Electromagnetic Resonance Sensors for Determination of Moisture Content in Concrete

The overall quality and the comprehensive strength, in particular, of concrete are critically dependent on the water content in the concrete mixture. It is also essential to know if the concrete has reached a stage of moisture equilibrium before surface finishes such as paint or carpet can be applied. At present, no reliable method or easy-to-use instrument exists for determining the moisture content of concrete once it is cast. To address this need, this proposal suggests the development of a resonance sensor system for in situ measurement of moisture content in concrete. The proposal is innovative in the use of an electromagnetic resonance sensor for accurately monitoring the changes in the dielectric constant due to change of moisture content in concrete. Phase I Technical Objectives include evaluation of frequency ranges at which the dielectric constant of concrete is most sensitive to moisture content, design and fabrication of resonance sensors, acquisition of families of test data on standardized concrete slabs, and optimization of an engineering model to be fabricated and extensively tested in the Phase II program. It is anticipated that the Phase I program will demonstrate the feasibility of this measurement technique, and the Phase II program will result in a demonstration system that can be used on construction sites for moisture measurement in concrete structures.