Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
MIX
PROPORTIONING
Concrete Technology
Designing Concrete Mixtures
Cement Water Air
FA
CA
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Designing Concrete Mixtures
Objective
 To determine the most economical
and practical combination of readily
available materials to produce a
concrete that will satisfy the
performance requirements under
particular conditions of use.
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Concrete Technology
Designing Concrete Mixtures
Factors to be considered include:
 Workability
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Cohesiveness, slump
Placement conditions
Strength
Durability
Appearance
Economy
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Minimize the amount of cement, Minimize w/c ratio
Minimum amount of water, to reduce cement
content
do not sacrifice the quality
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Proportioning
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Absolute volume method
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Most commonly used method
Other methods
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Concrete Technology
Designing Concrete Mixtures
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Concrete mixture
proportions are
usually expressed on
the basis of the
mass of ingredients
per unit volume.
The unit of volume
used is either a cubic
yard or a cubic
meter of concrete.
Absolute Volume
1 yd
1 yd
1 yd
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Factors to consider- aggregates
Economical consideration
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Minimize water and cement, Stiffest possible mix
Largest practical max size of aggregate, Shape,
Surface Texture
Optimize ratio of fine to coarse aggregate
Grading (Particle Size distribution, PSD) and its
significance, Consistency, Strength, Finishability
Size and shape of members
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Max size of aggregate (MSA)
Physical properties
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Strength
Exposure condition
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Air entraining or not, sulfate attack
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Concrete Technology
Factors to consider - aggregates
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Max size-The size of smallest sieve through which
all Material passes.
(Nominal Aggregate Size: One sieve size larger than the first sieve to retain more than 10%).
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Nominal max size-The largest size of aggregate
present in sufficient quantity to center.
The larger the nominal sizes of aggregate, the
lower the water content to produce a given slump.
The most economical mix is the one with the
largest possible max size aggregate.
Max size of aggregate:
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Professor Kamran M. Nemati
Winter Quarter 2015
< 1/5 of narrowest dimensions of form
or ¾ of spacing between rebars
or in unreinforced slabs < 1/3 thickness
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Fineness Modulus of Sand
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The fineness modulus is calculated from
the particle size distribution of the fine
aggregate (sand).
Values for sand suitable for concrete
should range between 2.3 and 3.1.
Coarse sand has a higher fineness
modulus than fine sand.
The fineness modulus influences the bulk
volume of coarse aggregate.
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Concrete Technology
Bulk Volume of Coarse Aggregate
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Once the MSA and FM of sand are determined,
these values can be used to determine bulk
volume of coarse aggregate (CA) per unit volume.
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Air Content
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Entrained air must be used in concrete that will
be exposed to freezing and thawing and can be
used to improve workability even when not
requires.
The amount of air required in concrete depends
on:
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Maximum aggregate size (MSA)
Level of exposure
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Concrete Technology
Air Content
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Requirements of ACI 318 Building Code and ASTM C 94
Typical (entrapped) air contents in non air-entrained
Concrete
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Factors to consider-Water to cement ratio
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Compressive strength is inversely
proportional to W/C
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Define fc’ = Specified compressive strength at 28
days.
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The average compressive strength of concrete tested
at 28 days should be equal or greater than fc’.
Typical values fc’ = 4000 - 5000 psi
Strength
Water to cement ratio
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Concrete Technology
Determining Required w/c Ratio
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The w/c ratio is determined from:
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Durability considerations
Required strength
Requirements of ACI 318 Building Code
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Determining Required w/c Ratio
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Requirements of ACI 318 Building Code
for Sulphate Exposure
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Concrete Technology
W/C Ratio Required for Strength
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Use data from field or trial mixtures using the
same materials
Where no data are available, estimate using the
table shown below:
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Factors to consider - Durability
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Choice of slump
Maximum size of aggregate
W/C
Minimum cement content
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Factors to consider: finishability,
appearance, water resistance,
permeability
Admixtures
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Concrete Technology
Procedures
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Slump table 9-1
Max size of aggregates
Estimate mixing water and air content
 Tables 9-2, 9-3, 9-4
 use minimum specified of the two.
 Required air entrainment from table 9-2
Cement content compute from w/c and water content
Coarse aggregate table 9-5
Fine aggregate content from volumetric calculations
Adjust for aggregate moisture
Trial batches
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Concrete Mix Proportioning Tables
TABLE 9.1- ACI RECOMMENDED SLUMPS FOR VARIOUS TYPES
OF CONSTRUCTION
Slu m p (in.)
Maximu m * Minim u m
Typ es of Constru ction
Reinforced fou nd ation w alls and footings
Plain footings, caissons, and
substru cture w alls
Beam s and reinforced w alls
Bu ild ing colum ns
Pavem ents and slabs
Mass concrete
3
3
1
1
4
4
3
2
1
1
1
1
* May be increased 1-in. for methods of consolidation other than vibration.
