International Journal of Advancements in Research & Technology, Volume 2, Issue4, April‐2013 429 ISSN 2278‐7763 COROSSION PROPERTIES OF CONCRETE CONTAINING
MICRO SILICA
Mr SARATH S1, Mr R VANDHIYAN2 & DR.E B PERUMAL PILLAI3
1
P G student,Department of Civil Eng., PSNA College of Engineering & Technology,
Dindigul.
2
Associate prof, Department of Civil Eng PSNA College of Engineering & Technology,
Dindigul.
3
The Principal, R M K CET, Tiruvallur District, Tamilnadu
Email: sarassarath@gmail.com, vandhianr@gmail.com
ABSTRACT
Concrete is a uniform a mixture of aggregates, binder material and water. The concrete thus
formed is weak in many aspects or properties such as permeability, durability corrosion
resistance, etc. All over the past and present researches were going on regarding development
of concrete having good strength and which overcomes the above shortcomings. This is
achieved by incorporating certain materials in the concrete mix. One such material that can
be added in concrete to enhance various properties is micro silica. When micro silica is added
to concrete by partially replacing (10%) the binder material, the hardened concrete seems to
have more strength. This is achieved because micro silica particles are of very small size
(1/100th size of cement particle) and these particles enters to very minute pores in concrete
and fills the voids thereby making the concrete more denser and stronger. Since its fills up
the pores, there will be very less and small amount of pores and internal passages in the
structure thus retarding the movement of water and other corrosion causing salts to be in
contact with the embedded reinforcements.
The project aims at studying the corrosion properties of micro silica incorporated concrete.
This includes the study of bond strength in concrete reinforcement interface, permeability of
water and other salts in to the concrete and flexural behavior of reinforced silica incorporated
concrete beam.
Copyright © 2013 SciResPub. International Journal of Advancements in Research & Technology, Volume 2, Issue4, April‐2013 430 ISSN 2278‐7763 ingredients
1 . INTRODUCTION
proportioned
and
selected to contribute efficiently to the
1.1 GENERAL
various properties of cement concrete
One of the important and
most
are
widely
used
in fresh as well as in hardened states.
artificial
engineering material is concrete. It
consists of hard inorganic materials
One major remarkable quality,
called aggregates such as gravel sand
in the making of UHPC is the virtual
crushed stone slag etc cemented
elimination of voids in the concrete
together with binding material and
matrix, which are mainly the cause of
water . When these materials are
most of the
mixed together
deterioration.
workable
so as to form a
mixture
it
gives
ills that generate
Important governing
factors for UHPCs are strength, long
considerable freedom to the designers
term
and engineers to mould the structural
determined by crack and deflection
element to any desired shape or form.
control, as well as response to long
In
term environmental effects. UHPCs
most
structural
applications,
concrete is employed primarily
to
durability,
serviceability
are concretes with
properties
attributes
the one of the most important and
performance criteria.
useful properties of concrete. The
concretes with higher strengths and
compressive strength as well as many
attributes
other
concretes
are
inversely
superior
satisfy
or
resist compressive stresses which is
properties
which
as
the
Generally ,
to conventional
are desirable in
the
proportional to the mass ratio of the
construction industry. UHPC can be
amount of water and cement used in
considered as a logical development of
the mix. The lower this ratio stronger
cement concretes in
the concrete. Ultra High Performance
ingredients
Concrete
recent
selected to contribute efficiently to the
material technology
various properties of cement concrete
(UHPC)
development in
and
is
a
far superior to conventional
cement concrete and Other high
strength concrete. UHPC can be
considered as a logical development of
cement concretes in
Copyright © 2013 SciResPub. which the
are
which the
proportioned
and
in fresh as well as in hardened states.
International Journal of Advancements in Research & Technology, Volume 2, Issue4, April‐2013 431 ISSN 2278‐7763 of
1.2 MICRO SILICA
about
3.15.
