Abstract: In the present work, behavior of inoxydable steel as
reinforcement bar in composite concrete is being investigated. The
bar-concrete adherence in reinforced concrete (RC) beam is studied
and focus is made on the tension stiffening parameter. This study
highlighted an approach to observe this interaction behavior in
bending test instead of direct tension as per reported in many
references. The approach resembles actual loading condition of the
structural RC beam. The tension stiffening properties are then
applied to numerical finite element analysis (FEA) to verify their
correlation with laboratory results. Comparison with laboratory
shows a good correlation between the two. The experimental settings
is able to determine tension stiffening parameters in RC beam and
the modeling strategies made in ABAQUS can closely represent the
actual condition. Tension stiffening model used can represent the
interaction properties between inoxydable steel and concrete.
Abstract: Basic objective of this study is to create a regression
analysis method that can estimate the length of a plastic hinge which
is an important design parameter, by making use of the outcomes of
(lateral load-lateral displacement hysteretic curves) the experimental
studies conducted for the reinforced square concrete columns. For
this aim, 170 different square reinforced concrete column tests results
have been collected from the existing literature. The parameters
which are thought affecting the plastic hinge length such as crosssection
properties, features of material used, axial loading level,
confinement of the column, longitudinal reinforcement bars in the
columns etc. have been obtained from these 170 different square
reinforced concrete column tests. In the study, when determining the
length of plastic hinge, using the experimental test results, a
regression analysis have been separately tested and compared with
each other. In addition, the outcome of mentioned methods on
determination of plastic hinge length of the reinforced concrete
columns has been compared to other methods available in the
literature.
Abstract: The use of additions in cement in manufacturing,
mortar and concrete offers economic and ecological advantages. Cements with additions such as limestone, slag and natural
pouzzolana are produced in cement factories in Algeria. Several studies analyzed the effect of these additions on the physical and
mechanical properties as well as the durability of concrete. However,
few studies were conducted on the effect of local metakaolin on
mechanical properties and durability of concrete. The main purpose
of this paper is to analyze the performance of mortar and concrete with local metakaolin. The preparation of the metakaolin was carried
out by calcination of kaolin at a temperature of 850 °C for a period of 3 hours. The experimental results have shown that the rates of
substitutions of 10 and 15% metakaolin increases the compressive
strength and flexural strength at both early age and long term. The durability and the permeability were also improved by reducing the
coefficient of sorptivity.
Abstract: The article presents findings from the study and
analysis of the results of an experimental programme focused on the
production of concrete and fibre reinforced concrete in which natural
aggregate has been substituted with brick or concrete recyclate. The
research results are analyzed to monitor the effect of mechanicalphysical
characteristics on the durability properties of tested
cementitious composites. The key parts of the fibre reinforced
concrete mix are the basic components: aggregates – recyclate,
cement, fly ash, water and fibres. Their specific ratios and the
properties of individual components principally affect the resulting
behaviour of fresh fibre reinforced concrete and the characteristics of
the final product. The article builds on the sources dealing with the
use of recycled aggregates from construction and demolition waste in
the production of fibre reinforced concrete. The implemented
procedure of testing the composite contributes to the building
sustainability in environmental engineering.
Abstract: This paper presents the experiment results of investigating the effects of adding various types and proportions of fibre on mechanical strength and permeability characteristics of recycled aggregate concrete (RAC), which was produced with treated coarse recycled concrete aggregate (RCA). Two types of synthetic fibres (i.e., barchip and polypropylene fibre) with various volume fractions were added to the RAC, which was calculated by the weight of the cement. The hardened RAC properties such as compressive strength, flexural strength, ultrasonic pulse velocity, water absorption and total porosity at the curing ages of 7 and 28 days were evaluated and compared with the properties of the control specimens. Results indicate that the treated coarse RCA enhances the mechanical strength and permeability properties of RAC and adding barchip fibre further optimises the results. Adding 1.2% barchip fibre has the best effect on the mechanical strength performance of the RAC.
Abstract: The purpose of this paper is to improve electromagnetic characteristics on grounding grid by applying the conductive concrete. The conductive concrete in this study is under an extra high voltage (EHV, 345kV) system located in a high-tech industrial park or science park. Instead of surrounding soil of grounding grid, the application of conductive concrete can reduce equipment damage and body damage caused by switching surges. The focus of the two cases on the EHV distribution system in a high-tech industrial park is presented to analyze four soil material styles. By comparing several soil material styles, the study results have shown that the conductive concrete can effectively reduce the negative damages caused by electromagnetic transient. The adoption of the style of grounding grid located 1.0 (m) underground and conductive concrete located from the ground surface to 1.25 (m) underground can obviously improve the electromagnetic characteristics so as to advance protective efficiency.
