RECYCLING WASTE FOR THE PRODUCTION OF SUSTAINABLE MORTARS FOR BRICK MASONRY

For many years bedding mortars have been considered a secondary component in structural brick masonry walls and they were classified only on the base of their binder (see, e.g., the Italian law DM 20/11/1987 concerning the Regulation for designing, building, testing and strengthening masonry) rather than characterized for their actual mechanical performance. This approach has recently changed and joint mortars have gained higher and higher attention, as they substantially influence the final mechanical performance of masonry. At the same time, a growing awareness of the sustainability issue has been registered in the field of building materials (Bignozzi, 2011), given the extremely high environmental impact of the construction sector (Franzoni, 2011) and its expected increase due to the global population growth (estimated to pass from 6.5 billion in 2005 to about 9.0 billion in 2035 (Dixit and Fernandez-Solis, 2010)). In this scenario, mitigating the consumption of raw materials and energy the manufacturing of building materials is of paramount importance and recycling waste and by-products appears as a feasible route toward this goal. Nevertheless, while recycling waste in concrete was widely investigated and has now entered the building practice, even if with some limitations and die-hard prejudices, the use of not hazardous waste and by-products for masonry (and in particular for mortar joints) is much less considered, despite the widespread presence of structural masonry and wall plug all over the word. In this paper, different mortars with improved sustainability were prepared, partially or totally substituting the fine aggregate with recycled fractions (sand from grounding demolished concrete or end-use tyre rubber) or replacing the cement with a low-carbon binder (alkali-activated binder). After a first characterization of the mortars in terms of strength and microstructure, some brick masonry triplets were built and characterized to assess their properties, with particular reference to their shear behaviour, in view of their possible use in masonry buildings in seismic zones of the world