Applying New Epoxy over Old Epoxy

February 13, 2015

I frequently get calls and emails from folks who want to install our epoxy over an existing epoxy floor or coating that they have. They want to know if it is okay to go over it and what they have to do to properly prepare the surface.

If the existing epoxy is a good hard solid one that is well bonded to a well prepared substrate it is possible. On the other hand if you are replacing it, what is wrong with the existing epoxy? Has the existing epoxy been badly abused by heavy sharp objects being dragged on it? Was the exiting epoxy damaged by chemicals beyond the chemical resistance of the existing epoxy? Are you just trying to upgrade the look of the existing epoxy?

You should be concerned about going over epoxy that is coming loose from the substrate. That may mean that there was poor surface preparation. It may also mean that the quality of the epoxy might not be what it should be. You need to be concerned about epoxy that is wearing out. If it is wearing out you want to know why. My company and I personally started out as installers of epoxy. I have never seen or been made aware of any of Epoxy.com coatings and/or flooring systems that have worn out have come loose from the concrete. I have seen concrete so pounded by traffic that it came loose, but our epoxy was still attached and still doing its job. That is based on over 30 years of field experience with the products.

Back to the question, “can I put epoxy over epoxy?” I always assume that the reason that the epoxy is wearing out or coming loose is that the epoxy is low quality or the installation was poorly done or both until I can prove otherwise. The way that I do that is to attempt to grind or shot blast off the existing epoxy. If after a substantial effort the epoxy cannot be removed and I cannot hear a hollow sound under the existing epoxy, I feel I have proven that the existing material is solid and well bonded.

Let’s take a moment to discuss that dreaded hollow sound above. If the flooring system or coating is very poorly bonded you will get a sound from your grinder like you are dragging a piece of paper or a piece of stone under the grinder, or rubbing stone. When you tap it with a hammer you get a hollow higher pitch noise than you get when you tap solid concrete or a solid floor over concrete.

You must be sure that the substrate is free of all types of contamination, including but not limited to oil, grease, food fats, curing compounds, sealers, laitance, dirt, wax etc. The existing epoxy left behind must be well bonded, and sanded until it has no shine. See Epoxy Surface Preparation Procedures for more information on this subject.

The beauty of trying to get it off is you are removing all the shine and getting it ready to accept another layer of epoxy. Just before I install the new layer of epoxy I solvent wipe with xylene, let it dry. Then I recommend a coat either Epoxy.com Product #899 Primer or Epoxy.com Product #12 Chemical Resistant Primer. Then install epoxy as usual. For more surface preparation and installation tips please visit or “Where to Start” page at: http://www.epoxy.com/start/default.aspx

Related Resources on Epoxy

Where to Start” page may be the best way to get you off to a quick start.

Epoxy Coatings

Epoxy Primers and Sealers

Chemical Resistant Epoxy

Epoxy Chemical Resistance Chart

www.epoxy.com

Epoxy.com Technical Support
Norm Lambert, President – Technical Support Director
352-533-2167
info@epoxy.com

 

 

 


Epoxy Education- The Strengths of Epoxy

June 18, 2012

Epoxy Educational Pages Anouncement:

The newest addition to Epoxy.com Education Pages is “Epoxy Resin Strengths Explained” which explains the 4 primary strengths that are very important for most civil and mechanical engineering applications of epoxy: compressive strength, tensile strength, flexural strength, and bond strength. “Epoxy Resin Strengths Explained” also discusses the test methods to measure these strengths.


Pot Life of 100% Solids Epoxy

June 7, 2012

As the Technical Support Director of Epoxy.com  I get a lot of email and phone calls about how to work with the relatively short potlife (typically 30-40 minutes) of 100% Solids Epoxy and similar resin systems.

It is important to understand that  Epoxy (and epoxy like resins) generate their own heat when mixed. So larger batches of epoxy  will generate more heat then smaller ones. The result of this is that larger batches of epoxy set faster than smaller batches. Start by mixing smaller batches of epoxy and then increase your batch size slowly.

To give you longer working times:

  • Make small batches that you can use in about 1/2 the working time of the material.  That will give you a little wiggle room and it will make your epoxy easier to use.
  • Be sure the product is cool when you mix it.  For best handling properties I like my material in the upper 60’s or lower 70’s. F.

See To Do With Epoxy for more installation tips.

Norm Lambert – Epoxy.com Technical Support Director


Epoxy Stone Overlay – How Much Material Do I need

April 27, 2010

Q: How Much Epoxy.com Product #17 Do I need?

I am interested in your Epoxy  Product #17 – www.epoxy.com/17.htm – to overlay a patio and walkway.  I live in Michigan – is there a dealer or will you ship to Michigan?  My patio of 600 sq. ft. – how much epoxy #17 is required? 

You did not say what size stone you are using or how deep you are looking to install it at.

Each stone will take a different amount of resin to bond it in place, depending on the size, shape and how clean it is.  Also each stone size will have a different yield.  But here is how it is calculated (to a theoretical area and coverage).

The recommended starting point is 1.5 gallons of resin plus or minus to each 150 lbs of stone.

I measured a stone that I had that was 1/8 x 1/16,  and got about 0.6 cubic feet per 50 lbs.

So a yield of 3 gallons of #17 and 300 lbs of stone would produce about 0.6x 6 bags or 3.6 cubic feet.

600 square feet at ½ inch thick is (144/2)x600 or 43,200 cubic inches or 25 cubic feet (43,200/1728)

25 cubic feet /3.6 = 6.9 units

The unit size is 3 gallons or ( 7×3)  21 gallons.

