Vorschlag für ein neues Verfahren zur Prüfung der Druckfestigkeit von bestehendem Mauerwerk

Proposal for a new testing method of compression strength of existing masonry.

The compression strength of masonry can be tested much better on masonry samples with bricks and mortar together than by separate testing because thereby also the influence of the interaction between bricks and mortar is recorded. These results describe best the real strength of masonry. In the calculation of the permissible compressive stresses in accordance with applicable standards this leads generally to higher permissible capacities because not so high reductions for uncertainties of the interaction must be taken into account.
The usual methods of testing bodies of masonry, however, are relatively expensive and often cause considerable damage. Therefore the experiments were carried out with smaller specimens, which can be cut out of one side of the wall, while still keeping the principle of testing bricks and mortar together. Thus, test specimens with the base of equilateral triangles and at least three layers of stone height arised. The experiments were carried out with three different masonry types. The results of these small specimens were compared with those of the standardized specimens.
The results matched relatively well. The deviation of the mean values generally caused by scattering and additionally by the influence of the test specimens maximally was 15 %, however, the number of tests has not yet been sufficient to establish a conversion factor. A certain minimum strength of mortar is also here a requirement that specimens can be collected and tested. This is relatively low because the vibrations during the sampling can be kept low and the small specimens may be transported carefully and with a slight temporary prestress.