Showing papers on "Ettringite published in 2020"
TL;DR: In this article, the authors investigated the properties of seawater for concrete manufacturing and showed that seawater can promote the early hydration of tricalcium silicate (C3S) during the hydration acceleration period.
104 citations
TL;DR: In this article, the carbonation of portlandite, ettringite, and calcite was investigated at 57% RH and 91% RH using X-ray diffraction, thermogravimetric analysis, infrared spectroscopy, and the phenolphthalein spray test.
91 citations
TL;DR: In this article, the effects of mechanical activation on the potential pozzolanic activity, hydration properties of iron ore tailings (IOTs), and their application as supplementary cementitious materials in cement were studied.
85 citations
TL;DR: In this paper, the effect of different factors on sulfate requirement in C3S/C3A systems was explored, and it was observed that reaction rates of both C 3S and C 3A have an influence on the overall sulfate balance, as they affect the amount of sulfate adsorbed on C-S-H and the amount ettringite formed, respectively.
60 citations
TL;DR: In this article, two geopolymers synthesized from aluminosilicate sources, fly ash and metakaolin, were investigated to determine their effectiveness in stabilizing shrink-swell behavior of high sulfate expansive soil.
Abstract: High sulfate expansive soils present special challenges during stabilization. Traditional stabilizers such as lime and cement which are rich in calcium are ineffective in controlling shrink/swell behavior of these soils due to formation of the expansive mineral, ettringite. In this study, two geopolymers synthesized from aluminosilicate sources, fly ash and metakaolin, were investigated to determine their effectiveness in stabilizing shrink-swell behavior of high sulfate expansive soil. Geopolymers were modified with lime and gypsum to improve their efficacy as stabilization agents for sulfate bearing soil. Modifier contents were optimized to achieve maximum reduction in swell potential and at the same time prevent ettringite formation. Microstructural analyses were performed on lime and gypsum added geopolymer to determine the mechanism of modification. Swell tests were conducted on high sulfate soil treated with modified geopolymer at different concentrations and optimum concentration of modified geopolymer required to achieve minimum swell was established.
53 citations
TL;DR: In this article, a calcium sulphoaluminate cement (SAC) was used to improve the properties of β-HPG, and the results showed that SAC can improve the mechanical strength and waterproof properties significantly.
52 citations
TL;DR: In this article, the influence of sodium sulfate (Na2SO4) content on the properties of lime (CaO) activated slags to overcome the slow strength evolution of CaO activated slag binders was investigated.
51 citations
TL;DR: The combined iodine K-edge extended X-ray absorption fine structure (EXAFS) spectra and first-principles calculations using density functional theory (DFT) suggested that IO3- was stabilized in ettringite by hydrogen bonding and electrostatic forces, providing valuable insight into the long-term stabilization of anionic iodine species and their migration in cementitious nuclear waste repository or alkaline environments.
51 citations
TL;DR: The behavior of sulfoaluminate (CSA) cements hydrated in neutral or alkaline solutions (0,M, 0.1, 1M, 1/M, 4,M and 8,M NaOH) was studied in this paper.
51 citations
TL;DR: In this article, the effects of limestone replacement fraction, limestone specific surface area and water-to-binder (W/B) ratio on the threshold chloride concentration (TCC) for steel corrosion were evaluated.
50 citations
TL;DR: In this article, the optimal proportion of slag, gypsum and clinker in the blended cements containing slag is designed to promote the green degree of the blended cement.
Abstract: Increasing the gypsum and slag contents in the blended cements containing slag is conducive to promote its green degree. The blended cement was prepared by mixing slag, gypsum and Portland clinker. Contour maps were designed to determine the optimal proportion of slag, gypsum and clinker by comprehensive considerations of strength, expansion, hydration, microstructure and crystallization stress. The strength contour map shows that there are two separate regions with high cement strength in the ternary slag-gypsum-clinker system; and the expansion deformation of these two regions are relatively low. The Rietveld XRD and pore solution analysis reveal that the occurrence of the destructive expansion results from the high crystallization stress of ettringite. It is illustrated that the gypsum content could be increased up to 25% when the clinker content is less than 5%, while the gypsum content should be limited below about 10% when the clinker content is more than 20%. The [CaO][SO3]/[Al2O3] molar ratio is suggested to direct the optimization of the slag, gypsum and clinker in blended cement. As long as the [CaO][SO3]/[Al2O3] ratio is not up to 1.5, more gypsum and slag could be added into the blended cement to obtain relatively excellent performance.
TL;DR: In this article, the mechanical properties and hydration of green concrete which is made from ground granulated blast-furnace slag (GGBS), desulfurization gypsum (DG) and electric arc furnace reducing slag as cementitious materials were studied using isothermal calorimetry (IC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy equipped with energy dispersive X-Ray spectroscopy (SEM-EDX).
