New methods for accurate water dosage in concrete central mix plants

Online mixer measurements appear as being essential to the improvement of concrete manufacturing methods, as imposed by new economical and environmental demands. However, the lack of a well-established calibration procedure contributes to the poor reputation sometimes given to these measurements. The original in situ method developed and evaluated herein requires installing a sampler, yet only slightly disturbs the production process. By using this calibration method the mixing power becomes a reliable online indication of concrete water content (measurement standard deviation of 2.85 l/m(3)). A procedure for improving the regularity of water content in truck mixers has been presented to illustrate the benefit of well-calibrated online water content measurements in batch concrete in a central mix plant. The correction algorithms proposed herein have the potential to be automated and may improve up to 5 times the water content regularity in the truck mixers.