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    DETAILED STUDY ABOUT NANO MATERIALS AND THERE EFFECTS ONCONCRETE BEHAVIOUR

    Various nano materials used in concrete and construction industry are

    1. nano-Fe 2O3 and

    2. nano-SiO 2

    3. Titanium dioxide (TiO 2)

    4. CaCO 3 Nanoparticles

    5. Carbon Nanotubes (CNT)

    6. zinc dioxide nanoparticles

    7. Al 2O3 nanoparticles

    8. Nano- Flyash9. ZrO2 Nanoparticles10.CuO nanoparticles11.Zinc Oxide Nanoparticles (ZnO)12.Silver Nanoparticles (Ag)13. Wolfram (Tungsten) Oxide Nanoparticles (WO3)

    NANOMATERIALS AND NANOTECHNOLOGIES FOR CONCRETE:

    The nanotechnologies can be defined as the design, characterization, production

    and application of structures, devices and systems by controlling shape and size atthe nanoscale. Nanotechnology requires advanced imaging techniques for studyingand improving the material behavior and for designing and producing very finepowders, liquids or solids of materials with particle size between 1 and 100 nm,known as nanoparticles

    Currently, the use of nanomaterials in construction is reduced, mainly for thefollowing reasons: the lack of knowledge concerning the suitable nanomaterials forconstruction and their behavior; the lack of specific standards for design andexecution of the construction elements using nanomaterials; the reduced offer of nanoproducts; the lack of detailed information regarding the nanoproducts content;high costs; the unknowns of health risks associated with nanomaterials.

    In order to be able to use in the construction industry the nanomaterials at widescale it is necessary that the researches to be conducted following the next stages:the choice of nanomaterials with potential use in construction and the study of theircharacteristics; the behavior study of the building elements that containnanomaterials under various loads; the development of specific design andconstruction standards.

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    This paper is part of the first stage of research and represents a synthesis of nanomaterials behaviour, properties developed and the short comings that it is to beused in construction.

    NANOMATERIALS FOR CONSTRUCTION

    Because the size of the particles is a critical factor, the material propertiessignificant differ at the nanoscale from that at larger scales. Physical phenomenabegin to occur differently below the boundary limit: gravity becomes unimportant,electrostatic forces and quantum effects start to prevail. In the same time, theproportion of atoms on the surface increases relative to those inside, creating so-called nano-effect. All these nano-properties actually affect the materials behaviorat macro-scale and, from this point, the power of nanotechnology is emphasized: if the elements are proper manipulated at the nanoscale, the macro-properties areaffected and new materials and processes can be developed.

    We will discuss in detail each nano materials and there effects in concrete andconstruction industry

    1. Carbon Nanotubes

    Nanotubes are members of the fullerene structural family and exhibitextraordinary strength and unique electrical properties, being efficient thermalconductors.

    Carbon nanotubes are in the structural family of fullerene. They are moleculescomposed entirely of carbon atoms. The carbon atoms are usually arranged in ahexagonal pattern, bonded together with extremely strong covalent bonds. A carbonnanotube can be visualized as a finite number of carbon graphite shells arrangedaround a hollow center axis with a constant spacing of around 0.34 nm, a tubulardiameter normally ranging from 2-25 nm, and with lengths up to several microns. Thisnumber of graphite shells is the basis for the major division in carbon nanotubes,

    i. One layer or wall - single walled nanotube (SWNT)and

    ii. More than one wall - multi walled nanotube (MWNT).

    CNT can be produced with different types of chirality

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    (the orientation of the hexagons formed by the carbon atoms with respect to the tubeaxis). Two tubes with the same diameter may therefore have different structuresdespite being formed solely of carbon atoms. The concept of either single walled ormulti-walled carbon nanotubes is important because the properties changesignificantly with respect to each other. The remarkable properties of CNTs are thecause of intense research around the world on possible applications.

    1.1.1 Properties of CNTMechanically, CNT appear to be the strongest material yet to be discovered.

    1. have 5 times the Youngs modulus than steel and that exceed 1 TPa.2. 8 times (theoretically 100 times) the strength of steel whilst being 1/6th

    the density. Measurements of the yield strength of SWNT of 63 GPa aswell as yield strains are on the order of 6%.

    3. CNT are also highly flexible, being capable of bending in circles orforming knots. Like macroscopic tubes, they can buckle or flatten underappropriate loadings.

    4. Multi-walled tubes slide telescopically without resistance5. They can be ballistically electrically conducting (with no resistance) or

    semi-conducting depending on the exact structure.6. Thermal conduction is also very high along the tube axis, but very low

    perpendicular to it.7. CNT are excellent reinforcing materials because of their extremely high

    strength, toughness and aspect ratios.

    Benefits of using CNT in concrete