| The rapid development of information technology in recent years has led toconsiderable increase in the demand for thin-film transistor liquid-crystal display(TFT-LCD) panels. The manufacturing and consumption process inevitably produce alarge amount of waste, so in the future there will be a great deal of waste to be disposed.TFT-LCD waste glass can be used as a raw material in the production of geopolymerbecause it is amorphous and contains relatively large amounts of silicon and aluminum.Geopolymer is a novel type of high-performance cementitious material. Due to the special3D network structure, it has good performances that the traditional cement and othermaterials do not have. Geopolymerization involves a chemical reaction betweenaluminosilicate oxides and alkali-metal silicate solutions under highly alkaline conditions,yielding amorphous-to-semi crystalline3D polymeric structures consisting of Si–O–Albonds. The mechanical characteristics and structural properties of the products ofalkali-activated metakaolin reactions are affected by the raw material composition and theconcentration of the alkali activator used. Alkali activating solution is important for thedissolving of Si and Al atoms to form geopolymer precursors and finally aluminosilicatematerial. Nano particles have a great significance on the development of high-performancepolymers because their size effect and surface effect and so on. There are lots ofresearches and literatures of nano-SiO2added to cement paste to improve property.This study presents a discussion on the effects of different solid-to-liquid (S/L) ratios(0.97to1.19), SiO2/Na2O molar ratio (1.00to2.00) and nano-SiO2percentages (0%to3%)on some properties of metakaolin-based geopolymers. When get the optimal proportion,the pure metakaolin was replaced by0%~40%TFT-LCD waste glass to preparegeopolymer samples. The bulk density, porosity, setting time, compressive strength andflexural strength was investigated. Mercury intrusion porosimetry, thermogravimetricanalyze, fourier transform infrared spectroscopy, and scanning electron microscopy wereused to determine the microstructure of the samples.The results show that the setting time of the nano-SiO2-metakaolin-based geopolymerincreased with the S/L ratio and SiO2/Na2O ratio because of the increased weight ofpowder and the viscous property of the sodium silicate. The setting time was shortened with the addition of nano-SiO2, and increased along with the replacement level of theTFT-LCD waste glass. The metakaolin-based geopolymer sample added1%nano-SiO2with the S/L ratio of1.03and SiO2/Na2O ration of1.50exhibits more strength and lessporosity. The compressive strength of geopolymer specimen added nano-SiO2was largerthan that of pure metakaolin-based geopolymer, and the matrix became denser and morehomogeneous. The best addition amount of nano-SiO2was1%. If the nano-SiO2wasadded too much, the strength value decreased because the excessive nanoparticles wereunable to gelatinize so that it would hinder the geopolymerization.Applying nano-SiO2to the geopolymer enhances compactness and increases strength.Therefore, nanotechnology can be used to improve geopolymers. TFT-LCD waste glasscan be the replacement partly of aluminosilicate minerals as the raw materials which canbe alkali activated. So this study provides a kind of feasible technology to recycle thewaste by the way of geopolymer. It increase the recycling ways and improve theutilization rate of the TFT-LCD waste glass, so it would implement the objective of thecleaner production and recycling waste. |
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