Crystallization and phase transition of tobermorite synthesized by hydrothermal reaction from dicalcium silicate

Wu, Yan; Pan, Xiaolin; Li, Qiwei; Yu, Huan

doi:10.1111/ijac.13469

Cited by 14 publications

(7 citation statements)

References 41 publications

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“…Typically, tobermorite is synthesized using SiO2-rich materials, such as quartz, silica powder, lime, and silica-rich fly ash [91], [92], [93]. It can be synthesized from dicalcium silicate also [102]. Tobermorite constitutes the primary component of energy-efficient building materials [94], [138], [101].…”

Section: X-ray Diffraction (Xrd) Analysismentioning

confidence: 99%

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

Kumar Darapu,

Vindula

2023

IOP Conf. Ser.: Earth Environ. Sci.

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Alkali contamination induces swelling in the inherently non-swelling soils, resulting in heave severely damaging the sub and superstructures. Stabilization measures must be taken in vulnerable areas to prevent such colossal losses. Considerable research has been conducted regarding the swelling behavior of soils contaminated with alkalis and the impact of subsequent stabilization techniques utilizing different industrial byproducts and pozzolanic materials. However, there is a paucity of such studies on the Red Earth (RE) of the Visakhapatnam region. Furthermore, limited attention was given to the effects of extremely low concentrations of alkalis on the swelling behavior of soils. RE in the study area of the Visakhapatnam region predominantly consists of quartz, kaolinite, and hematite. In phase 1 of the experimental analysis, RE was contaminated with a highly dilute NaOH solution (0.05 N), and the resulting swell characteristics were investigated. A free swell of 10% was observed. One-dimensional standard oedometer tests revealed an equilibrium swelling of 5.6%, indicating significant potential for substantial heave and subsequent damage. X-ray diffraction (XRD) analysis revealed the formation of natrolite and analcime zeolites with a hollow structure, which caused the swell. Peaks of silicate minerals like paragonite and ussingite were also observed, indicating the dissolution of authigenic minerals and new precipitations even at lower concentrations of NaOH. In phase 2, swell tests were conducted on a mixture of contaminated red earth (50% w/w), fly ash (25% w/w), and ground granulated blast furnace slag (GGBS, 25% w/w), and it was observed that the swelling was completely arrested. XRD analysis unveiled that even though siliceous zeolites were formed, the development of chrysotile, attapulgite, tobermorite, and dicalcium silicate effectively inhibited the swelling with their pozzolanic behavior.

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Section: X-ray Diffraction (Xrd) Analysismentioning

confidence: 99%

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

Kumar Darapu,

Vindula

2023

IOP Conf. Ser.: Earth Environ. Sci.

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“…Sodium hydroxide was roasted with the residue, followed by leaching and filtrating. Silicate could react with sodium hydroxide, while iron compounds did not react with sodium hydroxide [21,22]. The filtrate (liquor 5) contains sodium silicate.…”

Section: Preparation Of Silica and Iron Concentrate From The Residuementioning

confidence: 99%

Comprehensive Utilization of Boron-Concentrate by Hydrometallurgy

Duan

Wang

Fang

et al. 2021

J. Sustain. Metall.

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A new eco-friendly process to comprehensively utilize boron-concentrate is proposed in this paper. In this process, Ironconcentrate, silicon dioxide, magnesium oxide, and boric acid could be produced from boron-concentrate. The highlight of this process was minimal waste discharge during the whole process. Iron removal was a key step to ensure the quality of boric acid and magnesium oxide. The introduced goethite precipitation method could remove iron to a very low level. With the addition of 3 cm 3 H 2 O 2 (5 vol. %) as an oxidizing agent, more than 99% of iron was removed from the leaching liquor. After the removal of iron, the resulting liquor was used to prepare magnesium precipitate. And the optimal preparation conditions were: the temperature of 30 °C and precipitation time of 60 min, ammonium-magnesium ratio of 1.5, the magnesium ion concentration of 34.8 g•L −1 . Under those conditions, the magnesium precipitation efficiency was up to 98.5%. Magnesium oxide was obtained by roasting magnesium precipitate at 550 °C for 2 h. Then the mixed crystals of ammonium sulfate and boric acid were obtained by evaporating the liquor after iron removing and magnesium precipitating. Boric acid was separated from ammonium sulfate by dissolving the mixed crystals in ethanol solution.The contributing editor for this article was Hiromichi Takebe.

