## 2 Materials and Methods
### Test Methods  
The geopolymers' chemical composition and surface microstructure were analysed using a scanning electron microscope (Hitachi Co., Ltd., Tokyo, Japan, TM3000) with an EDS analyser (Bruker Co., Billerica, MA, USA, Bruker Quantax EDS). The specimens with a surface area of about 2 cm\({}^{2}\) and thickness of up to 3 mm were prepared by cutting from the central part of the cubic specimens. The specimens were sprayed with the gold and palladium alloy in the vacuum chamber to increase the surface electrical conductivity. SEM photographs with a magnification of 100 \(\times\) to 800 \(\times\) were obtained for analysing the geopolymers' microstructure.  
The density of the geopolymers and reference cement mortar was calculated using the geometric method to determine the mass-to-volume ratio. The specimens' masses were measured with a precise scale PS6000.X2 (RADWAG, Radom, Poland).  
Figure 1: Particle size distribution of fly ash (FA) and waste glass (WG).  
The thermal parameters were determined by a non-stationary method. The method is based on the heat flux analysis at the unsteady flow. The apparatus uses the superficial or pin probes with a specific thermal conductivity range. The superficial probe (Applied Precision, Bratislava, Slovakia, Isomet 2114) was used in the experiment. The cubic specimens 40 \(\times\) 40 \(\times\) 40 mm\({}^{3}\) in dry state were used for tests after 28 days of curing. The specimens were stored in the laboratory in dry conditions until their mass stabilised. The thermal conductivity \(\lambda\), volumetric specific heat c\({}_{v}\), and thermal diffusivity \(a\) were registered.  
The compressive and flexural strength were determined on the dry geopolymers and RCM after 28 days of curing. Tests were carried out using the strength machine (Toni Technik GmbH, Berlin, Germany) at a maximum load of 100 kN. The compressive strength was measured on the cubic specimens 40 \(\times\) 40 \(\times\) 40 mm\({}^{3}\) with an accuracy of 0.1 MPa. The specimens were placed centrally on the strength machine's plate so that the rubbed surface was on the side. The load was uniformly raised at the rate of 2400 \(\pm\) 200 N/s during the whole test, until the specimen was destroyed. The flexural strength was measured on the beams 40 \(\times\) 40 \(\times\) 160 mm\({}^{3}\) using the strength machine (Toni Technik GmbH, Berlin, Germany) and the mortar testing attachment. A three-point loading method was employed. The strength machine (Toni Technik GmbH, Berlin, Germany) was equipped with a bending mechanism consisting of two steel supporting rollers with a diameter of 10 \(\pm\) 0.5 mm and an axial distance of 100 \(\pm\) 0.5 mm, and a third roller (loading) placed centrally between the supporting rollers. The test consists of placing the beam 40 \(\times\) 40 \(\times\) 160 mm\({}^{3}\) perpendicularly to the rollers, so that the central roller is above the beam's centre, i.e., at a length of 8 cm from its beginning. The load is transferred by the loading roller to the side surface of the beam at a rate of 50 \(\pm\) 10 N/s until the beam breaks. The flexural strength \(R_{t}\) is calculated from the formula:  
\[R_{t}=\frac{1.5\cdot F_{t}\cdot 1}{b^{3}}\]  
where \(R_{t}\)--flexural strength [MPa];  
\(F_{t}\)--breaking load at the beam's centre [N];  
\(b\)--side length of the beam's section [mm];  
\(l\)--distance between the supports [mm].  
Tests were conducted according to the European Standard [46].