Nano Tecnology in Civil Engineering by Md Saif Ahmed

8/8/2019 Nano Tecnology in Civil Engineering by Md Saif Ahmed

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NANOTECHNOLOGY IN CIVIL ENGINEERING

Prepared by:Md. Saif Ahmed ,2nd year Civil Engineering Branch,Regd. No. 0901294182Raajdhani Engineering College

ABSTRACTCivil engineering is always restricted to cement, sand and stonesbut it is something

beyond that. It deals with innovations in each and every step of constructing astructure. This paper deals with the nanological treatment in civil engineering.

Nanotechnology is the use of very small particles of material either by themselves or by their manipulation to create new large scale materials. The size of the particles,though, is very important because at the length scale of the nanometer, 10-9m, the

properties of the material actually become affected. Nanotechnology is not a newscience and it is not a new technology. It is rather an extension of the sciences andtechnologies that have already been in development for many years and it is thelogical progression of the work that has been done to examine the nature of our worldat an ever smaller scale. The construction business will inevitably be a beneficiary of this nanotechnology; in fact it already is in the fields of concrete, steel and glass.Concrete is stronger, more durable and more easily placed, steel tougher and glassself-cleaning. Increased strength and durability are also a part of the drive to reducethe environmental footprint of the built environment by the efficient use of resources. At this moment the main limitation is the high costs of nanotechnology. Alsoconcerns with the environmental effects

The waves of change being propagated by progress at the nano-scale will therefore befelt far and wide and nowhere more so than in construction due its large economic andsocial presence.INTRODUCTIONAs people involved in construction, we are very familiar with the concept of gettingraw materials, bringing them together in an organized way and then putting them

together into a recognizable form. Construction then is definitely not a new science or technology and yet it has undergone great changes over its history. The industry wesee today is the result of a progression in science, technology, process and business.In the same vein, nanotechnology is not a new science and it is not a new technologyeither. It is rather an extension of the sciences and technologies that have already beenin development for many years and it is the logical progression of the work that has

been done to examine the nature of our world at ever smaller and smaller scale.So what is nanotechnology?

Nanotechnology is the use of very small pieces of material by themselves or their manipulation to create new large scale materials.

Nano, which comes from the Greek word for dwarf, indicates a billionth. One

nanometer is a billionth of a meter, that is, about 1/80,000 of the diameter of a humanhair. Nanotechnology can best be considered as a 'catch-all' description of activities


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(any application of science and technology) at the nanometer scale that haveapplications in the real world. Definitions of 'nanotechnology' vary, but it generally

refers to understanding and manipulation of matter on the nano-scale, say, from 0.1run to 100 nm.Nanotechnology is an enabling technology that allows us to develop materialswith improved or totally new properties

What is a Nanoparticle ?A nanoparticle is a microscopic particle whose size is measured in nanometres(nm). It is defined as a particle with at least one dimension less than 200nm.Nanoparticles made of semi conducting material (material that is between aconductor and insulator e.g. silicon) may also be labeled quantum dots if they aresmall enough (typically sub 10nm) such that jumps in energy levels occur. Theimportance of this is that the same material of different sizes can emit differentcolours when energized with, for instance, UV light. Carbon Nanotubes are a subset of nanoparticles.

INTRODUCTION TO NANO MATERIAL

Carbon Nanotube (CNT)Carbon nano tubes are a form of carbon. They are cylindrical inshape, as shown in figure below, and their name comes fromtheir nanometer diameter. They can be several millimetres inlength and can have one layer or wall (single walled nanotube) or more than one wall (multi walled nano tube). Theyhave 5 times the Youngs modulus and 8 times (theoretically100 times) the strength of steel whilst being 1/6th the density.

Titanium dioxide (TiO2)Titanium dioxide is a widely used white pigment because of its

brightness. It can also oxidize oxygen or organic materials;therefore, it is added to paints, cements, windows, tiles, or other

products for sterilizing, deodorizing and anti-fouling propertiesand when incorporated into outdoor building materials cansubstantially reduce concentrations of airborne pollutants.Additionally, as TiO 2 is exposed to UV light, it becomesincreasingly hydrophilic (attractive to water), thus it can be usedfor anti-fogging coatings or self-cleaning windows.

NANO- TECHNOLOGY AND CONCRETEConcrete is a mixture of cement, sand (fine aggregate), coarse aggregate and water.As concrete is most usable material in construction industry its been required toimprove its quality. Silica (SiO 2) is present in conventional concrete as part of thenormal mix.


