Evaluation of nanoparticles on the behavior of concrete
immersed in chloride media.
Waleed H. sufe
1.
Ass. Prof in Housing and Building National Research Center, P.O. Box 1770, Cairo, Egypt.
Abstract
Concrete science is a multidisciplinary area of research where
nanotechnology potentially offers the opportunity to enhance the
understanding of concrete behavior, to engineer its properties and to
lower production and ecological cost of construction materials.
This paper presents the effect of hydration time to mechanical and
corrosion properties of concrete include different types of nanoparticles
CaCo3, SiO2, Al2O3 and magnesium oxide. Concrete immersed in highly
aggressive media (5% HCl). Corrosion behavior is studied by using
linear polarization techniques. Linear polarization plot and tafel analysis
used to determine the corrosion rate. Results show the significant effect
of nano particles to reduce the effect of aggressive media. The resistance
to corrosion with time is shown clear in presence of SiO2, Al2O3 and this
effect decreases in present of CaCo3 nanoparticles. Magnesium oxide
doesn't get promising effect as nanoparticles additives.
1. Introduction
The most widely conducted studies on the use of nanoparticles in
cement and concrete have been on nano oxides, especially SiO 2 and
Fe2O3 [1–7]. The addition of these nanoparticles to cement paste
containing high volumes of fly ash and to sludge ash concrete mortars
resulted in an increase in compressive strength. Nano-Fe2O3 and nanoSiO2 were also used to increase the abrasion resistance of concrete for
pavement [5]. Nano Ca(OH)2 particles have been prepared and their
thermal properties were characterized to study the anomalous behaviors
of Ca(OH)2 in cement paste [8]. Also, other nano to sub-micro inorganic
particles, such as zeolite, have been added to cement systems with the
goal to improve the overall microstructure [9]. Synthetic C-S-H has also
been used as seeding agent during the hydration of cement phases [10].
The use of CaCO3 was first considered as filler in cement to
replace OPC. However, the results from a number of studies have shown
positive effects of CaCO3 additions in terms of strength and acceleration
of hydration rate. A study on the accelerating effect of finely ground
CaCO3 addition on the hydration of C3S showed that the higher the
CaCO3 addition, the greater was the accelerating effect [11]. The
accelerating effect of the finely ground CaCO3 addition on the hydration
of cement paste was also observed [12].
2. Experimental.
The materials used in this investigation were nano particles of
calcium carbonate, magnesium oxide, silicon oxide and aluminum oxide
and size is equal 15nanometer. As well as ordinary Portland cement
(OPC) produced from Egypt Cement Company. The chemical analysis of
the starting materials is shown in Table (1.a).
Table 1.b, 1.c, 1.d represent the the mechanical properties the used
gravel and sand, Main physical and mechanical properties of the used
ordinary Portland cement and Concrete mix ingredients respectively
Table 1: Chemical composition of the starting materials.
-----------------------------------------------------------Chemical composition (%)
OPC
CaO
64.80
SiO2
21.40
Al2O3
6.36
Fe2O3
3.35
MgO
1.85
SO3
1.77
K2O
0.54
Na2O
0.28
TiO2
0.02
L.O.I
0.81
BaO
Table (1.b) Main physical and mechanical properties for the used gravel and sand
Gravel
Unit Weight
Specific Gravity
Crushing Coefficient
Sand
1.60 t/m3
2.86
13.76%
Unit Weight
Specific Gravity
1.67 t/m3
2.5
Table (1.c) Main physical properties of the used ordinary Portland cement
Initial setting time
Final setting time
Hr
2
Hr
5
min
20
min
30
Table (1.d) Concrete mix ingredients
Material
Content
Cement
Basalt
Sand
Water
350 kg/m3
1291 kg/m3
633 kg/m3
175 liter
2.1 The electrochemical measurement.
The electrochemical behaviors of reinforcing steel were determined
by linear polarization techniques and the
measurements were determined after the rods
were mechanically polished and degreased with
acetone then coated with epoxy and wax at all
point without a certain area(10cm2). The coating
by cement pastes was applied to steel.
Fig(1) : Reniforcement concrete cylinders.
reinforcement in moulds have certain volume. The electrochemical
measurements were determined by voltalab 10 PGZ100 ”all- in -one“
Potentiostate / Galvanostate system (made in France).
3. Result and dissection
3.1Mechanical behavior according to hydration time:
Variation in compressive strength according to time of hydration of
concrete includes different types of nanoparticles recorded in Table (2).
Nano particles (CaCo3, SiO2, Al2O3 and MgO) added to concrete with
partculae percent concentration of 3%. The concrete was immersed in 5%
HCl. Compressive strength in the absence of nanoparticles was also
presented. These relations are plotted in Fig (2).
