# Lightweight Insulating Geopolymer/Phase-Change Materials Applied Using an Innovative Spray Method
## 4 Conclusions  
Among the key advantages of foamed geopolymers are their high thermal resistance and non-flammability, resistance to chemically aggressive environments, fine mechanical properties, and durability against biological factors, including rodent activity. Their thermal insulation performance can be further improved by the incorporation of PCMs. This study presents a novel technology enabling the effective application of such materials to various substrates, ensuring uniform coverage and minimising material losses. The described system operates by spraying a hydrated geopolymer mixture and foaming it after exiting the spray unit, either directly onto building surfaces or into moulds, with a foaming agent added at the final stage of material delivery. A single sprayed layer created with this system enables the formation of a foamed geopolymer coating up to 2 cm thick. The proposed solution is innovative in the field of spray process automation, thanks to the use of a controllable arm/manipulator, as well as the implementation of a thermal curing process using infrared (IR) radiators. The geopolymer/PCM foamed coatings produced using this method were subjected to testing, and the results can be summarised as follows:  
* The high adhesion strength of the geopolymer/PCM foam, consistently exceeding 1 N/mm\({}^{2}\) across various substrates, underscores its potential as a durable protective coating for construction applications. Cohesive failure was observed in the foam layer for steel and geopolymer substrates, whereas failure occurred within the gypsum board itself at the gypsum-cardboard interface. Direct application to steel, concrete, and gypsum board without priming gave satisfactory results. * Microstructural analysis confirmed a relatively uniform pore size distribution, indicating effective control over the foaming process. No significant clustering of excessively large or small pores was observed, demonstrating consistent foaming. * The thermal conductivity of the foamed geopolymer/PCM composites averaged 0.0776 W/m-K. The addition of the PCM increased the specific heat capacity by approximately 15%, reaching 1.398 J/g-K, thereby enhancing the material's thermal storage capacity. * The proper solid-to-liquid ratio for the geopolymer/PCM mixture was determined to be 0.24:1. This formulation enabled sufficient adhesion, foam stability, and uniform layer formation. The solution developed and presented in this paper provided several benefits, including the following:  
* A \"Delayed foaming\" effect, occurring only at the stage of spraying onto the substrate, which prevents premature volume expansion in the mixing system and supply lines. This significantly reduces the risk of system clogging and material loss due to uncontrolled foaming inside the device. Furthermore, it enables more precise control over the porous structure directly at the application site. * Uniform pore distribution can be achieved, since foaming occurs immediately after application. This ensures even expansion of the material while maintaining high flowability and adhesion of the sprayed geopolymer. As a result, microcracks and surface irregularities are filled more effectively. * Improved material stream control results in better surface coverage and more uniform coating thickness. Enhanced spraying accuracy contributes to increased material efficiency, minimising waste and improving the final aesthetic and uniformity of the applied layer. * Infrared-assisted curing accelerates the hardening of the applied material and enhances the stability of the porous structure by preventing slump or collapse. The system's capability for pulsed heating allows for better control over the reaction kinetics, enabling targeted activation of the setting only after spraying. Rapid surface curing minimises the risk of sagging or deformation and, under favourable conditions, permits the faster application of successive layers, thereby shortening the overall application time.