The
bulk
density
(uncompacted unit weight) f silica fume
Micro silica, also referred to as
varies from 130 to 430 kg/m3 (8 to 27
silica fume or condensed silica fume, is a
lb/ft3). Silica fume is sold in powder form
byproduct material that is used as a
but is more commonly available in a
pozzolan. This byproduct is a result of the
liquid. Silica fume is used in amounts
reduction of high-purity quartz with coal in
between 5% and 10% by mass of the total
an electric arc furnace in the manufacture
cementitious material. It is used in
of silicon or ferrosilicon alloy. Silica fume
applications where a high degree of
rises as an oxidized vapor from the 2000°C
impermeability is needed (Fig. 3-9) and in
(3630°F) furnaces. When it cools it
highstrength concrete. Silica fume must
condenses and is collected in huge cloth
meet ASTM C 1240. ACI 234 (1994) and
bags. The condensed silica fume is then
SFA (2000) provide an extensive reviewof
processed to remove impurities and to
silica fume.
control particle size. Condensed silica
fume is essentially silicon dioxide (usually
more
than
85%)
in
noncrystalline
(amorphorous) form. Since it is an
1.3 CONCRETE CONTAINING
MICRO SILICA
airborne material like fly ash, it has a
spherical shape (Fig. 3-8). It is extremely
fine with particles less than 1 μm in
diameter and with an average diameter of
about 0.1 μm, about 100 times smaller
than average cement particles. Condensed
silica fume has a surface area of about
20,000
m2/kg
method).
For
(nitrogen
comparison,
adsorption
tobacco
smoke’s surface area is about 10,000 m2/
kg. Type I and Type III cements have
surface areas of about 300 to 400 m2/kg
and
500
to
600
m2/kg
(Blaine),
respectively. The relative density of silica
fume is generally in the range of 2.20 to
2.5. Portland cement has a relative density
Copyright © 2013 SciResPub. Micro silica, also known as silica
fume, has been used as a concrete property
enhancing material and as a partial
replacement for Portland cement for over
25 years. Micro silica is a by-product in
the
production
of
silicon
metal
or
ferrosilicon alloys. . Micro silica is a
mineral admixture composed of very fine
solid glassy spheres of silicon dioxide
(SiO2). Most micro silica particles are less
than 1 micron (0.00004 inch) in diameter,
generally 50 to 100 times finer than
average cement or fly ash particles. Micro
International Journal of Advancements in Research & Technology, Volume 2, Issue4, April‐2013 432 ISSN 2278‐7763 silica in concrete contributes to strength
to the change in chemical reactions. Micro
and durability two ways:
silica is also known to affect the time of
setting and bleeding of fresh concrete.
Mechanical
properties
of
silica-fume
As a pozzolan, micro silica provides a
concrete, such as creep and drying
more uniform distribution and a greater
shrinkage, have been known to be lower
volume of hydration products. [Ref:8]
than that of concrete without micro silica.
As a filler, micro silica decreases the
average size of pores in the cement paste
[Ref:8]
At 28 days, the compressive strength of
micro silica concrete is significantly higher
than concrete without silica fume. Micro
silica is also linked to the decrease of
permeability, chemical attack resistance,
Micro silica for use in concrete is
available in slurry or dry forms. In either
and enhancement of the chloride ion
penetration resistance of concrete. [Ref 8]
form, micro silica is a very reactive
pozzolan when used in concrete due to its
fine particles, large surface area, and the
high silicon dioxide content. There are
several effects on the properties of fresh
and hardened concrete when micro silica is
used along with fly ash and chemical
admixtures. In fresh concrete, micro silica
affects the water demand and slump. The
concrete water demand increases with the
increased amounts of silica fume, due
primarily to the high surface area of the
micro silica. Fresh concrete containing
micro silica is more cohesive and less
prone to segregation than concrete without
micro silica. Since micro silica is used
with other admixtures, such as waterreducing or high-range water-reducing
admixtures, the slump loss is actually due
Copyright © 2013 SciResPub. Concrete containing micro silica makes
concrete
a
better
performing
material, allowing designers to use it
efficiently
in
increasingly
slender
structures. Architects prefer using these
type of concrete in high-rise construction
in order to design thinner floor slabs and
slimmer columns, in addition to it being
aesthetically
more
appealing.
