The documents presents a new approach of mix design used a packing density method

1. Indian Institute of Technology Delhi
Department of Civil Engineering
Advanced Concrete Technology
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Prepared By:
Imam Mahdi Burhani
Hafizullah Sadat
Professor B.Bhattacharjee
2017

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3.  Packing density is new kind of mix design method
used to design different types of concrete; Normal
concrete, high strength concrete, no-fines
concrete and self compacting concrete.
 The concept of packing density as a fundamental
principle for designing HPC mixes.
 High performance concrete (HPC) has become
more and more popular in recent years.
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4.  However, the various required performance
attributes of HPC, including strength,
workability, dimensional stability and
durability…often impose contradictory
requirements on the mix parameters to be
adopted, thereby rendering the concrete mix
design a very difficult task.
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5.  The conventional mix design methods are no longer
capable of meeting the stringent multiple
requirements of HPC.
 The packing density method concept is based on the
belief that the performance of a concrete mix can
be optimized by maximizing the packing densities of
the aggregate particles and the cementitious
materials.
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6.  Multi-sized aggregate can be packed together
much more effectively to achieve a much higher
packing density than single size.
 With the paste volume fixed, increase in packing
density of the aggregate increase the workability
of the concrete at the same water/cementitious
ratio.
 Increase the strength of the concrete by reducing
the water/cementitious ratio while maintaining
the same workability.
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7.  Increase in packing density of the aggregate could
also be employed to improve the dimensional
stability of the concrete.
 The concept of packing density can be extended to
apply also to the cementitious materials.
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8.  The packing density of the cementitious materials
has great impact on the strength of the concrete
produced.
 Lower water/cementitious ratio
 Better packing would reduce the permeability
 Reduce the porosity of the transition zone
 Major factors affecting the packing density of an
aggregate; size range, grading, particle shape,
surface roughness, and effectiveness of the mixing
and compaction processes. 8

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10. Procedure:
First step: Determination of aggregate fractions
1. Considering different coarse aggregates size.
2. Determine the bulk density of coarse aggregates
separately.
3. Mix coarse aggregates in different proportions.
4. Determine the bulk density of mix different size
aggregates.
5. Draw the graph of bulk density against fraction of
different size proportion aggregates.10

11. 6. Based on the graph optimal aggregate fractions is
selected( fraction corresponding to maximum bulk
density)
 Two size fractions of coarse aggregates are selected
for the mix design, 20mm and 12.5mm down size, the
coarse aggregate 20mm and 12.5mm were mixed in
different proportions by mass, such as 90:10, 80:20,
70:30 and 60:40 etc.
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12.  Then Fine aggregate is added in the total coarse
aggregates (20mm and 12.5mm) in different
proportions, the bulk density and weight fraction of
each mixture is determined.
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13.  For coarse aggregates:
 From standard test:
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14. From the above graph the maximum bulk density is
corresponding to fraction of x=0.3. Therefore, the
coarse aggregates proportion is (70:30).
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15.  For coarse aggregates + Fine aggregate: (60:40)
 From standard test:
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16. From the above graph the maximum bulk density is
corresponding to fraction of x=0.4 Therefore, the mix
proportion is: Coarse aggregates: Fine aggregate=(60:40)
So aggregates proportion is: (42:18:40)
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17. Second Step: Determination of Packing Density
Total packing density of the mixture is sum of packing density
of different size coarse aggregates and fine aggregate.
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19. Third step: Determination of Voids Contents
 The voids content in percentage volume of
aggregate or mixture of three aggregate is
determined from its bulk density from the
following relations.
 The value of specific gravity should be taken as
average.
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20. Minimum voids contents (0.2866) is corresponding
to x=0.4 20

21. Fourth step: Determination of paste content
 Minimum paste content is sum of the void
content in combined aggregate and excess paste
over and above it to coat the aggregate
particle.
 Concrete mix containing minimum paste content
should be cohesive, free from segregation and
bleeding.
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22.  Minimum paste contents is determined from
Flow table test (carry out for workability)
Excess 10% voids content
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23. Fifth step: Determination of aggregates content
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24. Weight of aggregates
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25. Sixth step: Cement and water content
 For M20 grade concrete keeping in mind the
target mean strength suitable water-cement ratio
is fixed as per trial mixes.
W/C ratio = 0.56
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26. Final mix proportions for M20 grade concrete
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27. Following the above procedure all the ingredients of concrete were
obtained for 5%, 10% and 15% in excess of paste content and water
cement ratio 0.56 and 0.58, the values are presented in Table .
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