Characterisation of cotton fibre-reinforced geopolymer composites

This paper describes the physical, mechanical and fracture behaviour of fly-ash based geopolymer reinforced with cotton fibres (0.3–1.0 wt%). Results show that the appropriate addition of cotton fibres can improve the mechanical properties of geopolymer composites. In particular, the flexural strength and the fracture toughness increase at an optimum fibre content of 0.5 wt%. However, as the fibre content increases, the density of geopolymer composites decreases due to an increase in porosity and tendency of fibre agglomeration

Synthesis and mechanical properties of cotton fabric reinforced geopolymer composites

Geopolymer composites reinforced with different layers of woven cotton fabric are fabricated using layuptechnique. Mechanical properties, such as flexural strength, flexural modulus, impact strength andfracture toughness of geopolymer composites reinforced with 3.6, 4.5, 6.2 and 8.3 wt% cotton fibresare studied. The fracture surfaces of the composites are also examined using scanning electron microscopy.The results show that all the mechanical properties of the composites are improved by increasingthe cotton fibre contents. It is found that the mechanical properties of cotton fabric reinforced geopolymercomposites are superior to pure geopolymer matrix

Characterization, reactivity and rheological behaviour of metakaolin and Meta-halloysite based geopolymer binders

The type of aluminosilicate precursor used in the synthesis of geopolymer binders plays a huge role in the resulting performance. Thus, it is critical to understand the properties of precursors and how they influence the corresponding performance of geopolymer binders. In this study, metakaolin and meta halloysite are used as the aluminosilicate precursor in the synthesis of geopolymer binders. These precursors are obtained locally in order to propel the sustainable development and application of geopolymers. The precursors were characterized and the corresponding influence on the reactivity, rheology and setting times of geopolymers was investigated. In addition to the influence of precursor type on the properties of the geopolymers, the effect of two silica moduli (i.e. 1.3 and 1.5) was also evaluated. The results from this study indicated that increasing the activator silica modulus from 1.3 to 1.5 extended the setting times and increased the stress strain of the geopolymer binders. Characterization of the precursors indicated that metakaolin has a higher amorphous content compared to that of meta halloysite. However, the finer particles of meta halloysite embodied it with the ability to participate in a faster geopolymerization and result in more formation of activation products

Characterisation of mechanical and thermal properties in flax fabric reinforced geopolymer composites

This paper presents the mechanical and thermal properties of flax fabric reinforced fly ash based geopolymer composites. Geopolymer composites reinforced with 2.4, 3.0 and 4.1 wt% woven flax fabric in various layers were fabricated using a hand lay-up technique and tested for mechanical properties such as flexural strength, flexural modulus, compressive strength, hardness, and fracture toughness. All mechanical properties were improved by increasing the flax fibre contents, and showed superior mechanical properties over a pure geopolymer matrix. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) studies were carried out to evaluate the composition and fracture surfaces of geopolymer and geopolymer/flax composites. The thermal behaviour of composites was studied by thermogravimetric analysis (TGA) and the results showed significant degradation of flax fibres at 300 °C

Synthesis and characterization of mechanical properties in cotton fiber-reinforced geopolymer composites

Geopolymers are inorganic aluminosilicate materials that possess relatively good mechanical properties and desirable thermal stability but they exhibit failure behavior similar to brittle solids. This limitation may be remedied by fiber reinforcement to improve their strength and toughness. This paper describes the synthesis of cotton fiber-reinforced geopolymer composites and the characterization of their mechanical properties. The effects of cotton fiber content (0-1.0. wt.%) and fiber dispersion on the mechanical characteristics of geopolymer composites have been investigated in terms of hardness, impact strength and compressive strength. A fiber content of 0.5. wt.% was observed for achieving optimum mechanical properties in these composites. © 2013

Mechanical and thermal properties of ambient cured cotton fabric-reinforced fly ash-based geopolymer composites

