Civil Engineering Reference
In-Depth Information
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FIGURE 8.6
Inside corners and concave surfaces needing extra detailing.
Surface preparation described for bond-critical applications is not
necessary here. However, surface preparation should enable a con-
tinuous and effective contact surface. Contact surfaces must be flat
or convex to help engage the FRP system during loading. Surface
spalls or voids need patching with a compatible repair material.
Soft materials covering columns, like gypsum plaster, must be
removed prior to applying the FRP system.
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Surface preparation for NSM application
A diamond saw is typically needed to cut grooves into the con-
crete cover surface. Existing steel needs to be kept intact during
the groove making. The cut grooves should leave sound concrete
surfaces and be free of loose materials that prohibit a good bond.
The grooves should be dry and should be completely filled with
resin. Once the FRP reinforcement is placed into the groove, the
extra adhesive resin needs to be scraped off. This resin is specified
by the NSM manufacturer.
5. Resin mixing
Resins are best to be mixed by hand stirring in disposable plastic pots.
However, small electric mixing blades may be used for stirring if clean-
ing them afterwards is not difficult or time consuming. Mixing should
be in small quantities to make sure that the resin can be applied within
its pot life. Once the pot life is exceeded, the mixed resin should be dis-
carded, since it becomes very viscous to the point that it can no longer
effectively saturate the fibers.
All resin parts should be mixed in the proper ratio prescribed by
the manufacturer until the mix is uniform. Resin parts are typically
color coded so that proper mixing is indicated by the removal of color
streaks. All mixing factors need to be provided by the manufacturer
(mixing proportions, methods, time, etc.).
6. Installation of FRP system
A generic schematic showing the sequence of FRP layers installed is
presented in Figure 8.7.
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