View source for 712 - Bridge Rehabilitation, Concrete

====[[#Mixing|Mixing]]====
When daytime high temperatures will not reach 70°F epoxy and aggregate should be stored in a warm location for several hours prior to placing at the site.  If it is either impractical or impossible to keep both materials warm, drum heaters set at 100°F should be used to ensure the epoxy is not too viscous for proper mixing.  

[[File:Fig712.14.png|600px|thumb|center|Figure 712.14 Contained mixing station with clock ensures material is mixed thoroughly.]]

Mixing the epoxy must be done in a controlled fashion to eliminate any variances during the process.  Ratios range from 1:1 to 4:1 depending on the brand. The epoxy should be measured in containers that are clearly labeled “A” and “B”.  After measuring the correct portions, place them in an oversized mixing container of 150 percent larger volume to prevent spills.  Placing a tarp underneath the mixing containers and having an absorption kit nearby is helpful to capture any spilled material.  

[[File:Fig712.15.png|600px|thumb|center|Figure 712.15 An electric drill with jiffy mmixing paddle combines the resin and hardener.]]

Use a half inch electric or gas powered drill with a jiffy mixing paddle.  Keep the entire paddle beneath the surface of the epoxy to prevent entraining air.  All brands need to be mixed for exactly three minutes. A watch or other timing device must be used for accuracy.  Less mixing will lead to improper curing and jeopardize adhesion of the product.  Over mixing may result in premature setting of epoxy in the mixing containers.  

Pumps are available that mix the epoxy at the nozzle.  These pumps are calibrated based on the epoxy being used and the required mixing ratio established by the manufacturer.  It is the contractor’s responsibility to ensure proper calibration of pumping equipment, however, it is wise to verify calibration is correct prior to beginning application.  

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