This contribution presents the preparation and characterization of new geopolymer-based mortars obtained from recycling waste deriving from the production process and the “end-of-life” of porcelain stoneware products. Structural, morphological, and mechanical studies carried out on different kinds of mortars prepared by using several types of by-products (i.e., pressed burnt and extruded ceramic waste, raw pressed and gypsum resulting from exhausted moulds) point out that these systems can be easily cast, also in complex shapes, and show a more consistent microstructure with respect to the geopolymer paste, with a reduced amount of microcracks. Moreover, the excellent adhesion of these materials to common substrates such as pottery and earthenware, even for an elevated concentration of filler, suggests their use in the field of technical-artistic value-added applications, such as restoration, conservation, and/or rehabilitation of historic monuments, or simply as materials for building revetments. For all these reasons, the proposed materials could represent valuable candidates to try to overcome some problems experienced in the cultural heritage sector concerning the selection of environmentally friendly materials that simultaneously meet art and design technical requirements.

The recent introduction of the Next Generation EU packages on the circular economy and the Italian Ecological Transition Plan has further boosted the research of effective routes to design materials with low energy and low environmental impact, in all areas of research, including art and design and cultural heritage. In this work, we describe for the first time the preparation and characterization of a new sustainable adhesive material to be used in the art and design sector, consisting of a geopolymer-based composite with polyvinyl acetate (PVAc), both considered more environmentally acceptable than the analogous inorganic or polymeric materials currently used in this sector. The key idea has been the development of organic–inorganic composites by reacting low molecular weight polymers with the geopolymer precursor to obtain a material with reduced brittleness and enhanced adhesion with common substrates. Structural, morphological, and mechanical studies pointed out the consistent microstructure of the composite materials if compared to the neat geopolymer, showing lower density (up to 15%), improved flexural strength (up to 30%), similar water absorption and a relevant toughening effect (up to 40%). Moreover, the easy pourability in complex shapes and the excellent adhesion of these materials to common substrates suggest their use as materials for restoration, rehabilitation of monuments, and decorative and architectural intervention. The organic–inorganic nature of these new materials also makes them easily recognizable from the support on which they are used, favoring, in line with the dictates of good restoration practices, their possible complete removal. For all these reasons, these new materials could represent promising candidates to overcome the limits related to the creative industry for what concerns the selection of environmentally friendly materials to meet design requirements with low environmental impacts.

This study explores the feasibility of employing bottom ash obtained from biomass combustion as the exclusive precursor for the synthesis of alkali-activated foamed materials with potential applications in thermal insulation. The bottom ash, sourced from a biomass-fired power plant in Italy utilizing woody feedstock, was subjected to comprehensive chemical and mineralogical characterization. The analyses revealed a calcium-rich composition, indicating its suitability for activation using sodium silicate and sodium hydroxide solutions. The foaming behavior of the system was investigated using hydrogen peroxide (H₂O₂) and aluminum powder as foaming agents. Among these, H₂O₂ demonstrated superior effectiveness, particularly in the presence of highly alkaline activating solutions (e.g., 12 M and 15 M NaOH). Curing temperature was found to play a pivotal role in determining the microstructure and physical properties of the resulting materials. Samples cured at 60 °C exhibited enhanced porosity and lower thermal conductivity, thus favoring insulation performance. In contrast, those cured at 40 °C showed higher compressive strength, attributed to reduced shrinkage during the curing process. X-ray diffraction (XRD) and infrared (IR) spectroscopy confirmed the formation of hydrated calcium silicate phases, while scanning electron microscopy (SEM) revealed a more homogeneous and compact microstructure in samples activated under high alkalinity conditions. Notably, thermal conductivity values below 0.1 W/m·K were achieved in samples with high open porosity. Several formulations were identified that offer an optimal balance between mechanical strength and thermal insulation, thereby demonstrating the potential of these materials for structural insulation applications. The findings underscore the viability of utilizing biomass bottom ash as a sustainable and innovative raw material for the development of advanced insulation solutions in the construction sector.