Investigation on the hydration of hemihydrate phosphogypsum after …
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 …
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DM Exam 6 Flashcards
Study with Quizlet and memorize flashcards containing terms like Plaster is also known as Type _____, and Stone is known as Type _____ gypsum. III, II II, I I, II II, III, Which of the following will decrease the setting time of a gypsum product? Decreased mixing Higher water/powder ratio (thinner mix) Addition of a chemical accelerator (i.e., potassium) …
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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 …
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Hydration Mechanism and Hardening Property of …
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, …
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Effect of hemihydrate fraction within cement gypsum phase …
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 ...
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Innovative synthesis of high-strength α-hemihydrate gypsum…
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 …
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Synthesis and Characterisation of Hemihydrate Gypsum…
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, this fabricated material exhibited a significantly longer initial setting time and higher mechanical strength compared to α-HHG. The …
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Hydration Behavior of Portland Cements with Different Hemihydrate
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 ...
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Dental Materials Chapter 9 Flashcards
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 …
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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 ...
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Density and strength characteristics of ed gypsum
The necessary retarder ratio for ing these samples was determined to be 0.5% through the process of establishing the hardening time. This ratio is revealed to be 0.2% for the gypsum samples ed with sodium lauryl sulphate which is added to the mixing water of gypsum in the ratios varying between 0.1% and 0.4%.
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Hydration and condensation hardening of hemihydrate gypsum
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 …
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Indirect dental materials-Gypsum Products Flashcards
gypsum products are inexpensive mold-making materials that have been used in dentistry since the 1850s gypsum: found in nature in mineral and rock form mineral: ... when calcium sulfate hemihydrate is mixed with water (suitable proportions) it forms a. slurry or paste which sets to yield a rigid mass
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Microstructure and mechanical properties of β-hemihydrate …
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 …
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Synthesis and Characterisation of Hemihydrate Gypsum…
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, this fabricated material exhibited a significantly longer initial setting time and higher mechanical strength compared to α …
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Setting and Hardening of Gypsum-Portland Cement-Silica Fume Blends
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 …
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Gypsum (2) | PPT
(dihydrate) 40-45oc (hemihydrate) Gypsum Plaster or Stone 2. CaSo4.1/2H2o γ CaSo4 90-100oc (hexagonal anhydrite) [soluble form] 3. γ CaSo4 β CaSo4 300-400oc (orthorhombic anhydrite) [insoluble form] ... Material w/p ratio Comp strength Model plaster 0.45 12.5 0.50 11.0 0.55 9.0 Dental …
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Hydration reaction and microstructural characteristics of …
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 …
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Rapid hardening cement-gypsum composites for
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 …
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Effect of borax on the hydration and hardening of β …
As a society-owned publisher with a legacy of serving scientific communities, we are committed to offering a home to all scientifically valid and rigorously reviewed research. In
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a Type High-Strength Gypsum, Alpha Gypsum Powder
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.
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Effect of borax on the hydration and hardening of β-hemihydrate gypsum …
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.
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Effects of mortar ratio on the properties of super early strength …
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 …
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Microstructure and mechanical properties of β-hemihydrate …
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 ...
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Preparation of Medium–Low Strength Hemihydrate Gypsum …
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 …
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Effect of particle size distribution on the hydration and …
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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Dental Materials: Chapter 15 Gypsum Products Flashcards
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 ...
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Effect of the phosphogypsum calcination time on the …
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 …
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Gypsum hydration: a theoretical and experimental study
material because of its excellent fire resistance, aesthetics, and low price. Hemihydrate occurs in two formations of α- and β-type. Among them β-hemihydrate is mainly used to produce gypsum plasterboard since the hydration product of the α-hemihydrate is too brittle to be used as building material /10/. This article addresses the hydration of
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Hemihydrate
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 …
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