Effect of High-Speed Mixing on Properties of High Calcium Fly Ash Geopolymer Paste

Geopolymers are produced by mixing alumino-silicate materials with alkaline activators, and the mixing process has a considerable impact on the dissolution of raw materials. This research studies the effects of mixing time, with a high-speed centrifuge mixer (1,000 rpm), on the setting and hardening properties of high calcium fly ash-based geopolymer paste. Setting time, strength, phase development, microstructure and porosity of the pastes were investigated. The results indicated that the increase in mixing time retarded the setting time which provided time for dissolution of starting materials. The optimum mixing time at high speed should be 1 min in order to obtain high strength and dense matrix in contrast to 10 min for the normal mixing. The mixing time also had an effect on the pore structure hence the total porosity of the paste

Effect of nano-clay on mechanical and thermal properties of geopolymer

The effect of nano-clay platelets (Cloisite 30B) on the mechanical and thermal properties of fly ash geopolymer has been investigated in this paper. The nano-clay platelets are added to reinforce the geopolymer at loadings of 1.0%, 2.0%, and 3.0% by weight. The phase composition and microstructure of geopolymer nano-composites are also investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) techniques. Results show that the mechanical properties of geopolymer nano-composites are improved due to addition of nano-clay. It is found that the addition of 2.0 wt% nano-clay decreases the porosity and increases the nano-composite's resistance to water absorption significantly. The optimum 2.0 wt% nano-clay addition exhibited the highest flexural and compressive strengths, flexural modulus and hardness. The microstructural analysis results indicate that the nano-clay behaves not only as a filler to improve the microstructure, but also as an activator to facilitate the geopolymeric reaction. The geopolymer nano-composite also exhibited better thermal stability than its counterpart pure geopolymer

Effect of nanoclay on durability and mechanical properties of flax fabric reinforced geopolymer composites

The main concern of using natural fibres as reinforcement in geopolymer composites is the durability of the fibres. Geopolymers are alkaline in nature because of the alkaline solution that is required for activating the geopolymer reaction. The alkalinity of the matrix, however, is the key reason of the degradation of natural fibres. The purpose of this study is to determine the effect of nanoclay (NC) loading on the mechanical properties and durability of flax fabric (FF) reinforced geopolymer composites. The durability of composites after 4 and 32 weeks at ambient temperature is presented. The microstructure of geopolymer matrices was investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results showed that the incorporation of NC has a positive impact on the physical properties, mechanical performance, and durability of FF reinforced geopolymer composites. The presence of NC has a positive impact through accelerating the geopolymerization, reducing the alkalinity of the system and increasing the geopolymer gel. © 2017 The Ceramic Society of Japan and the Korean Ceramic Society