Some
contractors favour the use of this because
they can remove the form work earlier. In
addition to reducing creep and shrinkage,
increasing the use of silica containing
concrete
in
high
–rise
construction
increases the stiffness of the structure. As
a result, deflections of concrete members
are reduced.
International Journal of Advancements in Research & Technology, Volume 2, Issue4, April‐2013 433 ISSN 2278‐7763 1.4 FEATURES
OF
CONCRETE
CONTAINING MICRO SILICA
Reinforcing steel in concrete is
normally protected from corrosion by the
Some of the salient features of micro
passive film formed at the steel/concrete
silica containing which make it superior
interface inside the alkaline cementitious
to other concretes are :
matrix . However, this passivation can be
eliminated either by a decrease in the pH
value (pH < 9) due to carbonation, or by
 High early compressive strength
the presence of chloride salts, which
 High tensile and flexural strength
initiates an expansive corrosion of the
 High modulus of elasticity
reinforcing steel and eventually damages
 Low permeability to chloride and
the
water intrusion
surrounding
concrete.
Concrete
structures such as bridges, buildings,
 Discontinues internal pores
sanitary and water facilities, and other
 Enhanced durability and toughness
reinforced concrete structures might suffer
 Superior resistance to chemical
severe damages due to corrosion of the
attack
reinforcing steel. Damages caused by the
 Higher bond strength
consequent cracking and spalling of the
 High electrical resistivity
concrete cost billions of dollars each year.
Steel corrosion reduces the cross section
1.5
CORROSION
IN
CONCRETE
STRUCTURES
area as well as the continuity of the surface
of steel. Such reductions lower the tension
strength of steel and decrease the bond
strength due to a slip between steel and the
Corrosion of embedded steel is
one of the major causes of concrete
deterioration
in
reinforced
concrete
structures. This type of corrosion results
when a corrosive species, water and air,
penetrate through the concrete pores to the
steel’s surface. The key to inhibiting rebar
surrounding concrete, and, consequently
deteriorate
member
strength
In
addition to the economic losses incurred,
public safety is also jeopardized, even
culminating in loss of lives due to
incidents like collapsing of bridges and
structures .
corrosion is to restrict the permeability of
Experimental
concrete.
design
Copyright © 2013 SciResPub. the
investigations
and
mix
International Journal of Advancements in Research & Technology, Volume 2, Issue4, April‐2013 434 ISSN 2278‐7763 2.0 RESULTS OF MATERIAL TESTS
be incorporated in concrete in two ways:
Basic material results
SL
TEST
VALUE
(a) addition to binder material
NO
І
containing concrete also. Micro silica can
TEST FOR
(b) replacement to binder material
CEMENT
1
Consistency
31
2
Specific gravity
3.1
3
Fineness
0.33
П
TEST FOR FINE
gives an increased strength than addition.
AGGREGATES
It is clear that 10 % replacement of the
From
former
studies
and
researches, it showed that replacement
1
Specific gravity
2.56
binder
material
2
Fineness
2.75
Further replacement retards the strength of
3
Bulk density
1693Kg/m3
Ш
TEST FOR
high
strength.
concrete.
Concrete
COARSE
gives
S
C
FA
CA
Ordinary 0
1
1.54
3.2
M silica
0.9
1.54
3.2
M20
AGGREGATES
1
Specific gravity
2.70
2
Fineness
6.64
3
Bulk density
1527Kg/m3
0.1
4.0 EXPERIMENTAL SET UP
Since the study deals with corrosion,
certain small set ups must be made ready
to create an artificial environment to
induce corrosion. Some of the required set
ups are briefly explained below:
3.MIX PROPORTION (W/C= 0.53 )
As my work is on the study of micro silica
(a) IMPRESSED CURRENT
VOLTAGE METHOD
containing concrete it is necessary to
It is one of the most widely used methods
incorporate the mix design for micro silica
for inducing corrosion in reinforcement. In
Copyright © 2013 SciResPub. Internation
nal Journal of A
Advancements in
n Research & Teechnology, Volu
ume 2, Issue4, A
April‐2013 435 ISSN 2278‐7763 this meethod a stanndard amouunt of voltage
coorrosion, haalf cell poteentiometer is used.
