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Combined
effect of fly ash and GGBS on durability of concrete
under freeze-thaw conditions
Muhammad
Ashraf, Hattori Kunio, Ogata Hidehiko and Ajay Goyal
Freeze-thaw
tests were carried out on air-entrained concrete specimens
as per Japan Industrial Standards (JIS) A 1148-2001.
Concrete samples were prepared with four different
admixture ratios (i.e. control mix, 25 percent fly
ash, 25 percent fly ash plus 25 percent blast furnace
slag and 50 percent blast furnace slag). The durability
of concrete specimens exposed to 300 cycles of freezing
and thawing was monitored by measuring density, ultrasonic
pulse velocity (UPV) and dynamic modulus frequency
after every 30 cycles. The experiment demonstrated
that the durability factors of concrete were substantially
influenced by the mineral admixtures. More than 100
percent durability factor was observed in concrete
made of fly ash and slag. The fly ash samples exhibited
either similar or slightly enhanced values as compared
to control. The UPV of specimen incorporated with
slag and also the mixture of slag plus fly ash was
remarkable during freeze-thaw cycling.
Proportions
of concrete ingredients and their significance in
compressive strength development
A.M.
Pande and L.M. Gupta
Advances
in concrete technology have scaled new heights in
the recent past. High Volume fly ash Concrete (HVFAC)
has now become a common terminology and fly ash is
gaining recognition as an important ingredient in
concrete. These developments have resulted in a significant
shift from w/c ratio to w/c+p ratio. The benefits
of fly ash in improving workability and thus reducing
water content are well documented. Five different
samples of concrete containing fly ash partially replacing
cement with proportions 0-50% have been tested and
results are presented in this paper. The data generated
was first clubbed with data published in standard
reports and research papers, and then analysed using
graphs and SPSS software. For the analysis, only proportions
of the ingredients are considered overlooking basic
properties of the ingredients. The results reveal
that two ratios play significant role in compressive
strength development and they are: water to cementitious
component ratio (W/(C+kF) ratio), and cementitious
component to inert component ratio, (C+kF/((1-k)F+S+CA)
ratio). Values of k were found to be different for
various ages of testing.
An
investigation on the effect of sustained temperatures
on the strength properties of fibrous ferrocement
using steel fibres
K.B.
Prakash and N.K. Patil
The
applications of ferrocement and fiber reinforced concrete
(FRC) are increasing because of their many advantages.
Ferrocement does not require any special construction
technique and skilled labour. Its cracking resistance,
ductility and fatigue resistance are higher than those
of concrete. In addition impermeability of ferrocement
elements is far superior to that of ordinary concrete.
FRC has gained widespread acceptance as a suitable
construction material for a wide variety of non-structural
applications. FRC possesses higher compressive strength,
toughness, resistance to wear and tear, and higher
post cracking strength. But, these two materials have
limitations also. They cannot be employed where high
vibrations, high tensile forces and high impact are
to be resisted. Fibrous ferrocement, which is a combination
of ferrocement and fibre reinforced concrete, shows
better improvement in some of the mechanical properties
such as toughness and impact resistance. This new
composite also shows higher compressive, tensile and
impact strength. In this paper an attempt has been
made to study the effect of different sustained temperatures
on the strength characteristic of fibrous ferrocement
especially compressive strength, flexural strength
and impact strength. The percentages of flat fibres
used were 0%, 0.5%, 1.0%, 1.5%and 2.0% by volume fraction.
Also, the specific surface area of welded mesh and
chicken mesh was varied. The temperatures adopted
in the experimentation are 200oC, 400oC and 600oC.
Influence
of box shape on structural behaviour of RC box-girder
bridges
Manoj
Kumar and Sagar Samaria
The
present study is concerned with the analytical investigations
on influence of box cross-sectional shape on the structural
behaviour of reinforced concrete (RC) box girder bridges.
In this paper the structural behaviour of box girder
bridges has been studied in terms of deflection, longitudinal
and transverse bending stresses, and the shear lag
coefficient. To this end two box shapes namely, rectangular
and trapezoidal have been considered for the aforementioned
study. ANSYS, a general purpose finite element analysis
software, has been used as the basic platform for
modelling and carrying out the three dimensional linear
elastic finite element analysis of box girder bridges
considered in this study. The outcome of this study
has shown that as a whole the structural response
of bridge with rectangular box section is better than
trapezoidal box section.
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