Title : AN OVERVIEW ON EFFECTS OF NANOSILICA ON DURABILITY OF CONCRETE
Authors : Lincy Varghese,VVL.Kanta Rao and Lakshmy Parameswaran
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Price : 250
Abstract : Concrete is the most widely used building material due to its high strength and durability. However, present day concrete structures are facing more durability problems than those of ancient times. Many concrete structures are failing before their design life due to durability concerns caused by deleterious agents getting access into concrete and reacting physically or chemically with the constituents of concrete. Hence the present day challenge of concrete technologists is to make the concrete more resistant to the environment to which it is exposed during its service life. Nano-modification of concrete is a novel advancement to improve its durability. Nanotechnology is influencing all fields of science and technology due to its immense potential in improving the existing properties as well as to impart new properties. The most commonly used nanomaterials in concrete are nano-silica, carbon nanotubes, nano-titanium oxide, nano-alumina and nano-iron. Among them, nanosilica (1-100 nm) is the most commonly used nanomaterial for concrete durability modification. With a very little addition of nanosilica (maximum of 3-5%), majority of the durability issues of concrete structures can be addressed as it modifies its microstructure and makes it resistant to harsh environment. High surface area of nanosilica helps in accelerating the hydration of cement and it acts as a nucleation site for generation of more Calcium Silicate Hydrate (C-S- H) results in more compact and dense morphology with better Interfacial Transition Zone (ITZ) characteristics. Also due to reduction in Ca(OH)2, calcium leaching will be restrained and extent of carbonation is reduced. Nano-modification makes concrete relatively inert by making it impermeable due to less interconnected pores resulting in reduced conductivity and mobility of the chloride ions which in turn reduces the risk of corrosion of steel in reinforced cement concrete. Also, it offers very high resistance to freeze and thaw and the effect of varying temperature on concrete. This paper reviews the durability issues of present day concrete and the effects of nanosilica on microstructure and durability properties of concrete. Sustainability aspects and future scope of nano based concrete are also discussed.