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Concrete Seminar Report
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INTRODUCTION
Concrete is a composite construction material composed of aggregate,
cement and water. There are many formulations that have varied
properties. The aggregate is generally coarse gravel or crushed rocks
such as lime stone or granite, along with a fine aggregate such as sand.
The cement commonly Portland cement and other cementitious materials
such fly ash and slag cement, serve as a binder for the aggregate.
Various chemical admixtures are also added to achieve varied properties.
Water is then mixed with this dry composite which enables it to be
shaped and then solidified and hardened into rock-hard strength
through a chemical process called hydration. The water reacts with the
cement which bonds the other components together, eventually creating
a robust stone-like material. Concrete has relatively high compressive
strength, but much lower tensile strength. For this reason it is usually
reinforced with material that are strong in tension (often steel). Concrete
can be damaged by many processes, such as freezing of trap
HIGH PERFORMANCE CONCRETE
High performance concrete (HPC) is cement based concrete, in which
each ingredient performs effectively to contribute towards fresh concrete
as well as hardened concrete properties. There is neither a unique
definition nor any specification for HPC. The American Concrete Institute
(ASI) defines HPC as “Concrete which meets special performance and
uniformity requirements that cannot always are achieved routinely by
using only conventional materials and normal mixing, placing and curing
practices, the requirements may involve enhancement of characteristics
such as placement and compaction without segregation, long term
mechanical properties, early age strength, toughness, volume stability or
service life in severe environments”. HPC consist of all ingredients of
Conventional cement concrete (CCC) with chemical admixtures as super
plasticizer and mineral admixtures are improving the utility of HPC. The
performance of cement concrete can be improved in terms of both
strength and durability considering impermeability characteristics, which
is achieved by adopting lower water-cement ratio and using pozzolanic
admixtures such as fly ash and WGP.
In HPC, generally the bond between cement and aggre
MATERIALS
The ingredients of concrete consist of Cement, fine aggregate
and coarse aggregates, water. When the reaction of water with cement
takes place hydration process is done and a hard material is formed. In
this research we used waste glass powder as a partial replacement and
filler material. The ingredients are used in proper proportion
CEMENT
Portland cement grade 53 is used in this test. It is the basic
ingredient of concrete, mortar and plaster. The cement used was a
commercial Portland cement type CEM II/A-V strength class 42.5N
conforming to BS EN 197- 1:2000. It is characterized by a normal rate of
strength development was used in all six different mixes. The surface
area of the cement was 350 kg/m3. Cement is an amorphous (glassy)
powdered siliceous material that responds to the alkali content in
cements to react with lime in the high pH environment in concrete to
form additional CSH (calcium silicate hydrate) binder within the pore
structure of the concrete. Pozzolana are effective as minus 325 mesh
powders. Pozzolana vary widely in reactivity, color, water demand, and in
chemical composition. Much of the chemistry associated with certain
Pozzolana, such as sulfides, carbon, sulfates, and alkalis can be quite
deleterious to the long-term durability of concrete. The starting materials
PHYSICAL PROPERTIES
The glass as natural sand replacement in concrete trials was a
crushed product with a size distribution between 3mm ~ 0.3mm. The
clear and green glass was very clean with no materials passing 150 and
75 micron fractions.
SEGREGATION AND BLEEDING
Glass powder reduces bleeding significantly because the free water
is consumed in wetting of the large surface area of the glass powder and
hence the free water left in mix for bleeding also decreases. Glass powder
also blocks the pores in the fresh concrete, so water within the concrete
is not allowed to come to the surface
WASTE GLASS WORKING IN CONCRETE
The crushed glass powder contained contaminants in the form of
traces of polymers, polyvinylbutylene (PVB) from the ELV glass content,
traces of acrylic from the architectural glass content. Ninety percent of
the contaminant material was considered to be PVB. It was established
that there was a small amount of organic material present in the crushed
glass, but this was considered to be paper residue from the labels on the
bottle glass. The moisture content of the glass as supplied was
considered insignificant at 0.29%. Following loss on ignition analysis, a
0.02% loss was recorded. The free lime content of crushed glass and
glass powder is 1.22% and 0.26% respectively
FINENESS OF CEMENT BY DRY-SEIVING METHOD
The principle of this is that we determine the proportion of cement
whose grain size is larger than specified mesh size. The apparatus used
are 90µm IS Sieve, Balance capable of weighing 10g to the nearest 10mg,
a nylon or pure bristle brush, preferably with 25 to 40mm, bristle, for
cleaning the sieve
Standard Consistency of Cement Paste
The principle of standard consistency of cement is that the consistency
at which the Vicat plunger penetrates to a point 5-7mm from the bottom
of Vicat mould. Apparatus used are Vicat’s apparatus using 10mm
diameter plunger fitted into the needle-holder, vicat mould, gauging
trowel, measuring jar, balance, glass plates, stop watch, mixing tray, and
sample of cement.
