Concrete Products

JUL 2019

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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www.concreteproducts.com July 2019 • 93 INNOVATIONS REPORT MOISTURE MEASUREMENT simultaneously read the moisture from the sensor. For our calibration example, we have used the AquaSense 2280D moisture sensor. The oven-dry test results, plus the moisture sensor readings, are entered into the sensor calibration table on the connected computer. The software will then find the best-fit straight line and perform the calibration. If you do the oven-dry tests correctly, halting at the SSD condition, the internal moisture will not appear in your readings after the calibration is complete. Subsequent readings will be the "SSD readings" or the values over and above the SSD condition. CALIBRATION FAILURE If your calibration fails, you are probably not selecting a big enough range of moisture during your tests. If the range from driest to wet- test is only 2 percent and your oven-dry tests have a ½ percent error, the slope of the calculated line can be off by a wide margin. Consequently you will get huge errors when the material moisture is outside the range of your samples. Robin Shepherdson is Owner/President of Scale-Tron Inc. and has also developed most of the company's products. An engineering graduate from the 1960s, he has been a professional engineer all his life and still visits jobsites regularly to help and train dealers and customers. His blogs on this and similar subjects are posted on the company website, www.scaletron.com. Recent blogs include a shorter version of this article entitled "Surface moisture or free moisture" and "Find the best moisture sensor for your application." Weighing the aggregate sample before and after the oven-dry test. After the sampling and oven-dry tests are complete, the results and AquaSense sensor readings taken during sampling are entered into the calibration software. PHOTO: National Precast Concrete Association

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