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Showing 1 to 20 of 30 for “"Ettringite"”.
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Early-age hydration and volume change of calcium sulfoaluminate cement-based binders
… (main component in CSA cement), amount of ettringite (the main phase responsible for expansion in CSA cement), supersaturation with respect to ettringite in cement pore solution, total pore volume, and material stiffness were monitored to examine early-age expansion characteristics. This …
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Expansive mineral growth and concrete deterioration: a microstructural and microanalytical study
… was evidenced that two major expansive minerals, ettringite and brucite, were responsible for premature deterioration. Severe expansion cracking of cement paste was often associated with ettringite locations, and strongly suggests that secondary ettringite was a major cause. Brucite forms in …
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First Principles Method for Complex Cement Structure and High Entropy Alloys
… Both materials possess a complex structure. Ettringite and thaumasite are two of the relevant by-products in Portland cement minerals with high water content. The calculations focus on the comparison of their structures and properties to gain insights that can reveal the minute difference in …
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Sulfate soil stabilisation with silica fume-based binders
… expansion as a result of the formation of ettringite. Therefore, this research examines the viability of using silica fume (a by-product of silicon industry) as a partial replacement of different high/low/non-calcium-based binders to restrict the ettringite formation and suppress the …
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The amendment of acid soil with an ettringitic waste and its effects on plant growth
… saline water. The waste is dominated by ettringite (CauAJ4(OH)24(S04) 6.52H20) with calcite (CaC03) as a minor phase (17.7% for the sample used in this study). Apart from the presence of calcite, the ettringite itself is alkaline due to the presence of OH ions. Following a submission that …
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Stabilisation of sulphide rich soil: problems and solutions
… to a less dense, more porous material. Also ettringite forms during mellowing allowing expansive reactions to occur prior to compaction, consuming both calcium and sulphate in the process and leading to slightly reduced pH levels compared to similar unmellowed samples. Further additions of …
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Cementitious stabilization of soils in the presence of sulfate
… as replacement. The average length and amount of ettringite crystals, in general, inversely correlated with the magnitude of expansion. A three-stage expansion model was developed to explain increased sulfate attack resistance provided by the SCMs, attributable to their consumption of calcium …
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Factors influencing the strength development in pfa-lime systems
… observed sequence of events :<br/>Surface ettringite formation on the pfa particles; initial formation of gel coating; ettringite decomposition and release of sulphate; hydrogarnet formation and colloidal membrane development; membrane bursting and precipitation of C-A-S-S -H …
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ΠΡΟΣΡΟΦΗΣΗ U, TH, BA ΚΑΙ CS ΑΠΟ ΟΡΥΚΤΑ ΤΗΣ ΑΡΓΙΛΛΟΥ ΚΑΙ ΣΥΝΘΕΤΙΚΑ ΟΡΥΚΤΑ-ΕΚΛΕΚΤΙΚΟΤΗΤΑ ΚΑΙ ΔΕΣΜΕΥΣΗ ΤΟΥ CS
… AQUATION. THE SYNTHETIC MINERAL FAUJASTICE AND ETTRINGITE WERE FOUND TO BE VERY SENSITIVE AND UNSTABLE IN THE ACID ENVIRONMENT OF THE URANIUM AND THORIUM SOLUTIONS. CASSIUM SELECTIVITY COEFFICIENTS (KG) THAT WERE DETERMINED WITH RESPECT TO NA-, MG-, CA-, SR- AND BO- IONS FOR KENT AND LIBBY …
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Soft Soil Stabilisation Using a Novel Blended Cementitious Binder Produced From Waste Fly Ashes
… silicate hydrates (C-S-H), Portlandite (CH) and ettringite. The formation of these hydrates reveals the developments gained in the geotechnical properties of the treated soil. A solid, coherent and compacted soil structure was achieved after using T+FGD, as confirmed by the formation of C-S-H, CH …
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Examination of hydrated and accelerated carbonated cement-heavy metal mixtures
… cement pastes, aluminium was partitioned in ettringite or calcium carboaluminate. After carbonation, this work revealed that aluminium was in the tetrahedral form, forming mixed AlCVSiC^ branching or three-dimensional networks. This thesis presents the new structural models for C-S-H gel and …
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The Neutralisation of acid mine drainage by fly ash
… (Ca(OH)z). Between pH values of 12 and 10.3, ettringite (Ca6A'2(SO4)3(OH) 1226H2O) precipitates and acts as a weak pH buffer. Below pH 10.3 ettringite dissolves incongruently to form gypsum and amorphous Al(OH)3. Gypsum was identified by XRD to pH values of 5.6, although thermodynamic …
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Development of Sustainable Concretes for the Gulf Region
… properties of CSAB cement paste established that ettringite content increased with increasing the gypsum content and hence it can be used to control the ratio of AFm/AFt hydrates. The lowest paste porosity and permeability was observed for the mixture having 23% w/w gypsum which matches that …
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Steam Cured Self-Consolidating Concrete and the Effects of Limestone Filler
… research also examines the resistance to delayed ettringite formation when the concrete is steam cured at 70°C and 82°C and its secondary consequences on the freeze-thaw resistance. The effect of several experimental variables related to the concrete mix design and also the curing conditions are …
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Synthesis and Multi-Scale Characterization of Calcium Silicate Hydrate at Multiple CaO/SiO2 Mixture Ratios
… produces C-S-H, Calcium hydroxide (CH), ettringite, and other hydration products are also acquired from this process and make it difficult to characterize C-S-H exclusively. C-S-H was first synthesized by mixing calcium oxide (CaO), created by calcining calcium carbonate (CaCO3) that was …
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The Durability of Mortar with Ground Clay Brick as Partial Cement Replacement
… it seems likely that water intake due to ettringite formation and adsorption of water by the resultant colloidal product are the primary causes of expansion. Sulphate content, glass content and oxide chemistry of brick are key factors as to its performance when used as a cement replacement …
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Development of low-clinker concrete: partial replacement of cement with calcined clay and limestone, based on selected African raw materials
… of carboaluminate phases, stabilisation of the ettringite phase, and the internal surface area of the clay.
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Response of kikuyu grass (Pennisetum clandestinum) to irrigation with saline, sodic wastes and nitrogenous, manganiferous effluent
… attributed to the formation of an undocumented ettringite-like mineral. Kikuyu exhibited both a fertilization effect and a Mn toxicity effect with manganous sulphate applications. An increase in yield occurred between Mn applications of 800 and 1600 mg/kg soil. This effect was attributed to …
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Water absorption and salt attack resistance of coal ash brick made of different percentage of foam content
… foam addition on HL-GGBS coal ash brick portrays ettringite formation were attributed to disruption of brick structure. The use of coal ash with HL–GGBS and PC-GGBS combination as binder agent has been observed to be lightweight, low in water absorption, and advantageous in protection to salt …
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Lime Stabilised Murram as a Building Material in Kenya
… is present the principal reaction * product is ettringite which is a calcium sulpho-aluminate hydrate (C3A3CSH32 ).
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