Dominik Smyczek

This study provides new experimental evidence indicating that powdered mineral wool waste traditionally classified as a non-reactive, non-recyclable insulation residue can function as a genuinely pozzolanic supplementary cementitious material when incorporated into Portland cement systems. Unlike previous work that has treated mineral wool exclusively as an inert filler, this research demonstrates that its amorphous silicate–aluminate phase becomes chemically active under high-alkalinity conditions. A combined experimental programme, including mechanical testing, assessment and SEM/EDS microstructural analysis, was used to evaluate replacement levels of 20%, 25%, and 40% in CEM I mortars, with CSA cement employed as a contrasting binder system. The results indicate a potential contribution of powdered mineral wool to strength development; however, this effect cannot be unequivocally attributed to pozzolanic activity alone. It may also be partially related to physical effects such as filler action and particle packing. SEM/EDS observations confirm the formation of secondary C–S–H and C–A–S–H gels, can function as a genuinely pozzolanic supplementary cementitious material. Therefore, the applied assessment approach should be treated as indicative, and further verification using complementary methods is required. This study provides new experimental evidence indicating mineral wool can potentially contribute to cementitious performance as a Supplementary Cementitious Material (SCM). However, these observations should be treated as qualitative and indicative rather than definitive proof of pozzolanic reaction. The study provides an environmentally relevant valorisation pathway for a problematic waste stream, showing that mineral wool residues containing only trace levels of immobilizable formaldehyde can be safely and effectively integrated into low-carbon binder technologies. These findings position powdered mineral wool as a previously overlooked, yet technically viable SCM, offering new opportunities for clinker reduction, waste circularity and sustainable cementitious material design.

Glass wool waste constitutes a rapidly increasing fraction of construction and demolition residues, yet it remains one of the most challenging insulation materials to recycle. Its non-combustible nature, extremely low bulk density, and high fibre elasticity preclude energy recovery and severely limit conventional mechanical recycling routes, resulting in long-term landfilling and loss of mineral resources. Converting glass wool waste into a fine mineral powder represents a potentially viable pathway for its integration into low-carbon construction materials, provided that industrial scalability, particle-size control, and chemical compatibility with cementitious binders are ensured. This study investigates the industrial-scale milling of end-of-life glass wool waste in a ventilated horizontal ball mill. It compares two grinding routes: a corundum-free route (BK) and an abrasive-assisted route (ZK) employing α-Al₂O₃ corundum to intensify fibre fragmentation. Particle size distribution was quantified by laser diffraction using cumulative and differential analyses, as well as characteristic diameters. The results confirm that abrasive-assisted milling significantly enhances fragmentation efficiency and reduces the coarse fibre fraction. However, the study demonstrates that this gain in fineness is inherently coupled with the incorporation of α-Al₂O₃ into the milled powder, introducing a chemically foreign crystalline phase that cannot be removed by post-processing. From a cement-oriented perspective, this contamination represents a critical limitation, as α-Al₂O₃ may interfere with hydration reactions, aluminate–sulfate equilibria, and microstructural development in Portland and calcium sulfoaluminate binders. In contrast, the corundum-free milling route yields a slightly coarser, chemically unmodified powder, offering improved process robustness, lower operational complexity, and greater compatibility with circular economy objectives. The study establishes that, for the circular reuse of fibrous insulation waste in cementitious systems, particle fineness alone is insufficient as an optimization criterion. Instead, the combined consideration of fineness, chemical purity, and binder compatibility governs the realistic and sustainable reuse potential of recycled glass wool powders.

The increasing accumulation of mineral wool waste, especially from construction and demolition sources, presents a major environmental burden. This study investigates a scalable grinding enhancement strategy using bauxite and glass cullet additives to improve the comminution of glass wool, rock wool, and mixed mineral wool waste. Mechanical grinding assisted with the use of 10 wt% and 20 wt% of hard mineral additives reduced milling time by up to 50% compared to unmodified samples, with bauxite consistently outperforming glass cullet. Laser diffraction confirmed a marked reduction in particle size, reaching sub-50 µm targets essential for alkali activation, while SEM analysis revealed smoother, fractured surfaces conducive to improved geopolymer reactivity. Energy consumption estimates suggest substantial efficiency gains; however, upstream impacts such as additive production and transport warrant further evaluation. Compared to conventional thermal and chemical pretreatments, this abrasive-assisted approach demonstrates a lower-energy pathway for producing geopolymer-compatible powders. The findings also offer guidance for developing standardized protocols and open avenues for testing these powders in future binder formulations.