Abstract: One of the most common practices for strengthening
the reinforced concrete structures is the application of FRP (Fiber
Reinforce Plastic) sheets to increase the flexural and shear strengths
of the member. The elastic modulus of FRP is considerably higher
than that of concrete. This will result in debonding between the FRP
sheets and concrete surface. With conventional surface preparation of
concrete, the ultimate capacity of the FRP sheets can hardly be
achieved. New methods for preparation of the bonding surface have
shown improvements in reducing the premature debonding of FRP
sheets from concrete surface. The present experimental study focuses
on the application of grooving method to postpone debonding of the
FRP sheets attached to the side faces of concrete beams for shear
strengthening. Comparison has also been made with conventional
surface preparation method. This study clearly shows the efficiency
of grooving method compared to surface preparation method, in
preventing the debonding phenomenon and in increasing the load
carrying capacity of FRP.
Abstract: Due to growing environmental concerns of the cement
industry, alternative cement technologies have become an area of
increasing interest. It is now believed that new binders are
indispensable for enhanced environmental and durability
performance. Self-compacting Geopolymer concrete is an innovative
method and improved way of concreting operation that does not
require vibration for placing it and is produced by complete
elimination of ordinary Portland cement.
This paper documents the assessment of the compressive strength
and workability characteristics of low-calcium fly ash based selfcompacting
geopolymer concrete. The essential workability
properties of the freshly prepared Self-compacting Geopolymer
concrete such as filling ability, passing ability and segregation
resistance were evaluated by using Slump flow, V-funnel, L-box and
J-ring test methods. The fundamental requirements of high
flowability and segregation resistance as specified by guidelines on
Self Compacting Concrete by EFNARC were satisfied. In addition,
compressive strength was determined and the test results are included
here. This paper also reports the effect of extra water, curing time and
curing temperature on the compressive strength of self-compacting
geopolymer concrete. The test results show that extra water in the
concrete mix plays a significant role. Also, longer curing time and
curing the concrete specimens at higher temperatures will result in
higher compressive strength.
Abstract: The main objective of this paper is to determine the
isolated effect of silica fume on tensile, compressive and flexure strengths on high strength lightweight concrete. Many experiments
were carried out by replacing cement with different percentages of silica fume at different constant water-binder ratio keeping other mix
design variables constant. The silica fume was replaced by 0%, 5%,
10%, 15%, 20% and 25% for a water-binder ratios ranging from 0.26
to 0.42. For all mixes, split tensile, compressive and flexure strengths
were determined at 28 days. The results showed that the tensile, compressive and flexure strengths increased with silica fume incorporation but the optimum replacement percentage is not
constant because it depends on the water–cementitious material (w/cm) ratio of the mix. Based on the results, a relationship between
split tensile, compressive and flexure strengths of silica fume concrete was developed using statistical methods.
Abstract: Reinforced concrete stair slabs with mid landings i.e.
Dog-legged shaped are conventionally designed as per specifications
of standard codes of practices which guide about the effective span
according to the varying support conditions. Presently, the behavior
of such slabs has been investigated using Finite Element method. A
single flight stair slab with landings on both sides and supported at
ends on wall, and a multi flight stair slab with landings and six
different support arrangements have been analyzed. The results
obtained for stresses, strains and deflections are used to describe the
behavior of such stair slabs, including locations of critical moments
and deflections. Values of critical moments obtained by F.E. analysis
have also have been compared with that obtained from conventional
analysis. Analytical results show that the moments are also critical
near the kinks i.e. junction of mid-landing and inclined waist slab.
This change in the behavior of dog-legged stair slab may be due to
continuity of the material in transverse direction in two landings
adjoining the waist slab, hence additional stiffness achieved. This
change in the behavior is generally not taken care of in conventional
method of design.
