seminar_ashish.docx

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NANOTECHNOLOGY IN CONCRETE

CE 613: Mtech Seminar Report

Submitted By: G ASHISH

Roll No12304T001

Under the supervision of:

PROF. PRAKASH NANTHAGOPALAN

Department Of Civil Engineering

Indian Institute of Technology Bombay

Powai, Mumbai400076.


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CONTENTS PAGE NO

1. Nanotechnology and its fundamental aspects 3

2. Application of Nanotechnology in Civil Engineering Aspect 3

3. How Nanotechnology helpful for concrete 4

4. Nano-cement 5

5. Effect of Nano-Silica on Concete 6

6. Effect of Nano-Fly Ash on Concete 7

7. Effect of Nano-Fibre on Concete 8

8. Effect on permeability by addition of nano-Fe2O3 ,TiO2 and Nano-clay 11

9. Conclusion 12

10.Reference 13


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NANO TECHNOLOGY ANS ITS FUNDAMENTAL ASPECT:

Nanotechnology is manipulation of materials at molecular and atomic scale .It is a advance

technology which deals with materials ,devices and structures which is having at least one

dimension 1 to 100 nano-meter. Itll more suitable to define nanotechnology as use of very

small pieces of materials themselves or manipulating them to create a large materials. There

is a drastic change in situation when we are dealing the materials at nano-scale. So it very

much possible to create new materials with improved properties by using Nano-technology.

Because of this it is one of the most active research areas among various engineering

discipline including civil engineering.

NANOTECHNOLOGY APPLICATION IN CIVIL EMGINEERING:

For the last decade It is seen that Nanotechnology can be contribute hugely to civil

engineering field because of its ability to produce unique characteristic components which

may solve many civil engineering problems.

This can form products that has

Lighter and stronger structural components.

Enhancing cement and concrete properties

Improving pipe joining materials and techniques

Increasing sound absorption of acoustic absorber.

Reducing the thermal transfer rate of fire retardant and insulation

Low maintenance coating.


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HOW THIS CAN BE HELPFUL FOR CONCRETE:

Concrete is one of the most common complex materials which is used in construction field

without knowing its properties completely. The rapid development of new experimental

technology makes us to understand the properties of concrete from macro level to nano level

which could be very useful to further enhance the properties of concrete.

Concrete is a porous material, ranging from air voids to pores of order some nano-meter.

These Pores contribute hugely towards the strength and durability because it contain calcium

silicate hydrate hydration product. So, we can change the properties of concrete by modifying

and exploiting this nano-scale pores.

Besides that, by adding this new technology in adequate manner can enhance tension

characteristic of concrete. The scale of various concrete component shown in figure below

Fig-[]

It can be argued that concrete utilizes nano-technology because it contains the nano-particle

as ingredient including nano water particle or air void as mentioned before. It is not just the

application technology at nano-level but if it is possible to create technological tools or


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organise the amount and location of nano-ingredient in a scientific way .then concrete can

experience advance in technology.

This can be done two ways: either by reducing the size of cement or by adding certain nano -

materials to concrete which enhances its properties.

NANO-CEMENT:

Avg. size of cement particle is 50 micron. If we reduce its size by order 10,then it is called as

nanocement. It has been proven that some properties of cement can be further improved by

reducing the size of particle. This lead to invent Nano-cement .As its name indicates that it ismuch finer than OPC particle. Due to high surface area it is more reactive as compared to

OPC. So, Setting Period of this cement is less as compared to OPC and It give high initial

strength and flexural strength.

But there are several drawbacks which dontallow complete replacement of OPC with this

fine cement. Those are

Ultimate strength of Nano-cement is less than that of OPC because when excessive

Nano-particle when added to cement the particle became aggregated, not well

dispersed .So thisll create a lot of voids. So it results in low strength.

Another possibility that rapidly hydration of nano-cement causes the high early

strength and more cement gel will form. If large quantity of gel is formed rapidly

because of a large surface of nano-cement ,the inhibiting mature of gel also take effect

Sooner .So extra fine grinding cement is only efficient for 7 days and later stage,

fineness became very important factor determining strength.

