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Space missions will require the capability to build structures on site using local resources. Before 2040, NASA and the European Space Agency want to ensure the possibility of a permanent human residence in shelters on the Moon or Mars. The article analyzed the state of the art in this area based on the literature research. It shows innovative and energy efficient solutions for manufacturing the lunar and Martian shelters based on geopolymer composites. Firstly, the possible materials solutions, with particular attention to the geopolymer composites, are discussed. Next, the previous research is presented, including work based on different kinds of simulants of lunar and Martian regolith. Then, a different approach for manufacturing technologies is presented and the advantages of 3D printing technology are clarified. Eventually, the challenges for further projects are discussed, including energy and cost efficiency problems.

The aim of this paper is to analyze the influence of hybrid fiber reinforcement on the properties of a lightweight fly ash-based geopolymer. The matrix includes the ratio of fly ash and microspheres at 1:1. Carbon and steel fibers have been chosen due to their high mechanical properties as reinforcement. Short steel fibers (SFs) and/or carbon fibers (CFs) were used as reinforcement in the following proportions: 2.0% wt. CFs, 1.5% wt. CFs and 0.5% wt. SFs, 1.0% wt. CFs and 1.0% wt. SFs, 0.5% wt. CFs and 1.5% wt. SFs and 2.0% wt. SFs. Hybrid reinforcement of geopolymer composites was used to obtain optimal strength properties, i.e., compressive strength due to steel fiber and bending strength due to carbon fibers. Additionally, reference samples consisting of the geopolymer matrix material itself. After the production of geopolymer composites, their density was examined, and the structure (using scanning electron microscopy) and mechanical properties (i.e., bending and compressive strength) in relation to the type and amount of reinforcement. In addition, to determine the thermal insulation properties of the geopolymer matrix, its thermal conductivity coefficient was determined. The results show that the addition of fiber improved compressive and bending strength. The best compressive strength is obtained for a steel fiber-reinforced composite (2.0% wt.). The best bending strength is obtained for the hybrid reinforced composite: 1.5% wt. CFs and 0.5% wt. SFs. The geopolymer composite is characterized by low thermal conductivity (0.18–0.22 W/m ∙ K) at low density (0.89–0.93 g/cm3).

The intensive development of 3D Concrete Printing (3DCP) technology causes constantly increased its share in the construction sector. However, in order to produce products with controlled properties, optimization of the technological process is still required. Automation of production based on additive manufacturing methods streamlines the process by comprehensively manufacturing building components that meet, among others, strength, visual, and insulation requirements. Moreover, the possibility of using computer simulations to assess the properties of the designed elements allows for a multitude of analyzed versions of the constructed partitions, which can be verified at the design stage. Thanks to such an opportunity, the process of designing building elements can be significantly improved. The article presents results related to the assessment of the level of thermal insulation of products that can be produced by additive technology, depending on the applied spatial geometry of the vertical partition and the amount and type of materials used. Eight original solutions of in-fill pattern were designed, for which both Finite Element Method (FEM) computer simulations of thermal conductivity and experimental measurements of thermal conductivity of samples were performed. On the basis of the obtained results, both the correctness of the simulation results for the various analyzed materials and their consistency with the practical results were found. Depending on the investigated geometry, for samples of the same dimensions and using the same material, the differences in the U-factor obtained by FEM analysis amounted to 61%. The best solution from the investigated spatial geometries of the vertical partitions has been indicated. The U parameter in the variant with the best thermal insulation was 0.183 W/m2K, which meets the requirements of Polish construction law. The issues discussed in this work can be the basis for the selection of the best solution possible for practical use during the production of building walls using the 3DCP method fulfilling the guidelines of applicable standards. Furthermore, they can be used as a tool for optimizing geometry in terms of energy savings and reducing waste production by both engineers developing 3DCP technologies and architects using innovative techniques for manufacturing building structures.

The research described in this article was aimed at determining the influence of hydraulic additives on the foaming process and the stability of the produced geopolymer foams. These foams can be used as insulation materials to replace the currently commonly used insulations such as expanded polystyrene or polyurethane foams. Geopolymers have low thermal conductivity, excellent fire- and heat-resistant properties, and have fairly good mechanical properties. Research on foamed materials shows that they have the highest class of fire resistance; therefore, they are most often used as insulation products in construction. Geopolymer foams were made of aluminosilicate materials (fly ash) and foaming agents (H2O2 and Al powder), and the stabilizers were gypsum and portland cement. Additionally, surfactants were also used. It was found that better foaming effects were obtained for H2O2—it is a better foaming agent for geopolymers than Al powder. When using a hydraulic additive—a stabilizer in the form of cement—lower densities and better insulation parameters were obtained than when using gypsum. Portland cement is a better stabilizer than gypsum (calcium sulfates), although the effect may change due to the addition of surfactants, for example.