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Concrete Technology
Concrete Mix Proportioning Tables
TABLE 9-2 - APPROXIMATE MIXING WATER AND AIR CONTENT REQUIREMENTS FOR DIFFERENT
SLUMPS AND MAXIMUM SIZES OF AGGREGATES
Water, lb./ yd 3 of concrete for ind icated m axim u m sizes of aggregate
Slu m p , in.
3/8 in.*
½ in.*
¾ in*
1 in.*
1½ in.*
2 in.*†
3 in.*†
6 in.*†
220
245
270
-0.3
190
210
--0.2
N on-air-entrained concrete
1 to 2
3 to 4
6 to 7
More than 7*
Ap p roxim ate am ou nt of
entrap p ed air in non-airentrained concrete, p ercent
350
385
410
-3
335
365
385
-2.5
315
340
360
-2
1 to 2
3 to 4
6 to 7
More than 7*
Recom m end ed average
total air content, p ercent
for level of exp osu re:
Mild exp osu re
Mod erate exp osu re
Severe exp osu re
305
340
365
--
295
325
345
--
280
305
325
--
270
295
310
--
250
275
290
--
240
265
280
--
205
225
260
--
180
200
---
4.5
6.0
7.5
4.0
5.5
7.0
3.5
5.0
6.0
3.0
4.5
6.0
2.5
4.5
5.5
2.0
4.0
5.0
1.5**††
3.5**††
4.5**††
1.0**††
3.0**††
4.0**††
300
325
340
-1.5
275
300
315
-1
260
285
300
-0.5
Air-entrained concrete
* These qu antities of m ixing w ater are for u se in com p u ting cem ent factors for trial
batches. They are m axim a for reasonably w ell-shaped angular coarse aggregates
grad ed w ithin lim its of accepted specifications.
† The slum p values for concrete containing aggregate larger than 1½" are based on
slum p tests m ad e after rem oval of p articles > 1½" by w et-screening.
Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Concrete Mix Proportioning Tables
TABLE 9-3 - RELATIONSHIP BETWEEN WATER/CEMENT RATIO AND COMPRESSIVE
STRENGTH OF CONCRETE
Compressive strength at 28
days, psi
6000
5000
4000
3000
2000
Water/cement ratio, by weight
Non-air-entrained
Air-entrained
concrete
concrete
0.41
0.48
0.57
0.68
0.82
---0.40
0.48
0.59
0.74
TABLE 9-4 - MAXIMUM PERMISSIBLE WATER/CEMENT RATIOS FOR CONCRETE IN
SEVERE EXPOSURES
Type of
Structure
Thin sections
(railings, curbs, sills,
ledges, ornamental
work) & sections
with less than 1-inch
cover over steel
All other structures
Structure wet continuously
or frequently exposed to
freezing & thawing*
Structure
exposed to
seawater
0.45
0.40
0.50
0.45
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* Concrete should also be air-entrained.
Concrete Technology
Concrete Mix Proportioning Tables
TABLE 9-5 - VOLUME OF COARSE AGGREGATE PER UNIT OF VOLUME OF CONCRETE
Maximum size
of aggregate
(in.)
3/8
1/2
3/4
1
1½
2
3
6
Volume of dry-rodded coarse aggregate*
per unit volume of concrete for
different fineness moduli of sand
2.40
0.50
0.59
0.66
0.71
0.75
0.78
0.82
0.87
2.60
0.48
0.57
0.64
0.69
0.73
0.76
0.80
0.85
2.80
0.46
0.55
0.62
0.67
0.71
0.74
0.78
0.83
3.00
0.44
0.53
0.60
0.65
0.69
0.72
0.76
0.81
* Volumes are based on aggregates in dry-rodded condition as described in ASTM
C29 Unit Weight of Aggregate. These volumes are selected from empirical
relationships to produce concrete with a degree of workability suitable for usual
reinforced construction. For less workable concrete such as required for concrete
pavement construction they may be increased about 10 percent. For more
workable concrete, such as may sometimes be required when placement is to be
by pumping, they may be reduced up to 10 percent.
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Proportioning of a Concrete Mix
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Proportioning of a concrete mix consists of
determining the relative amounts of materials
which will produce a concrete of desired
workability of the fresh concrete, and the
desired strength, consistency of volume,
durability, and economy in the hardened
concrete.
These proportions may be determined either by
calculations making use of published data (e.g.
American Concrete Institute (ACI)
“Recommended Practice for Selecting
Proportions of Concrete”, or by direct laboratory
test -- called the “trial method”.
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Concrete Technology
Proportioning of a Concrete Mix
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In the production of concrete, proportioning of
materials is of primary importance in as much as
such procedures provide means of meeting
specified requirements of quality.
Proportioning involves also consideration of
available materials and costs.
The source and the type both of the aggregate
and of the cement have a marked effect upon
the quality of concretes produced. It is
necessary, therefore, where concrete
construction is of considerable magnitude, to
make laboratory tests in advance of establishing
the desired proportions.
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Proportioning of a Concrete Mix
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The constituent materials themselves must
satisfy quality requirements
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Aggregates should be sound, clean, wellshaped and properly graded.
The portland cement should be of the
appropriate type, have normal setting
characteristics and should fulfill specification
requirements.
