Sustainability of gypsum products as a construction material. N. Lushnikova, L. Dvorkin, in Sustainability of Construction Materials (Second Edition), 2016 β-Hemihydrate binder. β-Hemihydrate (also known as plaster of Paris) is the most commonly used gypsum binder in construction.It is produced in an apparatus connected to air. Different equipment is …

Rapid hardening cement-gypsum composites for shotcreting on the base of Bulgarian raw ... hemihydrate gypsum and water in the presence of active mineral additives. This point of view can be summarized below. ... quantities. Besides, the price of that type of zeolite is considerably lower in Bulgaria. Table 6 Zeolite-Cement Ratio in …

Phosphogypsum (PG) which is a waste byproduct of fertilizer production is the promising source of the gypsum industry. In order to explore the application of hemihydrate PG (HPG) as a substitute of hemihydrate gypsum, the setting and hardening characters of HPG plaster at different pH after neutralization were examined …

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High-strength gypsum is the recognized designation for α-hemihydrate gypsum, often referred to as α-HH (CaSO 4 ·0.5H 2 O), which is a cementitious material with low water requirement and high strength [8].The strength of α-HH is generally between 25 and 50 N/mm 2, which is three times that of ordinary building plaster, and …

There are three steps in the hydration of paste: the dissolution of hemihydrate (CaSO 4 ·1/2H 2 O) leading to a supersaturated solution regarding gypsum, nucleation, and growth of gypsum crystals and a solid material is finally formed by the interlocking of gypsum crystals with complete consumption of hemihydrate. SL has a …

When compared with the PPSS, the SPMS had a lower water content and a higher dry density at the same water/gypsum ratios. When the water/gypsum ratio was low (e.g., 0.30), the SPMS exhibited more ...

The crystallization kinetics of gypsum from a dense suspension of calcium sulfate hemihydrate (weight ratio water/hemihydrate = 20) are followed by a conductimetric method. All …

Study with Quizlet and memorize flashcards containing terms like The desirable strength of gypsum materials is ___ related to the amount of water used. a) Directly (b)Indirectly (c)Not (d)Partially, for gypsum products, a suitable accelerator and retarder, respectively would be: a) ethyl alcohol and oleic acid (b)oleic acid and glycerin (c) borax and potassium …

In the meantime, the picture was filled with the poor crystal of tiny size irrespective of the much smaller scale at pH 11.08 after 2 h hydration, and it was a …

The difference between the initial and final setting times also increased, and the fluidity of the gypsum slurry was improved. When the borax dosage reached 0.5%, the flexural strength of β -hemihydrate flue-gas desulfurization gypsum ( β -HFGD) increased from 5.2 to 6.3 MPa and the compressive strength increased from 4.7 to 9.3 MPa after 28 d.

This work systematically investigates the effects of coarse aggregate (CA) type, dosage, and slurry concentration on the backfill slurry's setting, bleeding, and hardening strength properties.

The main components of building gypsum and high-strength gypsum are β-type hemihydrate gypsum and α-type hemihydrate gypsum, which are mixed with water; semi-water gypsum will be rehydrated to form dihydrate gypsum, which will release heat and solidify into a certain strength. Hardened body. The hemihydrate gypsum is first …

High-strength gypsum is the recognized designation for α-hemihydrate gypsum, often referred to as α-HH (CaSO 4 ·0.5H 2 O), which is a cementitious …

Two types of hemihydrate gypsum materials exist: α-type hemihydrate gypsum and β-type hemihydrate gypsum. The α-type hemihydrate gypsum is formed through the heating of dihydrate gypsum under pressurized steam or in acid or salt solution, which are both complicated processes . The β-type hemihydrate gypsum is formed through the …

Hydration of hemihydrate is a highly exothermic reaction and occurs as: CaSO 4 · 0.5 H 2 O + 1.5 H 2 O ⇒ CaSO 4 · 2 H 2 O + Q where Q the amount of heat …

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, …

Chemically, the mineral gypsum is a hemihydrate of calcium carbonate. b. To form the raw material into a powder, the manufacturer heats it and adds water. ... Dental stone, high strength (Type IV), b-Hemihydrate is commonly used for: a. diagnostic models b. working casts c. die stone d. dental investment and more. ... Model plaster has a water ...

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 …

The Portland cement was ASTM type I, having a standard compressive strength of 30 MPa and a specific mass of 3100 kg/m 3 (a product of Nesher Industries, Israel). The calcium sulfate hemihydrate was of the β-type, 93% pure, produced by Gesher Gypsum Works, Israel. The silica fume was of 18.2 m 2 /g specific surface area, with …

This study used a powder-to-water ratio of 2:1 following the Type II dental gypsum ratio. SIRIUS ® gypsum manufacturer recommends a 3:1 powder-to-water ratio, which is a type III gypsum ratio. 10 SIRIUS® gypsum is thought to be an Orthodontic plaster containing type II gypsum and type III gypsum. 19 Α-hemihydrate particles …

When compared with the PPSS, the SPMS had a lower water content and a higher dry density at the same water/gypsum ratios. When the water/gypsum ratio …

Mixtures with hemihydrate form more ettringite in the first hours, increasing the sulfate consumption and anticipating sulfate depletion [6,25, 97].Thus, from these observations, it is expected ...

The use of hemihydrate, which has a higher solubility than gypsum, increases the amount of sulfate on the solution and changes the ettringite morphology from spherical or stubby rod to elongated ...

Super early strength grouting materials, prepared by ternary complex system of sulphoaluminate cement, aluminate cement and gypsum with high mortar ratio, have the performance of high early strength. 2 h compressive strength of the sample produced with mortar ratio of 1.91 can reach 42.6 MPa, and 3 d compressive strength …

This study explored the production of a medium–low strength α-hemihydrate gypsum (α-HH) from phosphogypsum using an autoclaved method. The influence of slurry concentration, spreading thickness, crystallizing agents, slurry pH, autoclaving …

This study combined inorganic α-hemihydrate gypsum (α-HHG) with organic polyacrylamide (PAM) hydrogel to create a novel α-HHG/PAM composite material. Through this facile composite strategy, …

The difference between the initial and final setting times also increased, and the fluidity of the gypsum slurry was improved. When the borax dosage reached 0.5%, the flexural strength of β-hemihydrate flue-gas desulfurization gypsum (β-HFGD) increased from 5.2 to 6.3 MPa and the compressive strength increased from 4.7 to 9.3 MPa after 28 d.

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 …

High strength gypsum is a kind of gypsum with high strength. Dihydrate gypsum is evaporated under 1.3 atmospheric pressure and saturated water vapor at 124 ° C α High strength gypsum powder is obtained by grinding type hemihydrate gypsum. High strength gypsum: 1. Suitable for high-strength plastering engineering.