Studies on Cement Hydration in Presence of Nanosilica,

8/13/2019 Studies on Cement Hydration in Presence of Nanosilica,

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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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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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Studies on Cement Hydration in Presence of Nanosilica,

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