specified quality is furnished.
1.10
PROPORTIONS OF MIXTURE
Trial batches shall contain materials proposed to be used in the project.
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 (w/c) ratios. Trial mixtures
shall be proportioned to produce concrete matching the qualities specified.
In the case where ground granulated iron blast-furnace slag conforming to
ASTM C 989 is used, the mass of the slag will be substituted in the
equations for the term P which is used to denote the mass of pozzolan.
Trial mixtures shall be designed for maximum permitted slump and air
content. The concrete and mortar patching mixtures shall be designed using
the lowest practical w/c ratio. The temperature, slump, and air content of
the concrete and mortar mixtures in each trial batch shall be reported.
For each w/c ratio at least three test specimens for each test age shall be
made and cured in accordance with ASTM C 192/C 192M and ASTM C 109/C 109M.
They shall be tested at 7 and 28 days in accordance with ASTM C 39/C 39M
for concrete and ASTM C 109/C 109M for mortar. From these test results a
curve shall be plotted showing the relationship between w/c ratio and
strength. For each strength of concrete the maximum allowable w/c ratio
shall be that shown by these curves to produce an average strength as
specified in paragraph Average Strength. Materials, physical and chemical
properties, and composition of concrete and mortar patch mixtures shall
match the existing concrete to be repaired, except that patching mixtures
shall have the lowest total chlorides content practical and shall conform
to ACI recommendation for maximum permitted total chloride content.
1.10.1
Average Strength
In meeting the strength requirements specified, the selected mixture shall
produce an average compressive strength exceeding the specified strength by
the amount indicated below. Where a concrete production facility has test
records, a standard deviation shall be established. 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
within 3.5 MPa 500 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 specimens made from the same sample of
concrete and tested at 28 days or at other test age designated for
determination of the specified strength.
1.10.2
Test Records Exceeding 29
Required
average compressive strength used as the basis for selection of
concrete
proportions shall be the larger of the specified strength plus the
standard
deviation multiplied by 1.34 or the specified strength plus the
standard
deviation multiplied by 2.33 minus 3.5 MPa 500 psi.
1.10.3
Test Records Less Than 29
Where a concrete production facility does not have test records meeting the
above requirements but does have a record based on 15 to 29 consecutive
tests, a standard deviation may be established as the product of the
calculated standard deviation and a modification factor from the following
Table:
SECTION 03900
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