*2.2. Research Methodology*

#### 2.2.1. Leachability of Mineral Wool

The research procedure included the preparation of water extracts from waste mineral wool (rock and glass), executing chemical tests, and assessing criteria to allow the waste to be stored. The tested waste was mechanically milled for chemical analysis; also, water extracts were carried out on the pre-prepared samples. The samples were tested for the content of organic carbon (TOC)—EN 1484:1999 [46]. Loss on ignition (LOI) was determined according to EN 15935:2013-02 [47]. However, the determination of calorific value by calorimetric bomb combustion to PN-ISO 1928:2020-05 [48]. The procedure for preparing water extracts from solid waste was carried out according to EN 12457- 2:2006 standard [49]. Water extracts for waste were prepared at a liquid to solid ratio of L/S = 10 dm3/kg (basic test). The prepared water extracts were shaken on a laboratory shaker for 24 h, after which time the obtained extracts were filtered. The leaching liquid was distilled water with a pH of 7.1 and a specific conductivity of 61.18 μS/cm. The analysis of water extracts from waste included several determinations. First, the pH of water extracts was determined using the potentiometric method using the Elmetron CPC-501 apparatus available in Silesian University of Technology in Gliwice, Poland [50]. Chloride (Cl−) contents were determined by the Mohr method with the use of silver nitrate (V) as a titration reagent and potassium chromate (VI) as an indicator (PN-ISO 9297:1994) [51]. Determination of sulphates (VI) (SO4 <sup>2</sup>−) was carried out using the gravimetric method with barium chloride according to PN-ISO 9280:2002 [52]. Determination of phosphorus was according to EN ISO 6878:2006 [53]. The sodium, calcium, potassium, lithium, and barium content in water extracts were determined by flame emission spectrometry—following PN-ISO 9964-3:1994 [54]. Using the GBC AVANTA PM spectrometer available in Silesian University of Technology in Poland, trace element concentrations were determined by flame atomic absorption spectrometry.

## 2.2.2. The Leachability of the Wool-Based Geopolymer

The execution of water extracts from monolithic and fragmented geopolymers was executed following the EN 12457-4:2006 standard [49]. Monolithic geopolymers were mechanically grounded to grain sizes <10 mm. Water extracts were prepared from the prepared samples with a liquid to solid ratio of L/S = 10 L/kg (basic test). The leaching liquid was distilled water with a pH of 7.1 and a specific conductivity of 62.18 μS/cm. The extracts were then shaken on a laboratory shaker for 24 h, and the suspension was filtered. The analysis of water extracts from fragmented geopolymers covered several determiners. First, the pH of the solutions was carried out using an Elmetron CPC-501 apparatus [50]. Chloride contents were determined by the Mohr method with the use of silver nitrate (V) as a titration reagent and potassium chromate (VI) as an indicator (PN-ISO 9297:1994) [51]. In addition, the determination of sulphates (VI) (SO4 <sup>2</sup>−) was carried out with a gravimetric method with barium chloride, according to PN-ISO 9280:2002 standard [52]. The flame emission spectrometry method determined sodium, calcium, potassium, and barium content in water extracts from ashes and concrete according to the PN-ISO 9964-3:1994 [54] standard. Using the GBC AVANTA PM spectrometer, trace element concentrations were determined by flame atomic absorption spectrometry.

#### 2.2.3. The Mechanical Properties of the Wool-Based Geopolymer

The geopolymers were matured in laboratory conditions for 26 days. Ambient temperature 20 ◦C and humidity around 50%. After 28 days, the flexural and compressive strength of the wool-based geopolymers binders and mortars were tested (Figure 6) acc. EN 196-1:2016 [44].

**Figure 6.** The view of the sample of geopolymer mortar under testing of the compressive strength.