The article discusses the effect of additives of waste mineral wool fibers on geopolymer binder. This is an important study in terms of the possibility of recycling mineral wool waste. The paper describes an effective method for pulverizing the wool and the methodology for forming geopolymer samples, labeled G1 for glass-wool-based geopolymer and G2 for stone-wool-based geopolymer. The compressive and flexural strengths and thermal conductivity coefficient of the geopolymer with the addition of mineral fibers were determined. The key element of the article is to verify whether the addition of mineral wool fibers positively affects the properties of the geopolymer. The results obtained prove that the addition of fibers significantly improves the flexural strength. For the G1 formulation, the ratio of compressive strength to flexural strength is 18.7%. However, for G2 samples, an even better ratio of compressive strength to flexural strength values of 26.3% was obtained. The average thermal conductivity coefficient obtained was 1.053 W/(m·K) for the G1 series samples and 0.953 W/(m·K) for the G2 series samples. The conclusions obtained show a correlation between the porosity and compressive strength and thermal conductivity coefficient. The higher the porosity, the better the thermal insulation of the material and the weaker the compressive strength.

Innovative building materials should also be pro-environmental. This article discusses the environmental footprint of geopolymer and cement-based mortars. It describes the methodology for preparing geopolymer and cement mortars using mineral wool waste. The phenol–formaldehyde resin used in mineral wool is a source of phenol and formaldehyde emissions to the environment. The prepared mortar samples were subjected to durability tests to assess the correlation between the amount of mineral wool and the flexural and compressive strength of the samples. The key element of the paper is to test whether immobilisation of mineral wool in the geopolymer will reduce leaching of phenol and formaldehyde into the environment. The results revealed that cements prepared with mineral wool showed higher compressive strength, whereas geopolymer samples had better flexural strength. The study also proved that immobilisation of the wool in the geopolymer reduces phenol and formaldehyde leaching significantly.

Waste generated in fine wool production is homogeneous and without contamination, which increases its chances of reuse. Waste mineral wool from demolition sites belongs to the specific group of waste. However, the storage and collection require implementing restrictive conditions, such as improper storage of mineral wool, which is highly hazardous for the environment. The study focuses on the leachability of selected pollutants (pH, Cl⁻, SO₄²⁻) and heavy metals (Ba, Co, Cr, Cu, Ni, Pb, Zn) from the waste mineral wool. As a solution to the problem of storing mineral wool waste, it was proposed to process it into wool-based geopolymer. The geopolymer, based on mineral wool, was also assessed regarding the leaching of selected impurities. Rock mineral wool is very good for geopolymerisation, but the glass wool needs to be completed with additional components rich in Al₂O₃. The research involved geopolymer prepared from mineral glass wool with bauxite and Al₂O₃. So far, glass wool with the mentioned additives has not been tested. An essential aspect of the article is checking the influence of wool-based geopolymer on the environment. To investigate the environmental effects of the wool-based monolith and crushed wool geopolymers were compared. Such research has not been conducted so far. For this purpose, water extracts from fragmented geopolymers were made, and tests were carried out following EN 12457-4. There is no information in the literature on the influence of geopolymer on the environment, which is an essential aspect of its possible use. The research results proved that the geopolymer made on the base of mineral wool meets the environmental requirements, except for the pH value. As mentioned in the article, the geopolymerisation process requires the dissolution of the starting material in a high pH (alkaline) solution. On the other hand, the pH minimum 11.2 value of fresh geopolymer binder is required to start geopolymerisation. Moreover, research results analysed in the literature showed that the optimum NaOH concentration is 8 M. for the highest compressive strength of geopolymer. Therefore, the geopolymer strength decreases with NaO concentration in the NaOH solution. Geopolymers glass wool-based mortars with Al₂O₃ obtained an average compressive strength of 59, the geopolymer with bauxite achieved about 51 MPa. Thus, Al₂O₃ is a better additional glass wool-based geopolymer than bauxite. The average compressive strength of rock wool-based geopolymer mortar was about 62 MPa. The average compressive strength of wool-based geopolymer binder was about 20–25 MPa. It was observed that samples of geopolymers grout without aggregate participation are characterised by cracking and deformation.