α or β?-hemihydrates transformed from dihydrate calcium sulfate …

1. Introduction. Calcium sulfate is the subject of much research due to its wide scope and large-scale of industrial applications [1], [2], [3].It occurs in nature mainly in form of three different phases distinguished by the content of crystal water: dihydrate (DH, CaSO 4 ·2H 2 O), hemihydrate (HH, CaSO 4 ·0.5H 2 O), and anhydrite (AH, CaSO …

Investigation of hydration mechanisms of alpha and beta hemihydrate …

Gypsum-based binders are generally based on the reaction between calcium sulfate hemihydrate (HH) and water to form calcium sulfate dihydrate (DH). Often gypsum can be used as a raw material to obtain hemihydrate. In this study, the obtained alpha hemihydrate consists of large crystals that have more or less lattice defects according …

Anhydrite and gypsum

Anhydrite (CaSO 4) and gypsum (CaSO 4 ·2H 2 O) are the two most abundant minerals of ancient marine evaporite deposits and are also common in non-marine evaporite deposits. Sedimentary gypsum forms by direct precipitation out of evaporating seawater under arid climatic conditions in hydrologically restricted marine …

Gypsum | Properties, Formation, Uses and …

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4·2H2O). It is commonly found in sedimentary rock formations and is often associated with other minerals such as …

What is the Difference Between Alpha and Beta Hemihydrate

Conclusion. Both alpha and beta hemihydrates are forms of calcium sulfate hemihydrate, commonly known as plaster of Paris. The main difference between …

Recycling of waste gypsum from αlpha-hemihydrate …

Schematic diagrams of recycling between dihydrate and hemihydrate gypsum: (a) theoretical principles of recycling; (b) practical problems of recycling. ... (4 0 0) crystal planes also decreased with the decrease of the pH value of the reaction medium, but the difference between the pH values of 3.6 and 2.3 was not obvious. This …

12: Gypsum materials

Gypsum (calcium sulphate dihydrate) is a naturally occurring mineral used in dentistry to fabricate models (Figure 12.1a), casts and dies (Figure 12.1b). Calcination is the process of heating the gypsum to …

Effects of different carboxyl additives on the growth habits of

2.2. Preparation of hemihydrate gypsum whiskers. In this experiment, hemihydrate gypsum whiskers were prepared with the autoclave method. A YZF-2A type autoclave (Wuxi Xidong Building Material Equipment Factory, the diameter of the kettle body: 160 mm, the volume of the kettle body: 8.5L) was utilised for the preparation, and …

Gypsum Board Vs. Drywall: Understanding the Differences

Understanding the differences between gypsum board and drywall is critical for making sound decisions in construction and restoration projects. Gypcore, the …

Revealing maleic acid role in the preparation of α-hemihydrate gypsum …

1. Introduction. Titanium gypsum (TG) is the main solid waste produced during the processing of titanium dioxide, which mainly contains CaSO 4 ·2H 2 O (70–80 %) (Marian et al., 2023).TG is also known as red gypsum because of its high ferric ion (Fe 3+) content (Ju et al., 2022).Many strategies for using this byproduct have been evaluated, …

Setting time of construction gypsum, dental plaster, and …

Introduction. Gypsum is one of the natural minerals that contain calcium, hydrogen, water, and sulfur, known as calcium sulfate dihydrate (CaSO 4.2H 2 O). 1 Gypsum products are available in the form of a fine white powder which has undergone calcination or heating at a temperature of 110‒130°C in the open air. This process …

Structural characteristic and formation mechanism of hemihydrate …

There are two significant differences between the gypsum structure and the prepared HH-CSW structure: one difference is that there are two H 2 O channels in the gypsum structure ... cost-effective transformation of FGD gypsum to calcium sulfate hemihydrate whiskers. Particuology, 54 (2021), pp. 173-180.

Formation of α-Hemihydrate Inside of a Gypsum Crystal …

Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world. During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are mixed with water to form dihydrate again. Therefore, the dehydration process of gypsum and the rehydration of hemihydrate were investigated. …

Microstructure and mechanical properties of β-hemihydrate …

1. Introduction. Gypsum (CaSO 4 ·2H 2 O, also known as dihydrate) plaster is one of the earliest building materials elaborated by mankind, and gypsum plasterboard is used widely as indoor building material because of its easy fabrication feature, environmental friendliness, fire resistance, aesthetics, low price, etc. The global …

The dihydrate‐hemihydrate transformation in gypsum

A microscope study has been made of the development of crystals of calcium sulphate hemihydrate produced on, or in, sheets of the dihydrate in the form of selenite by calcining under controlled conditions. The crystal forms were shown to be strongly dependent upon both temperature and ambient water vapour pressure. A mechanism for …

Gypsum hydration: a theoretical and experimental study

Calcium sulphate dihydrate (CaSO4·2H2O or gypsum) is used widely as building material because of its excellent fire resistance, aesthetics, and low price. Hemihydrate occurs …

