Elcometer Pull Tester:

To use pull test you have to ‘glue’ down the dolly’s.

You sand 1” circles, wipe with Acetone.

Mix some ARCOR 25551 from tubes kits.

Apply to dolly & set dolly onto prepped area.

To get a good reading you will have to let cure for at least a couple of hours. Better if you can leave it overnight.

Directions are with the unit for setting & reading.

What you are doing is trying to pull off the dolly’s from the surface.

One of 4 things will happen;

• the glue(25551) will pull off; If the surface is not prepped well or the 25551 is not fully cured this could happen;
• the coating will pull off; this will then record the pull test in Lbs/SqIn;
• the coating will pull apart, this will then indicate that the adhesion of the coating to the concrete exceeds the internal strength of the coating;
• the concrete will pull apart; this will indicate that the coating adhesion is greater than the internal strength of the concrete.

Only #2 above will give the true measure of ‘pull off strength’ or ‘pull off adhesion’.

But this is not likely to happen. More than likely 1, 3, or 4 will happen. You will get a ‘pull off’ number from all of these.

The interpretation of those numbers is what is important.

But, you first you need to know what you are looking for i.e. what pull off adhesion do you need to meet or exceed. If you don’t know this you are unlikely to get any meaningful information from the whole process.

For example; the customer requires a ‘pull off’ adhesion to meet or exceed 1,200 Lbs/SqInch;

• You pull the dolly & #1 occurs at 1,000; you know that the coating is >1,000 pull off strength but the adhesion of the glue to the coating is only 1,000.
• You pull the dolly & #1 occurs at 1,300; you know that the coating is >1,300 pull off strength so you are good. You still don’t know the adhesion but you know it exceeds what you need.

• You pull the dolly & #2 occurs at 1,300; you know that the coating has 1,300 pull off strength so you are good & you have a real # you are looking for.
• You pull the dolly & #3 occurs at 1,000; you know that the coating is >1,000 pull off strength but internal strength of the coating is only 1,000. This should be the case. If it happens there is a cure problem or mix ratio problem.
• You pull the dolly & #3 occurs at 1,300; you know that the coating is >1,300 pull off strength so you are good. You still don’t know the adhesion but you know it exceeds what you need.
• You pull the dolly & #4 occurs at 700; you know that the coating is > 700 pull off strength but internal strength of the concrete is only 700. This is very probable, happens the most often with concrete applications. Concrete strength is usually 350-750 range.

• You pull the dolly & #4 occurs at 1,300; you know that the coating is >1,300 pull off strength so you are good. You still don’t know the adhesion but you know it exceeds what you need.

The above is why we don’t do this test on concrete as it generally will only show that the coating exceeds the internal strength of the concrete, but this is a good thing.

This is why most adhesion numbers are usually ‘meets or exceeds’ numbers. They are usually interpolated from various results. It is very tough to get a ‘true’ number from concrete applications.

We usually just whack it with a hammer. If the concrete breaks with the coating still attached then you are as good as you need to be.