D. KASTEN and W. EDEN Bundesverband Kalksandsteinindustrie e.V., Hannover
The most important property of masonry is its compressive strength. This is calculated from the compressive strengths of its components, units and mortar. The use of the formula in the European Code EC6 will mean it is standardized in future for the whole of Europe. In contrast there are still different testing methods in the various European countries for the compressive strengths of units, mortar and masonry. Harmonisation through European Standards (CEN) will eventually occur. Recent research on the relationship between compressive strength and the moisture content of units shows that the German test method could be continued. The reference method requires the testing of oven-dried samples, but the compressive strength thus obtained is converted to the air-dried condition by multiplying by 0.8. The German method uses air-dried specimens, without any subsequent conversion. Recent statistical analyses have shown that the maximum coefficient of variation (15%) allowed by the draft CEN standard when the number of test specimens is reduced to 6, is achieved.