Determining The Hardness Of Concrete; Choice Of Holder For Tool; Full And Half Sets Of Diamonds - Husqvarna PG 820 RC Manuel D'utilisation

Determining the hardness of
concrete
All concretes are measured by their compressive strength
and depending on which part of the world you are from,
different compressive strength indices (e.g. PSi & MPa)
are used. Generally, the higher the compressive strength
rating, the harder the concrete and therefore, the harder it
will be to grind.
But there are also factors other than compression
strength that determine how hard a floor is and which
therefore affect the choice of diamond tool. As it is most
often only the top layer (5 mm) that we are talking about
from a grinding point of view, the surface treatment of the
concrete and the condition of the concrete surface have
many times a greater impact on the choice of diamond
segment than the compression strength.
Surface factors to consider when making a diamond
selection
Generally, if a concrete surface is very smooth (i.e. Most
likely it has been heavily trowelled/helicoptered), the
concrete will behave as if it has a high compressive
strength and therefore, require a soft bond segment.
Accordingly, if a concrete surface is coarse/aggressive
(e.g. rain-damaged, shot blasted, scarified, exposed
aggregate e.t.c.), the concrete will behave as if it has a low
compressive strength and therefore, require a hard bond
segment.
Surface coatings/contaminants (e.g. Epoxy coatings,
ceramic tile adhesives, levelling compounds/screeds) will
often have a larger bearing on what diamond to select,
than will the compressive strength of the concrete.
As a general rule, when grinding a concrete slab for the
first time and you are unsure about its hardness, always
begin with harder bond diamonds under the machine.
This will ensure the least amount of wear on the diamond
segments. If a hard diamond segment is not suited to the
application, all it has cost is a little amount of time without
wearing out the diamonds.
If performed the other way around (i.e. a soft segment is
used to begin with) and the concrete is soft or possesses
an abrasive surface or surface contaminant, it is quite
possible to wear-out a considerable amount of diamond in
very short period of time.

Choice of holder for tool

They way diamond segments are set-up on the grinding
unit will greatly influence the performance of the machine,
the productivity levels and also the finished floor quality.
Metal bond diamonds
Redi lock holder disc - Used to fasten metal-bonded
diamond tools.
Resin bond diamonds
Resin holder disc - Used to fasten plastic-bonded
diamond tools.
OPERATING

Full and half sets of diamonds

General
The way in which the diamond segments are mounted on
the grinding discs is very significant for how the machine
will react, the grinding efficiency obtained and the quality
of the finished floor.
There are basically two types of diamond configurations
that can be used when using the grinder:
• Half set of diamonds – when there are diamonds
placed at three alternating positions on the diamond
holder discs.
• Full set of diamonds – when there are diamonds
placed at each of the six positions on the diamond
holder discs.
By changing the way the diamonds are set-up on the
diamond holder discs, an operator can significantly effect
the performance of the machine and therefore, the
finished product.
Half-set of diamonds
When the diamonds are set-up as a half-set, they tend to
follow the surface of the floor. Similar to a tripod for a
camera, which can be placed on an uneven surface and
yet still find a stable footing.
The half-set diamond configuration should only be used
when a flat floor finish is not required.
Full-set of diamonds
When the diamonds are set-up as a full-set, they tend not
to follow the surface of the floor. If the floor has
undulations, the machine will grind the high areas yet
miss the low spots.
The full-set diamond configuration should be used when
a flat floor finish is desired.
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