Strength testing is a paramount concern to the concrete industry.

Lab managers argued that they make serious efforts to ensure that all of their employees were certified. However, they conceded that not everyone is as diligent. “We know that there are some companies that don't use certified or licensed people in the field,” said Rich Hamilton of Advance Testing Company in New York. “We make sure that all of the testers in our company are ACI-certified and a level-one field technician. However, I'm not going to deny that using uncertified technicians does sometimes happen in the industry.”

Limited reporting of results

Getting the testing labs to send reports back to the ready-mix producers seems to be a whole other issue. More often, QC managers claimed that they only received reports on their product when the testers measured a failure. Even then, they would sometimes only hear about the negative finding and not get the numerical results.

“Though we always request the entire report, we usually only get the bad results, and even then it's not until the 28-day tests have failed,” explained John Webb of American Concrete Products in Iowa. “This is very unfortunate for us. We lose the chance to correct problems at the seven-day breaks. If we had information, we could catch problems early and fix them, instead of waiting a month to find out the product failed.”

But the lab managers see a different side. “The ASTM standards require that we send the test reports to our client,” said Dennis Ream of Bowser Morner in Ohio. “This means all of them, not just failures. Ready mix producers seem to overlook this. Often they are not our client. The only time we can send these reports to them is if the person who hired us tells us to do so. Sometimes the client is unaware that the producers even want a copy. Occasionally, we even get clients that don't want the producers to get it for one reason or another.”

Possible solutions

There are many approaches for dealing with the problems. Some QC managers took an aggressive approach to dealing with testing that they felt was performed incorrectly and provided incorrect results.

Naturally, most companies challenged such results. They would core samples from the walls and have them tested. If the samples were fine, then some producers would back-charge the owner for the extra cost. Unfortunately, this approach can also hurt the relationship between the producer and the customer. So other companies opted for more diplomatic solutions.

One preventive measure is to have people from the ready-mix company monitor the work. “Sometimes we have QC people onsite at the beginning of jobs to document the testing,” said David Wescott of Cemex in Florida. “If we think the testing was done improperly, we will alert the contractor. If the testing is really bad, we will request a meeting with the contractor and the testing company.”

Testing companies also seem open to this solution. Some technicians produce a checklist that they give to QC people onsite, showing the testing procedure according to ASTM standards. Each box can then be checked as this part of the process is done properly. When they are done, the list can then be mailed back to the testing company to inform them of proper or improper methods.

Education and communication are other approaches. “We started a free training program for the testers,” said Lipensky. “We feed them, and show videos and PowerPoint presentations. We not only try to teach them proper methods, but also just try to talk to them and make them understand where we're coming from.”

Telephone author Daniel Kokonowski at 617-232-2862. For more information,