Stones reveal their secrets with ultrasound system

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Although imperceptible to the human ear, stones scream when they are damaged. They emit an ultrasound that can reveal much about the state of health of the building or construction of which they are part. The secret sound of stones can show where the damage is located, and what might happen in future if the problem is not dealt with.

A research team of the University School of Technical Architecture of the University of Granada, supervised by professor Antolino Gallego Molina has developed a system based on acoustic emission for detecting what is happening inside structural stonework.

The system detects fissures and other damage that is imperceptible to the human eye, using piezoelectric sensors to pick up ultrasound and send them to a computer for analysis.

To date the researchers, who are applying the technique to civil engineering and construction, have only carried out laboratory tests, but they are now talking to companies about commercial applications. These include quality control of fibre reinforced concrete, to ensure uniform performance and strength and avoid fragile fractures in large structures, and quality and functionality analyses of mortars used to restore historical buildings.

In the case of fibre-reinforced concrete, which is reinforced with steel or glass fibres, instead of the traditional steel rods, it is impossible to do a fine quality control with the existing systems, as these are based on testing the material to destruction by loading it. Using the technique of acoustic emission it is possible to see what is happening inside the material without destroying it.

Quality analysis of mortars used in restoration is important because in many cases when new materials are used to restore a building there are adhesion problems as well as construction problems. Again, acoustic emission could be used to assess if new mortar has bonded properly.