(6-24 vvolt) is appliied to the reeinforcemennt.
A half cell potential
p
m
meter
is bassically a
For thiss a cell is crreated with the help off a
chhemical ceell containning an ellectrode,
DC batttery. The positive
p
terrminal of thhe
ellectrolyte. The
T electroode used iss copper
battery is connectted to the reinforceme
r
ent
rood and thee electrolytte used is copper
which iis to be corrroded and the negativve
suulphate soluution. The cell is placedd on the
terminaal is conneccted to a stainless
s
steeel
toop of the cooncrete surrface in whhich the
plate. Now
N
the concrete
c
coontaining thhe
coorroded steeel is presentt. The lower part of
reinforccement thatt is to be corroded
c
annd
thhe cell thus formed muust be permeable so
the stainnless steel plate
p
are to be immersed
thhat the bluue color off copper suulophate
in 3.5 % of NaCl solution.
s
A point that is
soolution com
mes in contacct with the concrete
c
to be keept while seetting up this apparatus is
suurface. Thuus a compleete cell is formed.
that the reinforcrm
mrnt that is too be corroded
The cell can
n be said too be compleete only
should not come in contact with the saalt
w
when
a multti meter is used in thee circuit.
p
solutionn. On applyying the vooltage for pre
The positivve end off multi meter
m
is
determiined time we
w can obtainn corrosion.
coonnected too the the reinforcemennt whose
pootential is to be measured
m
aand the
neegative end
d is connectted to the half
h cell.
V
Various
pootential can
n be calcullated by
vaarying the position of the half cell
pootentiometeer on the suurface of concrete.
c
W the hellp of the reeadings takeen using
With
m
multi
meter and usingg the Faraddays law
foor mass losss, we can calculate
c
am
mount of
coorrosion
that
have
taken
pllace
reeinforcemennt inside the concrete.
(b) HALF
CELL
C
P
POTENTIA
AL
METER
We neeed to callculate the amount of
corrosioon that has
h
happened to thhe
reinforccement embbedded in the concreete
due thee process of
o accelerated corrosioon.
In order to deteermine thee amount of
Copyrigh
ht © 2013 ScciResPub. in
Internation
nal Journal of A
Advancements in
n Research & Teechnology, Volu
ume 2, Issue4, A
April‐2013 436 ISSN 2278‐7763 (c) PREPARA
ATION OF
F TEST
SPECIME
ENS (CYLINDERS)
The aiim of my
y project is
i ultimateely
concenttrated on fiinding the bond
b
strenggth
that is existing beetween the concrete annd
the reinnforcement. For this thhe guidelinnes
from IS
S 2770 (paart1) was followed.
fo
Thhe
cylinderr was cast in such a manner
m
thatt a
5.. EXPECTIING RESU
ULT
The finall outcome of
o this invesstigation
iss to bring
g out thee performaance of
reeinforcemennt
in
various
v
c
corroded
ennvironments when micro silica is
i partly
ussed as abindding materiaal..
The pulll out
teest will give
g
the
bottom cover of 50
5 mm wass given. Aftter
vaariation in bond
b
streng
gth on the corroded
c
that a rood was centtered to thee cylinder annd
annd control specimensoof ordinary as well
a 50 mm
m ht concreete was pouured. Now thhe
ass micro silicca contaiingg concrete.
balancee rod was covered usinng a pvc pippe
of
moore than 25
2 cm ht. the aim of
providinng the pvc pipe was to avoid thhe
unnecesssary area of contactt. It helps in
avoid
water
to
have
c
contact
wiith
reinforccement. Speecimens aree prepared for
f
non corrroded ordiinary concrrete, corroded
ordinaryy
concreete,
nonn
corroded
microsiilica concreete, corrodeed microsiliica
concrete.
R
REFERENC
CES:
M Mazloom,
M
J J Brooks ; “Effect
1.
of silica
s
fumee on mecchanical
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c
“;
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and
c
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compposites 26, 2004
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morphous
silicaa” ; Construuction and bbuilding
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steel
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ound pumiice and
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Nagib ; “Characteristics of silicafume concrete”;
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materials; Engineering materials
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