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Concretes, depending on their application, may be exposed to elevated temperatures during their lifetime, especially when placed near or in a furnace or during an accidental fire. The thermal stability of alkali-activated mortars and hydrated mortars prepared using ladle slag and two different aggregates was studied. A commercial calcium aluminate cement was used as a comparison for the properties after exposure to temperatures up to 1000°C. All samples were characterised and analysed through a strength test, dilatometric analysis, thermogravimetric analysis, ultrasonic pulse velocity and scanning electron microscopy. The hydrated ladle slag mortars exhibited properties similar to or better than the commercial calcium aluminate cement, while the alkali-activated ladle slag’s thermal properties were inferior to the hydrated ladle slag mortars. The tests also showed that the use of ferrochrome slag aggregates in hydrated ladle slag mortars exhibited similar properties to those using sand aggregate mortars. The damage behaviours of the mortars were dependent on the temperature-induced dehydration, dehydroxylation and thermal incompatibility between the paste and aggregates. The results from this study specify the possibilities of using 100% industrial by-product-based mortar and near-zero carbon dioxide emissions as a fire-resistant material in furnaces, buildings and fireplaces.

This paper presents experimental results regarding the efficiency of using acoustic panels made with fiber-reinforced alkali-activated slag foam concrete containing lightweight recycled aggregates produced by using Petrit-T (tunnel kiln slag). In the first stage, 72 acoustic panels with dimension 500 × 500 × 35 mm were cast and prepared. The mechanical properties of the panels were then assessed in terms of their compressive and flexural strengths. Moreover, the durability properties of acoustic panels were studied using harsh conditions (freeze/thaw and carbonation tests). The efficiency of the lightweight panels was also assessed in terms of thermal properties. In the second stage, 50 acoustic panels were used to cover the floor area in a reverberation room. The acoustic absorption in diffuse field conditions was measured, and the interrupted random noise source method was used to record the sound pressure decay rate over time. Moreover, the acoustic properties of the panels were separately assessed by impedance tubes and airflow resistivity measurements. The recorded results from these two sound absorption evaluations were compared. Additionally, a comparative study was presented on the results of impedance tube measurements to compare the influence of casting volumes (large and small scales) on the sound absorption of the acoustic panels. In the last stage, a comparative study was implemented to clarify the effects of harsh conditions on the sound absorption of the acoustic panels. The results showed that casting scale had great impacts on the mechanical and physical properties. Additionally, it was revealed that harsh conditions improved the sound properties of acoustic panels due to their effects on the porous structure of materials.

The present study valorized Finnish mining tailings waste to identify opportunities for the use of ceramics technologies. On the basis of their mineralogical and chemical contents, the five selected tailings wastes represented felsic mining tailings (FMT) rich in quartz and alkali feldspars, mining tailings dominated by Mg- and Fe-bearing minerals (MgFeMT), and mining tailings rich in carbonate minerals (CMT). Preliminary pilot studies indicated that the FMT materials are potential secondary raw materials for mullite-type ceramics. An Al additive was needed, since the Al₂O₃ content of the studied tailings was too low for mullitization. In addition, carbonate-bearing tailings with Ca silicates can be applicable for chemically bonded phosphate ceramic (CBPC) synthesis. Based on a literature review, FMT are viable source materials for the production of geopolymers, but a high initial Si:Al ratio (in quartz-rich FMT) may lead to partial geopolymerization. Preliminary results from the geopolymerization of pre-heated phlogopite mica mixed with metakaolin gave promising findings, with the formation of a geopolymer having good compressive strength. The findings support the viability of MgFeMT materials rich in phlogopite mica for the production of alkali-activated ceramics