"The common law of business balance prohibits
paying a little and getting a lot. It can’t be done. If you deal with the
lowest bidder, it is well to add something for the risk you run, and if you
do that you will have enough to pay for something better."
-John Ruskin 1819-1900
Effects of Aggregate Loading:
(Click images to enlarge)
Heavily Loaded: A sample of heavily loaded resin shows the
abundance of aggregate. This makes the nosing material very dry, very
brittle, and very likely to fail under snow-plow impact, deflection of the
deck, and differential expansion in relation to the concrete and/or simply
as a consequence of normal traffic over time.
When snow plows hit heavily-aggregate-loaded nosings
shatter and send the shock into the adjacent nosing resulting in widespread
Conservatively Loaded: A sample of lightly loaded
resin shows a good balance of aggregates and resin. The result is
sufficient compressive strength to resist plow impact, and withstand traffic
rigors, while not sacrificing flexibility.
When snow plows hit conservatively loaded
nosing, it shaves locally, dissipates the shock, and leaves the joint
functional and watertight.
Inspection in June,
2004 of 8-year old THERMAFLEX nosing material at Ronald Reagan International
Airport, Middle/North parking garage, shows localized shaving of nosing
material to the right of the leading edge of the tire. Caused by errrant
snow-plowing the impact scarring is superficial and repairable and the joint
winter of installation, heavily-aggregate loaded nosing showed evidence of
lack of forgiveness to errant snow-plow activity. Shock propagation
through the rigid nosing material caused bond-line failure far beyond the
point of impact and in addition caused severe damage to the punched flanges
of the sealing extrusion.
So you've endured the usual parade of expansion joint manufacturers and
their reps through your office. The purpose of these visits is, of course,
to get you to specify or buy their joint systems. Seeing a difference
between systems and sorting out the litany of claims for performance is
you wade through the information, however, one topic that should come up (and
raise it if it doesn't) is aggregate loading.
you already know, the rubber extrusion of these "membrane/nosing" systems is
locked into the blockout at the concrete slab edge with a nosing material.
The nosing material is usually a mix of a flexible resin and an aggregate
aggregate serves two desirable functions:
1) it improves the compressive strength of the nosing material, and
2) it extends the yield of the resin.
Compressive strength is necessary to resist the effects of suddenly applied
vehicle loads especially during braking, turning, and under acceleration
from a standstill.
Extending the yield is good for the customer because it brings the cost of
the system down by thinning out the very-expensive resin. Extending
the yield as much as possible is a hidden temptation for manufacturers
because it translates into lower cost and higher profit.
Succumbing to the temptation to over-extend resins with aggregate has
disastrous effects on performance of the nosing material in this
Negative Effects of Heavy Aggregate Loading are:
2) Propagation of snow plow impact into bond lines causing extensive failure
3) Inability of material to handle concrete flexing--resulting in cracking
4) Inability of material to handle differential expansion--resulting in
cracking and leaking
5) Cracking over time caused by normal traffic--resulting in leaking
6) Installation difficulties including: long mix times, difficulty achieving
proper aggregate wetting-out, labor-intensive trowelling, and rough appearance.
suppliers are loading as much as one part resin to 4 1/2 and even SIX parts
aggregate. Not only this, but the choice of large mesh aggregate makes
the problem worse. EMSEAL chooses to supply a washed, dried,
dust-free, fine (30 mesh) sand for compressive strength, combined with a
chopped glass fiber (for extension without sacrificing flexibility).
As you can imagine, this is more costly to us than an aggregate of blended
mesh sands and inexpensive gravel, but the absence of call backs easily
justifies the choice.
may have heard differing interpretations of EMSEAL's claims of what constitutes
"conservative aggregate loading". You may also have been told that
EMSEAL is vague about its loading ratios. If you read our literature,
however, you will see that we clearly state our aggregate loading by volume
AND weight so as to avoid confusion. Here's what our
guide spec for our
THERMAFLEX systems say:
Ratio by Weight
of Liquid Resin to Aggregate
Not to Exceed
Ratio by Volume
of Liquid Resin to Aggregate
Not to Exceed 1:
your pick. Either way, if your supplier is giving you more than two
parts aggregate to one part resin you are
sacrificing a balance of hardness, strength, flexibility and
durability that has
set the standard for cold-applied nosing material over 15 years of supply.
may also have heard that, in the opinion of others, EMSEAL's nosing
material is "too soft". Once again we would point to the fact that
over 15 years and hundreds of thousands of feet of successful installation, "too soft" has never caused a
problem with performance.
