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Sodium silicate

About: Sodium silicate is a(n) research topic. Over the lifetime, 9967 publication(s) have been published within this topic receiving 101210 citation(s). The topic is also known as: water glass.


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Journal ArticleDOI
Abstract: Inorganic polymers based on alumina and silica polysialate units were synthesised from dehydroxylated aluminosilicate clay (metakaolinite) condensed with sodium silicate in a highly alkaline environment. Reaction of the aluminosilicate with alkali polysilicates yields polymeric Si–O–Al three-dimensional structures with charge-balancing positive ions such as hydrated Na+ in the framework cavities. A statistical study of the effect on the polymerisation process of the molar ratio of the component oxides and the water content of the mixture showed the latter to be a critical parameter. The polymerisation mechanism and structures of the products were investigated using NMR, XRD and FTIR spectroscopy. 29Si liquid-state NMR shows that some compositions do not cure properly because of incomplete reaction of the sodium silicate with the metakaolinite. FTIR confirms that during drying of the incompletely cured samples, Na migrates to the surface where it undergoes atmospheric carbonation. The cured polymers were found to be essentially X-ray amorphous, with bulk densities of 1.3–1.9. During polymerisation the coordination of Al in the metakaolinite reactant (IV, V and VI) changes almost completely to IV in all the polymer compositions. The environment of the Na is unchanged irrespective of the polymer composition. The solid-state 29Si NMR spectra indicate a range of Si–O–Al environments. Typical mechanical properties of the best polymers were: Mohs hardness >7, Vickers hardness about 54, and compressive strength (after drying for 1 h at 65°C) 48.1 MPa.

800 citations

Journal ArticleDOI
Abstract: This paper reports the results of the study of the influence of elevated temperature curing on phase composition, microstructure and strength development in geopolymer materials prepared using Class F fly ash and sodium silicate and sodium hydroxide solutions. In particular, the effect of storage at room temperature before the application of heat on strength development and phase composition was studied. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SEM were utilised in this study. Long precuring at room temperature before application of heat was beneficial for strength development in all studied materials, as strength comparable to 1 month of curing at elevated temperature can develop in this case only after 24 h of heat curing. The main product of reaction in the geopolymeric materials was amorphous alkali aluminosilicate gel. However, in the case of sodium hydroxide activator in addition to it, traces of chabazite, Linde Type A, Na-P1 (gismondine) zeolites and hydroxysodalite were also present. The type of zeolite present and composition of aluminosilicate gel were dependent on the curing history.

673 citations

Journal ArticleDOI
Abstract: This article presents an investigation into durability of geopolymer materials manufactured using a class F fly ash (FA) and alkaline activators when exposed to 5% solutions of acetic and sulfuric acids. The main parameters studied were the evolution of weight, compressive strength, products of degradation and microstructural changes. The degradation was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The performance of geopolymer materials when exposed to acid solutions was superior to ordinary Portland cement (OPC) paste. However, significant degradation of strength was observed in some geopolymer materials prepared with sodium silicate and with a mixture of sodium hydroxide and potassium hydroxide as activators. The deterioration observed was connected to depolymerisation of the aluminosilicate polymers in acidic media and formation of zeolites, which in some cases lead to a significant loss of strength. The best performance was observed in the geopolymer material prepared with sodium hydroxide and cured at elevated temperature, which was attributed to a more stable cross-linked aluminosilicate polymer structure formed in this material.

639 citations

Journal ArticleDOI
Abstract: This paper describes research into the use of granulated blast furnace slag as an active filler in the making of geopolymers. During this work it was found that geopolymer setting time correlates well with temperature, potassium hydroxide concentration, metakaolinite and sodium silicate addition. The physical and mechanical properties of the geopolymer also correlated well with the concentration of alkaline solution and the amount of metakaolinite that is added. The highest compressive strength achieved was 79 MPa. For fire resistance tests, a 10 mm thick geopolymer panel was exposed to a 1100 °C flame, with the measured reverse-side temperatures reaching less than 350 °C after 35 min. The products can be fabricated for construction purposes and have great potential for engineering applications.

606 citations

Journal ArticleDOI
Abstract: In this paper, the basic properties viz., workability and strength of geopolymer mortar made from coarse lignite high calcium fly ash were investigated. The geopolymer was activated with sodium hydroxide (NaOH), sodium silicate and heat. The results revealed that the workable flow of geopolymer mortar was in the range of 110 ± 5%–135 ± 5% and was dependent on the ratio by mass of sodium silicate to NaOH and the concentration of NaOH. The obtained compressive strength was in the range of 10–65 MPa. The optimum sodium silicate to NaOH ratio to produce high strength geopolymer was 0.67–1.0. The concentration variation of NaOH between 10 M and 20 M was found to have a small effect on the strength. The geopolymer samples with high strength were obtained with the following practices: the delay time after moulding and before subjecting the sample to heat was 1 h and the optimum curing temperature in the oven was 75 °C with the curing duration of not less than two days.

577 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20228
2021306
2020399
2019517
2018672
2017564