Detailed Vertical and Overhead Instructions
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instructions, please access the PDF Library.
Ensure that Surface is Clean and Dry: For most vertical work
such as Retaining Walls, Bridge Pillars, Columns, Ceiling Joists, and Curbs,
there is very little preparation necessary to ensure the area is clean and free
of contaminants. If needed, use chipping hammers, grinders, blasting equipment
to mechanically remove loose concrete, corrosion, dirt and all contamination to
produce a clean, dry, rough surface. Usually a wire brush is more than sufficient to clean the
concrete or any rusting rebar. If you are fixing a curb where the damage has
been painted over, you will want to grind the paint off with an angle grinder
equipped with a diamond cup wheel or stone. You will want to use a leaf blower
to get all the remaining dust and grit out of the cleaned area.
Tape or No Tape: If you want a flush to grade repair, you
do not need to use duct tape, although some applicators use duct tape to mirror
the damaged area. If you prefer an above grade-cut-out-look you will
want to use duct tape to symmetrically tape off around the repair.
Mixing and Applying FlexPrime
(Same as Horizontal/Flatwork - Except for special priming)
Estimate Amount of FlexPrime: You are going to mix
enough FlexPrime to paint a VERY THIN coat that completely
covers the concrete and voids within the repair area. A simple way to estimate
the amount needed is to estimate approximately 300 square foot of coverage per
gallon. (i.e. 2.5 sf. an ounce) (38 sf. a pint) (75 sf. a quart).
Mix and Apply FlexPrime: Mix equal parts of A & B for
1 to 3 minutes, and apply a VERY THIN COAT with a brush, roller, or spray.
Allow FlexPrime to Tack: For vertical repairs it is
critical to ensure that the FlexPrime is TACKY enough to hold the FlexKrete in
place while it cures. The FlexPrime should be tacky enough to ensure
the repair material achieves a mechanical bond to the repair area. Depending on
the temperature, FlexPrime can take 15 to 30 minutes at 70 degrees and much
longer when cold outside. If you do not want to wait for the FlexPrime to
reach it's VERY STICKY stage, a torch can be used to
preheat the concrete before applying FlexPrime so that it will tack more rapidly.
Fast Option - Overcoat Primer: If you are in a rush and cannot
wait for the FlexPrime to completely tack up, you can mix up a FlexKrete Resin
Priming Coat using the standard catalyst and our FlexTemp Accelerator / Additive.
The FlexKrete resin painted on top of the FlexPrime can speed up
the thermosetting and tackiness of both materials.
Fast Option 2 - FlexKrete Resin Priming Only - On dry concrete some
contractors omit the FlexPrime altogether and substitute with a thick coat of the FlexKrete priming coat
Mixing and Applying FlexKrete
Estimate The Volume of FlexKrete Slurry Needed: Since you will
want to mix enough slurry to fill the repair area but not throw any away, it is
a good idea to have all the repair areas in the immediate area, primed and
ready. The simplest method is to look at the repair and estimate the volume of
sand required to completely fill the void, and then divide by 2 to
determine the amount of FlexKrete needed. (Example: One gallon void
÷ 2 = ½ gallon of FlexKrete to 1 gallon of fumed
silica and 1 gallon of sand
Determine Consistency of FlexKrete Vertical/Overhead Slurry: A
good starting point for a stiff batch is 1 part FlexKrete, 2 parts amorphous
fumed silica, and 2 parts medium blasting sand. MORE FUMED SILICA MAKES IT
STIIFFER, LESS SAND MAKES IT LIGHTER. If you are doing overhead repairs that are
very thick, you may want to cut back on the sand to 1.5 parts to lighten up the
slurry. For curbs, you can cut back on the parts of fumed silica and replace
with sand if you do not need that stiff of a mixture. You can vary the ratios to
meet your needs.
Vertical Applications: After measuring and catalyzing FlexKrete,
mix in 2-parts blast sand and 2 to 3-parts fumed silica. 3-parts fumed silica produces a stiff,
dough-like material that can be hand-placed and toweled smooth. 2-parts fumed silica and 2-parts sand
produces a less-stiff material and recommended as a good starting point to evaluate ratios needed.
Overhead Applications: After measuring and catalyzing FlexKrete, mix 1-part blast sand
and 2 to 3-parts fumed silica. If material is too heavy, decrease amount of sand.
Mixing the Vertical/Overhead Slurry: The easiest way to mix in the
fluffy fumed silica is to catalyze the FlexKrete for one minute, then stop
mixing. Then add fumed silica and load most of the sand on top of it, working it
in manually with your rectangle paddle before paddle mixing. Some applicators also use
cardboard covers over their mixing bucket to prevent loss of fumed silica. You
should always wear respiratory protection when working around fumed silica.
Trowel Slurry: The vertical slurry mix is very stiff like bread
dough or silly putty, therefore, the easiest way to get the material out of the
bucket and onto the repair is to use a gloved hand to simply grab handfuls of
material and pack them into the void above grade. Then you can then slice to
grade or trowel above grade to the tape. Keep your stainless trowels clean by wiping with acetone frequently.
Retain Expansion Joints: On vertical and overhead repairs it
is usually easiest to place expansion joint strips at the point of movement,
while you are packing in the FlexKrete slurry.
Finishing: If you use the tape off method, you should
pull the tape before the repair is set up. If you use the “Flush-to-Grade”
method, and the area is not going to be painted, you may want to put some
finishing touches on the cured repair with an angle grinder or stone for final
smoothing, "dusting" and/or color matching.
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On this page we have shown you how to easily repair vertical and overhead damage to concrete that includes how to repair a concrete stoop, how to repair voids in a concrete a wall, how to repair concrete steps, how to repair swimming pool concrete coping, how to repair a concrete wall or ceiling and many more applications.