Economy is, of course, always a
consideration in mix proportioning.
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Concrete Technology
Proportioning of a Concrete Mix
 The purpose of selecting proportions for a
concrete mix is not necessarily to produce
a concrete of the highest possible quality,
but only of adequate quality required for
the intended use, consistent with the
economics of the project.
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A reinforced concrete bridge or a building, for
example, require concrete of comparatively
high strength, whereas in the construction of a
dam, a low rate of heat generation rather than
strength is of primary importance.
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Data Needed for Proportioning
Concrete Mixes

There are four principal properties of
aggregates which are needed in the
proportioning concrete mixes by the
ACI method. These properties are
given as follows:
 Free moisture and Absorption
 Specific Gravity
 Unit Weight of Aggregate in Bulk
 Gradation of aggregate
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Concrete Technology
ACI Method of Proportioning
Concrete Mixes
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The ACI (American Concrete Institute) Standard 211.1
is a “Recommended Practice for Selecting Proportions
for Concrete”. The procedure is as follows:
 Step 1. Choice of slump
 Step 2. Choice of maximum size of aggregate
 Step 3. Estimation of mixing water and air content
 Step 4. Selection of water/cement ratio
 Step 5. Calculation of cement content
 Step 6. Estimation of coarse aggregate content
 Step 7. Estimation of Fine Aggregate Content
 Step 8. Adjustments for Aggregate Moisture
 Step 9. Trial Batch Adjustments
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
ACI Method of Proportioning
Concrete Mixes
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For details on ACI Method of
Proportioning Concrete Mixes,
refer to the handout posted
on the class website.
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Concrete Technology
Determine the job parameters
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Step 1: Slump
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Step 2: Max aggregate size
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Table 9.1
Size 1/5 < Min dimensions
¾ clear spacing bars and strands
1/3 Slab Depth
Step 3: Estimate mixing water and air content
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Table 9.2
Slump, Aggregate Size, Water content lbs/yd3 and
air entrainment
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
ACI Method of Proportioning Concrete Mixes
Step 4: Water to Cement ratio, w/c
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Strength table 9.3, 28 day strength
Durability table 9.4 Exposure conditions
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Minimum w/c
Step 5: Cement content
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calculate from w/c and water content
Minimum cement content
Step 6: Estimate coarse aggregate
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For the same workability, Vcoarse aggregate , F.M. of
fine aggregate and Nom. Max. Size, Table 9-5
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Concrete Technology
ACI Method of Proportioning Concrete Mixes
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Step 7: volume of fine aggregates
Vfine agg. = Vtotal - Vwater-VCement-V
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Coarse Agg.
- Vair
V = Weight / (BSG *62.4)
Step 8: Consider the air content
volume
Step 9: Adjustment for moisture in
aggregates
Step 10: Volumetric Calculations
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Example
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For a residential street Paving in Boston, MA,
6” thick pavement, unreinforced, subjected
to freezing and thawing and deicing agent
anticipated. The required fc’ = 4000 psi.
Vibration will be used.
Sand FM = 2.7
Aggregate available = 1 ½”
BSG (FA)= 2.58
BSG (CA)= 2.6,  = 105 lbs/ft3
BSG (cement)= 3.15
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Concrete Technology
Example
1) Nominal Max size1/3 * 6 = 2”
since 1 ½” MSA is available, use
1 ½”
2) Air entrainment, definitely used, max
 Table 9-2
5.5% (%vol. of conc.)
 Table 9-1 (since vibrating)
Slump 1” – 2”
3) W/C Table 9-3, 9-4
0.48
4) Estimate water content Table 9-2
250 lbs/yd3
5) Calculate the cement content
250 /0.48 = 521
lbs/yd3
6) Estimate the coarse aggregate
 Table 9-5
0.72 ft3/ft3 of concrete
0.72 (27) = 19.44 cu.ft. of CA (OD condition)
Weight of C.A. = (19.44 cu.ft.) (105 lbs/ft3) = 2040 lbs/yd3
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Professor Kamran M. Nemati
Winter Quarter 2015
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Concrete Technology
Proportioning Concrete Mixes
Concrete Technology
Absolute volume measurement
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Cement = 521/(3.15*62.4)= 2.65 ft3 of cement / yd3 of
concrete.
Water =250/ 62.4 = 4.01 ft3 / yd3 of concrete.
CA = 2040/(2.6*62.4) = 12.57 ft3 / yd3 of concrete.
Air content = (0.055)(27 ft3/yd3) = 1.49 ft3/yd3 of concrete.
Abs. volume – fine = 2.65 + 4.01 + 12.57 + 1.49 = 20.72 ft3
Fine Aggregate Abs. volume = 27 – 20.72 = 6.28 ft3/yd3 of
concrete
Weight of F.A. = (6.28)(2.58)(62.4) = 1011 lbs/yd3
For 1 cubic yard
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Cement 521 lbs
Water 250 lbs
FA (dry) 1011 lbs
CA (dry) 2040 lbs
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Professor Kamran M. Nemati
Winter Quarter 2015
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