SonReb method

The SonReb method (short for Sonic Rebound ) is a combined in-situ measurement on concrete to determine the compressive strength . The determination of the ultrasound propagation speed (Sonic) is combined with sclerometry (surface hardness, measurement with a rebound hammer according to Schmidt, therefore rebound ) and empirical values ​​of the correlations between the measured values ​​and the compressive strength are used for the evaluation. The method is widely used in Italy , where it is standardized. The following describes the procedure according to the Italian standard .

The method was developed in the Tuscany region in order to be able to quickly determine the concrete strength in situ for earthquake safety issues ( Seismic Vulnerability of RC Buildings project, 2004).

Various influencing factors must be taken into account in order to be able to draw correct conclusions about the compressive strength, such as the age of the concrete, the moisture content, the composition of the concrete and the different consistency of surface concrete and concrete in volume (the ultrasonic measurement is a measurement in volume). The sclerometric rebound index increases with the age of the concrete, while the ultrasound speed decreases. As the moisture content increases, the sclerometric index is underestimated and the speed is overestimated. ${\displaystyle S}$ ${\displaystyle v}$ ${\displaystyle S}$

For the correlation, formulas of the type

${\displaystyle R_{c}=aS^{b}v^{d}}$

used with the concrete's cylinder or cube compressive strength , rebound index and ultrasonic velocity . The parameters are determined experimentally and depend on the material properties, e.g. B. the composition of the concrete Therefore, concrete samples are first crushed and the ultrasonic speed and rebound index are determined, then the parameters of the formula are determined using the method of least squares. The cylinder or cube compressive strength is determined destructively as usual by means of a compression test. Calibrating the method in this way is prescribed in the Italian standard. ${\displaystyle R_{c}}$ ${\displaystyle S}$ ${\displaystyle v}$ ${\displaystyle a,b,d}$

Once the parameters have been determined, non-destructive tests can be carried out on the building using the method by locally determining the ultrasonic speed (mean value from three measurements according to Italian standards) and rebound index (mean value from ten measurements).

Statistical analyzes carried out in 2007 and 2009, however, showed the large fluctuation range of the method, even with measurements on the same structure.

The rebound hammer method was also used in Germany. In Italy it is also combined with another in-situ procedure, the Windsor probe .

literature

• MT Christoforo, A. D'Ambrisi, M. De Stefano, M. Tanganelli, R. Puccinotti: Mechanical characterization of concrete from existing buildings with SonReb method . 15th WCEE, Lisbon 2012. (PDF)

Individual evidence

1. ↑ UNI EN 12504-2: 2001: Prove sul calcestruzzo nelle strutture - Prove non distruttive - Determinazione dell'indice sclerometrico
2. ↑ UNI EN 12504-4: 2005: Prove sul calcestruzzo nelle strutture - Part 4: Determinazione della velocità di propagazione degli impulsi ultrasonici
3. ↑ D'Ambrisi, M. Christofaro, M. De Stefano, M. Ferrini, P. Pelliccia, N. Signorini: Resistenza a compressione del calcestruzzo di strutture in about esistenti, XII ° Convegno L'Ingegneria Sismica in Italia 10- 14 giugno 2007, Pisa.
4. ↑ M. Christofaro: Metodi di valutazione della resistenza a compressione del calcestruzzo di strutture in ca esistenti. Dissertation, Florence 2009.