specific gravity of cement
specific gravity is normally defined as the ratio between the weight of
a given volume of material and weight of an equal volume of water. To
determine the specific gravity of cement, kerosene which does not recent
with cement is used. Apparatus used are specific gravity bottle, balance,
weigh box, cement, kerosene, cement
SLUMP TEST
Slump test is the most commonly used method of measuring
consistency of concrete which can be employed either in laboratory or at
site of work. It is not suitable method for very wet or dry concrete. It does
not measure all factors contributing to workability, nor is it always
representative of the place ability of the concrete. However, it is used
conveniently as a control test and givesan indication of the uniformity of
concrete from batch to batch.
COMPRESSIVE STRENGTH
Compressive test is the most common test conducted on hardened
concrete, partly because most of the desirable characteristic properties of
concrete are quantitatively related to its compressive strength.
The compression test is carried out on specimens cubical or cylindrical
in shape. Prism is also sometimes used, but it is not common in our
country. Sometimes, the compression strength of concrete is determined
using parts of beam tested in flexure. The end parts of the beam are left
intact after failure in flexure and, because the beam is usually of square
cross section, thin part of beam could be used to find out the
compressive strength. The cube specimen is of the size
150mm×150mm×150mm
GLASS POWDER
Waste glass was collected. Care to be taken that glass is free from
organic and other matter.
Then this glass was placed in the ABRASION TESTING MACHINE. Then
12 spheres were placed in the machine. Rotate it for 200 revolutions.
Then the crushed powder was sieved in 1.18mm sieve. Again repeat the
procedure.
The glass obtained from the Abrasion Testing Machine was now
placed in UNIVERSAL TESTING MACHINE (UTM) mould in three layers.
Apply 25 strokes with tamping rod for each layer. Apply convenient load
of then the mould was removed from the machine and then sieve with
1.18mm sieve. Repeat the process till get the required quantity.
AGGREGATES
The coarse aggregate was kept completely immersed in clean water for
24 hours for water absorption. After 24 hours, the aggregate was gently
surface dried with dry cloth. It was then spread out and exposed to the
atmosphere until it appears to be completely surface dry. For fine
aggregate, considering the huge time to be taken to become surface dry
from wet condition, it was not immersed in water. Instead the water was
sprinkled then it was spread out and exposed to the atmosphere until it
appears to be completely surface dry
COMPACTION FACTOR TEST
Compaction factor measures the workability in an indirect manner
by determining the degree of compaction achieved by a standard amount
of work done by allowing the concrete to fall through a standard height.
The sample of concrete to be tested is placed in the upper hopper
up to the brim. The trap door is opened so that the concrete falls in the
lower hopper. Then the trap door of the lower hopper is opened and the
concrete is allowed to fall into the cylinder. In the case of dry mix it is
likely that the concrete may not fall on opening the trap door in such a
case a slight pocking by rod may be required to set the concrete in
motion. The excess concrete remaining above top level in the cylinder is
then cut off with the cylinder is wiped clean and weighed to the nearest
gm. This weight is known as “ weight of partially compacted concrete
COMPACTING
The test cube specimens are made as soon as practicable after
mixing and in such a way as to produce full compaction of the concrete
with neither segregation nor excessive laitance. The concrete is filled into
the mould in layers approximately 5 cm deep. In placing each scoopful of
concrete. In order to ensure a symmetrical distribution of the concrete
within the mould. Each layer is compacted by either by hand or by
vibration. After the top of the layer has been compacted the surface of
the concrete is brought to the finished level with top of the mould, using
a trowel, the top is covered with a glass or a metal plate to prevent
evaporation.
