T. J. WIJFFELS and O. C. G. ADAN TNO Building and Construction Research, P.O. Box 49, 2600 AA Delft, The Netherlands


In the late 1990’s, some documented observations in Dutch building practice were reported, clearly indicating that bond strength in calcium silicate facing brick masonry might be a transient phenomenon. The present paper concisely describes the findings of a two year screening research programme addressing the key question of bond strength evolution with time. A selection of three mortars, primarily differing in types of binder, and two types of calcium silicate brick differing both in the binder to sand ratio and grain size distribution, formed the starting point.
According to the bond wrench test, prEN 1052-5, the study delivers experimental evidence that bond strength in calcium silicate brick masonry may decrease substantially in time under normal West European outdoor conditions, depending on calcium silicate brick and mortar type. In a two year period, a complete loss of bond strength may even occur.