Effect of additives on the properties of α-hemihydrate

Panpa, Withaya; Jinawath, Supatra

doi:10.1680/adcr.2006.18.4.145

Cited by 4 publications

(4 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Mix the gypsum and salt solution, and add in some deionized water to prepare the aqueous salt solution with gypsum. [5] Put the sample solution into reflux device, and heat at different temperature for 2h. [6,7] After heating, filter the solution immediately.…”

Section: Methodsmentioning

confidence: 99%

Research on the Microscopic Characterization of Preparing Alpha-Hemi Hydrate Gypsum from FGD Gypsum at Atmospheric Pressure

Zhang

Yin³

2011

AMM

View full text Add to dashboard Cite

The condition of preparing α-hemi hydrate gypsum from FGD gypsum at atmospheric pressure is easy to achieve. It acquires atmospheric pressure and low heating temperature. This paper introduces two different methods of preparing α-hemi hydrate gypsum, aqueous salt solution method and dry dehydration. Use the microscopic characterization of α-hemi hydrate gypsum to identify the product. Observe the crystal of product by stereo microscope and characterize the compounds with Fourier transforms infrared spectroscopy. Investigate the factors’ effects between the two methods.

show abstract

Section: Methodsmentioning

confidence: 99%

Research on the Microscopic Characterization of Preparing Alpha-Hemi Hydrate Gypsum from FGD Gypsum at Atmospheric Pressure

Zhang

Yin³

2011

AMM

View full text Add to dashboard Cite

show abstract

“…Typically, gypsum pastes have their pumpability impaired as thickening times are less than 20 minutes. For applications that require longer pumping times, retardant additives must be added to gypsum paste systems, and thickening time tests must be carried out (Panpa & Jinawath, 2006).…”

Section: Eq (1)mentioning

confidence: 99%

Gypsum slurries to apply in oil well: An insight into thickening time

Braga,

Freitas

2024

RSD

View full text Add to dashboard Cite

Gypsum is widely used in the construction industry, especially as a hydraulic binder. Studies have indicated the use of α-HH gypsum as an alternative material to Portland Cement in oilwell cementing operations, highlighting the reduction in environmental impacts from the reduction of Portland Cement. Calcium Sulphate α-Hemihydrate (CaSO4 . ½ H2O) has been shown to be a promising material to replace Portland Cement in some applications. The hydration of gypsum pastes goes through the process of saturation of the medium with Ca+2 and SO4-2 ions, then the physical phenomenon of crystallization, and finally the phenomenon of hardening, where the crystals formed precipitate producing Dihydrate (CaSO4 . 2H2O). Gypsum pastes harden very quickly, and their pumpability is impaired with thickening times of less than 20 minutes. For applications requiring longer pumpability times, the use of retarding additives is necessary. This research studied the effects of retarding additives in α-HH gypsum paste systems by varying the water-gypsum factor (FAG 0.4; 0.5 and 0.6) using a pressurized consistometer, under conditions of 54 °C and 9500 psi, with the aim of obtaining formulations with admissible thickening times for oil well cementing applications. The results showed that it was possible to develop paste systems with varying thickening times, with intervals of more than 120 minutes. The 0.5 FAG system proved to be more stable at the same retarder concentrations when compared to the 0.4 and 0.6 FAG systems.

show abstract

“…During this process, the formation of HH crystal is related to temperature, salt solution, time, and the crystal modifier (e.g., inorganic acids). [14][15][16] Li and Demopoulos [17,18] developed a chemical model for the solution process of DH, HH, AH, and constructed the phase-transition diagrams in the CaSO 4 -HCl-CaCl 2 -H 2 O system in which the region for forming a-HH was presented. Guan et al investigated the phase-transition behaviors of a-HH and DH in KCl solutions and found that the metastability of a-HH heavily relied on KCl concentration and temperature.…”

Section: Introductionmentioning

confidence: 99%

“…During this process, the formation of HH crystal is related to temperature, salt solution, time, and the crystal modifier (e.g., inorganic acids). [ 14‐16 ] Li and Demopoulos [ 17,18 ] developed a chemical model for the solution process of DH, HH, AH, and constructed the phase‐transition diagrams in the CaSO 4 –HCl–CaCl 2 –H 2 O system in which the region for forming a‐HH was presented. Guan et al.…”

Section: Introductionmentioning

confidence: 99%

Facile Preparation of Large‐Sized Columnar α‐HH Crystal via a NaCl Salt Bath Method

Nie

Wei

Yang

et al. 2023

Cryst. Res. Technol.

View full text Add to dashboard Cite

Alpha high‐strength hemihydrate gypsum (CaSO4·0.5H2O, α‐HH) with a large‐size columnar crystal (average size: 135.31 µm, maximum size: 500 µm) is successfully prepared via a NaCl salt bath method using salt gypsum as a raw material. The effects of preparation condition (salt solution concentration, salt bath time) on the crystalline phase and crystal grain size of the α‐HH and on the strengths of the cement bulks from α‐HH are investigated. Furthermore, to explore the formation mechanism of the large‐size columnar crystal of the α‐HH, the samples obtained by varying the salt bath time of the reaction system are characterized with field‐emission scanning electron microscopy, X‐ray diffraction, and laser particle size analysis. Based on the characterization results, a formation mechanism of the large‐sized α‐HH is proposed. That is, NaCl self‐diffusion creates a local high‐concentration salt solution environment, which is conducive to the recombination of small‐size HH crystals formed by dihydrate gypsum dissolution and HH recrystallization to grow into large‐sized α‐HH crystals.

show abstract

Effect of additives on the properties of α-hemihydrate

Cited by 4 publications

References 2 publications

Research on the Microscopic Characterization of Preparing Alpha-Hemi Hydrate Gypsum from FGD Gypsum at Atmospheric Pressure

Research on the Microscopic Characterization of Preparing Alpha-Hemi Hydrate Gypsum from FGD Gypsum at Atmospheric Pressure

Gypsum slurries to apply in oil well: An insight into thickening time

Facile Preparation of Large‐Sized Columnar α‐HH Crystal via a NaCl Salt Bath Method

Contact Info

Product

Resources

About