pozzolan content shall be 15 percent by weight of the total cementitious
material, and the maximum shall be 35 percent. Laboratory trial mixtures
shall be designed for maximum permitted slump and air content. Separate
sets of trial mixture studies shall be made for each combination of
cementitious materials and each combination of admixtures proposed for use.
No combination of either shall be used until proven by such studies,
except that, if approved in writing and otherwise permitted by these
specifications, an accelerator or a retarder may be used without separate
trial mixture study. Separate trial mixture studies shall also be made for
concrete for any conveying or placing method proposed which requires
special properties and for concrete to be placed in unusually difficult
placing locations. 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 withASTM C 192/C
192M. They shall be tested at 7 and 28 days in accordance with ASTM C 39/C
39M. From these test results, a curve shall be plotted showing the
relationship between water-cement ratio and strength for each set of trial
mix studies. In addition, a curve shall be plotted showing the
relationship between 7 day and 28 day strengths. Each mixture shall be
designed to promote easy and suitable concrete placement, consolidation and
finishing, and to prevent segregation and excessive bleeding.
1.9.2
Proportioning Studies for Flexural Strength Concrete
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NOTE: Retain this paragraph only when the design
requires flexural strength concrete.
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Trial design batches, mixture proportioning studies, and testing
requirements shall conform to the requirements specified in paragraph
Proportioning Studies for Normal Weight Concrete, except that proportions
shall be based on flexural strength as determined by test specimens (beams)
fabricated in accordance with ASTM C 192/C 192M and tested in accordance
with ASTM C 78. Procedures given in ACI 211.1 shall be modified as
necessary to accommodate flexural strength.
1.9.3
Proportioning Studies for Lightweight Aggregate Structural Concrete
Trial design batches, mixture proportioning studies, and testing
requirements shall conform to the requirements specified in paragraph
Proportioning Studies for Normal Weight Concrete, except as follows. Trial
mixtures having proportions, consistencies and air content suitable for the
work shall be made based on methodology described in ACI 211.2, using at
least three different cement contents. Trial mixes shall be proportioned
to produce air dry unit weight and concrete strengths specified in
paragraph GENERAL REQUIREMENTS. Trial mixtures shall be proportioned for
maximum permitted slump and air content. Test specimens and testing shall
be as specified for normal weight concrete except that [28-day compressive
strength] [splitting tensile strength in accordance with ASTM C 496/C 496M]
shall be determined from test cylinders that have been air dried at 50
percent relative humidity for the last 21 days. Air dry unit weight shall
be determined in accordance with ASTM C 567 and shall be designed to be at
least 32 kg/cubic meter 2.0 pcf less than the maximum specified air dry
unit weight in paragraph GENERAL REQUIREMENTS. Curves shall be plotted
using these results showing the relationship between cement factor and
strength and air dry unit weight. Normal weight fine aggregate may be
substituted for part or all of the lightweight fine aggregate, provided the
concrete meets the strength and unit weight. A correlation shall also be
SECTION 03300A
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