Insight into the influences of β-hemihydrate and dihydrate gypsum …

It is still uncertain whether β-hemihydrate and dihydrate gypsum influence the properties, especially the phase conversion, of white calcium aluminate cement (CAC). ... with 4% β-hemihydrate exhibited a higher compressive strength at 28 days when compared to E1 and the mortar with 4% dihydrate. These differences may be …

ALPHA GYPSUM POWDER VS BETA GYPSUM …

2. With the continuous progress of hydration, β-type hemihydrate gypsum produces more and more colloidal particles of dihydrate gypsum. These particles are smaller than the original, have a large specific surface …

Effects of glutaric acid, tricarballylic acid and citric acid on …

GA has two carboxyl groups, while TA and CA have three carboxyl groups. The difference between TA and CA is that CA has one more hydroxyl group at the middle carbon atom than TA. α-HH gypsum has a hexagonal prismatic crystal form (Fig. 1 c), and in the absence of crystal modifiers, the crystal grows fastest along the c-axis [32].

Transformation of Flue-Gas-Desulfurization Gypsum to (α …

Thermodynamic analysis revealed that phase transformation of calcium sulfate dihydrate to α-calcium sulfate hemihydrate occurs because of the difference in solubilities between the two solid ...

Influencing the Morphology of Gypsum | SpringerLink

Gypsum is a well-known mineral that is obtained from natural resources or from technological processes. Gypsum (calcium sulfate dihydrate) is burned to calcium …

The α- and β-Forms of Calcium Sulphate Hemihydrate

Kelley, Southard and Anderson1 have shown that the thermodynamic properties of calcium sulphate hemihydrate depend on whether the hemihydrate is produced from gypsum calcined in a steam-saturated ...

Gypsum hydration: A theoretical and experimental study

According to the data obtained for β-hemihydrate binder with SP and lime has low deformations started with low shrinkage in the initial time up to 0.04 mm/m with subsequent expansion up to 0.17 ...

Gypsum vs. Anhydrite: What's the Difference?

Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, whereas anhydrite is its anhydrous form, lacking water in its structure. Key Differences Gypsum, a widely used mineral, is known for its softness and is composed of calcium sulfate dihydrate.

The study on the effect of flotation purification on the performance …

Phosphogypsum (PG) is a massive industrial solid waste. In this paper, PG was purified by flotation method, and α-hemihydrate gypsum (α-HH) was prepared by the autoclaving method. The morphology ...

Difference Between Gypsum and Anhydrite

Difference Between Gypsum and Anhydrite Gypsum vs Anhydrite Gypsum, also called hydrated calcium sulphate (CaSO4 · 2H2O) and anhydrite (CaSO4), also called hydrous calcium sulphate are the major minerals in the sedimentary rocks of rock gypsum and rock anhydrite respectively. Gypsum consists of calcium, sulfur and …

Understanding gypsum in 3 diagrams

Gypsum is one of the most widely-used building materials in the world. It is applied in several interior building uses, including in wallboard. Normally, calcium sulphate dihydrate (CaSO 4 •2H 2 O) is used as a raw material and a subhydrate such as …

Microstructure and mechanical properties of β-hemihydrate …

The gypsum in Fig. 9 a and b was prepared with a w 0 /h 0 of 0.65 and 0.80, respectively. It is clear that the crystals in Fig. 9 a are much tighter and homogeneous …

Formation of α-Hemihydrate Inside of a Gypsum Crystal …

Gypsum (calcium sulfate dihydrate) is one of the most used inorganic binding materials in the world. During calcination, calcium sulfate subhydrates are formed and, for technical reasons, are ...

What Is the Difference between Gypsum and Plaster of Paris?

The primary difference between gypsum and plaster of Paris lies in their chemical composition and their uses. Gypsum is a naturally occurring mineral composed primarily of calcium sulfate dihydrate (CaSO₄·2H₂O). It is a stable, solid material that is commonly used in construction and agriculture.

Materials | Free Full-Text | Experimental Study and …

Flue-gas desulphurization (FGD) gypsum is a highly prevalent industrial by-product worldwide, which can be an excellent alternative to natural gypsum due to its high content of CaSO4·2H2O. The preparation of α-calcium sulfate hemihydrate is a high-value pathway for the efficient use of FGD gypsum. Here, a dynamic method, or an improved …

Gypsum vs. Plaster of Paris

Attribute Gypsum Plaster of Paris; Chemical Formula: CaSO4·2H2O: CaSO4·0.5H2O: Appearance: White or colorless: White or off-white: Hardness: 2 on Mohs scale: 2 on Mohs scale

Reuse of phosphogypsum as hemihydrate gypsum: The

The results indicates that H3PO4 accelerated hemihydrate gypsum dissolution and dihydrate gypsum precipitation, which included route I, involving Ca²⁺ and SO4²⁻, and route II, involving ...

Hydration characteristics and mechanism analysis of β …

Natural fibrous gypsum is a kind of high-quality gypsum resources, whose high-value added utilization pathway is to be transformed to α-calcium sulfate hemihydrate (α-HH), a cementitious material that can react with water to form pastes with mechanical strength.In this work, α-HH was prepared from natural fibrous gypsum in KCl mediated …

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