It is also known that strength of cement depend upon water content .As nano-cement

is having high surface area, It requires almost double the amount of water required for

OPC .which may decrease its ultimate strength.

But If Nano-cement can replace certain percentage of OPC may lead to high initial

strength also high final strength due to improved packing. So it can be very useful for

repairing work.

VARIOUS NANAO-TECH MATERIALS:

The properties of concrete at fresh state (flow properties and Workability) are instance

governed by particle size distribution but the properties of concrete at hardened state i.e

strength and durability, depend upon particle packing and grain size distribution. So one wayof improving the properties of concrete is by reducing the voids or increasing the packing.


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Packing can be done by adding Nano-materials(adding particle of order nm) .The

addition of following Nano-materials can be very helpful -

Nano-scale silica modifier.

Nano-clay

Nano-flyash

EFFECT OF NANO-SILICA ON CONCRETE:

In concrete as we know that addition of micro-silica improve the properties of concrete in

two ways:

Due pozzolanic reaction, it reacts with calcium hydroxide to form more C-S-H gel at

interfacial zone.

Since it 1/100thtime of cement, it can improve packing.

It also found that addition of 1kg of Silica fume can save 4Kg of cement.

Nano-silica is synthetic product with spherical particles in the range of 1-50 nano-meters. By

replacing, Micro-silica with Nano-silica which is 10 times smaller than Micro-silica

supposed to give following characteristic properties.

As it is having high surface area as compared to micro-silica it can give high initial

pozzolanic activity .So It will give high initial strength as compared to micro-silica cement.

Influence of Nano-silica(nS) on fresh properties: From previous experiment[12] it is seen

that addition of particle having higher surface directly influence the water amount required in

mixture. This behaviour shows that addition of nano-silica requires higher amount of water

and chemical in order to keep the workability of mixture. If the water content is kept

constant, addition of nano-content improves the packing and decreases the available water.

So there is higher internal friction. So initial and final setting time decreases drastically and

so dormant period.The addition of nS also increase of cohesion in the mortar.

The increasing nS also decreases the fresh density This reduction can be attributed to the

combined effect of air-entraining and the replacement of denser cement particles (3.1

g/cm3) by lighter nS particles (2.21 g/cm3).

It is also further seen that Since it very small compared to micro Silica , by optimizing its

dosage can give much improved packing as compared with cement containing micro-Silica.

So it is having less permeability and high chloride resistant. It also seen that adding nano-

silica makes C-S-H more stiff. Hence it improves modulus of elasticity of concrete.


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Again, due to small particle size it can save more cement as compared with micro-silica

replaced cement.

From the above explanation, it is concluded that Nano-silica increases the density,

reduces the porosity, increase durability and improve the bond between cement and

aggregates. So, It will give high initial compressive strength and flexural strength.

Drawbacks:

From the viscosity test it concluded that cement paste mortar with Nano-silica requires more

amount of water in order to make workable mixture.Also due to stronger tendency toagglomerates due to absorption of ionic species in aqueous medium.

But the later case may be minimized by addition of plasticizer which make the concrete

dispersive.

NANO-FLY ASH:

Flyash can be added to concrete as admixture because of its fineness , high specific area

,particle shape freeze thaw .It is having pozzolanic activity by which Ca(OH)2get converted

into C-S-H which makes the concrete strong and durable. Fly-ash not only improves the

strength of concrete but also it makes concrete mixture more durable. Beside that it makes the

concrete mixture more economical. By replacing this flyash with nano-flyash has shown that

several properties of concrete get improves.High Impact Collision required to bring down micro-crystalline structure to nano-

crystalline structure without any chemical change by which the surface properties of flyash

particle changes. The smooth, glassy and inert surface can be altered into rough surface by

which reactivity also increases which is shown in figures below:

.In industry high energy ball milling used to make such conversion.


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[3] (SEM PICTURE OF FLYASH)

[3] (SEM PICTURE OF NANO-FLYASH)

Since the nano-size particles are most active, Strength of concrete with nano-

flyash is found to be more than that of that of using concrete with flyash . High Early age

strength is due to high pozzolanic activity and final strength is dut to improved packing.

