الخميس، 8 مارس، 2012

Polymer Concrete

 Polymer Concrete  
by Methaq. M / Iraq - Babylon University 
      Polymer concrete is a material made up of different types of aggregates adhered by polyester resins. PC is a composite material in which resin is used as binder for aggregates such as sand or gravel instead of Portland cement. PC is an inert product that can be cast in almost any shape . Due to its rapid setting, high strength properties and ability to withstand a corrosive environment. It is increasingly being used as an alternate to cement concrete in many applications, construction and repair of structures,  highway pavements, bridge decks, waste water pipes and decorative construction panels. PC materials were originally developed as a  substitute for decorative stones.They become particularly popular in construction industry during the early 1950’s.
    Various resins such as epoxies, Polyesters and acrylics have been used as binder in polymer concrete production. However, recently vinyl ester, furan and polyurethane resins are also incorporated for special-purpose polymer concrete. Unlike other resins, application of polyester resins as binder to a weaker polymer concrete. Nonetheless, they are the more commonly used resins in PC due to their lower cost and reasonable performance.
  To produce PC, a monomer or a prepolymer (i.e., a product resulting from the partial polymerization of a monomer), a hardener (cross-linking agent) and a catalyst are mixed with the filler. Other ingredients added to the mix include plasticizers and fire retardants. Sometimes, saline coupling agents are used to increase the bond strength between the polymer matrix and the filler. To achieve the full potential of polymer concrete products for certain applications, various fiber reinforcements are used. These include glass fiber, glass fiber-based mats, fabrics and metal fibers. Setting times and times for development of maximum strength can be readily varied from a few minutes to several hours by adjusting the temperature and the catalyst system. The amount of polymer binder used is generally small and is usually determined by the size of the filler. Figure above show the principle components of PC. Normally the polymer content will range from 5 to 15 percent of the total weight, but if the filler is fine, up to 30 percent may be required.  A wide variety of monomers and prepolymers are used to produce PC. The polymers most frequently used are based on four types of monomers or prepolymer systems: methyl methacrylate (MMA), polyester prepolymer-styrene, epoxide prepolymer hardener (cross-linking monomer) and furfuryl alcohol.





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