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: The hydration of tri-calcium aluminate in the presence of gypsum has been examined by electron optical methods as a function of pH and hydration time.
Abstract: The hydration of tri-calcium aluminate in the presence of gypsum has been examined by electron optical methods as a function of pH and hydration time. The location of the alumino-sulphate phase has been related to the solubility of aluminate ions from the precursive platelet phase. At pH ∼ 11.5 the alumino-sulphate precipitate is crystalline and precipitates from solution. When first formed it is deficient in calcium and sulphate with respect to ettringite. If the deficiency is too great, transformation to calcium aluminate monosulphate hydrate may occur as an intermediate step before the equilibrium phases are obtained. At a higher pH (∼ 12.5) the fibres of alumino-sulphate are smaller and more rounded. Long tubular fibres similar to those seen in portland cement were not observed. This has been explained as a consequence of using pure tricalcium aluminate, rather than alkali-containing material. The information obtained has been used to predict the effect of some inorganic additives on the phases produced during the setting of portland cement.
25 citations
TL;DR: This paper presents one of the first reported attempts to characterize microstructural and chemical elements of hydration products for cementitious composites with CWA called K, P and X using Scanning Electron Microscopy (SEM).
Abstract: The durability of a cement-based material is mainly dependent on its permeability. Modifications of porosity, pore-structure and pore-connectivity could have significant impacts on permeability improvement, which eventually leads to more durable materials. One of the most efficient solutions in this regard is to use permeability reducing admixtures (PRA). Among these admixtures for those structures exposed to hydro-static pressure, crystalline waterproofing admixtures (CWA) have been serving in the construction industries for decades and according to ACI 212-chemical admixtures' report, it has proven its capability in permeability reduction and durability-enhancement. However, there is substantial research being done on its durability properties at the macro level but very limited information available regarding its microstructural features and chemical characteristics at the micro level. Hence, this paper presents one of the first reported attempts to characterize microstructural and chemical elements of hydration products for cementitious composites with CWA called K, P and X using Scanning Electron Microscopy (SEM). Backscattered SEM images taken from a polished-section of one CWA type-K-admixture were analyzed in ImageJ to obtain paste matrix porosity, indicating a lower value for the CWA-K mixture. X-ray analysis and SEM micrographs of polished sections were examined to identify chemical compositions based on atomic ratio plots and brightness differences in backscatter-SEM images. To detect chemical elements and the nature of formed crystals, the fractured surfaces of three different CWA mixtures were examined. Cementitious composites with K admixture indicated needle-like crystal formation-though different from ettringite; X and P admixtures showed sulfur peaks in Energy Dispersive Spectrum (EDS) spectra, like ettringite. SEM images and X-ray analyses of mixtures incorporating Portland Limestone Cement (PLC) indicated lower-than-average porosity but showed different Si/Ca and Al/Ca atomic ratios.
25 citations
Patent•
27 Jul 2011
TL;DR: In this paper, a recycled aggregate is made by pre-add water to carbonated curing wastes for forming balls which absorb carbon dioxide gas in industrial waste gas, which belongs to the building material technique field.
Abstract: The invention relates to a recycled aggregate made by pre-adding water to carbonated curing wastes for forming balls which absorb carbon dioxide gas in industrial waste gas, which belongs to the building material technique field. The recycled aggregate is made by adopting the following processes of: utilizing steel slag or cement containing carbonization compositions as a raw material, adding water for even mixture, and implementing the granulation for spheroidizing so as to make the recycled aggregate under the curing of carbonization gas; and the carbonization compositions include one or more than one of calcium oxide, calcium hydroxide, dicalcium silicate, tricalcium silicate, hydrated calcium silicate, hydrated calcium aluminate, hydrated calcium ferrite, ettringite, magnesium hydroxide and magnesium oxide, and the carbonization compositions have a weight percentage of no less than 30 percent in materials. The recycled aggregate has the main point that: the accelerated carbonization technique is utilized to treat industrial wastes such as steel slag, sludge and waste concrete, solidify and store carbon dioxide of greenhouse gas, and make the recycled aggregate. The pollution problem of wastes such as steel slag and waste gas is released; meanwhile, the light recycled aggregate with excellent performance is prepared.
25 citations
TL;DR: In this article, Liithium slag (LS) blended cement mortar was prepared under two replacement levels (0 wt% and 20※wt%) and two curing regimes (initial steam curing for 7 h and initial standard curing), and their hydration products and performances under partial immersion in 5 1/5% sodium sulfate solution were investigated.
25 citations
TL;DR: In this article, the formation of ettringite from monosulfate and gypsum was investigated by isothermal calorimetry and X-ray diffraction analyses, at constant temperatures from 30° to 80°C using deionized water and 2M, 05M, and 10M sodium hydroxide (NaOH) solutions.
Abstract: The formation of ettringite (3CaO·Al2O3·3CaSO4·32H2O) from monosulfate (3CaO·Al2O3·CaSO4·12H2O) and gypsum (CaSO4·2H2O) was investigated by isothermal calorimetry and X-ray diffraction (XRD) analyses Hydration was carried out at constant temperatures from 30° to 80°C using deionized water and 02M, 05M, and 10M sodium hydroxide (NaOH) solutions Ettringite was found to be the dominant crystalline phase over the entire temperature range and at all sodium hydroxide concentrations A sodium-substituted monosulfate phase was formed as a hydration product in the 10M sodium hydroxide solution regardless of temperature XRD and calorimetry demonstrate that hydration in increasing sodium hydroxide concentrations decreases the amount of ettringite formed and retards the rate of reaction The apparent activation energy for the conversion of the monosulfate/gypsum mixture to ettringite was observed to vary depending on the sodium hydroxide concentration Ettringite formation was observed to depend upon the concentration of calcium in solution; thus the formation of calcium hydroxide and sodium-substituted monosulfate phase competes with ettringite formation
25 citations