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Gypsum hydration: a theoretical and experimental study

Hydration Mechanism and Hardening Property of …

Many studies have confirmed that the morphology of HH is one of the most important factors for affecting mechanical strength of hardened paste, and the short hexagonal prism crystal with an aspect …

α-calcium sulfate hemihydrate preparation from FGD gypsum …

The pilot plant with a production capacity of 1000 kg/batch was constructed at Xiaoshan Power Plant, Zhejiang Province, China. Fig. 1 shows the schematic diagram of the pilot plant, which mainly consists of a salt solution tank (D 2.0 m × H 2.0 m), a homogenizer (D 2.0 m × H 2.0 m), two stirred bed reactors (D 2.0 m × H 2.0 m), a …

Effect of Fluorine and Phosphorus Impurities in …

In this study, phosphogypsum (PG) is simulated by doping fluorine and phosphorus ions in an analytically pure reagent of gypsum dihydrate. The influence of fluorine and phosphorus impurity and content on the dehydration reaction process of phosphogypsum and its crystalline micromorphology is assessed during the preparation …

Effect of calcium sulphoaluminate cement on mechanical strength …

The β-type hemihydrate gypsum is formed through the dehydration of dihydrate gypsum in a dry environment, but its products feature low mechanical strength, vulnerability to temperature, and poor ...

Microstructure and mechanical properties of β-hemihydrate …

This article addresses the microstructure and related mechanical properties of gypsum produced from β-hemihydrate using information of its hydration process, from …

Effect of modifiers on crystalizing habit and mechanical strength …

The results show that at high w/c ratios from 0.8 to 1.0, pregelatinized starch significantly improved the mechanical properties of gypsum, where the flexural and compressive strength of 3 d ...

Hardening performance of reclaimed gypsums for stabilizing …

The mass fraction of hemihydrate gypsum to the total gypsum is expressed as a G05 /a G that is referred to as hemihydrate ratio in this paper. Table 3 shows the …

Microstructure and mechanical properties of β-hemihydrate …

Some of the most important materials in the building industry is CaSO 4 ·2H 2 O, called gypsum (calcium sulfate hydrate), which is necessary for sound insulation at walls, in addition to many ...

Effect of Soluble P2O5 Form on the Hydration and Hardening …

The HPO 4 2− form has mainly two adverse effects. Firstly, it can lead to the formation of an insoluble compound of Ca 3 (PO 4 ) 2, which impedes the hydration process and extends the setting ...

DESIGN OF BETA-HEMIHYDRATE GYPSUM PLASTER …

calcium chloride on water-gypsum ratio, setting time, bending and compressive strength of gypsum. The gypsum pastes of normal consistency have been prepared at intensive mixing during 2 min.

Effect of phosphate rock acid insoluble residue on hydration …

The application of α-hemihydrate gypsum (α-HH) is limited by several factors, such as a rapid hydration rate, short setting time, poor water resistance, and high cost. Especially because of the high production cost, although α-HH has excellent mechanical strength, it is rarely used in the field of building materials. In this study, …

Strength Gypsum

α-Hemihypdrate (high-strength gypsum) is obtained by removing crystalline water in liquid state. The most common method is autoclaving with subsequent drying and grinding. …

Gypsum hydration: A theoretical and experimental …

Using setting time and early compressive strength as an analysis index as well as an extreme difference analysis, it was found …

Preparation of α-High Strength Gypsum from Flue Gas …

The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD) gypsum is a good way to realize the comprehensive utilization of FGD gypsum. To obtain α-CSH with the satisfactory performances, a facile hydrothermal-aging pretreatment process for FGD gypsum raw materials was proposed, where FGD …

Effect of Phosphoric Acid on the Preparation of α …

The effects of phosphoric acid (H3PO4) in pressurized aqueous solution on the dehydration of CaSO4·2H2O to form α-hemihydrate gypsum (α-HH) phase and the regulation of crystal shape …

Preparation of Large‐Grained α‐High Strength Gypsum with FGD Gypsum

This study found that, without added succinic acid or aluminum ions, the crystal transformation rate of α-calcium sulfate hemihydrate reached 96% with the average length-diameter ratio reaching ...

