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| Photo 2 |
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One
of the most troubling aspects of floor failures is the improper use of floor
patch products. These problems range
from delamination of the patch to the substrate, powdering of the patch,
tracking of rolling loads in the patch, and indentations into the patch. The majority of these are caused because the
person applying the patch put too much water into the mix. When too much water is used in the mix water
is non-compressible and where the excess water was after drying it will leave
voids in the set product. (Photo 1)
The more voids in the set product, the weaker the product becomes. Conversely, a floor patch mixed properly will
be the high compressive strength it was intended to have. (Photo 2)
Let’s take a hard look at some of the techniques of using a floor
patch:
Substrates
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| Photo 3 |
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Substrates
need to be free of residuals that will prevent a good bond of the floor patch
to the substrate. These include:
concrete sealers, curing compounds and parting compounds, oils, waxes,
silicones, soap, dirt residues, laitance or anything that might prevent a good
bond. Shiny concrete should be roughened up in order to achieve a good
mechanical bond. Photo 3 shows a case of hard trowel finished concrete with an
over-watered patch and rolling loads.
When should you use an additive?
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| Photo 4 |
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Many
installers use an additive for all circumstances, which is not necessary. When you use an additive with floor patch you
will give up compressive strength for flexural strength. There is a time when that is necessary. For instance, if you are going over a wood
substrate, skim coating an adhesive residue or you are using the floor patch as
an embossing leveler, this is where you need flexural strength. If you are going over a concrete substrate
you need to give up flexural strength for compressive strength. Then the floor patch should be mixed with
just plain water. It would be alright to
use the additive as a primer, but not in the mix.
When should you use a primer?
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| Photo 5 |
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The
purpose of a primer is to enhance the bond to the substrate. It will also stop the absorption of the mix
water into the substrate, causing the floor patch to set too fast. I feel this is why many installers add
additional water to their floor patch so it will go further and not set up so
fast. Many times you can use just plain
water as a primer. It will wet-out then
substrate stopping the rapid absorption of the substrate. If you are on wood substrate, care must be
taken not to over-wet the substrate. (Photo 4)
Substrate preparation
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| Photo 6 |
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The
norm is to buffer sand the substrate to remove and contaminates lumps and high
spots. (Photo 5)
Thoroughly remove any debris from cracks or joints by digging the soil and
debris out and using a vacuum to get it out of the void. (Photo
6)
Mixing Procedure
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| Photo 7 |
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The
following is the procedure for properly mixing the floor patch to the already
prepared substrate.
1. Use a clean plastic container
Mixing should be done in a clean container and NOT on the floor. Many installers make the mistake of mixing
their floor patch on the floor. The
reason for this is the floor patch is not mixed uniformly and many times the
residue left behind is an area of bonding concern or failure.
2. Add a measured amount of water to the container (water goes in first)
Determine the floor patch manufacturers mix ratio and add the water first. Adding the water first allows for a more
thorough mixing of the floor patch.
3. Add a measured amount of floor patch powder to the water
Next add the powder to the water. This
too needs to be measured, remember the strength of the hardened product depends
on the mix ratio of powder to water.
4. Use a drill motor to thoroughly mix the power and water
together
Many installers tend to omit this process.
The whipping of the water and powder together breaks the surface tension
of the water and actually thins out the mix. (Photo 7)
5. Wet out or prime the area to be patched
As I indicate above, the wetting out or priming of the area to be patched stops
the absorption of the substrate from absorbing the water in the mixed floor
patch. (see Photo 4)
