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Q&A. Checking the Water Content of Fresh Concrete in Less Than a Minute

Kristina Müller
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There are no limits for an engineer. This is what Kurt Köhler from IMKO thought when he started working on his latest invention. It led to the SONO-WZ, a handheld cement water analyzer for fresh concrete.

SONO-WZ received the innovation award at Bauma 2016 in the Components category. DirectIndustry e-magazine talked to Kurt Köhler.

DirectIndustry e-magazine: Why is it so important to determine water content in fresh concrete?

Kurt Köhler: It is important to guarantee the quality and longevity of concrete. Concrete construction, such as bridge pilings in saltwater, have to withstand all conditions and must be built with utmost accuracy. Fifteen years ago we developed sensors that could measure the moisture in cured concrete. They were used for over ten years on old bridges in the Netherlands that needed restoration. By then, we could already determine moisture content in cured concrete with 0.1 percent accuracy.

DirectIndustry e-magazine: How did you get the idea to develop an analyzer for fresh concrete?

Kurt Köhler: While working in a laboratory on the determination of water content in fresh concrete, I realized that it takes half an hour with the usual method, called kiln drying. A sample is heated over an open gas oven with constant stirring for half an hour until all the water is gone. This requires a lot of time, staff and money, especially when every load of concrete needs to be tested.

DirectIndustry e-magazine: How does the SONO-WZ change that?

Kurt Köhler: It’s a handheld device based on our sensors that measure the water content of the fresh concrete within a minute. In the past, this was not possible with electronic sensors because the cement in fresh concrete leads to extremely high conductivity values. We didn’t know how to measure water content under these conditions. In 2009, I realized our technology might be able to measure the water content.

DirectIndustry e-magazine: How does the SONO-WZ work?

Kurt Köhler: It works based on time domain reflectometry. Sensors measure the propagation speed of an electromagnetic pulse. It was a huge challenge to make it work, and took us five to six years to design this product. It was always two steps forward, one step back. Now, the next step would be to get a DIN certification.

Courtesy of IMKO
Courtesy of IMKO

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