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Povzetek: Technology of alkali activation is an alternative sustainable approach to producing paving paver, where reactive aluminosilicate precursor undergoes a reaction with an alkaline solution to form binded product. The case study presents the functional usability of a technology as part of the Georis project. The construction pavers are composed of over 75% industrial residues, with the majority of the materials sourced from steel slag industry. Laboratory testing of pavers confirmed the promising mechanical properties, demonstrating high compressive and flexural strength, as well as resistance to frost and abrasion. The results support the feasibility of scaling up from lab-scale to pilot manufacturing. The innovative approach in this project was the pilot production process itself, where more than 20 m² of pavers were manufactured and cured in a mobile unit. To assess their real-world performance, a demonstration case was implemented at the SIJ Acroni courtyard, where the pavers were installed to observe their application in a practical setting and to monitor their long-term durability. The valorisation of residues within GEORIS pavers highlights lower CO₂ emissions compared to conventional cement-based pavers and the potential of technology for industrial symbiosis and circular economy initiatives, making it an attractive solution for environmentally conscious industries.
Ključne besede: waste materials, alkali activated material, sustainable approach, slag, pavers
Objavljeno v DiRROS: 07.04.2025; Ogledov: 702; Prenosov: 418
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Povzetek: In building constructions, the tendency towards an ever-better material directs us to composite materials. In this work, we prepared an organic-organic and organic-inorganic composite material by incorporating fire retardants, ammonium polyphosphates, and 2,4,6-triamino-1,3,5-triazine, into a polyurethane network and an aluminosilicate network (ASN) of alkali-activated material. Polyurethane foams (PUR) are well-known materials that, due to their properties, such as low weight-to-strength ratio, low electrical and thermal conductivity, flexibility, and relatively simple preparation process, are used in various industries, also in the construction industry, e.g., for thermal insulation of windows and doors or fixing and sealing joinery. Opposite, the ASN of alkali-activated metakaolin, successfully paves the way for new applications, such as high-temperature protection. In this paper, these interactive properties of prepared composites are studied using thermal testing and mechanical analysis. It was found that inhibitors significantly increase the fire resistance of PUR systems while they slightly reduce the mechanical properties. Incorporating polymer flame retardant into ASN in building products, such as façade panels , can decrease the mechanical properties but can offer the non-flammable building envelope not get heated from burning surroundings, i.e., not becoming a convection heat source, but rather represent a fire-distinguisher for flammable materials.
Ključne besede: flame retardants, polyurethane, alkali activated material, metakaolin, microwave irradiation, mechanical strength
Objavljeno v DiRROS: 12.03.2024; Ogledov: 3948; Prenosov: 875
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Povzetek: Two synthesis pathways (one- and two-part) in alkali-activated binders were compared using ground granulated blast furnace slag (GGBFS), mineral wool (MW) activated using dry and liquid alkali activators with similar Na2O/SiO2 modulus. The effect of activator type on reaction kinetics, strength development, setting times, and durability shows that one-part synthesis does not only improve early strength, but also provide better durability properties. While the highest compressive strength (56 MPa, 90 days) was achieved for the one-part mix (DM), the reaction products (presence of Mg–Al layered double hydroxide and C–S–H-like phases) observed for both mortar mixes were similar. The DM mortars showed better resistance to sulfate attack than two-part mix (WM) mortars and sets faster. The results highlight the significance of the one-part pathways in the synthesis of alkali-activated materials.
Ključne besede: recycling, alkali activated material, mineral wool
Objavljeno v DiRROS: 11.03.2024; Ogledov: 1611; Prenosov: 1002
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Povzetek: Polyurethane foam (PUR) is a lightweight, thermally insulating, widely used, and highly flammable material that has after its use an adverse effect on the environment, i.e., PUR disposal is considered hazardous. Its flammability can be mitigated using various fire retardants, but they do not change the hazardous nature of waste PUR. Therefore, in the current study, waste PUR with and without flame retardants based on N and P was incorporated into a geopolymer, the alkali-activated material (AAM) based solely on metakaolin, to evaluate the potential recycling route of waste PUR while taking into account its flammability, so it can enter safely into the circular economy through the building industry. To enhance the mechanical properties of the composite, a fresh mixture was irradiated with microwaves. However, the irradiation of geopolymer containing PUR negatively influenced mechanical performance, which led to the evaluation of the behaviour of the complex dielectric constant of PUR and fire retardants. Materials and composites were evaluated regarding their chemistry, mineralogy, microstructure, and porosity to connect the structure with extrinsic properties like geometrical density, thermal conductivity, and fire properties. Nonetheless, positive influences of PUR being encapsulated in the geopolymer were lowered density (from 1.8 to 1.6 kg/l) and improved thermal insulation ability (from 940 to 860 mW/(m·K)) of the composites: with the inclusion of <5 % of PUR, thermal insulation improved by nearly 10 %. However, the contribution of PUR to the composite originated from its skeleton, which has more than 15 times bigger geometrical density (0.81 kg/l) compared to the density of the skeleton (0.047 kg/l). This offers an open field for further advancements of thermal properties, but would also lead to a decrease of the compressive strength, which was already lowered from 90 MPa for 30 % with <5 % of added grated PUR. Furthermore, the flammable nature of PUR and its other drawbacks can be controlled by permanent embedding in the noncombustible structure of geopolymer, making the envelope of sustainable buildings green and safer. Overall, including grated waste PUR in geopolymer represents a promising, easy, cost-effective recycling path with low energy consumption, where the composite cannot develop fire on a scale of pure PUR, even in the worst-case scenario, but only if the composite is designed in a way, that flammable materials cannot join flames during their combustion. This paper gives prospects to other flammable waste materials to be safely used in the circular economy, and to porous materials to shape properties of the composite by their intrinsic and/or extrinsic properties.
Ključne besede: waste polyurethane foam, polymeric flame retardants, alkali activated material, metakaolin, microwave irradiation, thermal-fire behaviour, mechanical strength
Objavljeno v DiRROS: 01.03.2024; Ogledov: 3158; Prenosov: 1634
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Povzetek: Mineral wool, i.e. rock and glass wool, represents considerable challenge after its functional-time runs out due to its small density leading to large volume consumption during transport and in landfills where it usually ends. Because rock wool is mineralogically and chemically a promising precursor material for alkali-activation, it was milled from few centimetres-decimeters long fibres to micron-sized fibres. Since fibres in alkali-activated materials generally show an increase in mechanical strength, especially the bending strength, 1 m% of additional fibres (basalt, cellulose (2 types), glass, polypropylene, polyvinyl alcohol and steel fibres) was used in the alkali mixture, that was curred at 40 °C for 3 days. Time dependence of the mechanical strengths of alkali- activated materials with and without additional fibres was followed. Maximal increase of compressive and bending strength after 28 days was reached with polypropylene fibres, i.e. it was 20% and 30% higher than compressive and bending strength of alkali- activated material without additional fibres respectively.
Ključne besede: secondary raw material, alkali activated material, foaming, homogenization, mechanical strength
Objavljeno v DiRROS: 21.12.2023; Ogledov: 1408; Prenosov: 633
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