Determining The Hardness Of Concrete; Diamond Selection - Husqvarna PG 400 Operator's Manual

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.
However, other factors beside compressive strength ratings
determine how hard the floor will be, and therefore, the
correct diamond selection. Since grinding normally only deals
with the surface of the concrete (top 5mm or 1/4 inch), often
the way the concrete floor has been finished or the condition
of the surface will have a greater bearing on what type of
diamond to select, rather than the compressive strength
rating of the concrete.
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.
GRINDING GUIDE

Diamond selection

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.
There are a number of different diamond configurations that
can be achieved on both the PG 400 and PG 280.
Metal bond diamonds
Full set - inner and outer row
Full set - outer row
Half set - inner and outer row
Half set - outer row
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