Multifrequency Reflectometry for the Analysis of Moisture and Salt Content in Historic Masonry (MuReMa)

ISAT subprojects: Development of an FEM simulation model; construction, set-up and commissioning of a laboratory test stand for the measurement of the manufactured masonry samples; measurement of the material samples, adaptation of the simulation model and further development of the evaluation algorithm

Project leader: Prof. Dr. Alexandra Troi, Faculty of Design, Coburg University of Applied Sciences

Project partners:

  • ISAT
  • Institute for Diagnostics and Conservation of Monuments in Saxony and Saxony-Anhalt e.V. (IDK)

Duration: 01.02.2021 – 31.01.2023

The aim of the project is the development of a measuring system for the determination of salt and moisture load in historic masonry. The depth-dependent time-resolved reflectometry by means of electromagnetic waves of different frequencies is applied. The measurement method of reflectometry ensures that only one-sided access to the masonry is required. Above a frequency of 100-200 MHz, the effect of salt and moisture on the real and imaginary parts of the complex dielectric constant can be separated and measured.

Optimal multi-frequency combination

The aim of the planned investigations is the identification of an optimal multifrequency combination, with which also thick walls of historical masonry can be measured in the depth of at least 50 cm in the reflection mode and allow a location-dependent statement about salt, moisture content and present salt types. Furthermore, it is to be investigated how measurement information can be extracted from signals that have so far been difficult or impossible to evaluate by applying “machine learning algorithms”. By means of a multi-frequency measurement, it should also be possible to draw conclusions about the moisture and salt content, irrespective of the type of masonry.

Machine learning algorithms

A laboratory test is planned on masonry models typical of buildings with different moisture and salt concentrations, moisture and salt profiles, and different types of salt at several frequencies. Based on the measured data, simulation models will be developed or adapted to describe the experiments. In addition, evaluation algorithms based on “machine learning algorithms” will be developed. After the models have been established in laboratory tests, a final test is carried out in the field on real masonry. In both the laboratory tests and the field tests, the values for moisture, salinity and salt types derived from the measured data are compared with reference data obtained via established methods.

The research project is funded by the Innovation Program Future Construction – Research Funding from the Federal Institute for Research on Building, Urban Affairs and Spatial Development. (Aktenzeichen: SWD-