For many years, construction costs have been on the rise. One approach to reducing these costs is to optimize construction processes and techniques. This is where the EstriPass project comes in. In this project, Fraunhofer IKTS is working with partners to further develop a sensor system for continuous residual moisture measurement in gypsum and concrete building materials. This will prevent damage caused by insufficient drying and increase durability.

Screed is used in a wide range of construction and renovation projects, especially as a substrate for floor coverings. Screed mixtures are usually applied to the prepared surface in a moist state and must then harden. The sooner the required degree of dryness can be verified, the sooner follow-up work, such as laying the floor, can begin.

Innovative sensor system monitors residual moisture

Currently, a standard drying period is assumed for floor screeding, followed by a CM measurement in accordance with DIN regulations (DIN 18560). If drying is delayed, this measurement may have to be repeated several times.

As part of the “EstriPass” project, a solution for moisture detection is being developed that can determine the residual moisture of building materials more accurately and continuously. This also allows subsequent water ingress, e.g. due to accidents, to be evaluated. At the same time, information about the building materials used should be documentable and readable for decades. The sensor is embedded in the screed and transmits the recorded information via wireless interfaces. The aim is to design the measuring system so cost-effectively that it can be used across large areas.

The sensor concept is based on an optical moisture sensor whose ceramic sensor element is similar to the building material in terms of porosity. Current developments of the sensor are already capable of detecting the residual moisture of selected gypsum screeds. The next step will be to extend this to other commercially available gypsum screeds.

Clever energy concept for long-term use

In addition to the ceramic development for the sensor, the desired miniaturization poses a challenge. To achieve this, the currently external electronics must be integrated together with the sensor electronics on a compact board with radio technology. An energy concept for the hardware and software needs to be developed to ensure that the system can quickly (within 60 days) collect and store the energy required to accurately determine the residual moisture and transmit it via radio. At the same time, the measured values obtained should be supplemented with product data, such as screed type or composition, and remain readable in the long term (10+ years).

Currently, there is no such combined, precise, and inexpensive system available on the market. Successful implementation of the system would result in a measuring system that, in addition to its cost-effectiveness and permanent moisture measurement, contributes to the digitization of construction sites through additional functionality.

About the project

The project “Robust radio-based sensor system for determining residual moisture in gypsum and concrete building materials with user-friendly, intuitive mobile application for visualization by the end user (EstriPass)” started in September 2024 and will run until February 2027. In addition to Fraunhofer IKTS, GGB Gesellschaft für Geomechanik und Baumesstechnik mbH and WiE GmbH are also involved in the project.