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Effect
of biological contaminated water on cement mortar
properties
I.V.
Ramana Reddy, N.R.S. Prasad Reddy, G.Reddy Babu, B.
Kotaiah and P. Chiranjeevi
Algae
is present abundantly in tropical water bodies (especially
in summer season) as well as in the industrial effluent
water. The effect of algae-mixed water on the initial
and final setting times of cement and compressive
strength development of cement mortars was investigated
under laboratory conditions. It was observed that
the presence of algae accelerates the initial and
final setting times at all concentrations, the maximum
acceleration occurring at 1460 cells/ml concentration.
The presence of algae increased the compressive strength
of mortar at early ages, mainly at 3-day and 7-days.
However, at higher ages, the trend reversed. The compressive
strength decreased continuously for all concentrations
in all samples from 14th day onwards. The percentage
of decrease in strength continued with age at all
concentrations. X-ray diffraction (XRD) studies indicated
the formation of hydroxides of calcium and aluminum
compounds during hydration. Extreme caution is needed
in using algae contaminated water in concrete construction.
Prediction
of structural behaviour of SIMCON plates
H.K.
Sharma
Slurry
infiltrated mat concrete (SIMCON) is a new kind of
high performance fibre reinforced composite (HPFRC).
The paper reports a study of the behaviour of SIMCON
plates with different support conditions, loading
conditions and fibre mat corresponding to various
fibre content using layered approach. Detailed analysis
is conducted to study effect of fibre mat in single
and double layers. The typical results are analysed
to investigate structural performance of SIMCON plates
in the form of load deformation response, ductility,
toughness, second fibre efficiency and predicted stress
distribution mapping. The proposed procedure predicts
well the load deformation response through different
failure stages. SIMCON plates are shown to possess
advantageous properties and the failure pattern is
predicted by multiple cracking and high ductility
patterns. Fibre mats are found to be more effective
when laid in multiple layers. Finally, an optimum
fibre content for SIMCON plates is proposed.
Evaluation
of seismic resistance of exterior beam-column joints
with detailing as per IS 13920 : 1993
P.
Asha and R. Sundararajan
An
experimental investigation of the behaviour of exterior
beam-column joints with detailing as per IS 13920
: 1993 under seismic conditions is presented. Five
quarter scale reinforced concrete exterior beam-column
sub assemblies were tested. The primary variable was
the type of confinement in the joint region extended
from the column. Four types of special confining reinforcement
according to IS 13920 : 1993 were provided in joint
region, namely, square hoop (SH), square spiral (SS),
circular hoop (CH) and circular spiral (CS). A control
specimen without any hoop in joint named as substandard
detail (SD) was also tested. The test specimens were
evaluated in terms of load-displacement relation,
ductility, stiffness, load ratio and cracking pattern.
Test results showed that exterior beam-column joint
with square spiral (SS) in joint region is the most
effective of all specimens tested and had excellent
seismic resistance than others.
Pseudo-ductile
behaviour of steel fibre reinforced high-strength
concretes
Raúl
L. Zerbino, Graciela Giaccio and Ravindra Gettu
The
benefits produced by the use of high strength (HSC)
concrete in structures include the increase in the
load carrying capacity, durability and, consequently,
longer service life Nevertheless, concrete with higher
strength exhibits more brittle behaviour. This phenomenon
can be compensated by the incorporation of distributed
steel fibre reinforcement. This paper analyses the
behaviour of steel fibre reinforced high-strength
concrete, with emphasis on toughness parameters determined
through the ASTM C 1018 procedure. The effects of
matrix strength level, fibre type and dosage have
been studied. The geometry of the specimens and loading
configuration have also been varied. In addition,
the failure mechanism under compressive loading has
been analysed using the critical stress concept.
A
comparison of effects of ultra fine fly ash and silica
fume in concrete
J.K. Dattatreya, M. Neelamegam and N.P. Rajamane
Mineral
admixtures such as fly ash (FA) and silica fume (SF)
are being extensively used in concrete for reasons
of strength, durability, and economy. While SF is
a very fine material with submicron particles, FA
can be processed to obtain the desired level of fineness
to improve its performance. The performance of ultra-fine
fraction of FA and SF was compared in an investigation
on HPC mixtures reported in this paper. The test results
indicate that ultra fine fly ash (UFFA) had only a
marginal effect on compressive strength when compared
to that with concrete containing SF. The use of both
SF and UFFA resulted in drastic reduction in chloride
permeability at all the ages.
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