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The
flexural behaviour of hybrid fibre reinforced concrete
beams with GFRP wrappings
Vishwanath
K.G., D.S. Prakash and K.B. Prakash
This
paper presents an experimental investigation on the
flexural behaviour of hybrid fibre reinforced concrete
beams with GFRP wrappings and without any wrappings.
Because addition of hybrid fibres enhances the flexural
strength and toughness indices for plain cement concrete
beam, fibres reinforcement to the beams was provided
with two types of hybrid fibres (i) steel fibres and
polypropylene fibres and (ii) waste steel coiled fibres
and waste plastic fibres. These beam specimens under
this experiment received two sets of wrappings. The
first set of wrappings was with glass fibre reinforced
plastic (GFRP) whereas the second was wrapped with
sandwich GFRP which was essentially a hexagonal steel
wire mesh sandwiched between two GFRP wrappings. The
sandwich wrapping was used to overcome the brittle
nature of failure of plain GFRP confinement. Flexural
strengths and toughness indices were determined. The
results show that wrappings in general improve the
flexural strength and toughness indices of fibre reinforced
concrete beams. Between GFRP wrapping and sandwich
wrapping, the latter offers a higher flexural strength
and toughness indices.
Higher
strength concrete using crushed brick as coarse aggregate
M.A. Rashid,
Tanvir Hossain and M. Ariful Islam
An
experimental investigation has been done to achieve
higher strength concrete using crushed brick as aggregate
and then to study its mechanical properties. It has
been found that higher strength concrete (f'c= 4500
to 6600 psi) is achievable whose strength is much
higher than that of the brick used. Experimental study
shows that the compressive strength of brick aggregate
concrete can be increased by decreasing its water-cement
ratio along with using admixture whenever necessary
for workability. The compressive strength as well
as the tensile strength and the modulus of elasticity
of the concrete have been studied. The cylinder strength
is found about 90% of the cube strength. The ACI Code
formula for determining the modulus of rupture has
been found to highly underestimate the test values.
Whereas the codal expression for elastic modulus gives
much higher values than the experimental ones for
brick aggregate concrete. Relations have been proposed
to estimate the modulus of rupture and the modulus
of elasticity of higher strength brick aggregate concrete.
Some
optimal values in geopolymer concrete incorporating
fly ash
R.V.
Ranganath and Mohammed Saleh
This
paper presents the results of experimental investigations
on effect of fly ash, water content, ratio of sodium
silicate to sodium hydroxide solution by mass and
the duration of elevated temperature curing on the
properties of fly ash based geopolymer concrete (GPC).
It was found that as the water content increases the
optimum fly ash content also increases to obtain maximum
strength. In addition for the given fly ash content
increase in the alkaline solution content does not
contribute additional strength. It has been found
that long curing at elevated temperature increases
the strength of geopolymer concrete, however elevated
temperature curing beyond 20 hours does not contribute
significant strength.
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