06-12-2012, 06:44 PM
NANOTECHNOLOGY IN CIVIL ENGINEERING
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Introduction:
Nano technology is an enabling technology that allows us to develop materials with improved or totally new properties.
It is the use of very small particles of a material.
A nanometer is a billionth of a meter.
Nanotechnology is not a new science and a new technology.
It is to examine the nature of science at even smaller scale.
Nanotechnology in construction:
The construction business will inevitably be a beneficiary of this technology.
It is employed in the field of concrete,steel and glass.
Concrete is stronger more durable and more easily placed.
Steel is made tougher.
Glass is self-cleaning.
Paints are made more insulating and water repelling.
Introduction to nano-materials:
Nano-particle:
• It is defined as a particle with atleast one dimension less than 200nm
Nano composite:
• It is produced by adding nano particle in bulk material in order to improve bulk properties.
Carbon nanotubes:
• They are cylindrical with nanometer diameter and can be several millimeters in length.
• The have 5 times the young's modulus and 8 times the strenght of steel.
• Thermal conduction is very high along the tube axis.
Titanium oxide:
Titanium dioxide is a widely used white pigment.
It can oxidize oxygen or organic materials and so added to paints, cements, windows , tiles or other products for sterilizing, deodorizing and anti-fouling properties.
When incorporated into outdoor building materials can substantially reduce concentration of air borne pollutants.
Concrete:
Concrete is a mixture of cement, sand, aggregate and water.
As concrete is most usable material in construction industry it's been required to improve its quality.
The mechanical behaviour of concrete materials depends on phenomena that occur on a micro and nano scale.
Nanotechnology in Concrete:
Nanotechnology can modify the molecular structure of concrete material to improve the material properties.
Nano-concrete is defined as "A concrete with Portland cement particles that are less than 500 nano-meters as cementing agent.
Concrete is a macro-material strongly influenced by its nano-properties.
If the nano-cement particles can be processed with ano tubes and reactive Nano-silica particles,conductive,tough and room temperature ceramics can be devoloped for both electronic applications and coatings.
Average size of portland cement particle is about 50 microns.
In thinner fine products and faster setting time,microcememt with a maximum particle size of about 5 microns is being used.
Therefore is reduced to obtain nano-portland cement.
What is Titanium Oxide?
Another type of nanoparticle added to concrete to improve its properties is titanium dioxide
(TiO2) (box 2, p7).
TiO2 is a white pigment and can be used as an excellent reflective coating.
It is incorporated, as nanoparticles, in sun-block to block UV light and it is added to paints,
cements and windows for its sterilizing properties since TiO2 breaks down organic pollutants,
volatile organic compounds, and bacterial membranes through powerful catalytic reactions.
It can therefore reduce airborne pollutants when applied to outdoor surfaces.
Additionally, it is hydrophilic (box 4, p9) and therefore gives self cleaning properties to surfaces to which it is applied.