This research aimed to investigate the potential of using alkali activation technology to valorize steel slag and bauxite residue for the production of high-performance pavement blocks. By utilizing these industrial by-products, the study seeks to reduce their environmental impact and support the development of sustainable construction materials. Lab-scale testing showed that bauxite pavers showed a decrease in mechanical strength with increasing replacement of ordinary Portland cement. Partial replacement up to 20% still exceeded 30 MPa in compressive strength. Steel slag-based pavers achieved the 30 MPa threshold required for the application with selected mix designs. Pilot-scale production-optimized formulations and standards testing, including freeze–thaw resistance, confirmed the technical viability of these products. Life cycle analysis indicated a 25–27% reduction in CO₂ emissions for slag-based tiles compared to traditional concrete tiles. Moreover, using industrial residue reduced mineral resource depletion. This study examined the properties of the resulting alkali-activated binders, their ecological benefits, and their performance compared to conventional materials. Through a comprehensive analysis of these applications, our research promotes the circular economy and the advancement of sustainable construction products.

This literature review critically examines the incorporation of mineral wool waste (MWW), a byproduct of insulation materials, into new construction materials as a sustainable recycling strategy. Covering research published between 2000 and 2025, the review focuses on the effects of MWW on various material properties and performance, including concrete, mortar, alkali-activated materials (AAMs), geopolymers (GPs), building ceramics, and asphalt. Experimental evidence demonstrates that MWW can enhance or alter the performance of these materials, offering promising opportunities for waste valorization. The review also identifies challenges related to optimizing material compositions and production methods, and highlights the need for further research to facilitate the industrial-scale application of MWW-recycled construction materials. By synthesizing current knowledge, this work aims to inform sustainable development and circular economy practices in the construction sector.

Efflorescence, a time-dependent and water-driven phenomenon, is a major concern in alkali-activated materials (AAMs), impacting their practical use and preservation in a time-frozen state for post-characterisation. Although a method for stopping chemical reactions in conventional cements exists, it is time-consuming and not chemical-free. Therefore, this study explored the effects of low-power microwave-induced dehydration on efflorescence, mechanical performance, and structural integrity in AAMs, to create an alternative and more “user-friendly” dehydration method. For this purpose, several mixtures based on secondary raw (slag, fly ash, glass wool, and rock wool) and non-waste (metakaolin) materials were activated with a commercial Na-silicate solution in ratios that promoted or prevented efflorescence. Characterisation techniques, including Fourier-transform infrared spectroscopy and X-ray diffraction, showed that microwave dehydration effectively removed water without altering crystallinity, while mercury intrusion porosimetry and compressive strength tests confirmed increased porosity. In addition to being an efficient, time-saving, and solvent-free manner of stopping the reactions in AAMs, microwave irradiation emerged as an innovative, chemical-free method for evaluating curing finalisation and engineering foams in a stage when all other existing methods fail. However, the artificially provoked efflorescence in aged dehydrated AAMs connected the slipperiness of AAM with the instant extraction of Na, which raised the need for further research into alternative alkali replacements to evaluate the practical use of AAM.

Efflorescence is a major concern in alkali-activated materials (AAMs), affecting their potential practical applications and challenging the preservation of the material in a time-frozen state for post-characterisation purposes. Efflorescence is a time-dependent phenomenon that may stop with complete water removal. Therefore, this study mixed chemically and physically different secondary raw (slag, fly ash, glass wool, and rock wool) and nonwaste (metakaolin) materials with Na-silicate solution in ratios that facilitated efflorescence and mixtures that could prevent it. The material was cured at 40 °C for 6 days. On the 7th day, half of the intact samples were additionally treated with low-power microwaves (2.45 GHz at 100 W) until complete dehydration to rapidly and gently influence the chemical reaction. The impact of microwave-irradiation-induced dehydration on the specimens was thoroughly examined on day 7, both chemically and physically, and compared with that of a set of samples that were not subjected to dehydration. Chemical alterations were examined using Fourier transform infrared spectroscopy, which revealed the removal of water. Further, X-ray diffraction revealed no changes in crystallinity upon irradiation. The irradiation-increased porosity was evaluated through Mercury Intrusion Porosimetry, whereas the mechanical resilience of the materials was evaluated through compressive strength tests and synchronised with the porosity development. Pores in the irradiated samples that required higher temperatures or longer curing times (glass wool, fly ash, and metakaolin) were spherical; otherwise, dehydration resulted in elongated cracks. This result provided side knowledge on the determination of finalisation of the curing of AAM, which cannot be determined by any surface-penetrating test. Efflorescence formation was evaluated on 1-year-old dehydrated samples, maintained at room temperature, before and after exposure to a water droplet using a low-vacuum scanning electron microscope. This explained the reason why the surface of AAMs exposed to water became slippery and the effect of the water droplet on the surface. The microwave treatment method successfully accomplished the complete dehydration of AAMs within a few minutes, effectively inhibiting reactions in the AAMs, terminating further development of the aluminosilicate network, and partially removing unbonded alkali elements from the chemically unfinished AAM system. Therefore, microwave irradiation can be used to evaluate the chemical compositions of time-evolving materials during dehydration. If the dehydrated samples are stored in a waterless environment, post-characterisation of the AAMs is possible at any later time. The procedure of stopping the reactions offers significant advantages over conventional techniques which require physical processing, such as grinding or milling, the use of solvents, and more time.