Wednesday, July 27, 2016
Benefits of externally bonded reinforcement toward concrete & masonry
If concrete or masonry structures contain inadequate strength, externally bonded reinforcement provides good solution. Externally bonded fiber-reinforced polymer (FRP) composite systems is considered as the greatest substitute to traditional methods for solidification and retrofit. But the epoxy matrix of FRP systems is unstable to failure in high-temperature or aggressive surroundings.
Fabric-reinforced cementitious matrix (FRCM) systems are gaining popularity as a feasible substitute to FRP systems. FRCM systems are originated as a progression of FRP where the epoxy matrix is substituted with a cementitious matrix. With the cementitious matrix, FRCM systems can function efficiently under high temperatures, humidity, and ultraviolet radiation as compared to FRP systems. The cementitious matrix can significantly enhance the stability of the strengthening system in moist and chemically aggressive atmospheres, or in applications where vapor conformity of the strengthening system is necessary.
Properties of FRCM
FRCM systems are externally bonded strengthening systems which contain a fabric mesh implanted in a cementitious matrix. Identical to FRP systems, the fabric in an FRCM system bears the pressures transmitted from the concrete or masonry substrate via the cementitious matrix. The fabric usually includes meshes formed with carbon, alkali-resistant glass, basalt, or polymeric fibers (like polyparaphenylene benzobisoxazole, PBO), or hybrid systems.
The cementitious matrix applied in FRCM is non-shrinkable and executable in order that it can be smoothly shoveled as well as pervade the fabric mesh openings. Both hydraulic and non-hydraulic cements are applied. Sands graded superiorly (grain size less than 0.02 inch) can make the functionality of the fresh mix better as well as the saturation of the fabric mesh. The water-to-mortar ratio by weight generally varies from 15% and 25%. The mortar mix contains chopped fibers to lessen cracking that may occur due to compression in plastic. Organic compounds are also applied to manage the hardening rate and the functionality of the fresh mix, to enhance the bond to the fabric mesh, and to improve the mechanical properties. The fiber content is usually restricted to below 5% by weight of cement to achieve a fireproof matrix.
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