In absence of nanoparticles, Table (2) shows increases in
compressive strength according to hydration time up 28 days then the
compressive strength were destroy sharply due to the effect of high
aggressive media. The compressive strength increases from 170 Kg/cm2
to 475 Kg/cm2 at 28-day. Then the compressive strength decreased to 389
Kg/cm2 at 90-day.
Compressive strength in presence of nano aluminum oxide,
silicon dioxide and calcium carbonate increased with hydration time. The
compressive strength increases with the increasing of curing time due to
the nature of hydrated phases formed during the hydration process. The
precipitation and accumulation of hydrated products fill a part of the
available pores. Hence, the total porosity decreased and the values of
compressive strength increased.
Table (2) The variation in compressive strength of concrete with
hydration time at 5% (HCl) and in presence of 3% nanoparticles.
CaCo3
SiO2
Al2O3
MgO
Without
Nano
2
2
2
2
(Kg/cm ) (Kg/cm ) (Kg/cm ) (Kg/cm ) nanoparticle
particles
128
190
196
160
170
3days
7 days
194
270
281
248
230
14 days
362
387
376
377
356
28 days
563
570
589
492
475
90 days
583
586
588
511
389
700
compresive strenght (Kg/cm2)
600
500
400
300
CaCo3
SiO2
Al2O3
200
MgO
100
Without
0
100
80
60
40
20
0
hydration time
Fig (2) The relation between compressive strength of concrete with
hydration time at 5% (HCl) in presence of 3% nanoparticles.
Generally, the gain of the strength at early days of hydration was
generally attributed to the formation of sulphoaluminate hydrate from the
alumina of OPC. The C3S and β-C2S phases were hydrated to form
calcium silicate hydrate and free lime. The liberated limes react with
alumina and accelerated the hydration process which leading to excessive
the accumulation of quantities of calcium sulphoaluminate as well as
(CSH). The hydration product (calcium silicate hydrate) contributes to
the improvement of the strength at intermediates and later ages of
hydration. Up to 28-day the compressive strength doesn't increases due to
the consuming of aluminum or portlandite. Also effects of aggressive
media were charged and the concrete layers were decayed.
In presence of nano aluminum oxide compressive strength
improved from 160 to 588 Kg/cm2 and recorded higher improvement in
strength compared to other types of nano particles. Nano alumina
improved the strength. Silicon dioxide improved the compressive strength
e from 190 to 586 Kg/cm2 and came in the second place after aluminum
nanoparticles. Calcium carbonates improved the strength and the
compressive strength increased from 128 to 583 Kg/cm2. Finally
magnesium oxide nanoparticles improved the strength from 160 to 511
Kg/cm2.
3.2Electrochemical behavior according to hydration time.
3.2.1. Corrosion potential.
The effect time of hydration of concrete included different types of
nanoparticles (CaCo3, SiO2, Al2O3 and MgO) added in concrete with
certain percent concentration 3% and the concrete immersed in 5% HCl
on the electrochemical behaviors of reinforcing steel was investigated
under the polarization conditions. The linear polarization and Tafel
extrapolation techniques were employed at scan rate 20 mV/ S. The
values of corrosion potential were calculated and presented in Table (3).
The corrosion potential of the reinforcing steel according to hydration
time was investigated and data are presented in Fig (3).
Table (3): The variation in polarization potential of concrete with
hydration time.
Nano
particles
E(i=0)(mV)
E(i=0)(mV)
SiO2
E(i=0)(mV)
Al2O3
E(i=0)(mV)
MgO
-370
-360
-423
3days
CaCo3
-392
7days
-374
-345
-342
-397
14days
-314
-312
-296
-365
28days
-281
-284
-249
-325
90 days
-313
-311
-298
-376
-200
100
80
60
40
20
0
-300
-350
E(i=0)(mV)
-250
CaCo3
SiO2
Al2O3
MgO
-400
hydration time (days)
-450
Fig (3): The relation between corrosion potential E(i=0) and hydration
time at 5% (HCl) in presence of 3% nanoparticles.
Table (3) shows the variation in E(i=0) according to time of
hydration. Generally, the corrosion potential increased with increasing
hydration time, in presence of CaCo3, E(i=0) shifted to more positive with
increase hydration time and potential shifted to -313 mV. in presence of
SiO2 corrosion potential shifted to more positive with increase hydration
time and potential shifted to -311 mV. E(i=0) got high value in presence of
Al2O3 with increase hydration time compared with other Nanoparticles
with increase hydration time and the potential shifted to -298mV.
Potential in presence of magnesium oxide with increase hydration time
has shown slightly shifted to more positive and the corrosion potential
record -376 mV. According to Stratfull , when its corrosion potential
value was more negative than -270 mV SCE, steel in concrete was
corroding. According to this role of stratfull the corrosion process in
reinforcing steel in presence of all nanoparticles with increase hydration
time up to 90 days take place.
