Highly-porous light-weight bricks produced recycling organic waste

Under the motivation (https://ec.europa.eu/programmes/horizon2020/) of the Horizon2020 program, increasing efforts have been addressed in recent years to the introduction of sustainable products into the marketplace and enhancing awareness on eco-labelling, promoting environmental protection, human health, and supporting sustainable development. Waste products generated by industry and other human activities may represent a new primary resource if reused in the production process, thus saving primary geo-resources, reducing manufacturing costs, and limiting extension of waste deposits, all pressing priorities for our society. Moreover, the growing demand of low cost and highly-porous bricks in building construction materials has provided improvement in thermal insulation of the final product. From literature, organic-type additives are the most frequently used as pore-forming agents because they combust during the firing process of brick production. In this work, residues from wine production were used to produced new highly-porous light-weight bricks. Following a multi-analytical approach, pores formed from this pore-forming agent were investigated also in terms of the properties they confer to this new type of bricks. Here we present the preliminary results on mineralogical evolution and physical properties of the experimental brick type obtained using clay materials chemically rich in SiO2 (57.77 wt.%) and Al2O3 (14.14 wt.%), where 10 % (vol.) of dry milled grapes were added with a grain-size up to 2 mm. Due to the large dimension of part of the pores, porosity was explored both by hydric texts and image analysis at the scanning electron microscope on three differently oriented large sections (4.5 x 3 cm2). Thermal insulation analysis was here interpreted in relation to the pore volume and distribution. All the data were compared with those obtained from standard bricks produced using the same base clay. Grapes combustion, indeed, increases the porosity of the final product both in terms of total efficient porosity (%) and in pore dimensions, resulting in enhanced thermal insulation properties. Large size of pores, moreover, favors a good durability moderating possible residual crystals trapped from salt solutions and damages caused by increased volume of ice when in freeze-thaw conditions. These characteristics and valuable aesthetic properties bode assessments for a possible implementation of the new mix into the market.