Abstract: Existing underground pipe jacking methods use a
reinforcing rod in a steel tube to obtain structural stiffness. However,
some problems such as inconvenience of works and expensive
materials resulted from limited working space and reinforcing works
are existed. To resolve these problems, a new pipe jacking method,
namely PST (Prestressed Segment Tunnel) method, was developed
which used joint to connect the steel segment and form erection
structure. For evaluating the flexural capacity of the PST method
structure, a experimental test was conducted. The parameters
considered in the test were span-to-depth ratio of segment, diameter of
steel tube at the corner, prestressing force, and welding of joint. The
flexural behaviours with the effect of load capacity in serviceability
state according to different parameters were examined.. The frame
with long segments could increase flexural stiffness and the specimen
with large diameter of concave corner showed excellent resistance
ability to the negative moment. In addition, welding of joints increased
the flexural capacity.
Abstract: The paper reflects current state of popularization of
static elasticity modulus of concrete. This parameter is undoubtedly
very important for designing of concrete structures, and very often
neglected and rarely determined before designing concrete
technology itself. The paper describes assessment and comparison of
four mix designs with almost constant dosage of individual
components. The only difference is area of origin of small size
fraction of aggregate 0/4. Development of compressive strength and
static elasticity modulus at the age of 7, 28 and 180 days were
observed. As the experiment showed, designing of individual
components and their quality are the basic factor influencing
elasticity modulus of current concrete.
Abstract: Demolitions of buildings have created a lot of waste
and one of it is clay bricks. The waste clay bricks were ground to
roughly cement fineness and used to partially replaced cement at
10%, 20% and 30% with w/b ratio of 0.6 and tested at 7, 28, 60, 90
and 120 days. The result shows that the compressive strength of GCB
concrete increases over age however, decreases as the level of
replacements increases. It was also found that 10% replacement of
GCB gave the highest compressive strength, however for optimum
replacement, 30% was chosen as it still attained strength of grade 30
concrete. In terms of durability performances, results show that GCB
replacement up to 30% was found to be efficient in reducing water
absorption as well as water permeability. These studies show that
GCB has the potential to be used as partial cement replacement in
making concrete.
Abstract: Data Structures and Algorithms is a module in most
Computer Science or Information Technology curricula. It is one of
the modules most students identify as being difficult. This paper
demonstrates how programming a solution for Sudoku can make
abstract concepts more concrete. The paper relates concepts of a
typical Data Structures and Algorithms module to a step by step
solution for Sudoku in a human type as opposed to a computer
oriented solution.
Abstract: High strength concrete (HSC) provides high strength
but lower ductility than normal strength concrete. This low ductility
limits the benefit of using HSC in building safe structures. On the
other hand, when designing reinforced concrete beams, designers
have to limit the amount of tensile reinforcement to prevent the
brittle failure of concrete. Therefore the full potential of the use of
steel reinforcement can not be achieved. This paper presents the idea
of confining concrete in the compression zone so that the HSC will
be in a state of triaxial compression, which leads to improvements in
strength and ductility. Five beams made of HSC were cast and tested.
The cross section of the beams was 200×300 mm, with a length of 4
m and a clear span of 3.6 m subjected to four-point loading, with
emphasis placed on the midspan deflection. The first beam served as
a reference beam. The remaining beams had different tensile
reinforcement and the confinement shapes were changed to gauge
their effectiveness in improving the strength and ductility of the
beams. The compressive strength of the concrete was 85 MPa and the
tensile strength of the steel was 500 MPa and for the stirrups and
helixes was 250 MPa. Results of testing the five beams proved that
placing helixes with different diameters as a variable parameter in the
compression zone of reinforced concrete beams improve their
strength and ductility.
Abstract: The aim of this work is to study the possible use of
stone cutting sludge waste in concrete production, which would
reduce both the environmental impact and the production cost .Slurry
sludge was used a source of water in concrete production, which was
obtained from Samara factory/Jordan, The physico-chemical and
mineralogical characterization of the sludge was carried out to
identify the major components and to compare it with the typical
sand used to produce concrete. Samples analysis showed that 96% of
slurry sludge volume is water, so it should be considered as an
important source of water. Results indicated that the use of slurry
sludge as water source in concrete production has insignificant effect
on compression strength, while it has a sharp effect on the slump
values. Using slurry sludge with a percentage of 25% of the total
water content obtained successful concrete samples regarding slump
and compression tests. To clarify slurry sludge, settling process can
be used to remove the suspended solid. A settling period of 30 min.
obtained 99% removal efficiency. The clarified water is suitable for
using in concrete mixes, which reduce water consumption, conserve
water recourses, increase the profit, reduce operation cost and save
the environment. Additionally, the dry sludge could be used in the
mix design instead of the fine materials with sizes < 160 um. This
application could conserve the natural materials and solve the
environmental and economical problem caused by sludge
accumulation.
