Assessment of the physical behavior of historic bricks and their mechanical characteristics via absorption and ultrasound tests

Capillary suction rate in construction materials is probably the main parameter controlling decay phenomena related to water together with environmental conditions and it is directly related to porosity. On site, when performing non-destructive tests on masonry such as acoustic tests the moisture content distribution or other building material physical properties, i.e. density or porosity, are generally unknown. These affect the acoustic signal propagation and attenuation and, in historic brick masonry, it is expected to find high variability of them. Guidance in this sense cannot be found in test standards because of the almost infinite number of masonries. The paper reports laboratory work conducted on several fired clay bricks sampled from historic buildings, of diverse dimensions, age and health-state conditions. Capillary rise tests were carried out and suction velocities were determined. Moreover, hydrostatic and saturated weights were measured. In addition, the bricks were mechanically characterised via high-frequency ultrasonic tests, repeated in dry and saturated material conditions. The results are useful for a better insight into the hygrophysical variations and behaviour of historic masonry and for a more accurate mechanical characterisation of structural elements in historic constructions.