Topic
Ettringite
About: Ettringite is a research topic. Over the lifetime, 2702 publications have been published within this topic receiving 67056 citations. The topic is also known as: woodfordite.
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TL;DR: In this article, the solubilities of pure hydrates and the mixture of hydrate existing in hardened cement paste to the ethylene glycol-methanol solution, the effects of coexisting Ca(OH) 2 upon solubility and rate of dissolution of each hydrate, and the limit of the amount of ettringite capable of being analysed in paste were investigated.
27 citations
TL;DR: In this paper, the effect of the accelerator on the hydration of C3A, C3S, and gypsum was investigated using X-ray diffraction, themogravimetric analysis and scanning electron microscopy.
27 citations
TL;DR: In this paper, an alkali activated blast furnace slag-based cementitious material was used to stabilize/solidify the fly ash at experimental level, including metal leachability, mineralogical characteristics and the distributions of metals in matrices.
Abstract: Fly ash is a hazardous byproduct of municipal solid wastes incineration (MSWI). An alkali activated blast furnace slag-based cementitious material was used to stabilize/solidify the fly ash at experimental level. The characteristics of the stabilized/solidified fly ash, including metal leachability, mineralogical characteristics and the distributions of metals in matrices, were tested by toxic characteristic leaching procedure (TCLP), X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) respectively. Continuous acid extraction was utilized to extract metal ions and characterize their leaching behavior. The stabilization/ solidification procedure for MSWI fly ash demonstrates a strong fixing capacity for the metals by the formation of CS-H phase, hydrated calcium aluminosilicate and ettringite. The stabilized/solidified fly ash shows a dense and homogeneous microstructure. Cr is mainly solidified in hydrated calcium aluminosilicate, C-S-H and ettringite phase through physical encapsulation, precipitation, adsorption or substitution mechanisms, and Pb is mainly solidified in C-S-H phase and absorbed in the Si-O structure.
27 citations
27 citations
TL;DR: In this paper, the chloride binding behavior of reinforced concrete structures with alumina compound addition is investigated, and the results show that alumina compounds exhibit a higher potential of forming AFm-type phases than metakaolin and therefore significantly improve the binding capacity.
Abstract: In order to prolong the service life of reinforced concrete structures either serving in chloride-rich environment or prepared with chloride contaminated ingredients, the chloride binding behaviors of cementitious materials with alumina compound addition are investigated in this work. The chloride binding capacity, phase conversion and solution chemistry of mixtures during chloride exposure were discussed. The applied alumina compounds are γ-Al2O3, γ-Al(OH)3 and colloidal nano-alumina, and metakaolin is used as a reference additive. The results show that alumina compounds exhibit obviously higher potential of forming AFm-type phases than metakaolin and therefore significantly improve the chloride binding capacity. During chloride exposure, the charge-balancing anions like hydroxyls, carbonates and sulfates can be replaced by chlorides to form Friedel'salt and increases the pH of exposure solution. The released sulfates reacting with SO4-AFm lead to delayed ettringite formation, binding large amount of mixing water and reducing calcium hydroxide content. Besides, the transformation of carboaluminate to Friedel'salt also accounts for partial reduction of calcium hydroxide in hydrated blended after chloride exposure, due to the released carbonates precipitating with calcium ions in the system.
27 citations