Influence of the In-Fill Pattern of the 3D Printed Building Wall on Its Thermal Insulation.

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.

Influence of Incorporating Recycled Windshield Glass, PVB-Foil, and Rubber Granulates on the Properties of Geopolymer Composites and Concretes.

Waste materials from the automotive industries were re-used as aggregates into metakaolin-based geopolymer (GP), geopolymer mortar (GM), and Bauhaus B20-based concrete composite (C). Specifically, the study evaluates the ability of windshield silica glass (W), PVB-Foils (P), and rubber granulates (G) to impact the mechanical and thermal properties. The addition of the recovered materials into the experimental geopolymers outperformed the commercially available B20. The flexural strength reached values of 7.37 ± 0.51 MPa in concrete with silica glass, 4.06 ± 0.32 in geopolymer malt with PVB-Foils, and 6.99 ± 0.82 MPa in pure geopolymer with rubber granulates; whereas the highest compressive strengths (бc) were obtained by the addition of PVB-Foils in pure geopolymer, geopolymer malt, and concrete (43.16 ± 0.31 MPa, 46.22 ± 2.06 MPa, and 27.24 ± 1.28 MPa, respectively). As well PVB-Foils were able to increase the impact strength (бi) at 5.15 ± 0.28 J/cm2 in pure geopolymer, 5.48 ± 0.41 J/cm2 in geopolymer malt, and 3.19 ± 0.14 J/cm2 in concrete, furnishing a significant improvement over the reference materials. Moreover, a correlation between density and thermal conductivity (λ) was also obtained to provide the suitability of these materials in applications such as insulation or energy storage. These findings serve as a basis for further research on the use of waste materials in the creation of new, environmentally friendly composites.

Surface Modification of Synthetic Zeolites with Ca and HDTMA Compounds with Determination of Their Phytoavailability and Comparison of CEC and AEC Parameters.

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.

Development of Geopolymers Based on Fly Ashes from Different Combustion Processes.

The main aim of this research is to assess different fly ashes as raw materials for the manufacturing of geopolymers. Three different fly ashes have been investigated. First, a conventional fly ash from the Skawina coal power plant (Poland), obtained at a temperature of 900-1100 °C. Second, ultra-fine fly ash from a power plant in China; the side product received at 1300 °C. The third fly ash was waste was obtained after combustion in incineration plants. To predict the properties and suitability of materials in the geopolymerization process, methods based on X-ray analysis were used. The applied precursors were tested for elemental and chemical compounds. The investigations of geopolymer materials based on these three fly ashes are also presented. The materials produced on the basis of applied precursors were subjected to strength evaluation. The following research methods were applied for this study: density, X-ray fluorescence (XRF), X-ray diffraction analysis (XRD), Scanning Electron Microscopy (SEM), flexural and compressive strength. The obtained results show that materials based on fly ashes had a similar compressive strength (about 60 MPa), while significant differences were observed during the bending test from 0.1 to 5.3 MPa. Ultra-fine fly ash had a lower flexural strength compared to conventional fly ash. This study revealed the need for process optimization for materials based on a precursor from a waste incineration plant.

Optimizing the L/S Ratio in Geopolymers for the Production of Large-Size Elements with 3D Printing Technology.

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.

Recycling of Mechanically Ground Wind Turbine Blades as Filler in Geopolymer Composite.

This paper concerns the recycling of waste material from wind turbine blades. The aim of the research was to determine the possibility of using ground waste material derived from the exploited structures of wind turbines as a filler in geopolymer composites. In order to determine the potential of such a solution, tests were carried out on three different fractions originating from the ground blades of wind turbines, including an analysis of the morphology and chemical composition of particles using SEM and an EDS detector, the analysis of organic and inorganic matter content and tests for multivariate geopolymer composites with the addition of waste material. The compression and flexural strength, density and absorbability tests, among others, were carried out. The composite material made of the geopolymer matrix contained the filler at the level of 5%, 15% and 30% of dry mass. The addition of the filler showed a tendency to decrease the properties of the obtained geopolymer composite. However, it was possible to obtain materials that did not significantly differ in properties from the re-reference sample for the filler content of 5% and 15% of dry mass. As a result of the research, it was found that waste materials from the utilization of used wind power plants can become fillers in geopolymer composites. It was also found that it is possible to increase the strength of the obtained material by lowering the porosity.

Development and Characterization of Lightweight Geopolymer Composite Reinforced with Hybrid Carbon and Steel Fibers.

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).

Review of Solutions for the Use of Phase Change Materials in Geopolymers.

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.

Determination of the Influence of Hydraulic Additives on the Foaming Process and Stability of the Produced Geopolymer Foams.

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.