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Centre for Cement Research and Independent TestingNational Council for Cement and Building Materials [email protected]
STUDIES ON CEMENT HYDRATION INPRESENCE OF NANOSILICA
S Harsh, A K Arora, Varsha Liju and M M AliNational Council for Cement and Building Materials
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2
Nanomaterials are ultrafine particleshaving dimensions of the order of1-100nm.
Nanoparticles are reported to improvethe properties of cement and concrete.
In the present studies, a significant
improvement in compressive strengthof cement samples has been reportedincluding hydration studies of OPCnanosilica blends using TGA, DTA andFTIR techniques.
BACKGROUND
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Sample
Code
LOI CaO SiO2 Al
2O
3 Fe
2O
3 MgO SO
3 Na
2O K
2O
OPC 2.67 62.28 20.76 4.96 4.63 1.19 2.13 0.18 0.41
NS - - 98.57 - - - - - -
43 grade OPC meeting requirement of IS 8112 : 1989
was used. Nanosilica used in the study had an average particle
size of 15nm.
Polycarboxylate ether based superplasticizer was used
in mortar of cement blends with nanosilica.
CHEMICAL CONSTITUENTS IN %
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SAMPLE CODE COMPOSITIONOPC Nano-silica %
OPC 100 0
OPC-NS3 97 3
OPC-NS5 95 5
Blending was carried out in a batch type laboratory
ball mill with only 10-15 balls. Homogeneity of the blend was checked by drawing
three random samples from the bulk and analyzing
SiO2content in them.
COMPOSITION OF BLENDS OF OPC ANDNANOSILICA
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Pastes of OPC and OPC-nanosilicablends were prepared using w/cratio of 0.4.
The pastes were stored in sealedplastic vials in a temperaturecontrolled cabinet at 271C.
The hydration was arrested at agesof 1, 3, 7 and 28 days by acetone.
The dried hydrated powders werethen subjected to DTA, TGA andFTIR investigations.
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TG/DTA CURVE OF 3 DAYS HYDRATEDOPC SAMPLE
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TG/DTA CURVE OF 3 DAYS HYDRATEDOPC-NS5 SAMPLE
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SAMPLECODE
Total wt loss % in hydratedsamples
Wt loss % from Ca(OH)2,formed in the hydrated
samples
1 D 3 D 7 D 28 D 1 D 3 D 7 D 28 D
OPC 15.54 18.06 19.69 22.45 2.12 2.64 2.82 3.19
OPC-NS3 17.32 19.77 20.95 22.91 1.86 1.53 2.13 1.97
OPC-NS5 18.21 18.72 21.77 22.94 1.76 1.51 1.70 1.71
In presence of nanosilica the Ca(OH)2gets assimilated as
evident from decrease in weight loss pattern
OBSERVATIONS OF TG/DTA STUDIES
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FTIR Spectra of Anhydrous OPC and
OPC hydrated for 1, 3, 7 and 28 Days
(cm-1)
Anhydrous OPC
7 D
3 D
1 D
28 D
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FTIR Spectra of OPC-NS5 hydrated for 1, 3, 7
and 28 Days
1 D
3 D
7 D
28 D
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PHYSICAL PROPERTIES OF BLENDS
PREPARED WITH OPC AND NANOSILICA
CODE NO. PHYSICAL PROPERTIES
Blaines,
m2/Kg
N.C.
%
SP.
GRAV.
IST
Mts.
FST
Mts.
OPC 281 27.6 3.15 120 180
OPC-NS3 567 36.2 3.07 60 168
OPC-NS5 719 41.2 3.01 20 100
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COMPRESSIVE STRENGTH OF OPC ANDNANOSILICA BLENDS AT w/c RATIO OF 0.4
CODE NO.SP
Dose
COMPRESSIVE STRENGTH, MPa
1 D 3 D 7 D 28 D
OPC 0.0 20.29 34.31 48.66 61.25
OPC-NS3 0.45 24.92 42.69 53.69 72.84
OPC-NS5 0.7 22.83 51.15 65.44 72.68
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RELATIVE COMPRESSIVE STRENGTHS OF OPCAND NANOSILICA BLENDS
0
20
40
60
80
100
120
140
160
180
1D 3D 7D 28D
Age (Days)
RelativeCompressive
Strength
OPC
OPC-NS3
OPC-NS5
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The studies on hydration of OPC-nanosilicapastes with TG/DTA and FTIR confirmedthe acceleratory effect of nanosilica oncement hydration and its pozzolanic
reaction even at early age of 1 day.
Nanosilica addition, in the range of 3-5percent resulted in substantial increase in
the Blaines fineness and normalconsistency of cement blends.
CONCLUSIONS
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CONCLUSIONS
Nanosilica caused shortening of settingtimes, which was attributed to theacceleratory effect of nanosilica on earlycement hydration.
3-5 percent nanosilica caused increase of10-49 percent in the compressivestrengths of OPC blends at ages of 1-28
days.
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