The submitted paper deals with the physical and mechanical properties of geopolymer composite materials reinforced with natural fibres. For this study, we aimed to develop a geopolymer composite reinforced with long flax fibres, which were implemented in the geopolymer in the form of a nonwoven fabric that reinforced the structure of the geopolymer over the entire thickness of the board. In order to compare the properties of the developed composite with natural fibres, a geopolymer without fibres and a geopolymer reinforced with basalt fibres were also produced. The monitored mechanical properties were impact bending, bending strength and compressive strength. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and microscopic analysis were also carried out. The results clearly showed the positive effect of the addition of natural fibres on impact bending and bending strength. However, the addition of natural fibres in the form of a nonwoven fabric significantly increased the variability of the properties of the developed composites. In addition, a different pattern of joint failure was noted between geopolymer reinforced with flax fibres and geopolymer reinforced with basalt fibres.

This paper presents an experimental research on the mechanical properties of the hybrid composite thin-plates of the short basalt fibers (CBFs)/carbon textile-reinforced geomortar. The effect of fiber contents and lengths of CBFs on the flexural behavior of carbon textile-reinforced geopolymer specimens (TRGs) was investigated by the four-point flexural strength and Charpy impact test. The experimental results of hybrid TRGs, on the one hand, were compared with reference TRGs, without CBF addition; on the other hand, they were compared with the results of our previous publication. According to the mixing manner applied, fresh geomortar indicated a marked reduction in workability, increasing the CBF loading. Furthermore, using CBFs with lengths of 12 mm and 24 mm makes it easy to form the fiber clusters in geomortar during mixing. According to all the CBF loadings used, it was found that TRGs showed a significant improvement in both static and dynamic flexural strength. However, the failure mode of these TRGs is similar to that of the reference TRGs, described by the process of fiber debonding or simultaneously fiber debonding and collapse. In comparison with our prior work results, neither the CBF dose levels nor the fiber lengths used in this work have yielded a positive effect on the failure manner of TRGs. According to the results of the Charpy impact test, this reveals that the anchoring capacity of textile layers in geomortar plays an important role in specimens’ strength.

The development of composite materials from alternative raw materials, and the design of their properties for the intended purpose is an integral part of the rational management of raw materials and waste recycling. The submitted paper comprehensively assesses the physical and mechanical properties of sandwich composite material made from particles of winter rapeseed stalks, geopolymer and reinforcing basalt lattices. The developed composite panel is designed for use as a filler in constructions (building or building joinery). The observed properties were: bending characteristics, internal bonding, thermal conductivity coefficient and combustion characteristics. The results showed that the density of the particleboard has a significant effect on the resulting mechanical properties of the entire sandwich panel. On the contrary, the density of the second layer of the sandwich panel, geopolymer, did not have the same influence on its mechanical properties as the density of the particleboard. The basalt fibre reinforcement lattice positively affected the mechanical properties of sandwich composites only if it was sufficiently embedded in the structure of the particle board. All of the manufactured sandwich composites resisted flame for more than 13 min and the fire resistance was positively affected by the density of the geopolymer layer.

Textile-reinforced Portland cement-based concrete has been researched and developed over the last few decades. It was widely used in a different range of applications, such as repair and/or strengthening of structural elements, thin walls, lightweight structures, façade elements, and others. Due to its varied application, this study aims to develop the carbon textile-reinforced geopolymer composite. Specimens of rectangular form with the dimensions of 400 × 100 × 15 mm³, reinforced with carbon textile, were produced. Four-point bending test was used to evaluate the effect of carbon textile on the mechanical strength of reinforced geopolymer composite based on the three factors: the different mortar compositions corresponding to the addition of the chopped basalt fiber (BF), the number of carbon textile layers, and the different thicknesses of the mortar cover layer. Besides that, a small part of the pull-out test was also considered to assess the adhesion strength at the interface between carbon textile and geopolymer mortar. The experimental results from the four-point bending test showed that the mechanical strength of composite specimens increased when the content of the chopped basalt fiber increased. With the increasing number of the textile layers, the specimens improved the flexural strength significantly. However, the flexural toughness of the specimens reinforced with three textile layers did not improve, as compared to those reinforced with two textile layers. The experimental results for the specimens related to the mortar cover thicknesses indicated that specimens with the mortar cover thickness of 2 mm provide the best strength. The experimental results from the pull-out tests showed that all the specimens have the same failure mode by slipping of the fiber yarn from the matrix.

Basalt fiber is a novel type of inorganic fiber which is produced from the extrusion of natural vocalnic basalt rocks through their melting process at high temperature. So the quality and strength characteristics of basalt fiber depend mainly on both the quality of raw material and manufacturing processing. Basalt fabric-reinforced cementitious composites (FRCM) are a novel composite and an extensive scientific investigation is still ongoing for geopolymer composite. Based on three types of basalt textile with respect to various net sizes, the aim of this paper is to evaluate the flexural performance of basalt textile-reinforced geopolymer composite through the four-point bending test. The specimens of rectangular form with the dimension of 400 × 100 × 15 mm³, reinforced with one to four layers of each type of basalt textile, were produced. They were then tested at the age of about 40 days after casting. On the other hand, the number of the specimens reinforced with four layers were considered to assess the mechanical strength of the specimens at longer periods of ageing time (60, 90, 150, 180 days). The experimental results showed that with the increasing number of reinforcing layers, the specimens significantly improved the mechanical strength, except for those reinforced with basalt textile of big net size. The specimens reinforced with basalt textile of big net size had no impact on post-crack mechanical strength, however, it helps to arrest the catastrophic brittle failure of the specimens; the failure of these specimens is due to localization of first crack. When the specimens were exposed to the further ageing times, the mechanical strength of the specimens were decreased over time. All the reinforced specimens have the same failure mode by flexural failure due to the rupture of fiber yarn in matrix, and no debonding of fiber yarn or a gradual peeling process of mortar matrix happened during testing.

This paper reports the results of an experimental investigation on the mechanical properties of geopolymer foams incorporating filler from the coke dust waste (CDW). In this work, CDW was used to replace a part of geopolymer paste at 5%, 10%, 20%, and 30% by geopolymer binder mass. The physico-mechanical properties and thermal resistance against high temperatures of CDW/geopolymer foams are presented. The primary results obtained show that the use of CDW in the production of geopolymer foam composites made it possible for them to achieve relatively good mechanical properties. However, the incorporation of the CDW into the geopolymer had a slightly negative effect on thermal conductivity, but significantly improved the mechanical strength of the final product. Moreover, this waste also helped the composite foam to achieve a structure with more uniform open pores distribution, compared to the pure foam. After exposure to elevated temperatures, the residual strength of the composite foams maintained well compared to the pure foams.