Finite Element Modelling to Design a Concrete Dual-Probe – An Innovative Tool for Monitoring the Drying of Concrete

The measurement of moisture in concrete has been of interest for many years due to the potentially devastating consequences of moisture problems within buildings. A range of techniques are available to measure the moisture content of concrete floors, such as concrete moisture meters, relative humidity probes and calcium chloride tests [1]. However, all these techniques have the limitation that they either measure the moisture content of the top inch of concrete or relative humidity inside concrete or vapor emissions from the surface of the concrete floor. To measure the moisture content at any depth in the concrete floor, an innovative ‘concrete’ dual-probe has been developed. Essentially, a short pulse of electrical energy is applied to a wire within the ‘heating’ needle. A separate ‘temperature sensor’ needle, which incorporates a calibrated Pt1000, records the resulting maximum temperature rise in the concrete at a certain distance from the heating needle from which the moisture content can be deduced. The most important benefit of the concrete dual-probe approach is that it can either monitor the concrete floor’s drying process during the building’s construction or measure the moisture content of the concrete floor after the building has been occupied. The moisture content of the concrete floor can be measured simply by burying the concrete dual-probe inside the concrete floor during construction. Extensive finite element modelling was carried out to design the ‘concrete’ dual-probe and build a prototype.