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
Some contractors prefer to prime with the FlexKrete Resin instead of
FlexPrime, especially in cold weather and some overhead repair situations.
To Prime with FlexKrete Resin: Measure out and catalyze enough material to paint a thick coat over the area. 1-2 minute mixing times and the use of FlexTemp Additive are recommended for tack times needed in less than 10 minutes. The coating must be very tacky and sticky in order to hold repair material.
To Prime with FlexPrime:
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 3+
minutes, and apply a VERY THIN COAT with a brush, roller, or spray. Make
sure that the FlexPrime is not puddled at all. If the surface is very rough you
may need to take a dry brush to thin out any puddles or ridges.
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. If you do not want to 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 rapidly.
Without torching the tacky stage can take about 30 minutes at 70 degrees, up to
several hours in colder temperatures.
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 as long as the
there are no more than 4 parts of fumed silica and sand to one part of
Mix FlexKrete Vertical/Overhead Slurry: The easiest way to mix
fluffy fumed silica is to catalyze the FlexKrete for one minute, then stop
mixing. Then add fumed silica and then load the sand on top of it, working it
in manually with your 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.
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.