In response to this article you may also have heard that the heavily
aggregate loaded resins of others feature compressive strengths that are
nearly three times that of EMSEAL's, or that the excessive loading is
desirable to achieve coefficients of expansion similar to that of concrete.
Firstly, these comments validate the fact that the materials are excessively
loaded--the more sand you add the higher the compressive strength, the more
sand you add the closer the coefficient of expansion of the material is to
concrete. The coefficient of expansion argument is irrelevant as the
flexibility imparted by a proper balance of physical properties will easily
handle the longitudinal expansion of the concrete along a deck edge.
Secondly, the admission of heavy loading through excessively high
compression strength values illustrates the failure to achieve balance in
hardness, flexibility and strength. This balance is
necessary to handle the forces and wear of expected traffic while also being
forgiving of more rigorous acitivities. If compressive strength and
thermal coefficent of expansion were the deciding physicals in the
successful nosing material performance then why not simply use concrete to
lock the expansion joint down? The answer is that concrete, like
excessively loaded nosing resin, is too brittle and lacks the balance of
physicals needed in the application.
nosing material with say 2000 psi compressive strength readings may
withstand the localized impact of a ball drop test, but it is unlikely to
be forgiving of errant snow-plow hits. While it is not expected
that any supplier warrant materials against snow-plow activity that violates
National Parking Association standards, we do live in a real world.
The occasional hit of a non-rubber tipped blade is likely. When this
occurs the conservatively-loaded nosing material will through its lower
compressive strength absorb the shock; and as a consequence of its
"softness" and strength shave away slightly at the point of impact if
necessary. This means that the shock is not propagated to the bondline
and that watertightness is preserved. By contrast, field
evidence shows that high-compressive strength materials will shatter, crack
and shock the bondline over an area considerably in excess of the point of
Request a bar of our nosing material
to compare for yourself the flexibility, and hardness (compressive
strength) with similar bars from other manufacturers. We are
confident you will agree that it is possible to offer the best possible
performance while remaining cost competitive.
a company like EMSEAL that has supplied the same conservatively-loaded
nosing resin for 15 years, the discussion of aggregate loading is easy.
This string of success is matched only by that of Watson Bowman in earlier
times who, while still supplying their proven hot-applied nosing, boasted
decades of justifiable successful performance.
worker health and safety concerns posed by hot-applied systems pushed the
pursuit of a reliable cold-applied system and for others who are new to the
game with "me too" products, or who are riding on the laurels of previous
employers, or who have changed their formulas as often as three times in the
last 8 years, this conversation is more difficult.
specifiers of parking deck systems have a 5-year proving period for the
acceptance of new products. EMSEAL has always respected this timeframe
and proved ourselves worthy of acceptance into the specifications of these
firms over time. These specifiers would serve their client well to
remove those from their specs who have not met this proving period with
their materials, or who have changed their formulas inside this timeframe.
this age of conglomerations, buyouts, consolidations and spin-offs, there do
remain a few suppliers whose integrity remains tied to that of their
owner/founders. That is not to say that these are the only reliable
sources of lasting joint sealing solutions but a healthy skepticism of bold
claims and rapid changes will serve your clients well.
Thank you for your consideration and continued support of EMSEAL's products.
As we move forward, one satisfied building owner at a time, we find
validation in our shared approach and in the words of a nineteenth century
observer of society and the construction arts, John Ruskin:
“It is unwise to pay too much, but it’s worse
to pay too little. When you pay too much you lose a little money—that is
all. When you pay too little you sometimes lose everything, because the
thing you bought was incapable of doing the things it was bought to do. The
common law of business balance prohibits paying a little and getting a lot.
It can’t be done. If you deal with the lowest bidder, it is well to add
something for the risk you run, and if you do that you will have enough to
pay for something better.”
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