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This study proposes the reuse of spent coffee ground and biomass fly ash in the development of green geopolymeric thermo-plastering for innovative building applications. The former waste is the major residue of the brewing process, that is usually used as fertilisers or disposed of in landfill with extreme harmfulness for the natural environment. The latter is an industrial waste generated during the Kraft paper-pulp process, that is usually landfilled. The mortar is produced with a combination of metakaolin (30 wt.%) and biomass fly ash (70 wt.%), and natural siliceous sand filled with spent coffee ground (up to 17.5 wt.%). The high amount of reused waste makes the material an optimum candidate for the Environmental Minimum Criteria (CAM) assessment as ruled by the National Action Plan on Green Public Procurement. The overall manufacturing process occurred at ambient conditions (20 °C, 65% RH) contributing to the materials sustainability. 28-days cured specimens were analysed to assess the material engineering properties and delineate the possible applications in construction. Finally, virtual energy simulations were implemented to study the possible energetic performance benefits in a simplified building model. The major results are that the used wastes considerably improve the technological material performance making it suitable for effective use in construction. While the slurry workability is significantly affected by the waste introduction, and the mechanical resistance is still high, the thermal conductivity outlines a possible energy application. All considering, coffee waste can be effectively reused to manufacture green bio-composite materials with satisfactory performance considering the main requirements of a building making them exploitable in various applications in construction, especially in energy-saving functions, in line with the European directives towards zero-energy building.

This work investigates the production a green geopolymer-based concrete for a sustainable construction material using biomass wastes from a kraft pulp industry: fly ash (as main alumina-silicate source) and grits (as aggregate). Moreover, a simple, reproducible, ambient temperature, and low-cost manufacture is followed. Mix design aims to maximize wastes incorporation and optimize the mechanical performance. Preliminary tests indicate that the used wastes may be successfully employed to produce green geopolymeric concretes with satisfying mechanical performance (up to 18 MPa), according to the European standards. Furthermore, they represent a viable solution to reduce the environmental footprint associated with waste disposal.

Calcareous sludge is an alkaline waste produced by the paper pulp industry that is commonly disposed of in land-fill. However, recent studies and the European regulations discourage such practice. This work investigates an alternative and innovative way to recycle and reuse this waste, as filler, in the production of green geopolymeric mortars intended for applications in construction. This is the first time that this calcareous sludge is used to produce novel waste-based materials, in both construction and geopolymer technology. The novel alkali-activated mortar also uses biomass fly ash – another slightly investigated waste stream – to substitute the metakaolin (70 wt% substitution) and the manufacture process is performed at ambient conditions. All of that reduces the overall process footprint. The implemented mix design is aimed at maximising the waste incorporation and improving the material properties, such as workability and mechanical performance. The main results demonstrate that 10 wt% of calcareous sludge can be efficaciously used as filler in the geopolymeric mortars, generating up to 30% improvement in the mechanical resistance. This alternative use of such wastes will contribute to increase the sustainability of the novel construction materials also granting environmental advantages and a financial surplus for the industry.

This work discusses the influence of the aggregate granulometry and the binder/aggregate ratio on the engineering properties of novel green geopolymeric mortars. Two wastes generated by a Portuguese Kraft pulp industry are employed to manufacture the material: lime slaker grits (used as aggregate) and biomass fly ash (to partially replace the metakaolin − 70 wt% substitution). The novel geopolymeric mortars could find innovative applications as sustainable construction materials. The studied mix design foresees the use of several grits granulometric ranges and ratios binder/aggregate to discuss workability, water sorptivity, and mechanical performance of the novel mortars. To date, these factors are fairly unknown in geopolymeric materials. The raw materials are also characterized. The main results demonstrate that the formulated geopolymeric mortars can be efficaciously used for masonry application in construction and predict potentialities and limits. Reuse of such wastes will increase the sustainability of the novel construction materials also granting a financial surplus for the industry. Furthermore, manufacture and curing are conducted at ambient conditions (20 °C, 65% RH), avoiding any external source of energy, and involve a simple, reproducible, and low-cost process.

Sustainability in construction is a major concern worldwide, due to the huge volume of materials and energy consumed by this sector. Associated supplementing industries (e.g. Portland cement production) constitute a significant source of CO2 emissions and global warming. Valorisation and reuse of industrial wastes and by-products make geopolymers a solid and sustainable via to be followed as a valid alternative to Portland cement. In this work the mix design of a green fly ash-based geopolymer is evaluated as an environmentally friendly construction material. In the pursuit of sustainability, wastes from a regional kraft pulp industry are exploited for the material processing. Furthermore, a simple, reproducible, and low-cost manufacture is used. The mix design is hence optimised in order to improve the desirable mechanical performance of the material intended for structural applications in construction. Tests indicate that geopolymers may efficiently substitute the ordinary Portland cement as a mortar/concrete binder. Furthermore, valorisation and reuse of wastes in geopolymers is a suboptimal way of gaining financial surplus for the involved industrial players, while contributes for the implementation of a desirable circular economy.