Due to improved packing, lesser amount of water required for preparation of this

kind of workable concrete. The workability of the concrete with nano fly-ash was also found

to be 90 to 140% higher than that of Normal Cement Concrete.

NANO-FIBRE:

Failure of cement is a gradual multi scale process. When load is small ,small micro or nano

level cracks are formed and they gradually increases to macro level. Due to multi scale

nature of cracks, the influence of fibre in reinforced concrete depends upon the scale of the

reinforcement. Macro-fibre (Dia. Less than 500 micron) can improve post-peak toughness bybridging macro cracks. Similarly micro fibre (less than 50 micron) can be effective after


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formation of micro cracks. So itll not effective while nano-cracks are formed .So Nano-

Fibres are can increase the durability of concrete drastically. It is also seen that using the

carbon nano tubes as reinforcing agent significantly increases the flexural strength and tensile

properties of concrete and also from Nano-Imaging of fracture it is seen that Multi wall Nano

carbon tubes reinforce the cement paste by bridging nano-cracks and pores.

Various experiments also show that 3,7,28 days strength of nano-composite

reinforced cement is greater than that of OPC cement. The flexural strength ,Youngs

modulus and toughness also increases with reinforcing nano-tubes. It is also impressive that

with small addition of nano-tubes improves the concrete properties drastically. During the

early stage of loading nano-fibres provides materials provide the concrete high load carrying

capacity and later stage they dont allow the cracks to propagate. It is also seen that CNF

embedded into hydration products, showing good bonding between the nano-fibres and the

matrix formed.

As nano-tubes inherent tendency to agglomerate due to high surface area and high

vanderwal force, It cantbe well dispersed .So in order to make efficient nano-concrete mix

,it is quiet necessary to have uniform mix i.e. well dispersed carbon nano-tubes. In order to

achieve well dispersed structure in is essential to add some surfactant or ultrasonic energy.

[14](Evidence of carbon nano-tubes having well-dispersed structure using ultrasonic energy

or surfactant agent)

This can be proved from following stress strain graph-

PCC are control cement mortar

PCCF is cement mortar containing untreated CFs,

PCNT is cement mortar containing 0.5% treated CNTs by weight of cement


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[ 14](Typical load-displacement curves of cement-based materials)Besides that the autogenouus shrinkage test shows that the nano-composite reduces

shrinkage at least 30% after 96 hours compared to that of the -based materials without CNTs.

Figure-[14]

[14](The autogenous shrinkage result of cement paste (w/c=0.3) and cement paste

reinforced with 0.048% wt of cement CNTs)Further it is also seen that CNTs decreases the porosity of nano-composite by filling the gaps

between hydration products. Therefore it became more packed. So It may lead to high

workability and strength.

It is also seen that it behave as nucleating agent for formation of C-S-H instead of un-

hydrated cement grains and this nucleation occurs over entire length which result dense C-S-

H formation which tightly holds CNTs. Hence it provides reinforcing behaviour.


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[ 14] ( Growth of C-S-H over whole CNTs)

FURTHER IMPROVEMENT BY ADDITION OF NANO-MATERIALS:

Concrete being porous material may subjected to chloride and sulphate attack. Excessive

accumulation of such materials may deteriorates the concrete properties and reduce its life

type. Certain nano-materials are very helpful to improve concretes durability. Various

electro migration tests showed that for cement mix of same design mix the incorporation

nano-materials like nano -Fe2O3, Al2O3, nano-clay improves the chloride penetration resistance

of mortar as indicated by reduced apparent diffusion of Cl-ion. The following graph shows,

how by adding various nano-materials by 1% the apparent chloride diffusion decrease.

[12] (Apparent diffusion coefficient of Cl in cement mortars (m2/s).)

The reduction of diffusion chloride induced by the nano-materials was in the order of nano-

clay > SiO2 > TiO2 > Al2O3 > Fe2O3, which is exactly the order of specific

surface area (SSA) of these nano-materials.


