MEGHA BALLARI AND PRACHI BORKAR VI SEM CIVIL NANO CONCRETE MEGHA BALLARI AND PRACHI BORKAR VI SEM CIVIL

INTRODUCTION 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.

NANO MATERIALS Carbon Nanotubes. Nano-silica. Polycarboxylates.

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

PROPERTIES CNT are also highly flexible. Mechanically, CNT appear to be the strongest material. The smaller diameters. Stiffest and strongest fibers.

NANO SILICA 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.

NANO SILICA

PROPERTIES 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 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.

POLYCARBOXYLATES

RESULTS 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.

CONCLUSION 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.

SCOPE 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.

REFERENCES [1] Balaguru, P. N. (2005), “Nanotechnology and Concrete: Background, Opportunities and Challenges.” Proceedings of the International Conference application of Technology in Concrete Design. [2] Boresi, Arthur P.; Chong, Ken P.; Saigal, Sunil. Approximate Solution Methods in Engineering Mechanics, John Wiley, New York, 2002, 280 pp. [3] Balaguru, P.; and Shah, S.P. Fiber Reinforced Cement Composites, McGraw-Hill, New York, 1992, 530 pp. [4] “Concrete”, Wikipedia, http://en.wikipedia.org/wiki/Concrete. [5] Srivastava, D.; Wei, C.; and Cho, K. “Nanomechanics of carbon nanotubes and composites.” Applied Mechanics Review, 56, 2003, 215-230. [6] LI, G. Properties of high-volume fly ash concrete incorporating nano-SiO2. Cement and Concrete Research. 34. 2004. P. 1043 – 1049. [7] McCARTHY, M.J. & DHIR, R.K. Development of high volume fly ash cement.

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