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• Nanotechnology is one of the most active research areas which has wide applications in almost all the fields.
• As concrete is most usable material in construction industry it’s been required to improve its quality.
• Improving concrete properties by addition of nano particles have shown significant improvement than conventional concrete.
Why nanotechnology for concrete?
• Improves the materials’ bulk properties.
• Ability to control or manipulate materials at the atomic scale. NANOSCALE ATTACK ON ASR (ALKALI SILICATE REACTION)
• To obtain thinner final products and faster setting time.
• Cost effectiveness.
• Lowered levels of environmental contamination.
What is nano concrete?
• A concrete made with portland cement particles that are less than 500nm as a cementing agent.
• Currently cement particle sizes range from a few nano-meters to a maximum of about100 micro meters.
• Carbon Nanotubes.
CARBON NANO TUBES
• Carbon nanotubes are molecular-scale tubes of graphitic carbon with outstanding properties.
• They can be several millimetres in length and can have one “layer” or wall (single walled nanotube) or more than one wall (multi walled nanotube).
• SINGLE WALLED CARBON NANO TUBES
• MULTI WALLED CARBON NANO TUBES
• CNT are also highly flexible.
• Mechanically, CNT appear to be the strongest material.
• The smaller diameters.
• Stiffest and strongest fibers.
• Is the first nano product that replaced the micro silica.
• Advancement made by the study of concrete at nano scale have proved nano silica much better than silica used in conventional concrete.
• High compressive strengths concretes ( 15 MPa and 75 MPa at 1 day; 40 MPa and 90 MPa at 28 days and 48 MPa and 120 MPa at 120 days.)
• High workability with reduced water/cement ratio.
• Use of super plasticizing additives is unnecessary.
• Fills up all the micro pores and micro spaces.
• Cement saving upto 35-45%.
• Polycarboxylates or polymer based concrete admixtures are High Range Water Reducing admixture (HRWR).
• low dosage-reduce water as much as high dosage of conventional admixtures.
• Higher dosage-produce Self Compacting Concrete (SCC).
• This admixture type is very suitable for underwater anti-washout concrete.
• Resistance to compression - 40 to 90MPa in 1 day.Resistance to compression from 70 a 100 MPa (or more) in 28 days.
• Produces high resistance even with low addition (1 to 1.5 % of the cements weight) and gives self compacting characteristics with higher proportions (2.5 %).
• Meets the norms of environmental protection.
• 70% less use of additives as traditional silica, super plasticizers or traditional fibres.
BENEFITS OF NANO CONCRETE
• Cessation of contamination caused by micro silica solid particles.
• Lower cost per building site.
• Concrete with high initial and final compressive and tensile strengths.
• Concrete with good workability.
• Cessation of super plasticizing utilization.
• Cessation of silicosis risk.
• Well dispersed nano particles increase the viscosity of the liquid phase, improves the segregation resistance and workability of the system.
• Accelerates the hydration.
• Better bond between aggregates and cement paste.
• Improves the toughness,shear,tensile strength and flexural strength of concrete.
• If Portland cement can be formulated with nano-size cement particles, it will open up a large number of opportunities.
• The cement will not only be more economical than organic polymers but also will be fire resistant.
• A number of investigations have been carried out for developing smart concrete using carbon fibers.
• This will become a reality with nano-cement because nano-carbontubes are much more effective than carbon fibers. The thickness of the composite can be reduced to microns and hence flexible and smart cement composite can be manufactured.