Crystal Structure of Ettringite

Moore, Adrian J.; Taylor, H. F. W.

doi:10.1038/2181048a0

Cited by 117 publications

(90 citation statements)

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“…It is known that the structure of ettringite is based on two distinct structural components 5) ; columns of {Ca 6 [(Al,Fe)(OH) 6 ] 2 · 24H 2 O} 6ϩ and channels of {(SO 4 ) 3 · 2H 2 O} 6Ϫ which contain four sites, of which three are occupied by sulfate and one by two water molecules. With this structure a modest deviation in composition can be tolerated without causing a change in structure.…”

Section: Immobilization Mechanismmentioning

confidence: 99%

Immobilization of Fluorine in Aqueous Solution by Calcium Aluminum Ferrite and the Mixture of Calcium Aluminate and Gypsum.

Suito

2002

ISIJ International

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Section: Immobilization Mechanismmentioning

confidence: 99%

Immobilization of Fluorine in Aqueous Solution by Calcium Aluminum Ferrite and the Mixture of Calcium Aluminate and Gypsum.

Suito

2002

ISIJ International

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“…Most of the crystal structure models used in this study were taken from published data. [33][34][35][36] In general, the refinement proceeded in steps where diffraction patterns of selective extractions of the cements were refined and the structural and peak shape profile parameters were established. These parameters were subsequently fixed to avoid correlation problems in the more complex mixtures.…”

Section: Tracking Hydration and Microstructure Developmentmentioning

confidence: 99%

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

et al. 2011

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Equilibrium thermodynamic calculations, coupled to a kinetic model for the dissolution rates of clinker phases, have been used in recent years to predict time-dependent phase assemblages in hydrating cement pastes. We couple this approach to a 3D microstructure model to simulate microstructure development during the hydration of ordinary portland cement pastes. The combined simulation tool uses a collection of growth/dissolution rules to approximate a range of growth modes at material interfaces, including growth by weighted mean curvature and growth by random aggregation. The growth rules are formulated for each type of material interface to capture the kinds of cement paste microstructure changes that are typically observed. We make quantitative comparisons between simulated and observed microstructures for two ordinary portland cements, including bulk phase analyses and two-point correlation functions for various phases. The method is also shown to provide accurate predictions of the heats of hydration and 28 day mortar cube compressive strengths. The method is an attractive alternative to the cement hydration and microstructure model CEMHYD3D because it has a better thermodynamic and kinetic basis and because it is transferable to other cementitious material systems.

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“…The present analysis uses the comprehensive experimental results from the U.S. Bureau of Reclamation research on sulfate resistance of concrete (4). Concrete cylinders measuring 76 ϫ 152 mm were cast with stainless-steel gauge studs inserted into the ends of the cylinder to establish a gauge length of 127 mm.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…For Ͼ40 years until 1991, the U.S. Bureau of Reclamation collected data of concrete expansion due to sulfate attack (4)(5)(6)(7). A wide range of concrete mixture proportions were selected to determine the effect of water-to-cement ratio, cement composition and fineness, curing temperature, and admixtures on the expansion of cylinders exposed to realistic conditions.…”

mentioning

confidence: 99%

Scaling and saturation laws for the expansion of concrete exposed to sulfate attack

Monteiro

2006

Proc. Natl. Acad. Sci. U.S.A.

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Reinforced concrete structures exposed to aggressive environments often require repair or retrofit even though they were designed to last >50 years. This statement is especially true for structures subjected to sulfate attack. It is critical that fundamental models of life prediction be developed for durability of concrete. Based on experimental results obtained over a 40-year period, scaling and saturation laws were formulated for concrete exposed to sulfate solution. These features have not been considered in current models used to predict life cycle of concrete exposed to aggressive environment. The mathematical analysis shows that porous concrete made with high and moderate water-to-cement ratios develops a definite scaling law after an initiation time. The scaling coefficient depends on the cement composition but does not depend on the original water-to-cement ratio. Dense concrete made with low water-to-cement ratios develops a cyclic saturation curve. An index for ''potential of damage'' is created to allow engineers to design concrete structures with better precision and cement chemists to develop portland cements with optimized composition.T he challenge of designing concrete structures capable of withstanding aggressive environmental conditions over an extended period has attracted the attention of engineers and scientists for Ͼ2,000 years. The Egyptians and Greeks used lime in their construction practices, and the Romans achieved technological excellence in their built structures by developing what is called ''Roman concrete'' (1). Unfortunately, the quality and durability of building construction using hydraulic cements decreased after the fall of the Roman Empire and was not considered again until the mid-18th century. In 1756, John Smeaton (see ref.2), who coined the term ''civil engineering,'' was charged with constructing a new lighthouse on Eddystone Rock. Taking into consideration that the lighthouse would be subjected to the most severe weather and water conditions, he embarked on an extensive research project to design more robust cements. Eventually, he developed the optimum combination of materials, and the lighthouse he engineered stood for 126 years, at which point it was replaced by a more modern lighthouse. Fundamental research on chemistry of hydration reactions began during the late 19th century with the work of Le Chatelier in France and Michaelis in Germany (2). Technology improvements in the 20th century resulted in concrete made with portland cement becoming the most used construction material in the world. The present worldwide consumption of concrete is of the order of 10 billion tonnes yearly (3). Except for water, no other material reaches this remarkable level of consumption.Dry-mixed concrete begins in a powdery form. Once in contact with water, it turns into a slurry that can be manipulated into desirable shapes. After a few hours, concrete hardens and starts to gain strength. The sizes of the pores in the cement paste matrix range from several nanometers in the calcium sil...

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Crystal Structure of Ettringite

Cited by 117 publications

References 1 publication

Immobilization of Fluorine in Aqueous Solution by Calcium Aluminum Ferrite and the Mixture of Calcium Aluminate and Gypsum.

Immobilization of Fluorine in Aqueous Solution by Calcium Aluminum Ferrite and the Mixture of Calcium Aluminate and Gypsum.

Coupling thermodynamics and digital image models to simulate hydration and microstructure development of portland cement pastes

Scaling and saturation laws for the expansion of concrete exposed to sulfate attack

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