| "What type of blades
should I use on My power trowel?" At some point a customer
confronts every salesperson with this question. In order to provide
an accurate answer it is important to thoroughly understand the various
stages of floor finishing.
Trowel blades, by design, are the first component of a power trowel
that will require replacement. The rotating motion of the blades
against the abrasive concrete slab makes wear inevitable. Whiteman
trowel blades are manufactured from high quality materials in order to
deliver the longest life possible.
The first pass made with a power trowel on a concrete slab is known as floating.
This opens up the surface crust and enables it to cure, or set, from the
bottom up. If it does not set properly a weaker finished product
will result.
Floating removes humps (high spots) and fills in valleys (low
spots). It also compacts the concrete by embedding large aggregate
just beneath the surface and consolidating mortar at the surface in
preparation for other finishing operations.
Prior to floating with a power trowel the slab should be harder than
what is typically required for hand floating to support the machine.
This can be determined by using a footprint test. If the contractor steps
onto the slab and leaves a 1/8" impression on the surface then it is
ready for the trowel.
During floating the blades are in a flat position with the trowel
operated at 1/2 to 3/4 of the rotor speed. Having the blades level
evenly distributes the weight of the machine and prevents it from gouging
the surface. Similarly, running the throttle at less than full rpm
prevents it from slinging fresh concrete and kicking up aggregate.
Each pass should overlap the previous by half the width of the machine.
The second trowel pass is sometimes referred to as crossover
floating because the contractor is traveling in a direction
perpendicular to the first pass. At this point the blades will be
slightly pitched to increase the pressure on the slab surface and the
trowel is operated at about 3/4 the rotor speed.
Crossover floating enables the contractor to reach spots that may have
been previously missed. In addition, it provides the finisher with
his best opportunity to level out the slab.
At this point the concrete has lost its
plasticity but is not stiff enough to prevent the leveling of the
surface. Once completed the contractor will allow the slab to set
for a short period of time in preparation for the final finish. Mix
designs and weather conditions vary greatly so there is no way to
consistently measure the length of time takes for concrete to set.
Float blades are used initially on fresh
concrete. These blades are 10" wide and have the edges turned
up to prevent tearing of the fresh slab. Their large surface area
evenly distributes the weight of the machine on the slab.
|
|
This blade is designed to fit over a finish blade without any mounting
hardware (nuts, bolts etc.). Easily recognizable by the clip located
on top of the blade they are quickly removed when floating is completed.
Float pans - steel disks with an upturned outer
edge, have increased in popularity in recent years. Contractors
prefer using pans, particularly on ride-on trowels, because it allows them
to wait longer to get on the slab. Pans are available in either
standard (slightly domed) or super flat configurations.
Standard pans provide a reduced coverage area. Usually the outer
3-4" of the pan will not make contact with the slab. However,
some contractors prefer it because it produces less drag making the trowel
easier to control.
Super flat pans provide optimum surface contact with the concrete.
This is the best pan to use on floors that require high F-numbers (Floor
flatness FF and Floor levelness FL).
Installation is simple as the trowel is simply set onto the pan(s) and
secured with latch pins. The blades should be perfectly flat against
the pan. Pitching the blades during pan usage can lead to uneven
wear.
Finishing - also referred to as sealing-closes surface pores and
produces a slab that is dense, durable and smooth. During finishing
the machine is run at full throttle with the blades pitched higher to
maximize the pressure on the slab surface. The contractor will make
successive passes until achieving the desired conditions. In many
instances contractors will burnish the slab causing it to have a
mirror-like appearance.
Finish blades - as their name implies, allow
floating and finishing with the same set of blades. They are 8"
wide-right between float and finish models in terms of width-and have the
leading edge turned upward. The mounting bar is located about 3/4 of
the way up on top of the blade. This gives the blade a certain
degree of flex preferred by some contractors.
Whiteman also offers a Quick Change option for
all combination and finish blades. These blades have a steel
channel. rather than a solid mounting bar, located on top of the
blade. The mounting bar is a separate reusable item that is
permanently bolted to the trowel arm. Snap pins are then used to
securely fasten the blade to the trowel arm.
This design eliminates the hassle of removing bolts in order to install
new blades. Without any tools the customer can simply remove the
snap pins holding them in place and install the new blades.
Another option available to the customer in Enduro-blades.
These blades are made out of thicker gauge steel and tests have shown they
last up to 50% longer than regular blades.
As far as whether it is better to use separate float and finish blades
in place of combination blades there is no clear-cut answer. It
really comes down to a matter of customer preference.
Every concrete finisher had different ideas as to what techniques
produce quality floors. For these reasons it is best to inform the
customer of the options available and allow them to decide for themselves
how to equip their trowels.
|
