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What to expect in the First
Year After Construction of Your New Industrial Floor...
What to Do When the Expected Occurs
YOUR NEW FLOOR
As the owner of a new industrial facility, you are probably still
settling in, working the bugs out of your operations. Although you
may not have noticed, your floor is also adjusting to its
environment. How your floor settles in over the next year, and how
you respond can have a significant effect on the long term
durability of your floor. You need to realize that the durability of
your floor will forever affect your operations and productivity.
The purpose of this article is to give you a condensed view of what
is going on with your floor during its first year. Consider this an
abbreviated owner's manual without the technical jargon or complicated
formulas. Just a simple explanation of a very complex object.
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Does this look familiar?
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Minor Joint Spalling
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CRACKS
As much as you are displeased to hear it, all concrete cracks. There
are many causes of cracking, but most of them are rooted in the fact
that all concrete shrinks.
The standard concrete mix contains far more water than is needed to
hydrate (harden) the cement. This excess water, used mostly to make
the mix workable, will evaporate slowly over a long period of time.
As the moisture leaves the concrete, the slab actually shrinks in mass. This
causes stress buildup, friction with the base the slab rests upon
and lifting at the ends of the pour. All of these results can cause
cracks. Other causes include restraint at fixed objects such as
docks, improper joint spacing, late joint cutting, etc.
The question for you as the floor owner is not whether you have
cracks. You definitely do. The important questions to ask are:
1. What caused the cracks?
2. How many do I have?
3. How wide are they ; how deep?
4. Have they significantly weakened the floor?
5. Will they get worse?
6. Will they affect my operations?
7. Can they be permanently corrected?
8. Should they be corrected?
JOINT
DETERIORATION
In the traffic-bearing areas of your floor you have two types of
joints: construction and control joints. Construction joints are
those joints at the ends of pour sequences. Control (contraction)
joints are joints within each pour designed to induce the
anticipated cracks to crack in a straight line. Generally, you will
find joints at intervals from perhaps 12 to 25' grids.
Joints are affected by shrinkage. Conventional concrete shrinks at a
rate of approximately 1/8' or more in each 20'. This means that over
the one-to-two year period during which concrete shrinks, your
joints may open an additional 1/16 to 1/4'. This can have a dramatic
effect on any joint filler that is used.
Joints in traffic bearing surfaces should always be filled. The
function of a filler should be to protect (support) the joint edges
from damage caused by hard wheel impact. This damage is called 'spalling'.
Once spalls occur they continually get wider and deeper. Spalls
damage vehicle wheels, result in bumps that material handling
vehicles (MHV) drivers slow down for and eventually costs $$$ to
repair.
To be effective, the filler should be fairly stiff, like a very hard
rubber. This means it will not expand as the joint opens. There are
only two ways to overcome this dilemma: (1) install the filler late
in the schedule to allow for as much of the shrinkage as possible;
and (2) provide for repair or replacement of the filler after the
shrinkage seems to have stabilized, usually after the first full
heating season.
If you are experiencing joint filler separation (adhesive or
cohesive), contact the sales office at Absolute Storage Products,
LLC for our
recommended corrective procedures.
If you are already experiencing joint edge spalling, don't delay in
reacting. Identifying the cause and taking the appropriate action before the spalls become too severe
are the simplest and cheapest to correct. The longer you wait,
the more it will cost you - in more ways then one!
There are many causes of joint edge spalling for you to consider,
including the following:
1. Joints not filled or not
filled correctly.
2. Filler was too soft to support traffic.
3. Filler was installed too early and separated badly as joints
opened wider.
4. Filler was installed too low in joint to protect edge.
5. Filler was installed too shallow to support hard wheel load
(filler should be full depth in saw cut joints, 2' deep in
construction joints).
6. Filler was of poor quality, deteriorated with time.
7. The concrete edge itself was weak.
8. The joint was higher on one side, leaving it vulnerable to
wheel impact.
JOINT EDGE CURL
One type of a joint condition
could be caused by a phenomena known as a 'curl'. Concrete shrinks at
a faster rate on its top surface because it is exposed to the air.
As shrinkage occurs the ends of each pour curl upward. (You can see
the same effect by examining dried mud). To determine if you have a
curled joint, simply lay a straightedge across the joint and see if
it rocks. Another is to listen for a 'thump' as vehicles cross, or
visually watch for slab deflection.
A curl can leave joint edges at different elevations, leaving the high
one vulnerable to wheel impact. But a curl can cause even worse
problems than that.
As the top edge of a slab curls upward, the bottom of the slab may
actually lift up off the ground. As MHV's cross, the two adjacent
slab segments may actually "rock" as they deflect under load. This
means that both slabs may be the exposed high point at given times
in the vehicles progress. The rocking effect also causes any joint
filler used to de-bond and become worthless. Generally, replacing the
filler will not solve the problems of rocking.
Curl is a natural phenomena that is almost impossible to avoid
although, it can be minimized. The important questions for you, the
owner, are:
1. How severe is the curl with
regard to joint edge elevation? Will it affect my operations?
2. Do the slab ends "rock"? How much?
3. Can the rocking be eliminated easily or are more sophisticated
measures necessary?
4. Is the rocking in my floor "normal" or did faulty design or
construction practices contribute to the problem?
SURFACE
DEFECTS
The surface is obviously the most critical part of any floor.
Surface defects can also be the most difficult floor problems to
repair since it is subject to constant abrasion, wear and impact.
For the purposes of brevity, this article will cover only a few of
the more common surface defects.
DUSTING
Dusting is a condition that usually occurs as a result of poor
finishing techniques and/or poor curing. This dusting indicates that
the surface is relatively soft and weak. There is no sure cure for
correcting this weakness, but treating the floor with a liquid
hardener will reduce dusting and improve wear ability.
DELAMINATION (Scaling)
This condition is where the top 1/16' or 1/8' of the surface comes
off, leaving the underlying aggregate exposed to wear. The causes
are usually improper finishing, although certain aggregates can
cause popouts that yield a similar appearance.
The correction of this condition requires that the entire surface be
stripped away down to sound concrete, often 1/4' to 3/8'. The
surface is then replaced with an epoxy or polymeric grout overlay.
The cost of this procedure is high, the results seldom 100%
successful and special equipment is almost always advisable.
CRAZING CRACKS
Crazing is a defect that looks like a series of cracks in the
surface resembling a chicken wire pattern or a map. Crazing is
seldom a serious problem, especially if the cracks remain tight and
relatively shallow.
The typical cause of crazing is rapid drying of the surface caused
by wind, heat, poor curing, etc. If there is concern as to the long
term durability/wear ability of the surface, a treatment with a high
solids sealer is usually appropriate. If the floor starts to
delaminate, resurfacing may be required.
There are many additional problems that can befall a new floor
besides those discussed in this abbreviated article. We hope you
will contact us if you need help or even just information on any of
them. There is never a charge nor any obligation for any technical
assistance we provide via phone or fax. Your new floor is vital to
the productivity of your operations. We hope you will consider
Absolute Storage Products, LLC as your floor resource center.
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