall
be included in the equations for the term P, which is used to denote the
mass of pozzolan. If pozzolan is used in the concrete mixture, the minimum
pozzolan content shall be 15 percent of the total cementitious material.
Trial mixtures shall be proportioned for maximum permitted slump and air
content with due consideration to the approved conveying and placement
method. The temperature of concrete in each trial batch shall be reported.
For each water-cement ratio, at least three test cylinders for each test
age shall be made and cured in accordance with ASTM C 192/C 192M. They
shall be tested at 7 days and at the design age specified in paragraph
DESIGN REQUIREMENTS in accordance with ASTM C 39/C 39M. From these test
results, a curve will be plotted showing the relationship between
water-cement ratio and strength.
2.2.6
Required Average Compressive Strength
In meeting the strength requirements specified in paragraph CONCRETE
STRENGTH, the selected mixture proportion shall produce a required average
compressive strength f'cr exceeding the specified strength f'c by the
amount indicated below.
2.2.6.1
Average Compressive Strength from Test Records
Where a concrete production facility has test records, a standard deviation
shall be established in accordance with the applicable provisions of ACI
214R. 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
strength or strengths (f'c) within 6.89 MPa 1,000 psi of that specified for
proposed work, and shall consist of at least 30 consecutive tests. A
strength test shall be the average of the strengths of two cylinders made
from the same sample of concrete and tested at 28 days or at another test
age designated for determination of f'c.
Required average compressive strength f'cr used as the basis for selection
of concrete proportions shall be the larger of the equations that follow
using the standard deviation as determined above:
SECTION 03301A
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