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The valorization of wastes as an alternative or secondary raw material in various products and processes has been a solution for the implementation of sustainability, a safer environment, and the concept of circular economy in the efficient use and management of natural resources. To promote sustainability through a circular economy approach, this work tries to demonstrate the environmental gains that are obtained by bringing together, in an industrial symbiosis action, two large industrial sectors (the pulp and paper and the road pavement sectors) responsible for generating large amounts of wastes. A sustainability assessment, based on a life cycle and circular economy approach, is presented here, and discussed using a simple case study carried out on a real scale. Two wastes (dregs and grits) from the pulp and paper industry (PPI) were used to partially replace natural fine aggregates in the production of bituminous mixtures used on the top surface of road pavements. The impacts at a technical, environmental, economic, and social level were assessed and it was shown that this simple waste valorization action is not only positive for the final product from a technical point of view, but also for the environment, causing positive impacts on the different sustainability dimensions that were evaluated.

The sustainability and economic competitiveness of alkali activation technology greatly depends on expanding the raw materials database with locally available resources. Therefore, a notable trend has been witnessed toward the exploitation of common clays as alternatives to well-established solid aluminosilicate precursors due to their availability and wide geographical distribution. However, common clays are complex and dedicated research is needed to tailor synthesis procedures and mix designs for different clay resources. This paper describes the outcomes of a study conducted to investigate the influence of several synthesis parameters (solid-to-liquid ratio, NaOH molarity, Si availability, and curing conditions) on the properties of alkali activated binders produced from different thermally modified clays. Optimal synthesis conditions for benchmark metakaolin systems have been identified and binders were produced with progressive dosages of metakaolin replacement by common local clays. Fundamental physical and mechanical properties such as apparent density, open porosity, water absorption, and compressive strength were examined at different curing ages, and X-ray diffraction (XRD) was used to provide complementary mineralogical insights. By combining the effects of the parameters studied, mortar specimens were produced with the developed binders, reaching compressive strength values exceeding 28.2 ± 0.1 MPa, a bulk density as low as 1.78 ± 0.0 g/cm3, and open porosity and water absorption values lower than 15% and 8%, respectively. These properties are comparable to those of conventional hydraulic products, which presents them as interesting candidates for construction. Ultimately, this work aims to contribute with valuable insights toward the valorization of a large group of unexploited clay precursors by demonstrating the feasibility of producing technologically competitive alkali activated materials with little or no use of the prime precursors, thus adding to the extant knowledge and contributing to future scientific and industrial developments in this field.

Waste valorisation as secondary or alternative raw materials in several sectors products and processes has been an important way to implement a more sustainable and circular way to manage the efficient use of natural resources. This action contributes not only to save natural resources but also to prevent sending large amounts of wastes, some of them dangerous, to landfill disposal, creating a major environmental, economic and social impact. To promote circular economy, this work attempts to demonstrate the environmental gains in a competitive way, by bringing together in an industrial symbiosis action, two large producing sectors (the pulp and paper industry and concrete construction sector), which are also able to consume significant amounts of resources and to generate large amounts of wastes. A sustainability evaluation based on a life cycle and circular approach is presented and discussed using a simple case study performed at real industrial scale. The lime ash waste from the pulp and paper industry is used to replace 100% of the natural filler used in precast concrete production and the impacts and benefits from the technical, environmental, economic and social level were assessed. It was demonstrated that this simple action causes positive impacts in the evaluated dimensions of sustainability without causing any changes in production time and causes no degradation on relevant concrete properties.

Lightweight construction is experiencing a significant market implementation with sustained growth both for new buildings and retrofitting purposes. Despite the acknowledged advantages of this type of construction, their reduced thermal inertia can jeopardize indoor thermal comfort levels while leading to higher energy consumption due to high indoor temperature fluctuations and overheating rates. The incorporation of phase change materials (PCMs) into constructive solutions for lightweight buildings is a promising strategy to guarantee adequate thermal comfort conditions. Particularly, the utilization of mortars embedding PCMs as an indoor wall coating for new and existing buildings represents a solution that has not been widely explored in the past and needs further development and validation efforts. This work pursues the analysis of the thermal regulation effects generated by two thermally-enhanced mortars incorporating microencapsulated PCMs with different operating temperature ranges. To that end, an experimental campaign was conducted in Valladolid (Spain) to address the investigation of the proposed solution under a real-scale relevant environment. The proposed mortars were applied as an indoor coating to the envelope of a single-zone lightweight construction that was monitored (under different weather conditions along 1-year monitoring campaign) together with an identical building unit where the mortar was not added to the constructive base layer. The analysis of indoor temperature fluctuations under free-floating operating mode as well as the energy consumption of HVAC equipment under controlled-temperature operation was specifically targeted. Results derived from the continuous monitoring campaign revealed lower temperature fluctuations during summer and shoulder seasons, reducing indoor temperature peaks by 1–2 °C, and producing a time delay of 1–1.5 h into the temperature wave. A clear reduction in energy use due to the incorporation of the PCM-based indoor coating panels is also observed. Thus, this experimental research contributes to proving that the use of innovative mortars incorporating embedded PCMs enables the development of high-end efficient building solutions with innovative materials towards a sustainable built environment.