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“…28,33 Research exploring tobermorite synthesis from calcium silicates and calcium aluminum silicates has demonstrated that alkaline solutions are required for precipitation. 16,17,34,35 Sodium bases, such as NaOH, have been shown to facilitate the precipitation of tobermorite better than other alkali metals. 17,35 Tobermorite precipitation from calcium silicates has also been described as the crystallization of CSH gel.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Research exploring tobermorite synthesis from calcium silicates and calcium aluminum silicates has demonstrated that alkaline solutions are required for precipitation. ,,, Sodium bases, such as NaOH, have been shown to facilitate the precipitation of tobermorite better than other alkali metals. , Tobermorite precipitation from calcium silicates has also been described as the crystallization of CSH gel. ,− The formation of tobermorite and other CCSH phases from pseudowollastonite has been shown to increase when exposed to both sodium and CO 2 ; CCSH phases have precipitated when the carbon is delivered as a salt, for example, as Na 2 CO 3 or NaHCO 3 or CO 2 gas and NaOH. − However, the effects of CO 2 and sodium concentrations on the amount and phases of precipitated CCSH have not been explored in detail. Prior work in our laboratory suggested that the crystal structure and dissolution characteristics of the parent silicate were a major factor impacting CCSH precipitation .…”

Section: Introductionmentioning

confidence: 99%

Coprecipitation of Crystalline Calcium Silicates and Carbonates from the Hydrothermal Reaction of Pseudowollastonite

Tolliver,

Nguyen,

Dela Cerna

et al. 2024

ACS Sustainable Chem. Eng.

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Calcium silicates are abundant but sparingly soluble feedstocks of interest for making low-carbon alternative cements. Under hydrothermal and alkaline conditions, they can form crystalline calcium silicate hydrate (CCSH) products, which are abundant in Roman concrete, or they can form carbonates when CO 2 is present. To understand when coprecipitation of CCSH and carbonate phases is possible, we studied the hydrothermal carbonation of a model calcium silicate, pseudowollastonite (α-CaSiO 3 ), at 150 °C and high pH as a function of CO 2 source [CO 2 (g) or Na 2 CO 3 ] and different concentrations of sodium, alumina, and silica. Our experiments produced a range of CCSH phases including tobermorite−13 Å, rhodesite, and pectolite, as early as 1 day after the start of our experiments. After 7 days of curing in a 2 M NaOH solution, over 10% of the samples had been converted to these CCSH phases. We also observed the formation of CaCO 3 as both aragonite and calcite when carbon was introduced to our experimental system. The carbon source impacted the ratio of the CaCO 3 to CCSH phases in the reaction products. The availability of Na 2 CO 3 produced a balance between the CaCO 3 and CCSH phases, whereas CO 2 (g) produced more CaCO 3 , with samples that were over one-third carbonate by mass. Higher concentrations of Na + increased the precipitation of both the CaCO 3 and CCSH phases. The presence of excess silica, in the form of dissolved borosilicate glass from our reaction vessels under alkaline reaction conditions, also enhanced the formation of CCSH phases formed in some experiments. Supplemental Al 2 O 3 , a common constituent in many silicate feedstocks, also enhanced CCSH formation, likely by forming aluminum-substituted phases under the conditions tested here. These chemical insights can enable the design of formulation and curing guidelines for novel cementitious materials.

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Crystallization and phase transition of tobermorite synthesized by hydrothermal reaction from dicalcium silicate

Cited by 14 publications

References 41 publications

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

Comprehensive Utilization of Boron-Concentrate by Hydrometallurgy

Coprecipitation of Crystalline Calcium Silicates and Carbonates from the Hydrothermal Reaction of Pseudowollastonite

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