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Ultrasonic methods have been developed in the past few decades to study the properties of cement based materials in fresh and hardened state. However, most of the methods consider only a certain type of ultrasonic waves. To derive elastic parameters of fresh concrete like the Poisson’s ratio and elastic modules it is required to measure shear waves as well as compression waves. It is relatively much more difficult to establish a setup to transmit and record shear waves in a way that the onset of these slower waves can be detected sufficiently clear to calculate the shear velocity with the required accuracy. In this paper, an experimental setup for testing concrete with different ultrasonic waves is presented and methods for automated onset determination of p- and s-waves are described.

Monitoring of cultural heritage structures is an application area for Wireless Sensor Networks (WSNs) which is implemented in the project “Smart Monitoring of Historic Structures (SMooHS)”, funded by the European Commission within the 7th Framework Programme. The project aims at the development of a WSN system especially designed for use on real structures to enable smart interpretation of acquired data and comparison of results with those obtained from established laboratory tests in an effort to evaluate the usefulness of the WSN system. While the development of the WSN system is still ongoing by the partners, many sensor types are already supported. This paper presents WSN implementations on the Holy Cross Minster in Schwabisch Gmund, Germany, Schonbrunn Castle Chapel in Vienna, Austria, archaic houses in Hebron, Palestine, and Bode Museum in Berlin, Germany. The system design, including hardware and software, sensor types and their characteristics, and their adaptation to the system is described. System setup is described for each case study and results of initial measurements are shown, including smart automatic interpretation mechanisms. An assessment of the wireless monitoring system concludes the paper, stating research needs and future work.

The recrystallization of salts due to changes in moisture content is one of the major damage mechanisms in historic materials like natural stones, bricks, plasters, and mortars. This paper presents a new development in the field of wireless monitoring the salt content in historic mineral materials. In this investigation ion selective potential sensors (electrodes) are used for monitoring salt displacement in time, influenced by changes in moisture content. Different kind of electrodes and electrode couplings are tested in laboratory, and in field measurements. For measuring the potential, low power data acquisition hardware was developed that is optimized for using it in wireless sensor networks. Data acquisition uses a competitive wireless sensor network system that is further developed in the SMooHS-Project (Smart Monitoring of Historic Structures, Collaborative Project in the 7th Framework Programme of the EU) to operate under harsh environments. First results of the laboratory and field test are presented, showing that long-term monitoring of salt content is feasible.

Monitoring of civil structures is a growing application in nondestructive testing. Wireless systems supersede wired systems mainly by being easily deployable under various local structural conditions. The vast majority of today’s existing structures are not equipped with monitoring systems by design. Wireless systems can still be installed as a retrofit. In the demonstration project described here, a 1350 m long motorway bridge over the Neckar River near Heilbronn, Baden-Wurttemberg, Germany was equipped with ambient and material temperature sensors as well as humidity sensors. The test setup is described in detail and interpretation of the data from initial measurements is provided. Furthermore, an assessment of the wireless monitoring system is presented, giving information about the packet drop rate, radio frequency calculations and wide-area network connectivity.

Changes in the moisture content and the resulting recrystallisation of the entrained salts is one of the major damage causes in historic materials like natural stones, tiles, plasters and mortars. This paper presents a new development in wireless monitoring of the moisture content in historic mineral materials. In this ongoing research, electrical impedance measurements are carried out to monitor the changes in the measured electrical conductivity of materials, as affected by both the total moisture content and the salt concentration. A measurement system consisting of a pair of electrodes, a sensor board and a low power data acquisition hardware was developed which was optimised for use in wireless sensor networks. Initial results of the laboratory validation tests are presented in the paper.