Request PDF | Thermodynamic, mechanical, and electronic properties of ettringite and AFm phases from first-principles calculations | The aluminate containing hydration products of Portland cement ...
The involvement of expansion cracks in reducing compressive properties was experimentally evaluated. Concrete specimens deteriorated by delayed ettringite formation were subjected to three loading ...
Mechanical and structural properties of Ettringite and AFm phases were analyzed.. Atomic occupancy and coordinates of all the structures are refined. • Non-bonding electrons are found in the O-p orbitals of CO 3 2– in Monocarbonate.Friedel's salt formation from Monocarbonate can increase the solid volume by 12.5%
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The ettringite has an expansive characteristic when formed late, which spreads throughout the cement paste matrix and the transition zone, leading to cracks in the system that progress over time ...
Ettringite is a hexacalcium aluminate trisulfate hydrate mineral that forms during Portland cement hydration. Its presence plays an important role in controlling the setting rate of the highly reactive aluminate phases in cement paste and has also been associated with severe cracking in cured hardened cement.
Ettringite is a hexacalcium aluminate trisulfate hydrate mineral that forms during Portland cement hydration. Its presence plays an important role in controlling the setting rate of the highly reactive aluminate phases in cement paste and has also been associated with severe cracking in cured hardened cement. To understand how it forms and how its properties …
A few low carbon binders with ettringite as one of the major binding phases have been developed e.g. calcium sulfoaluminate (CSA) cement [9], supersulfated cement (SSC) [10] and excess-sulfate phosphogypsum-slag cement [11].The detailed information of these binders is shown in Table 1.The calcium sulfoaluminate cement contains mainly …
Ettringite is a primary constituent of hydration of Portland cement concrete. Its formation plays an important role in the control of setting. Minor amounts of secondary ettringite …
Reinforced concrete (RC) members are subject to map cracking owing to the delayed ettringite formation (DEF) by excessive core temperature during the first few days of hydration. Studies on the mechanical properties of concrete with DEF expansion have been conducted to identify the variation in moduli and strength of the material.
Stress-strain simulations are performed to find that Ca-O bonds are responsible for failure of the calcium sulfate and tricalcium aluminate column in ettringite during uniaxial compression and tension and that hydrogen bond re-formation during compression induces an increase in plastic strain beyond the material's stress-strains …
Mechanical and structural properties of Ettringite and AFm phases were analyzed. Atomic occupancy and coordinates of all the structures are refined. Non …
We applied mechanochemistry to synthesize ettringite, a significant constituent of the cementitious materials. Besides the importance for cementitious …
Concerning the thermal stability of ettringite crystals, many studies have suggested that the decomposition temperature of ettringite is generally considered to be 70–80 °C [27, 32, 39, 40].To investigate the temperature limit and the generation of ettringite, the temperature interval was narrowed by 5 °C to study the generation of …
Mechanical strength and calorimetry analyses showed the best behavior using gypsum as a source of calcium sulfate. ... For the thermal analysis (TGA), the SDT Q-600 equipment was used and the selected parameters were sample mass of 10 mg, heating ... The scanning electron microscopy images showed neoformed ettringite in …
The previous results agree with Ehwailat et al. [19, 20], indicating that the use of lime (L) to stabilize sulfate-bearing (Kolin + Gypsum) (K–G) soil causes ettringite formation and leads to the deterioration of strength and increase in volume change.The outcome of this research showed improvement in the strength as the lime ratio …
constant and equal to K=1.66 W/m.°C, the thermal capacity of this concrete was adopted equal to 2400 Wh/m3.°C and the coefficient of thermal exchange was λ=6 W/m².°C because of the use of metal formwork. Figure 6 shows that the temperature reached about 83 °C in the middle of the pier and stayed
An environment-friendly mechanochemical synthesis of ettringite was mechanistically investigated. The two-step mechanosynthesis consists of a neat pre-grinding of the solid reactants (Ca (OH) 2, CaSO …
Given that the preference of growing in a less stressed direction for ettringite crystal, new structures of ettringite-based materials may improve its mechanic …
This reaction generates calcium sulfoaluminate hydrate, a precursor to ettringite. 2. Formation of Ettringite. Once sulfate ions react with aluminate compounds, ettringite begins to form. Ettringite has a …
Compared with polymer-modified ordinary-Portland-cement-based materials, research on cement materials based on polymer-modified sulfoaluminate is still in the preliminary stage and lacks an understanding of the mechanism of the interaction interface. The aim of this work is to study the bond performance of ettringite, the main hydration …
2. Formation of ettringite. Ettringite is a rare mineral phase in nature, while it exists commonly and largely in cement paste. Almost all alumina source, such as Al(OH) 3 gel, aluminium sulfate hydrate, C 3 A, can be reactive to form ettringite crystals [18], [27], [28]: with the addition of some calcium and sulfate source, the desired compound can be …
Ettringite and thaumasite are important hydrated phases of cementitious materials that contribute to the mechanical properties and stability of concrete. The authors have performed first principle density functional theory (DFT)-based calculations in order to predict structural and mechanical properties of these two minerals.
The expansion deterioration that occurs in concrete structures exposed to high temperature fluctuation in wet environments is often attributed to delayed ettringite formation (DEF). Due to the complex mechanism and various factors that influence DEF, it is difficult to establish effective methods for predicting the expansion and suppressing …
Rapid repair mortar (RRM) is widely used to repair infrastructures, which must achieve high early strength and long-term service. This study investigated the influence of hot/wet harsh environmental conditions on RRM prepared using solid-waste-based sulfoaluminate cement (WSAC). Orthogonal experiments were conducted to …
Delayed ettringite formation (DEF) is a chemical reaction with proven damaging effects on the mechanical properties of hydrated cementitious composite (concrete). Ettringite crystals can cause cracks and the widening of cracks due to pressure on the crack walls caused by the positive volume difference in the reaction. In this paper, …
the drop of mechanical properties. Extensive researches have been carried out on its formation and stability all over the world ISnl . There is a common view that ettringite ... Ettringite and M are both salts which are difficult to be dissolved, and their solubility product constants are 3.9 x 10 -46 and 1.35 x 10 -27, respectively. ...
Abstract— The paper presents results of a physicochemical study of ettringite, natural calcium hydrosulfoaluminate Ca6Al2(SO4)3(OH)12⋅26H2O, from N'Chwaning, Kalahari, South Africa, by X-ray powder diffraction, IR and Raman spectroscopy, thermal analysis, and calorimetry. The thermal transformation of …