Calculations
The measured compressive strength of the specimen shall be
calculated by dividing the maximum load applied to the specimen during
the test by the cross sectional area calculated from mean dimensions of
the section and shall be expressed to the nearest kg/cm2, average of all
values shall be taken as the representation of the batch provided and
individual variation is note more than 15 % of average.
Compressive strength = Max load / Area =P/A
Final values are adopted using standard deviations
Tests for flexural strength of concrete beams
Flexural strength, also known as modulus of rupture, bend strength,
or fracture strength a mechanical parameter for brittle material, is
defined as a material's ability to resist deformation under load. The
transverse bending test is most frequently employed, in which a
specimen having either a circular or rectangular cross-section is bent
until fracture or yielding using a three point flexural test technique. The
flexural strength represents the highest stress experienced within the
material at its moment of rupture. It is measured in terms of stress, here
given the symbol . This is conducted using UTM at a load of 40kN/mi
MIX DESIGN
Concrete is an extremely versatile building material because, it can
be designed for strength ranging from M10 (10Mpa) to M100 (100Mpa)
and workability ranging from 0 mm slump to 150mm slump
WATER / CEMENT RATIO
Water to cement ratio (W/C ratio) is the single most important
factor governing with strength and durability of concrete. Strength of
concrete depends upon W/C ratio rather than cement content. Abhram’s
law states that higher the W/C ratio, lower is a strength of concrete. As a
thumb rule every 1% increase in quantity of water added, reduces the
strength of concrete by 5%. A W/C ratio of only 0.38 is required for
complete hydration of cement. (although this is the theoretical limit, W/C
ratio lower than 0.38 will also increase the strength, since all the cement
CEMENT CONTENT
Cement is the core material in concrete, which act as a binding agent
and imparts strength to the concrete from durability considerations
cement content should not be reduced below 300kg/m3 for RCC. IS 456
2000 recommends higher cement contents for more severe conditions of
exposure of weathering agents to the concrete. It is not necessary that
higher cement content would result in higher strength. In fact latest
findings show that for the same W/C ratio, a leaner mix will give better
strength. However, this does not mean that we can achieve higher grade
concrete by just lowering the W/C ratio. This is because lower W/C
ratios will mean lower water contents and result in lower workability. In
fact for achieving a given workability, a certain quantity of water will be
required if lower W/C ratio is to achieved without disturbing
COMPRESSION TESTING MACHINE
The compression testing machine we used is of hydraulic one. It
uses fluids and works. The maximum load that can be bared is 3000KN
load rate is 4.9 KN/sec. compression testing machine has a digital load
indicator which comprises pek bold facility and relay contact for
protecting the machine from overloading
SLUMP TEST
Slump test is most commonly used method of measuring
consistency of concrete which can be employed either in laboratory or at
site of work. It is not suitable method for very wet or very dry concrete. It
is not measure of all the factors contributing to workability, not is it
always representative of the place available to the concrete. However, it is
used conveniently as a control test and gives an indication of the
uniformity of concrete from batch to batch.
CONCRETE MIX DESIGNS
The bureau of Indian standards recommended a set of procedures
for design of concrete mix mainly based on the work done in national
laboratories. The mix design procedures are covered in IS10262- 82.
Their methods can be applied for both medium and high strength
concrete. The following mixes are designed based on Indian Standard
Recommended Method of concrete mix design of IS10262-82.
CONCLUSION
From our experimental investigations, the strength of traditional concrete
cubes for 28 days were found to be 28.5 N/mm2. As we further continued
our investigation by adding waste glass powder to concrete by 10%, 20%,
30%. After 28 days the compressive strengths are 43.99, 54.32, 47.56
respectively. When we compared the strengths of traditional concrete and
concrete with partially replaced fine aggregate with glass powder exhibits
more strengths. We have also found that the concrete cubes exhibit more
strength when 20% of glass powder is added.
We have also conducted the split tensile strength and flexural strength of
the concrete cylinders and beams and found out that the beams exhibit
maximum strength at 20%.