The Influence of the Material Structure on the Mechanical Properties of Geopolymer Composites Reinforced with Short Fibers Obtained with Additive Technologies.

Kinga Korniejenko,Petr Louda,Pavel Kejzlar

doi:10.3390/ijms23042023

Abstract

Additive manufacturing technologies have a lot of potential advantages for construction application, including increasing geometrical construction flexibility, reducing labor costs, and improving efficiency and safety, and they are in line with the sustainable development policy. However, the full exploitation of additive manufacturing technology for ceramic materials is currently limited. A promising solution in these ranges seems to be geopolymers reinforced by short fibers, but their application requires a better understanding of the behavior of this group of materials. The main objective of the article is to investigate the influence of the microstructure of the material on the mechanical properties of the two types of geopolymer composites (flax and carbon-reinforced) and to compare two methods of production of geopolymer composites (casting and 3D printing). As raw material for the matrix, fly ash from the Skawina coal power plant (located at: Skawina, Lesser Poland, Poland) was used. The provided research includes mechanical properties, microstructure investigations with the use of scanning electron microscope (SEM), confocal microscopy, and atomic force microscope (AFM), chemical and mineralogical (XRD-X-ray diffraction, and XRF-X-ray fluorescence), analysis of bonding in the materials (FT-IR), and nuclear magnetic resonance spectroscopy analysis (NMR). The best mechanical properties were reached for the sample made by simulating 3D printing process for the composite reinforced by flax fibers (48.7 MPa for the compressive strength and 9.4 MPa for flexural strength). The FT-IR, XRF and XRD results show similar composition of all investigated materials. NMR confirms the presence of SiO4 and AlO4 tetrahedrons in a three-dimensional structure that is crucial for geopolymer structure. The microscopy observations show a better coherence of the geopolymer made in additive technology to the reinforcement and equal fiber distribution for all investigated materials. The results show the samples made by the additive technology had comparable, or better, properties with those made by a traditional casting method.

Highlights

Fourier-Transform Infrared Spectroscopy (FT-IR) clearly shows the presence of aluminum silicates and/or aluminosilicates in geopolymers
The main elements of the composite structure are: oxygen (O), silica (Si), and aluminum (Al). These elements come from raw materials used and are the basic element for creating the structure of the geopolymer
The obtained data are coherent with the applied raw materials; in particular, they confirmed the applied fly ash has a composition relevant for the class F

Summary

Introduction

Geopolymers are sometimes called inorganic aluminosilicate polymers and are generally obtained in the reaction of ortosilican polycondensation [1,2]. Common raw materials for the geopolymerization process are metakaolin, calcined clays, industrial waste and by-products (e.g., ash, slag, glass waste, red mud, mine tailings, for example: copper, vanadium), gauges, etc. The most spectacular examples are the Global Change Institute (GCI) building at the University of Queensland in Australia and the Wellcamp airport in Brisbane, Australia [5,6]. These materials are used in the production of construction materials such as the fire-resistant wood panels, sandwich panels and other building elements, heat shields for space shuttles, as well as fire barriers in the construction industry, protective coating in emergency repair runways, material for the support to the stabilization of toxic waste, including radioactive substances and other applications [7–10]. The surplus environmental benefits could be achieved by using the appropriate production technology, such as additive manufacturing [15–17]

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