21-04-2014, 04:42 PM
NANOTECHNOLOGY IN CIVIL ENGINEERING
CIVIL ENGINEERING.pptx (Size: 74.54 KB / Downloads: 78)
What is Nanotechnology
Nanotechnology is the art and science of manipulating matter at nanoscale.
Nanotechnology can be considered as one of the emerging technologies of the future. (‘Nano’ means one- billionth of meter).
A nanometer is one billionth of a meter, roughly the width of three or four atoms. The average human hair is about 25,000 nanometers wide
For comparison
typical carbon-carbon bond length are in range 0.12-0.15nm
DNA has a diameter around 2nm.
bacteria of genus Mycoplasma are around 200nm in length.
Physical Characteristic of Nanomaterial
At Nano scale physical properties of system or particles substantially change.
Nano materials and particles can act as catalyst to increase the reaction rate along with that produce better yield as compared to other catalyst.
Traditional materials show radically enhanced properties when engineered at the nanoscale.
Some of the most interesting properties when particle gets converted to nano scale are substances which usually stop light become transparent (copper); it becomes possible to burn some materials (aluminum); solids turn into liquids at room temperature (gold); insulators become conductors (silicon). A material such as gold, which does not react with other chemicals at normal scales, can be a powerful chemical catalyst at nanoscales. These special properties which we can only see at the nano scale are one of the most interesting things about nanotechnology.
Nanotechnology in Construction
The construction business is a beneficiary of nanotechnology
In fact it is already in the fields of concrete, steel, glass and many more.
Concrete is more durable and more easily placed.
Steel is made tougher, glass as self cleaning
Paints are made more insulating and water repelling
Titanium Dioxide
Titanium dioxide is a widely used white pigment.
It can oxidize oxygen or organic materials, and so added to paints, cement, windows & tiles or other products for sterilizing, deodorizing and anti fouling properties.
When incorporated into outdoor building materials can substantially reduce concentrations of airborne pollutants.
Additionally as Tio2 is exposed to UV light, it becomes increasingly hydrophilic , thus can be used for anti clogging coatings or self cleaning windows.
When it is used in concrete has a white colour that it retains its whiteness effectively unlike the stained buildings of the materials of the pioneering past.
Photocatalytic Tio2 added to concrete to reduce carbon monoxide and Nox emissions on road ways
Nano concrete
Defined as the concrete made with portland cement particles that are less than 500nm as the cementing agent.
Currently cement particle size ranges from a few nm to a max of 100000nm( 50 microns), and for micro cement the average particle size is reduced to 5000nm
Hydration tests indicated that a nano cement had a more rapid hydration rate than the portland cement.
CNT’s in concrete
If these nano cement particles can be processed with Nano tubes and reactive Nano size silica particles strong, tough and room temperature processed ceramics can be developed both for electronic application and coatings.
The addition of small amount (1%wt) of CNT’s can improve the mechanical properties
Oxidized multi walled Nano tubes show the best improvements both in compressive strength (+25 N/mm2) and flexural strength (+8 N/mm) compared to normal samples without reinforcement.
A number investigations have been carried out for developing smart concrete using carbon fibres.
Nanoadditive Fire Retardents
Use of nanoadditive fire retardants prompted bans on halogenated flame retardants enacted in many states.
Polymer nanocomposites filled with clay , CNTs etc., posses improved flammability resistance while maintaining or improving mechanical properties.
Reduce heat release rate during fire event by formation of surface char which insulates underlying material.
Conclusion
In conclusion, nanotechnology offers the possibility of great advances whereas the conventional approach at best offer only incremental improvements.
At this moment the main limitation is the cost of nanotechnology and also concerns with the environmental concerns.
The waves of change being propagated by progress at the nano scale will therefore be felt far and wide in construction due to its large economic and social presence.