Norton GC25E, Owner'S Manual

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16
Green Concrete Cutting Important Considerations
Green concrete is concrete that is still in a plastic state that is the concrete
still has a lot of moisture in it, in other words it is not fully cured or dry. As the
concrete starts to hydrate (Dry or Cure), the concrete will change slightly in
volume. Concrete normally shrinks about 1/16” for each 10 feet during the
hydration process. This change in size creates internal stress in the concrete
which will develop into cracks. Joints also known as Crack Control Joints and
or Expansion Joints are normally cut into the concrete in order to relieve the
internal stress and to create an area where a controlled crack will occur. With
the joint in place the concrete will normally crack in a straight line underneath
the joint. The idea behind cutting the green concrete is that the sooner the
stress relieving joints are made the better control over the random cracking
will be obtained. For most green cutting the depth of cut is made at 25% of
the overall thickness of the concrete, for example if the concrete is 6” thick,
the cutting depth would be set to 1-1/2” deep. One important fact to
remember is that Green Concrete is any concrete that has set up but not
hardened. For concrete to become fully hardened it may take 5 to 7 days.
There are a few factors that affect green concrete cutting quality, and time
that the cutting can begin. The following list is extremely important to follow
and to understand in order to create a good quality cut with no spalling or
chipping of the cut line.
1. The concrete must set up long enough to hold the aggregate in place. If
not the aggregate will tumble and move when the Diamond Blade contacts
it, causing internal damage to the concrete and possible tearing or spalling
of the concrete surface. The aggregate along with the concrete must be
cut for proper crack control. With out proper set up the aggregate will roll
or move within the concrete creating voids and spalling or chipping of the
cut line will occur. Concrete set up is the MOST important issue to
obtaining a quality cut line when green concrete cutting. Factors that
affect the concrete set up are:
a) Concrete Mixture – PSI, concrete type, sand type and amount, and
other materials.
b) Water to Cement Ratio – more water the longer the set up
c) Aggregate Size and Type
d) Concrete Additives – some speed up while others slow down the set
up time.
e) Environmental Factors – Sun, Wind, Rain, Temperature
f) Concrete Temperature – cooler the concrete the longer the set up time.
2. Flat surface. Flat surfaces help to insure that the blade is perpendicular to
the concrete which reduces the chances of damaging the concrete