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Large-scale
production of SCC: A new approach to robustness
Jonhson
W. Rigueira, Emilio G. Taengua and Pedro Serna
Use
of self-compacting concrete (SCC) is rising because
of their advantages over conventional concretes. But
the possibility of large-scale SCC production with
good mix reliability needs more investigations particularly
for robustness of SCC mixes. Robustness of an SCC
mix is the stability of its properties when the original
proportion is affected by errors in weighing of ingredients.
To evaluate the effect of such errors, six different
SCC mixes were selected. Variations introduced were
such that they simulated large-scale production errors.
Also, tolerances normally accepted by codes were compared
with statistical distributions of errors obtained
from plant data provided by select Spanish concrete
producers.
Cost
competitive steel fibre reinforced SCC for structural
applications
Joaquim A.O.
Barros, Lúcio A.P. Lourenço, Rajendra
K. Varma and Delfina M.F. Gonçalves
A
mix design for Steel Fibre Reinforced Self-Compacting
Concrete (SFRSCC) was developed for application in
lightweight panels as building facades. Concrete precast
industry is one of the most suited industries for
the use of SFRSCC, as it has the potential not only
to use the mix composition but also other steps leading
to make structural elements. Since precast elements'
demoulding should be carried out as soon as possible
for economic reasons, the influence of age on mechanical
properties of SFRSCC was assessed by compression and
flexural tests. Compression and monotonic cyclic tests
were also performed to assess performance of the mix.
To understand the full potential of SFRSCC in structural
applications such as panels, prototypes were made
and subjected to flexural and punching loads. The
results confirmed the advantages of fibre reinforcement.
Finally, a scale panel was made and tested in an industrial
environment, to prove the technology transfer from
laboratory to factory.
Reinforced
cement concrete pipes made with SCC technology
M. Lakshmipathy,
K.S. Satyanarayanan, G. Jayasree and V. Mageshwaran
Self-Compacting
Concrete (SCC) is one of the High Performance Concretes
with excellent strength and durability properties.
However, its mix proportioning and testing methods
for flow characteristics are different from those
of the ordinary concrete. SCC has high powder content
and a super plasticizer for enabling flow while keeping
coarse aggregate in a viscous suspension. The powder
is usually cement and a filler material. The relative
proportion of filler in powder influences the properties
of SCC both in fresh and hardened state. An attempt
has been made to develop cost-effective SCC with supplementary
cementitious materials such as fly ash (25%), GGBS
(20%) and Silica Fume (5%) and examine its strength
properties in comparison to the conventional concrete.
Although much of the current research concentrates
on developing SCC mixes and exploring their application
in major construction projects, in this study Re-inforced
Cement Concrete (RCC) pipes made with SCC are compared
with conventional concrete pipes. In summary, SCC
showed better homogeneity in concrete mix and the
pipes made had better performance than conventional
concrete pipes.
Rheological
properties of SCC using direct shear box
S. Girish,
C. Indumathi, Jagadish Vengala and R.V. Ranganath
The
fresh properties of concrete can be characterised
by its flow behaviour. Most of the tests which measure
flow of concrete are empirical in nature. Rheological
tests conducted using rheometers such as BML rheometer,
BTRHEOM rheometer, IBB rheometer, CEMAGREF-IMG rheometer
and Two-point rheometer attempt to measure yield stress
and plastic viscosity. However, there is no concurrence
among these test values and hence there is no instrument
which is acceptable to all. Further, these rheometers
are very expensive. In this study, an attempt has
been made to find the rheological properties of concrete
using strain controlled direct shear box. An important
characteristic of direct shear box test is the very
low shear rate applied on the specimen. Ten different
concrete mixes with different paste contents (0.38,
0.41 and 0.43) and different max size of coarse aggregates
were studied. One of the mixes was of normal concrete
using coarse aggregate of max. size 10 mm and the
remaining nine, Self Compacting Concrete mixes, using
three different sizes of crushed stone coarse aggregate
(10 mm, 8 mm and 6 mm). Three different displacement
rates namely, 1.25 mm/min, 0.625 mm/min and 0.25 mm/min;
were employed. Different normal stresses were applied
on the specimen. Relative yield stress and relative
plastic viscosity values were obtained along with
the corresponding measured slump flows. The results
show that direct shear box can be used to find rheological
parameters (relative values of yield stress and plastic
viscosity) of fresh concrete. The values obtained
in this study are higher, by 10 times for yield value
and 104 times for plastic viscosity, respectively,
as compared to the values obtained by other rheometers.
This could be due to inter-particle interference.
However, the trends reported are very similar to the
studies using rheometers i.e. higher the flow, lower
is the yield strength and plastic viscosity. The test
is static.
Study
of the properties of SCC with quarry dust
M. Rame Gowda,
M.C. Narasimhan, Karisddappa and S.V. Rajeeva
Granite
fines or rock dust is a by-product obtained during
crushing of granite rocks and is also called quarry
dust (QD). This paper deals with using quarry dust
as an alternative to fine aggregate (FA) in SCC and
reports the strength behaviour and hardened properties
of such SCCs. Although in normal concretes, introducing
QD increases the water demand, in SCC, it has been
successfully used for increasing the deformability
and passing ability of fresh concrete. Also, it was
noted that by increasing the pouring heights of an
SCC, the compressive strength and splitting tensile
strength of concrete were unaffected.
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