Laboratory investigation of damp rise in porous masonry construction materials

A laboratory work has been initiated within the framework of a 7°FP European project, (SMooHS) aimed at monitoring and evaluating the evolution of environmental degradation in historical structures and its consequences. One of the major causes of decay in masonry is moisture and salt capillary rise in the materials, thus, a better comprehension of the damp rise phenomenon in masonry walls and of salt crystallization is necessary. In order to achieve this aim, the hygrothermal properties of both the constituent materials and the masonry considered as a whole, have to be known. The few available standards related with these phenomena are concerned with the behaviour of single units of building materials in contact with water and allow the determination of parameters such as the water absorption coefficient. Testing standards considering masonry assemblies or regarding the mechanical effects of salt rise in construction materials do not exist. Consequently, an experimental work has become necessary to satisfy the research requirements. Several absorption tests have been conducted in the laboratory, in a controlled environment, on brick units, mortar samples and simple masonry assemblies by using water or aggressive agents’ solutions (sodium chloride brine at different concentrations). In this paper, preliminary results of the on-going experimental research are reported comparing the values of the suction velocities determined for the different brines rising in single materials with the values obtained for small masonry specimens. These parameters are interesting from different points of view, as they can be used to understand possible changes in the masonry diffusivity, to create a data bank which does not exist in these terms or as input values for numerical simulations aimed at properly modelling the diffusion processes in porous materials.