Abstract: High strength concrete has been used in situations
where it may be exposed to elevated temperatures. Numerous authors
have shown the significant contribution of polypropylene fiber to the
spalling resistance of high strength concrete.
When cement-based composite that reinforced by polypropylene
fibers heated up to 170 °C, polypropylene fibers readily melt and
volatilize, creating additional porosity and small channels in to the
matrix that cause the poor structure and low strength.
This investigation develops on the mechanical properties of mortar
incorporating polypropylene fibers exposed to high temperature.
Also effects of different pozzolans on strength behaviour of samples
at elevated temperature have been studied.
To reach this purpose, the specimens were produced by partial
replacement of cement with finely ground glass, silica fume and rice
husk ash as high reactive pozzolans. The amount of this replacement
was 10% by weight of cement to find the effects of pozzolans as a
partial replacement of cement on the mechanical properties of
mortars. In this way, lots of mixtures with 0%, 0.5%, 1% and 1.5% of
polypropylene fibers were cast and tested for compressive and
flexural strength, accordance to ASTM standard. After that
specimens being heated to temperatures of 300, 600 °C, respectively,
the mechanical properties of heated samples were tested.
Mechanical tests showed significant reduction in compressive
strength which could be due to polypropylene fiber melting. Also
pozzolans improve the mechanical properties of sampels.
Abstract: Steel corrosion in concrete is considered as a main
engineering problems for many countries and lots of expenses has been paid for their repair and maintenance annually. This problem
may occur in all engineering structures whether in coastal and offshore or other areas. Hence, concrete structures should be able to
withstand corrosion factors existing in water or soil. Reinforcing
steel corrosion enhancement can be measured by use of concrete
electrical resistance; and maintaining high electric resistivity in concrete is necessary for steel corrosion prevention. Lots of studies
devoted to different aspects of the subjects worldwide. In this paper, an evaluation of the effects of W/C ratio, cementitious materials, and
percent increase in silica fume were investigated on electric resistivity of high strength concrete. To do that, sixteen mix design
with one aggregate grading was planned. Five of them had varying amount of W/C ratio and other eleven mixes was prepared with
constant W/C ratio but different amount of cementitious materials.
Silica fume and super plasticizer were used with different proportions
in all specimens. Specimens were tested after moist curing for 28 days. A total of 80 cube specimens (50 mm) were tested for concrete
electrical resistance. Results show that concrete electric resistivity can be increased with increasing amount of cementitious materials
and silica fume.
Abstract: This research investigates the effects of the opening
shape and location on the structural behavior of reinforced concrete
deep beam with openings, while keeping the opening size unchanged.
The software ANSYS 12.1 is used to handle the nonlinear finite
element analysis. The ultimate strength of reinforced concrete deep
beam with opening obtained by ANSYS 12.1 shows fair agreement
with the experimental results, with a difference of no more than 20%. The present work concludes that the opening location has much more effect on the structural strength than the opening shape. It was
concluded that placing the openings near the upper corners of the
deep beam may double the strength, and the use of a rectangular
narrow opening, with the long sides in the horizontal direction, can save up to 40% of structural strength of the deep beam.
Abstract: A research program is conducted to evaluate the
mechanical properties of Ultra High Performance Concrete, target
compressive strength at the age of 28 days being more than 150 MPa.
The methodology to develop such mix has been explained. The
material properties, mix design and curing regime are determined.
The material attributes are understood by studying the stress strain
behaviour of UHPC cylinders under uniaxial compressive loading.
The load –crack mouth opening displacement (cmod) of UHPC
beams, flexural strength and fracture energy was evaluated using
third point loading test. Compressive strength and Split tensile
strength results are determined to find out the compressive and tensile
behaviour. Residual strength parameters are presented vividly
explaining the flexural performance, toughness of concrete.Durability
studies were also done to compare the effect of fibre to that of a
control mix For all the studies the Mechanical properties were
evaluated by varying the percentage and aspect ratio of steel fibres
The results reflected that higher aspect ratio and fibre volume
produced drastic changes in the cube strength, cylinder strength, post
peak response, load-cmod, fracture energy flexural strength, split
tensile strength, residual strength and durability. In regards to null
application of UHPC in India, an initiative is undertaken to
comprehend the mechanical behaviour of UHPC, which will be vital
for longer run in commercialization for structural applications.