Polymer Concrete

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POLYMER COCNCRETE

1. Introduction
Despite being thought of as a modern material, concrete has been in use for hundreds of years. The word concrete comes from the Latin concretus, which means “mixed together” or compounded. Concrete is an extremely popular structural material due to its low cost and easy fabrication. Concrete is made up of sand or stone, known as aggregate, combined with cement paste to bind it. Aggregate can be of various sizes. It is broadly categorized as fine (commonly sand) and coarse (typically crushed stone or gravel). The greater proportion of concrete is aggregate which is bulky and relatively cheaper than the cement. As much of the constituents of concrete come from stone, it is often thought that concrete has the same qualities and will last forever. Concrete has been called artificial stone, cast stone, reconstructed stone and reconstituted stone. However, concrete must be thought of as a distinct material to stone. It has its own characteristics in terms of durability, weathering and repair. Concrete is a relatively durable and robust building material, but it can be severely weakened by poor manufacture or a very aggressive environment. A number of historic concrete structures exhibit problems that are related to their date of origin. It is referred that the concrete is porous. The porosity is due to air-voids, water voids or due to the inherent porosity of gel structure itself. On account of the porosity, the strength of concrete is naturally reduced. It is conceived by many research workers that reduction of porosity results in increase of strength of concrete. Therefore, process like vibration, pressure application spinning etc., have been practiced mainly to reduce porosity. All these methods have been found to be helpful to a great extent, but none of these methods could really help to reduce the water voids and the inherent porosity of gel which is estimated to be about 28%. The impregnation of monomer and subsequent polymerization is the latest technique adopted to reduce the inherent porosity of the concrete to improve the strength and other properties of concrete. These problems can be solved by application of polymer in concrete construction. A polymer is a large molecule containing hundreds or thousands of atoms formed by combining one, two or occasionally more kinds of small molecule (monomers) into chain or network structures. The main polymer material used in concrete construction are polymer modified concrete and polymer concrete. Polymer modified concrete may be divided into two classes: polymer impregnated concrete and polymer cement concrete. The first is produced by impregnation of pre-cast hardened Portland cement concrete with a monomer that is subsequently converted to solid polymer. To produce the second, part of the cement binder of the concrete mix is replaced by polymer (often in latex form). Both have higher strength, lower water permeability, better resistance to chemicals, and greater freeze-thaw stability than conventional concrete. Polymer concrete (PC), or resin concrete, consists of a polymer binder which may be a thermoplastic but more frequently is a thermosetting polymer, and a mineral filler such as aggregate, gravel and crushed stone. PC has higher strength, greater resistance to chemicals and corrosive agents, lower water absorption and higher freeze-thaw stability than conventional Portland cement concrete. The pioneering work for the development of polymer concrete was taken up by United States Bureau of Reclamation (USBR). The initial exploratory works carried out at the Brookhaven National Laboratory (BNL) in cooperation with USBR and US in Atomic Energy Commission (AEC) revealed great improvement in compressive strength, permeability, impact resistance and abrasion resistance. The development of concrete-polymer composite material is directed at producing a new material by combining the ancient technology of cement...
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