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However, one of the advancements made by the study of concrete at the nano-scale isthat particle packing in concrete can be improved by using nano-silica which leads to

a densifying of the micro and nanostructure resulting in improved mechanical properties. Nano-silica addition to cement based materials can also control thedegradation of the fundamental C-S-H (calcium-silicate hydrate) reaction of concretecaused by calcium leaching in water as well as block water penetration and thereforelead to improvements in durability.

Another type of nanoparticle added to concrete to improve its properties is titaniumdioxide (TiO 2) It is incorporated, as nanoparticles, in sun-block to block UV light andit is added to paints, cements and windows for its sterilizing properties since TiO 2

breaks down organic pollutants, volatile organic compounds, and bacterialmembranes through powerful catalytic reactions. It can therefore reduce airborne

pollutants when applied to outdoor surfaces.

A further type of nanoparticle, which has remarkable properties, is the carbon Nanotube and its benefits in using in concrete is, The addition of small amounts (1%wt) of CNTs can improve the mechanical properties of samples consisting of themain Portland cement phase and water.

NANO-TECHNOLOGY AND STEELSteel has been widely available since the second industrial revolution in the late partof the 19 th and early part of the 20 th Century and has played a major part in theconstruction industry since that time. Fatigue is a significant issue that can lead to thestructural failure of steel subject to cyclic loading, such as in bridges or towers. Thiscan happen at stresses significantly lower than the yield stress of the material and leadto a significant shortening of useful life of the structure. Stress risers are responsiblefor initiating cracks from which fatigue failure results and research has shown that theaddition of copper nanoparticles reduces the surface unevenness of steel which thenlimits the number of stress risers and hence fatigue cracking.Advancements in this technology would lead to increased safety, less need for monitoring and more efficient materials use in construction prone to fatigue issues.

NANO-TECHNOLOGY AND GLASSMost of glass in construction is, of course, on the exterior surface of buildings and thecontrol of light and heat entering through building glazing is a major sustainabilityissue.The current state of the art in cladding is an active system which tracks sun, wind andrain in order to control the building environment and contribute to sustainability, butthis is unreliable and difficult to calibrate and maintain.

Consequently, there is a lot of research being carried out on the application of nanotechnology to glass and some of the most promising areas are outlined below:

Titanium dioxide (TiO 2) is used in nanoparticle form to coat glazing since it hassterilizing and anti-fouling properties. The particles catalyze powerful reactions which

breakdown organic pollutants, volatile organic compounds and bacterial membranes.


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In addition, TiO 2 is hydrophilic and this attraction to water forms sheets out of raindrops which then wash off the dirt particles broken down in the previous process.

Glass incorporating this self cleaning technology is available on the market today.Fire-protective glass is another application of nanotechnology. This is achieved byusing a clear intumescent layer sandwiched between glass panels (an interlayer)formed of fumed silica (SiO 2) nanoparticles which turns into a rigid and opaque fireshield when heated.

Most of glass in construction is, of course, on the exterior surface of buildings and thecontrol of light and heat entering through building glazing is a major sustainabilityissue. A Researchinto nanotechnological solution to this centres around four differentstrategies to block light and heat coming in through windows. Firstly, thin film

coatings are being developed which are spectrally sensitive surface applications for window glass. These have the potential to filter out unwanted infrared frequencies of light (which heat up a room) and reduce the heat gain in buildings; however, these areeffectively a passive solution. As an active solution, thermo-chromic technologies are

being studied which react to temperature and provide thermal insulation to give protection from heating whilst maintaining adequate lighting. A third strategy, that produces a similar outcome by a different process, involves photo-chromictechnologies which are being studied to react to changes in light intensity byincreasing absorption. And finally, electro-chromic coatings are being developed thatreact to changes in applied voltage by using a tungsten oxide layer; thereby becomingmore opaque at the touch of a button. All these applications are intended to reduceenergy use in cooling buildings and could make a major dent in the huge amountsused in the built environment.

NANO-TECHNOLOGY AND COATINGS Nanotechnology is being applied to paints and insulating properties, produced by theaddition of nano-sized cells, pores and particles, giving very limited paths for thermalconduction are currently available. This type of paint is used, at present, for corrosion

protection under insulation since it is hydrophobic and repels water from the metal pipe and can also protect metal from salt water attack.

CONCLUSIONHuge potential has been predicted for nanotechnology applications in construction, and evenminor improvements in materials and processes could bring large accumulated benefits. In theshort to medium term, the greatest impact to the construction industry and the economy islikely to come from enhancement in performance of materials. In the medium to long term,nanotechnology development will lead to truly revolutionary approaches to design and

production of materials/structures with much improved energy efficiency, sustainability andadaptability to changing environment.

Ultimately, work on molecular nanotechnology offers the promise that building builds itself

(i.e. getting molecules to do the work).

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Nano Tecnology in Civil Engineering by Md Saif Ahmed