*2.1. Materials*

2.1.1. Mineral Rock and Glass Wool

The materials used for the tests were waste generated in the mineral wool production cycle. Rock wool (Figure 1a) and glass wool (Figure 1b) were tested.

According to the current Regulation [41], the examined wastes were assigned the 10 12 99 for rock wool and 10 11 03 for glass wool. These are non-hazardous waste. The advantage of the tested waste is its homogeneity and high purity. The manufacturer has introduced waste segregation at the "source" in the production cycle. However, the production cycle cannot use the tested waste due to its form. So far, it has been mainly deposited in landfills for non-hazardous and inert waste and stored in separate quarters due to their character and properties.

The wool density was 10 kg/m3. Mineral wool has a low coefficient of thermal conductivity (so-called lambda, λ). Products made of glass or rock mineral wool, most found on the market, have a thermal conductivity coefficient in the range of 0.030–0.045 W/(m·K). In the next stage of research, the chemical composition was checked. The investigated compositions of tested wools are given in Table 2. The chemical compositions of the rock and glass wool were also determined using the ICP-OES method [7].

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**Figure 1.** Shredded rock wool (**a**) glass wool (**b**) used for tests.

2.1.2. The Methodology of Making Wool-Based Geopolymers

The materials used for the tests were glass and rock mineral wool grounded in a ball mill as the target geopolymer powder (Figure 2). The wool was ground for one hour in a Los Angeles drum equipped with additional grinding balls. The density of green wool in the bulk state was 0.935 kg/dm3.

**Figure 2.** A view of a Los-Angeles drum and ground wool.

In case of an increase of Al in ground glass wool, a bauxite or Al2O3 power was used. In both cases, Geopolymers were made with ground bauxite or Al2O3 in 15% of grounded mineral glass wool. The geopolymers from ground rock wool were prepared without adding another component.

Bauxite contains overwhelmingly: hydrous aluminium oxides, aluminium hydroxides, clay minerals, and insoluble materials such as quartz, hematite, magnetite, siderite, and goethite. The aluminium minerals in bauxite can include gibbsite Al(OH)3, boehmite AlO(OH), and diaspore, AlO(OH). Table 3 presents the chemical composition of tested bauxite.



The geopolymerisation process requires the dissolution of the starting material in a high pH (alkaline) solution, and thus pH values of fresh geopolymer pastes are usually 11.2–13.2 [37,38]. Sodium oxide reacts exothermically with cold water to produce a sodium hydroxide solution. A concentrated solution of sodium oxide in water will have pH 14. Na2O+H2O → 2NaOH. When the OH- concentration of the aqueous solution is reduced by ten times, pH is decreased by only one. According to publications [1,3,7,19,24–31,37], NaOH and soda-silicon water glass are adequate alkane sources to achieve the high compressive strength of geopolymers. The study [37] analysed the effect of NaOH concentration (6–14 M) on the mechanical properties of kaolin geopolymers. Compressive strength results showed that the optimum NaOH concentration is 8 M. Moreover, according to research results [3,4,11–14,16–19,37–40,42,43], the soluble glass to 8 M of NaOH solution ratio should be around 2.5 to give geopolymers high compressive strength [37,40]. Therefore, such recommendations were adopted to design the ratio of the alkaline solution in the analysed studies.

For the preparation of paste and mortar was used 450 g of ground wool were and 225 g of alkaline solution were mixed previously in a magnetic stirrer (Figure 3b). The grounded wool to alkali weight ratio was 0.5. The alkaline solution was cooled down to 20 degrees Celsius before ground wool. The paste and mortar were mixed according to the methodology described in EN-196-1 [44]. The value of pH of fresh geopolymers was also tested (Figure 3a).

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**Figure 3.** (**a**) The view of pH-value of fresh geopolymers; (**b**) alkaline solution in magnetic stirrer.

In the case of geopolymer mortar, normalised sand according to EN-196-1 was used in an amount of 1350 g.

The slump flow of mortars was measured before and after the table was jolted (according to EN 1015-3 [45]).

The geopolymer paste and mortar was formed as 20 mm × 20 mm × 160 mm (Figure 4a) and 40 mm × 40 mm × 160 mm (Figure 4b) specimens, respectively, and were heat-treated for 48 h at 70 ◦C.

**Figure 4.** Geopolymer binder (**a**) mortar (**b**) with rock wool with bauxite (top sample) and with Al2O3 (downsample).

The tested geopolymers had been matured in laboratory conditions for 26 days. The air temperature of 20 ◦C and humidity was about 50%. After that time, they were crushed (Figure 5a,b), then water extracts were made.

**Figure 5.** Geopolymer rock wool binder with the addition of bauxite (SG\_B), fragmented form (**a**), Geopolymer Rock wool binder with the addition of Al2O3 (SG\_Al2O3), fine form (**b**).

The leachability of pollutants from geopolymers produced on the base of waste mineral wool might relate to the form in which they occur, translating into a harmful environmental footprint. In the case of monolithic structures, the leachability level may be determined by the surface release process and diffusion. However, in the case of fragmented forms, the leachability of pollutants determines the percolation process. Therefore, the article also presents.
