# Lightweight Insulating Geopolymer/Phase-Change Materials Applied Using an Innovative Spray Method
## 2 Materials, Methods, and Developed Technological Setup
The spraying manipulator, the hose delivering the mixture, and the spray nozzle were mounted on a movable arm, enabling the nozzle to move without the need for manual force or operator load. The manipulator allowed for effortless direction of the spray nozzle and hose, facilitating easy adjustment of the spray direction onto ceilings, walls, or floors. Both the manipulator and the infrared heater were mounted on a standard mobile platform. The manipulator and infrared heater were equipped with control systems and a synchronised system for rotating both devices around a vertical axis. The schematic of the developed geopolymer spraying solution is shown in Figure 1.  
Figure 1: Diagram of the innovative technological line for the application and curing of foamed geopolymers, presented in two variants: infrared heater not integrated with the mobile platform and manipulator (**a**); infrared heater and manipulator integrated on a shared mobile platform (**b**). The names of the parts are as follows: 1—spray gun, 2—infrared illuminator, 3—flow mixer designed for continuous operation with plastering units and mixing of re-prepared mortars, 4—mixing and spraying unit for plaster mortars, 5—frothing agent insertion spigot, 6—cable connecting the unit to the spray gun. The construction of the entire spraying line utilised a standard plastering unit that was significantly modified to remove the water circulation system, allowing the unit to operate without a water supply. Instead, a foaming agent was introduced just before the geopolymer mass entered the rotor (compressing part). As a result, the geopolymer mass only came into contact with the foaming agent (hydrogen peroxide) for approximately 2-3 s before being applied to the surface, causing the mass to begin foaming only after it was sprayed onto the wall. The described setup involved high-pressure units that incorporated a stator and rotor, with the foaming agent, in the form of liquid hydrogen peroxide, being introduced directly into the geopolymer mass before the stator and rotor module. From an application standpoint, this solution was highly advantageous, as it led to the formation of porous structures as the material exited the unit, with foaming occurring in the open space either during or immediately after application onto the surface. This made the foaming process more efficient than in other technologies, such as cup spraying (spray guns), hydrodynamic methods, and the use of concrete mixers with pumps. Additionally, the automation of the spraying process through the use of an adjustable arm/manipulator, as well as the thermal curing process using infrared heaters, eliminated some of the main barriers and challenges associated with the application of foamed geopolymer materials. The developed arm, with an extendable boom (manipulator), facilitated the application of geopolymer layers without the need to support the hose, making it easier to apply the material on floors, walls, and ceilings. This was an innovative approach, as it had never been used for such applications before. Figure 2 shows the prototype installation developed. As is well known, geopolymer materials require the application of thermal energy to achieve the desired mechanical parameters. This is particularly important in the case of geopolymer foams, whose structure is unstable. Furthermore, when these materials are applied to vertical surfaces, there is a significant risk of material sagging and the formation of so-called \"puddles\". In such cases, providing heating to these freshly applied coatings is crucial. In the developed solution, infrared heaters with adjustable radiation intensity and the ability to regulate their position and angle of incidence were utilised on a mobile platform. A visualisation of this solution is shown in Figure 3.  
Figure 2: _Cont._  
Figure 4 presents two solutions related to the spray nozzles/lances used.