3.2.2. Polarization resistance.
According to tafel plot, corrosion resistance was the property of
reinforcing steel in concrete to resist corrosion attack in a particular
environment. So that, polarization resistance Rp presents the resist of both
concert and passive layer. Relation between corrosion resistance and
hydration time were noted in Table (4). This relation obtained at 5% HCl
and certain concentration nanoparticles concentration 3%. Also this data
was plotted in Fig (4).
Table (4) The variation in polarization resistance of concrete with
hydration time.
Nano
particles
Rp(KΩ.cm2)
Rp(KΩ.cm2)
Rp(KΩ.cm2)
Rp(KΩ.cm2)
CaCo3
SiO2
Al2O3
MgO
3days
240
276
342
122
7days
286
343
423
233
14days
382
464
544
375
28days
477
523
736
489
90 days
322
512
613
312
800
700
500
400
300
200
Rp(KΩ.cm2
600
CaCo3
SiO2
Al2O3
MgO
100
0
100
80
60
40
20
0
hydration time (days)
Fig (4) The relation between polarization resistance Rp and
hydration time at 5% (HCl) in presence of 3% nanoparticles.
According to Table (4), the polarization resistance Rp increased
with increase hydration time, polarization resistance increases in presence
of Al2O3 with increase hydration time under aggressive media attack from
342 to 613KΩ.cm2 to present the highest increase in polarization
resistance followed by the increases in Rp in presence of SiO2 from 276 to
512 KΩ.cm2. The increasing in Rp was sligthlyly in presence of MgO
and CaCo3 and record decreasing from 122 to 312 and 240 to 322
KΩ.cm2 respectively.
Fig (4) shows the variation in hydration time and polarization
resistance of reinforcing steel in concert. Generally, the increase in
hydration time in all types of Nanoparticles was companied by increases
in polarization resistance. The results can be classified into two items;
alumina and silica present item effect directly on the micro structure of
concrete and follow by the formation of portlandite which increases the
passivation of reinforcing steel. On the other hand, CaCo3 and MgO
present the second item. CaCo3 and MgO don’t effect directly on the
microstructure of concrete, but the main effect was present in the
formation of passive layer. According to the classification of properties to
corrosion, if the polarization resistance was 250 < Rp then the passivation
process were produces. So that, each nanoparticle with increase in
hydration time can help to save passivation process. This result was
matching with corrosion potential results.
3.2.3. Corrosion rate.
According to tafel plot, rate of corrosion present the loss of mass
and diameter of reinforcing steel in concrete. Relation between corrosion
rate and concentration of HCl are shown in Table (5). This relation
obtained at 5% HCl and certain concentration nanoparticles concentration
3%. Also this data was plotted in Fig (5).
Table (5) The variation in corrosion rate of concrete with hydration
time.
Nano particles
Corr.Rat
(µm/y) CaCo3
Corr.Rat
(µm/y) SiO2
Corr.Rat
(µm/y) Al2O3
Corr.Rate
3days
0.12
0.080
0.040
0.13
7days
0.07
0.052
0.037
0.09
14days
0.05
0.025
0.005
0.07
28days
0.02
0.002
0.0008
0.06
90 days
0.07
0.011
0.004
0.08
(µm/y) MgO
0.14
0.1
0.08
0.06
0.04
Corrosion Rate (µm/y)
0.12
CaCo3
SiO2
Al2O3
MgO
0.02
0
100
80
60
40
20
0
hydration time (days)
Fig (5) The relation between corrosion rate and hydration time at 5%
(HCl) in presence of 3% nanoparticles.
According to Stern Garary equation, the corrosion rate in all cases
decreses with increasing of hydration time. Tafel equation and
determination of corrosion chance present in region 10 < p < 100 this
region were described as high chance to corrosion that mainly due to high
aggressive attack.
Corrosion rate in presence of aluminum oxide with increase in
hydration time changed from 0.12 to 0.07 µm/y and recorded higher
values to resist the corrosion. Corrosion rate in presence of SiO 2 with
increase in hydration time changed from 0.08 to 0.011 µm/y. corrosion
rate in presence of calcium carbonate nanoparticles with increase in
hydration time shifted from low corrosion at 0.12 µm/y to reach 0.07
µm/y. MgO recorded variation in corrosion rate from 0.13 to 0.08µm/y.
4. Conclusion
1. significant effect of nano particles to reduce the effect of
aggressive media.
2. The resistance of rainforcing steel to corrosion with time change
according to types of nanoparticles.
3. SiO2, Al2O3 nanoparicles shown significant effect to reduce
aggressive media effect especially at early days.
4. The corrosion behaviors in aggressive effect slightly change in
present of CaCo3 nanoparticles.
5. Magnesium oxide doesn't get promising effect as nanoparticles
additives.
6. Nanotechnology is a promising field in terms building materials.
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