Thank you for your interest in our products.  Please contact me with your questions.

Epoxy Systems, Inc.
Norm Lambert
President & Director of Technical Support
Available by Phone M-F 9AM-4PM Eastern Time (6 AM – 1 PM Pacific Time)
352-533-2167 (Voice)
352-465-3497 (fax)
norm@epoxy.com
www.epoxy.com     New Secure Login
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How to Epoxy inject Very Large Cracks – How Large a Crack can be Epoxy Injected

April 22, 2010

What is the Largest Crack that can be Repaired with Epoxy Injection

A reader writes:“What is the largest concrete crack that can be injected with an Epoxy Injection repair?”

For concrete outdoors and/or is going to see extreme temperatures, you
would typically want to limit your injection to about 1/4 inch.  If the
crack is larger than that you may experience some thermal coefficient issues, if
injected using normal epoxy concrete injection techniques. 
Thermal coefficient is the rate that materials expand and contract due to
temperature changes. Neat epoxy resin expands at a rate greater than
concrete. In small cracks this is not important, but as the mass of epoxy
gets greater, the potential for differential movement gets greater.When I have been forced to epoxy inject these cracks larger than 1/4 inch
I like to use Epoxy.com Product #301 – www.epoxy.com/301.htm.. 
Epoxy.com Product #301  is is a low mod (more “flexible”) injection
material and is less likely to create a thermal co-efficient problem than a
high modulus material.

If the crack is still bigger, I try to pack as much Epoxy.com Product
#703 – www.epoxy.com/703.htm
Low-Mod Epoxy Gel Adhesive as I can into the crack.  First I place
copper tubing as far back into the crack as I can.  Then I fill out to
the surface with the Epoxy.com Product #703.  If the crack is large
enough you can also mix up to 1 part silica sand with 1 part of mixed
Epoxy.com Product #703.  Mixing in the silica sand saves material
costs, and makes the Epoxy.com Product #703 easier to trowel. Most
importantly the thermal coefficient of the Epoxy.com Product #703 and silica
sand is much closer to that of concrete than the Epoxy.com Product # 703 alone.

After the Epoxy.com Product #703 has hardened, you can pump the Epoxy.com
Product #301 into the copper tubes that were inserted earlier.  This
results in a very effect, well designed and engineer solution for larger
cracks. When in doubt how to proceed with larger cracks, please contact me
at Epoxy.com Technical Support – 352-533-2167 or by email at
norm@epoxy.com.


Epoxy Injection – Minimum Crack Size

April 19, 2010

How Small a Crack in Concrete Can Be Epoxy Injected?

Norm:
Typically a crack that is 30 or 35 mils or larger (about 1/32 inch) can be epoxy injected. You can get into even smaller cracks under the right conditions with Epoxy.com Product #308 Ultra Low Viscosity Injection Resin for Load Bearing Applications an Ultra-Low Visocosity Epoxy Resin System for use as epoxy injection or low viscosity epoxy mortar resin. It is 100% solids and is mixed 2:1 by volume. Meets or exceeds the requirements for ASTM C881 Types I and IV, Grade 1, Classes B &C. Learn more on the Epoxy.com Website or contact Epoxy.com Technical Support by email or call 352-533-2167.

One of the most versatile, problem solving products available in epoxy systems today is Epoxy Injection Resin. Structural restoration of concrete by epoxy injection is very often the only alternative to complete replacement. It therefore results in large cost savings. Injection protects the rebar and stops water leakage.

Epoxy Injection Resin is a system for welding cracks back together. This welding restores the original strength and loading originally designed into the concrete. Epoxy injection restores the structural qualities the concrete design intended. In other words under most conditions it makes the concrete as good as new. It creates an impervious seal to air, water, chemicals, debris, and other contamination.

A crack, obviously, is a sign of failure caused by stresses, inadequate design, improper curing, etc. One of the dangers of a structural crack is the effect that it has on the reinforcing bar. The reinforcing represents one of the main structural values of the concrete.

Cracks left unprepared allow moisture, road salts and other contaminants to penetrate and attack the rebar. The rebar deteriorates, losing the structuEpoxy Injection of concreteral value. Loosing the entire structure is often the result.

Epoxy injection resin has two purposes. First, it effectively seals the crack to prevent the damaging moisture entry. Secondly, it monolithically welds the structure together. Most people assume that this welding of the structure is the most important result of the repair. Actually what is most important is the sealing.

The sealing properties of the injection prevents premature deterioration of the reinforcing. This can be of equal, or in some cases greater importance than the structural welding. It would theoretically always be desirable to get this welding effect.

Crack Analysis

As with all repair and rehabilitation of concrete, the initial job analysis is by far the most important step. Epoxy Injection Resin will weld concrete cracks but, of course, will not repair the cause of the cracking.

Analyze each potential injection application to determine the exact cause or causes of the cracking. Correcting the cracking problem can be fairly simple, or may be difficult involving design changes.

Consult a structural engineer when design changes are necessary. Do this before starting the injection. Repairing cracks by Injection is effective after these design changes. Prevent future cracks by fixing the original cause of the cracking, when ever possible.

Parking garages are an example of cracking problem that require a structural engineering analysis. Often inadequate design for expansion/contraction is the cause for parking garage structural cracking. Avoid weld injecting a crack if there are not enough expansion joints. Sometimes flexible overlays such as Epoxy.com System # 485 can be used to overcome this defect. This does not however encapsulate the rebar in a way that will totally stop the premature deterioration of the steel. Often times additional joints are needed, thus the analysis of cracking problems is critical. more…


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