A Concrete Solution

By Thomas R. (Randy) Glover

Years ago a co-worker told me that to find the source of a problem, “Look in the least obvious place.” At that time, I owned an auto repair shop. One day, a client brought in a car with a frustrating electrical problem--it kept blowing fuses. I knew there was a dead short, so I traced every wire in the car. But, perplexingly, everything was fine. After repeatedly searching--not to mention pulling my hair out and “colorfully verbally expressing” my aggravation--I got to thinking about “the least obvious place.” One more search and I found pennies in the car’s cigarette lighter. It turned out that the owner’s children had been putting the coins into the lighter when she wasn’t looking. The owner was embarrassed. I was relieved.

Since then, in my professional and private life, I have had occasion to remember that simple phrase: “Look in the least obvious place.”

What does all this have to do with concrete? Good question! Applying the above to my experience with coating specifications on projects involving concrete, I find that coating failures are many times found “in the least obvious place.”

Some times it’s just plain obvious. An example of obvious was in a specification shown to me regarding a project in India. The specification called for surface preparation on concrete to be “Abrasive Blast cleaned to NACE No. 1/SSPC SP-5 Standard.” That standard is well-known to be written for steel. In fact, it calls for steel to be blast cleaned to white metal.

Many times that “least obvious” part of the project to the specifying engineer is the surface preparation/coating application. Unfortunately, many times it is the last thing a specifying engineer thinks about when drafting a bid. I’ve asked engineering graduates what amount of time they spent learning about coatings, surface preparation, and standards. The usual answer is “zero.” That is disturbing. The trend in academia seems to be “bigger picture” rather than “real world.” Evidently their professors thought that designing and building were the most important topics, and the actual work of surface preparation and coating application the least important. But as we all know, without proper surface prep, a project is doomed.

As Obvious As Concrete

The most obvious thing about concrete is…it’s not steel! It is completely different and yet is many times thought of and treated the same. I once had an owner tell me that concrete was just a hard, solid rock. Changing his mind was a tough sell.

Concrete is the most coated building material in the world and unquestionably the most prone to coating failure. Unlike steel, concrete is very porous with air, water, water vapor, and contaminants going in, coming out, and sometimes staying. One of the most important characteristics for a coating or overlayment bonding is the texture or “profile” of the substrate. With concrete, the upper portion of a slab surface is often called the anchor profile or surface profile-- it is a measure of the surface roughness. To prepare steel for coatings, the surface is roughened by numerous methods, then a permanent replica tape is used to quantify profile. (ASTM D4417 Method C.)

There is a new ASTM standard, D7682 “Standard Test Method for Replication and Measurement of Concrete Surfaces Using Replica Putty” released in 2010. Within ASTM D7682 there are two methods of replicating the surface profile, then assessing that profile, either visually or quantitatively.

Method A provides a visual means of replicating the surface using a two-part anti-stick putty that is mixed thoroughly, encapsulated in a test area, and placed on the concrete profile. In minutes, temperature-dependent, the putty hardens and inversely replicates the tested surface area. There can then be visual comparison to the International Concrete Repair Institute’s 9 rubber CSP comparators.  These range from CSP number 1 as the least rough to number 9 being the most rough.

Method B is the quantitative method of replicating the surface using the same anti-stick putty to reproduce the surface area. Then, utilizing a specially developed micrometer, a number of readings (10 recommended), more if required, are taken of the height of the peaks and depths of the valleys on the replica. Remember, the replica is an inverse image. The valleys are the peaks, and the peaks are the valleys.  By subtracting the lowest reading from the highest reading a profile range is obtained. This range can be compared to the specification requirements.

With ASTM D7682 “Standard Test Method for Replication and Measurement of Concrete Surfaces Using Replica Putty,” surface profile, the “least obvious” area can now be visually and quantifiably inspected.


Mr. Glover is the President and owner of O.T.B. Technologies Inc. located in Scottsdale, AZ. He has over 40 years in the coating and surface preparation industry beginning in automobile restoration/painting/inspection, continuing on to aircraft painting/inspection, then to heavy industrial surface preparation, painting and inspection. He is an instructor for NACE International and SSPC. He is an active member of the ASTM DO1.46 subcommittee and a member of the surface preparation committee for ICRI.

Articles  |  Home