TL;DR: In this article, the early hydration of cementitious systems accelerated by an alkali-free aluminium sulphate-based product was investigated in the presence and absence of fine limestone, and it was shown that the first seconds after the accelerator is added to the wet mix play a key role: Simultaneously to the massive ettringite formation, the Al2(SO4)3 accelerator favours the dissolution of the major cement clinker phase alite and thereby leads to an oversaturation of the pore solution with respect to calcium-aluminium-silicate-hydrates
TL;DR: The main hydration products of this cement are a calcium-aluminosilicate hydrate type gel, ettringite, monosulfate, hydrotalcite, brucite and aluminate hydrate, while the extent of reaction and formation of reaction products significantly varied by MgO dosages.
TL;DR: In this article, the authors investigated the feasibility of belite-rich sulphoaluminate cement prepared from Bayer red mud, blast furnace slag, steel slag and carbide slag on synergistic theory.
TL;DR: In this paper, the authors investigated the early hydration reactions and resultant compressive strength in a 50:50 slag:cement binder in the presence of Na2SO4 and found that the early strength increases were due to a combination of increased alite hydration and increased slag dissolution.
TL;DR: In this paper, the performance of ordinary cast-in-situ recycled aggregate concrete subjected to sulfate attack under various service conditions, five different exposure conditions, full and partial immersion and drying-wetting cycles for 40 weeks were investigated.
TL;DR: In this paper, the effect of increasing sulfate contents on the hydration of white cement was studied with a multi-technique approach, combining isothermal calorimetry, advanced in-situ 1H nuclear magnetic resonance (NMR) and early scanning electron microscopy (SEM) observations.
TL;DR: The results show that the release of chloride is not only a diffusion-controlled process, as reported in the literature, but also a reaction-controlled phenomenon, during which the chloride-rich phases decompose and release chlorides that are associated with them via sorption/incorporation.
TL;DR: In this paper, the influence of different curing temperatures on the hydration of belite-calcium sulfoaluminate cement was investigated at 20, 40 and 60°C. The hydration kinetics and the hydrated phase assemblages were studied by isothermal calorimetry, X-ray powder diffraction, differential thermal analysis and thermogravimetric analysis.
TL;DR: In this article, an alkali-free liquid accelerator based on aluminum sulfate (F-AS-AF accelerator) was prepared and its effects on the setting time and compressive strength of cement, C3A and C3S were studied.
TL;DR: In this paper, the effects of steel slag on the hydration and strength development of calcium sulfoaluminate (CSA) cement were investigated, and the results indicated that at early ages (from 2h to 28h), steel slags worked like a filler and had a dilution effect on CSA cement hydration.
TL;DR: In this article, the authors used 10 and 20% phosphogypsum calcined at either 350 or 650°C, which were more or less soluble, respectively, and the largest ettringite formations were verified in samples with greater calcium sulfate availability.
TL;DR: In this article, the shrinkage behavior of sodium silicate activated slag (SSAS) incorporated with gypsum and Portland cement (PC) was investigated, and the hardened properties, namely flexural and compressive strength, were investigated as well.
TL;DR: In this paper, an industrial filter sludge (FS) with an extremely high content of several heavy metals (24.6% Pb, 21.7% Hg, and 9.00% Se) and sulfate via calcium sulfoaluminate-belite (CSAB) cement was tested.
TL;DR: In this article, the use of Phosphogypsum (PG) as a mixing ingredient in the magnesium phosphate cement (MPC) matrix and the influence of PG on the physical, mechanical and microstructural properties were explored over the courses of age.
TL;DR: In this paper, a new empirical force field is proposed to describe the interactions among species in ettringite, monosulfoaluminate, and tricalcium aluminate at the molecular level.
TL;DR: In this article, the authors investigated the resistance performance and resistance enhancement mechanism of cement mortar containing silica fume (SF) exposed to external sulfate attacks (ESA) at a temperature of 20°C.
TL;DR: In this paper, the influence of three doses of expansive agent on fresh state and on compressive strength and magnitude of free expansion under two curing environments was evaluated on a reference mixture of self-compacting concrete (SCC).
Abstract: Expansive concretes based on the formation of ettringite from calcium sulfoaluminate agents are presented as an effective alternative to minimize the problems derived from shrinkage and low tensile strength at the early ages of the concrete. However, determining the mechanism responsible for the expansion is still a controversial issue today. In this study, the influence of three doses of expansive agent on fresh state and on compressive strength and magnitude of free expansion under two curing environments was evaluated on a reference mixture of self-compacting concrete (SCC). The microstructural evolution of the hydrates and anhydrous related with the expansive phenomena was also studied. From our observations it seems that an eminently amorphous ettringite is formed and that this ettringite would be strongly related to expansion. As a result, the influence of the ratio w/cementitious material and curing environment on the magnitude of the expansion as well as the influence of this on the mechanical properties of the SCCs was identified.
TL;DR: Ettringite usually forms in lime and cement-stabilized gypseous soils, resulting in significant swelling upon wetting and thereby causing damage to pavements and foundation systems as discussed by the authors.
Abstract: Ettringite usually is formed in lime- and cement-stabilized gypseous soils, resulting in significant swelling upon wetting and thereby causing damage to pavements and foundation systems. To...