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CONCLUSION:

It is clear from this paper that Nano-technology play a vital role in understanding certain

properties of concrete and which may lead to develop concrete having better workability,

strength, durability, higher density .Besides that certain nano-particle and nano-reinforcement

also improve concrete properties drastically. Because of this development of improved

pozzolanic materials it may possible to substitute high cost cement with nano-materials. By

which not only construction became economical but also decrease environmental unfriendly

behaviour. But there is certain further research required for making of such kind nano-

materials efficiently which requires higher energy and reducing negative impact on

environment. Due to high surface area nano-particles like silica-fume, nano-cement etc

agglomerate which reduce the strength and durability of concrete. So while developing new

technique for production of nano-materials It should be always kept in mind that production

method should avoid formation of agglomerates .So that it can achieve better dispersion.


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REFERENCE:

[1]A.Maile, The Chemistry and Physics of Nano-Cement, Loyola Marymount

University,2006.

[2]G.QUERCIAand H.J.H. BROUWERS , Application of nano-silica (nS) in concrete

mixtures, Materials Innovation Institute M2i and Eindhoven University of Technology,

Building and Physics, 2011.

[3]Arulraj G. ;and Carmichael J. M., Effect of flyash on strength ofconcrete, International

Journal of Civil and Structural Engineering,Volume-2,No 2 , ,2011,pp 475-481.

[4]Z. S. Metaxa,;and M.S KonstaGdoutos, S.P Shah., Mechanical Properties of Cement

based Materials Reinforced with Carbon Nanofibres and Polyvinyl Alcohol Microfibres,SP-

270-10 ,pp115-124.

[5]B Bhuvaneswari ,S. Samal, Nanoscience to Nanotechnology for civil Engineering-Proof

of concepts,CSIR-Structural Engineering Research Center, ISBN: 978-1-61804-022-0,pp

230-235.

[6]M. Khanzadi ,M. Tadayon , H. Sepehri and M. Sepehri, Influence of Nano-Silica

Particles on Mechanical Properties and Permeability of Concrete,Coventry University and

The University of Wisconsin Milwaulee Centre for By-products Utilization, Second

International Conference on Sustainable Construction Materials and Technologies,

Universit Politecnica delle Marche, Ancona, Italy. June 28 - June 30,2010, ISBN 978-1-4507-1490-7.

[7]P. Mondal,S.P. shah, L.D.Marks and J.J. Gaitero, Cpmparative study of the Effects of

Microsilica and Nanosilica in Concrete , Journal of the Transportation Research Board, No.

2141, , 2010, pp. 69.

[8]M. Nili , A. Ehsani and K. Shabani ,Influence of Nano-SiO2 and Microsilica on

Concrete Performance , Coventry University and The University of Wisconsin Milwaulee

Centre for By-products Utilization, Second International Conference on SustainableConstruction Materials and Technologies , Universit Politecnica delle Marche, Ancona,Italy. June 28 - June 30,2010, ISBN 978-1-4507-1488-4.

[9]P.Balaguru and K. Chong,Nanotechnology and Concrete Research

opportunities,National Science Foundation,USA,November 7,2006,pp 13-27.

[10]K.Andrew and S. Palmquist , characteristic of carbon nano tube on reinforced concrete

composite,Department of physics , Western Kentucky University, Applied physics institute.

[11]Xiaodong He and Xianming Shi Chloride Permeability and Microstructure ofPortland Cement Mortars Incorporating Nanomaterials, Transportation Research Record:Journal of the Transportation Research Board, No. 2070, Transportation Research Board ofthe National Academies, Washington,2008,pp 13-21.


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[12]L. S. Joo, A. Labrincha , V. M. Ferreira ,D. Hotza and W. L. Repette Effect of nano-silica on rheology and fresh properties of cement pastes and mortars Construction and

Building Materials 23 ,2009,pp 24872491.

[13]http://en.wikipedia.org/wiki/Nanotechnology

[14] K. Gopalakrishnan, B. Birgisson, P.C. Taylor and N. O. Attoh-Okine, Nanotechnology

in Civil Infrastructure , Springer publication,2011,273 pp.
http://en.wikipedia.org/wiki/Nanotechnologyhttp://en.wikipedia.org/wiki/Nanotechnology

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