Formation of α-Hemihydrate Inside of a Gypsum …

It is obvious that in points 1 to 3 (points alpha-HH in crystal after furnace) and 6 (point beta-HH in crystal after furnace), the Ca/O and S/O ratio is comparable and lower than in points 4 and 5 (points DH in …

Effect of neutralization on the setting and hardening …

For FG:SS = 10:0, the initial setting time and final setting time are 103 min and 185 min, respectively, which is much longer than the setting time of hemihydrate gypsum [24] due to the fact that ...

Synthesis and Characterisation of Hemihydrate Gypsum…

Among these, α-type hemihydrate gypsum ... The softening coefficient f of the composite material can be determined by calculating the ratio of R2 to R1, as indicated in Equation (1). f = R2/R1 (1) 3. Results and Discussion. ... The variation in flexural strength of hydration-hardening and oven-dried specimens for both the pure water …

The Influences of Soluble Phosphorus on Hydration Process …

Phospho-gypsum is an industrial solid waste discharged from the phosphate production process. The waste includes complex impurities such as phosphoric acid and its salts, fluoride, and organics. Usually, retarders are mixed in gypsum-based building materials to extend setting time. Although the effects of the impurities on hydration …

Microstructure and mechanical properties of β-hemihydrate …

This finding also indicates the strength is independent on the type of the used hemihydrate. An extreme strength (σ 0, flexural strength and compressive strength), i.e. the strength of gypsum at zero void fraction, is also derived from the models, as listed in Table 3. We can see that the Schiller model (Eq.

α-Hemihydrate Phosphogypsum

Minerals 2019, 9, 733 3 of 15 of L-Asp (0.00, 2.50 mM) mixed solutions were preheated by an oil bath in a three-mouth flask. The solution temperature was measured by a thermometer and maintained ...

Leonid Dvorkin, Vadim Zhitkovsky HIGH-STRENGTH …

great importance for achieving high strength of gypsum binder and low water-gypsum ratio. Hand mixing, using of gypsum β-modification and additive lime + Melflux allows to get a plastic paste with a spread by Suttard 180 mm at values of W/G ≥ 0,45. The strength of such binders after 2 hours of curing does not exceed 5 MPa - 6 MPa.

Influence of HPMC on the capillary water absorption, pore

Capillary water absorption is an important parameter to evaluate the durability of cement mortars. For testing the capillary water absorption of cement mortars, drying is a necessary and crucial procedure. However, different standards have different requests on drying temperatures for doing the tests. Since the calcium aluminate cement …

What is the Difference Between Alpha and Beta Hemihydrate

The process of converting gypsum into alpha hemihydrate involves heating gypsum at a specific temperature to remove water molecules, resulting in a more concentrated and stable form of calcium sulfate. The term "alpha" in alpha hemihydrate refers to the unique crystal structure formed during this dehydration process. The alpha …

α-Calcium Sulfate Hemihydrate Preparation from FGD Gypsum …

A pilot scale preparation of α-calcium sulfate hemihydrate (α-HH) from flue gas desulfurization (FGD) gypsum was conducted for the first time in mixed salt solutions under atmospheric pressure.

Hydration Mechanism and Hardening Property of α-Hemihydrate Phosphogypsum

The hydration and hardening of α-hemihydrate phosphogypsum (HH) prepared in the absence and presence of L-Aspartic acid (L-Asp) were investigated by thermodynamic analysis, measurements of ion concentrations and crystal water content, and morphology observation. In addition, computed tomography (CT) scanning was …

Autoclave‐Free Formation of α‐Hemihydrate Gypsum

The β-type hemihydrate gypsum is formed through the dehydration of dihydrate gypsum in a dry environment, but its products feature low mechanical strength, vulnerability to temperature, and poor ...

Preparation of α-High-Strength Hemihydrate from Flue …

Preparation of α‑High-Strength Hemihydrate from Flue Gas Desulfurization Gypsum in AlCl 3−MgCl 2 Solution at Atmospheric Pressure Shuaifeng Liu, Edouard Asselin, and Zhibao Li* Cite This ...