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Another tester brought in to dispute test results.
08-09-2011, 04:20 PM
Post: #1
Another tester brought in to dispute test results.
It was a dark and stormy night...
All my stories should start like Snoopy always started his. This story takes place in a small medical building on the shore of Lake Michigan, circa 2007.

My Wagners are reading 92% - 96%, and the GC is chomping at the bit to get a floor in to keep on schedule. Mitigation is expensive, so a new testing company was brought in (I think they were recommended by the flooring installer).

I was informed this new testing company has conducted rH tests and their probes read 56%. The installer wants to begin installing, and unless I have some bulletproof reason why he shouldn't they are going to start.

In these situations I like to have the installer present on the job site when a meeting is held with the GC. Luckily the flooring owner and the other testing company could make it and we could walk the floor.

I always start with the concrete mix and placement, then the conditions of the slab, the finishing, and how often it was rewet. I show studies from the big testing labs on how long it takes concrete to dry. The idea is to get lay the groundwork for a realistic expectation on where the slab should be even before we start reading probes.

On this slab, it was down for 3 months, is 5 inches thick and the roof has been on for about a month. Doors are still missing and windows just went in. Drying for the most part has been minimal. The slab surface is burned black and shiny. Puddles are on the floor where people are working with water.

Now we discuss testing procedures and ASTM F2170. We discuss why 1869 is flawed, and why we measure at 40%. We discuss which direction the slab dries from and how long we expect this slab will take to reach 75% considering all the extenuating factors. (a 5 syllable word Jason!!! Big Grin )

By now the other tester is looking either completely lost or nervous, I can't read him. He was using probes manufactured by a major player I won't name because if I did you'd say GEE, they're big! We approach the first probe I put in and the GC asks me to read the probe so we can see where we are today. I put in my reader and it reads 97% and 67 degrees. He asks the other tester and he installs his probe and says it reads 75% and 82 degrees. The GC says that is still good enough to lay a floor on! and my heart sinks.... Did he listen to anything I have said to this point? I recap what we expected to see and explain the removable probes cannot be placed in a hole and read like that. My infrared thermometer shows the slab temp is 67 just as my reader said, yet this other probe is reading 82. We need to let that probe acclimate, even then I don't like the open sleeve design with holes punched out of the side. Further examination shows the sleeve is only about 1 1/4" in the hole and the bottom is cut off.

Now I really have this guy. Not testing according to the manufacturer's specs, or the ASTM, his integrity is shot. My probes make sense, they are NIST certified (he has never checked calibration), and my holes are spot on.

In the end, my readings are accepted as factual, the owner decides NOT to install and take the risk, and Munters driers are brought in for almost 5 weeks. The floor dries down to the low 90's before the owner pulls the trigger and orders a mitigation system.

While the system cost some money up front, it has been 4 years and the floors in the operating rooms are still performing flawlessly.
That is a success story! Smile

JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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Another tester brought in to dispute test results. - CC Solutions - 08-09-2011 04:20 PM