Polymer concrete
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Polymer concrete is conventional concrete made with ordinary Portland cement, wet cured, and impregnated with a liquid/gaseous monomer (methyl methacrylate) and polymerized by gamma radiation. It is used in marine works, pre- fabricated structural elements, nuclear power plants etc.
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Polymer concrete
- 1. Polymer Concrete Concrete is made up of three basic components- water, aggregate (rock, sand, gravel) and cement. Cement usually in the form of fine powders, acts as a binding agent. Two types of aggregates are used which has been classified into coarse aggregate and fine aggregate. The coarse aggregates used are usually rocks of different sizes or diameters and they give body to concrete. On the other hand, fine aggregates (sand) are known to fill up the voids between the constituents of concrete. However, these voids are most often not completely filled up and as a result the strength of concrete reduces. The porosity of concrete due to presence of water voids and air voids have led to reduced strength of concrete. Although the use of different methods of vibration reduce the pores and voids to some extent, the strength of concrete have not resulted in distinctive improvement. Hence impregnation of monomers and polymers in concrete is the latest technique to reduce the porosity of concrete, increase strength, toughness and durability of concrete. Polymers are a large class of materials consisting of many small molecules (called monomers) that can be linked together to form long chains, thus they are known as macromolecules. The types of polymer concrete are: a) Polymer Impregnated Concrete b) Polymer Cement Concrete c) Polymer Concrete d) Partially Impregnated & Surface coated Concrete
- 2. Polymer Impregnated Concrete- Previously cured and set concrete is impregnated with a low viscosity monomer which is subsequently polymerized in-situ by using radiation/ application of heat. The monomers used are- Methyl-methacrylate (MMA), Styrene, Acrylonitrite, t-butyl styrene, Thermoplastic monomers etc. Considerable improvements in abrasion resistance and Young’s Modulus have been observed. The use of plastic polymers and monomers modifies the behavior of concrete from elastic and brittle to ductile. Polymer Cement Concrete- Polymer cement concrete have been made by mixing cement, aggregates, water and monomer. The plastic mixture is then cast in moulds, cred, dried and polymerized. The monomers that are used in PCC are- Polyster styrene, Epoxy styrene, Furans, Vinylidene chloride etc. Polymeric latex emulsion (Styrene & Acrylics) lubricates the concrete mix, less water is usually needed for workability. Latex-type polymer-portland cement concrete exhibit excellent bonding to steel reinforcement and to concrete itself, imparts good ductility, resistance to penetration by water and salt and excellent durability to freezing and thawing. <Polymer concrete.jpg> Polymer Concrete- A thermoplastic polymer is used as a binder instead of Portland cement to bind the aggregate in concrete mix. Since OPC forms large number internal voids, polymer concrete highly reduces these voids. Proper grading and mixing of aggregates with polymers is done to obtain maximum density and minimum voids volume. However, such polymer concretes tend to be brittle hence the use of fibre reinforcements improves the toughness, ductility and tensile strength in concrete. Epoxy resins, vinyl monomers such as polyester-styrene, methyl-methacrylate, styrene and furane are commonly used in polymer concrete. Partially Impregnated & Surface coated Polymer concrete- Partially impregnated concrete/ surface treated concrete is produced by soaking the dried concrete specimen in liquefied monomer and then sealing them under hot water at 70◦ C (to minimize loss due to evaporation). Surface polymer treated concrete have improved the durability of bridge decks considerably as bridge decks are subjected to a lot of deterioration and abrasive wear. Brainware University