Various types of coatings are applied to the surface of an object or substrate to improve surface properties or extend service life, which in turn is associated with cost reductions. The main objective of this study was to develop a technique for the additive application of foamed geopolymers to existing structures and vertical surfaces. The base material was a fly ash-based geopolymer modified with sand. Hydrogen peroxide and aluminum powder were used as foaming agents. In this study, the feasibility of using an air gun with variable nozzles to apply the layers of foamed geopolymers was assessed, and the effects of nozzle diameter and the spray gun’s operating pressure were analyzed. The next stage of the study was a visual assessment of the layering of the foamed material. The foamed geopolymer layering tests verified the occurrence of the foaming process, and the applied geopolymer surface showed a reasonably good adhesive bond with the vertical wall. In addition, in this paper, we present the laser particle size results of the base materials and their oxide composition. In addition, thermal conductivity tests for the foamed geopolymer materials, compressive strength tests, and microstructure analysis via scanning electron microscopy were carried out.

Zeolites obtained from fly ash are characterized by very good anion- and cation-exchange properties and a developed porous structure. This paper presents the results of surface modification studies of synthetic zeolites obtained from calcined coal shale (clay materials). Calcium compounds and hexadecyltrimethylammonium bromide (HDTMA) were used as modifying substances. The characteristics of the raw material and the zeolite obtained as a result of its synthesis are presented. The surface modification method is described. Furthermore, the results of sorption and desorption of NO3, PO4, and SO4 from raw and modified samples are presented. The results of anion- and cation-exchange capacities for other zeolite types were also compared. Modification of the materials with Ca ions and HDTMA surfactant only improved the sorption of sulfates. The 90% desorption of nitrates, phosphates, and sulphates from the zeolite material without modification indicates a good release capacity of these compounds and their potential use as fertilizer additives.

This work aimed to determine the effect of the addition of different types of reinforcing fibers on the strength properties of geopolymers such as flexural and compressive strength. Geopolymers are an attractive alternative to conventional binders and building materials; however, one of the main problems of their widespread use is their low resistance to brittle fracture. To improve the mechanical properties, reinforcement in the form of glass, carbon, and basalt fibers (as grids) was applied to geopolymers in the following work. Additionally, composites with these fibers were produced not only in the matrix of pure geopolymer but also as a hybrid variant with the addition of cement. Furthermore, basalt grids were used as reinforcement for geopolymers not only based on ash but also metakaolin. An additional variable used in the study was the molar concentration of the alkali solution (5 M and 10 M) for the different types of geopolymer samples. The mechanical properties of geopolymer materials and geopolymer–cement hybrids are the highest when reinforcement in the form of carbon fiber is used. Strength values for geopolymers reinforced with basalt mats depend on the number of reinforcement layers and the concentration of the alkaline solution used. All produced composites were tested for compressive strength and bending strength. When using basalt mesh, it was possible to achieve a bending strength of 12 MPa. The highest compressive strength that was achieved was the value of 66 MPa, while for samples not reinforced with fibers, only about 40 MPa was achieved.

The paper deals with the possibility of using Phase Change Materials (PCM) in concretes and geopolymer composites. The article presents the most important properties of PCM materials, their types, and their characteristics. A review of the latest research results related to their use in geopolymer materials is presented. The benefits of using PCM in building materials include the improvement of thermal comfort inside the building, and also the fact that the additive in the form of PCM reduces thermal gradients and unifies the temperature inside the concrete mix, which can reduce the risk of cracking. The paper also presents a critical analysis related to the feasibility of mass scale implementations of such composites. It was found that the use of PCM in sustainable construction is necessary and inevitable, and will bring a number of benefits, but it still requires large financial resources and time for more comprehensive research. Despite the fact that PCM materials have been known for many years, it is necessary to refine their form to very stable phases that can be used in general construction as well as to develop them in a cost-effective form. The selection of these materials should also be based on the knowledge of the matrix material.

Geopolymer concretes can be a viable alternative to conventional Portland cement-based materials. In their design, it is important to maintain an appropriate liquid-to-solid ratio (L/S), which affects several properties, such as the compressive strength, water absorption, and frost resistance. The objective of this paper is to analyze the influence of the fly-ash and metakaolin precursor types for three different L/S ratios: 0.30, 0.35, and 0.45. The results of the physical and mechanical properties, including the apparent density and compressive strength, as well the durability parameters, including frost resistance and water penetration depth, are presented in this paper. It was found that as the L/S ratio decreased, the average compressive strength increased for all materials. After freeze–thaw cycles, decreases in the compressive strength properties were observed for all types of materials—metakaolin- and fly ash-based—irrespective of the L/S ratio. Moreover, the frost resistance of geopolymers increased with the increase in the L/S ratio. The printability of the mixes was also verified in order to confirm the application of the developed materials to additive manufacturing processes.

This paper presents the results of testing the adhesion of geopolymer coatings and varnishes with ceramic additives to concrete and steel substrates. The measurement method used and described in this article was the pull-off method. The pull-off method test provides an easy way to evaluate the degree of adhesion of coatings to metal surfaces. The pull-off device provides values for the peel stress, which not only allows a quick determination of the adhesion of the coating to the substrate, but also makes it easier to compare the adhesion of several coatings to each other. However, this method requires appropriate preparation, so an attempt was made to determine its suitability for geopolymer layers. The results of testing the adhesion of a geopolymer layer to a geopolymer substrate and a concrete substrate are presented. As a result of this study, a higher adhesion strength of the geopolymer layer to the geopolymer substrate was found in comparison to geopolymer coatings applied on conventional concrete. Adhesion tests were also conducted for steel substrates to which both geopolymer and acrylic lacquer were applied.