This paper presents the mechanical and thermal properties of cotton fabric (CF)-reinforced fly ash-based geopolymer composites cured under ambient condition. Setting and hardening of above composite at ambient temperature are achieved by partial replacement of small amount of fly ash with Ordinary Portland cement (OPC). The effects of different quantities of OPC on flexural strength, fracture toughness, impact strength and thermal stability of above composite are evaluated, and the microstructural characterisation of each composite and its matrix is also conducted. Results show that the mechanical properties of the composites are improved with the addition of OPC; however, SEM images of fracture surfaces reveal that OPC hinders toughening mechanisms by limiting the prevalence of fibre pull out and fibre debonding. At high temperatures, the thermal stability of the geopolymer composites increases with the presence of either OPC or CF layers

Synthesis and mechanical properties of flax fabric reinforced geopolymer composites

Geopolymer composites reinforced with different layers of woven flax fabric are fabricated using lay- up technique. Mechanical properties, such as flexural strength, flexural modulus and fracture toughness of geopolymer composites reinforced with 2.4, 3 and 4.1 wt% flax fibres are studied. The fracture surfaces of the composites are also examined using scanning electron microscopy. The results show that all the mechanical properties of the composites are improved by increasing the flax fibre contents. It is also found that the mechanical properties of flax fabric reinforced geopolymer composites are superior to pure geopolymer matrix. Micro-structural analysis of fracture surface of the composites indicated evidence of various toughening mechanisms by flax fabrics in the composites

Effect of fabric orientation on mechanical properties of cotton fabric reinforced geopolymer composites

This paper presents the thermal, mechanical and fracture behaviour of fly-ash based geopolymer composites reinforced with cotton fabric (0–8.3 wt.%). Results revealed that fly-ash based geopolymer can prevent the degradation of cotton fabric at elevated temperatures. The effect of cotton fabric orientation (i.e., horizontal or vertical) to the applied load on flexural strength, compressive strength, hardness and fracture toughness of geopolymer composites is also investigated. The results showed that when the fabricsare aligned in horizontal orientation with respect to the applied load, higher load and greater resistance to the deformation were achieved when compared to their vertically-aligned counterparts

Effect of Nanosilica on mechanical properties and microstructure of PVA Fiber-Reinforced Geopolymer Composite (PVA-FRGC)

This paper presents the effects of various nanosilica (NS) contents on the mechanical properties of polyvinyl alcohol (PVA) fiber-reinforced geopolymer composites (PVA-FRGC). Microstructure analysis with X-ray diffraction (XRD) and scanning electron microscopy (SEM) was used to characterize the geopolymer composites. The results showed that the mechanical properties in terms of compressive strength, impact strength, and flexural behavior were improved due to the addition of NS to the PVA-FRGC. The optimum NS content was 1.0 to 2.0 wt%, which exhibited highest improvement in the above mechanical properties. Microstructure analysis showed that the addition of NS up to an optimum level densified the microstructure of the matrix as well as the PVA fiber-geopolymer matrix interface

Reaction kinetics and microstructure of pegmatite-based geopolymer composites: influence of calcined clay nature

This research reports the investigations of threshold reactivity limit of blends of pegmatite with different calcined clays as well as the influence of calcined clay source on the geopolymerization kinetic, microstructural, and physicomechanical properties of feldspathic mineral-based inorganic polymer composites. These composites were designed from 85 to 94 wt% of the solid solution of pegmatite and calcined clay. The three-point flexural and compressive strengths, porosity, and microstructure as well as heat evolution rate of geopolymerization reactions of resulting composites were affected by the type of calcined clay. The four calcined clays provided the highest mechanical properties of the composites when added in the range of 12–15 wt%. Specifically, the values of flexural and compressive strengths ranged from 32 to 34 MPa and 101 to 105 MPa, respectively, for geopolymer composites with 15 wt% of metakolin added, while they ranged from 38 to 42 MPa and 106 to 107 MPa with 12 wt% of meta-hallosyte added. The polycondensation/polymerization process of calcined clay developed sufficient amounts of N-A-S-H and polysialate geopolymer to cover the incongruently dissolved fine particles of pegmatite. The resulting microstructure was dense and compact with the lower cumulative pore volume at about 91 mm3/g. It was concluded that designing the pegmatite/clay-based geopolymer composites with high mechanical strengths and low porosity resulted in sustainable, low energy consumption and environmental-friendly materials for civil engineering