This review paper begins with a brief introduction to the basic characteristics and industrial status of gypsum. Then the types of gypsum retarders and their retarding features on gypsum including setting time, mechanical strength, crystal morphology and other performances are reviewed in detail. ... the retardation mechanisms of various ...
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THE initial thickening of slurries of hemi-hydrate type gypsum plasters has been considered by many workers to be due to a colloidal mechanism, whereas the further hardening and final setting have always been attributed to a crystallization process. Recent work supporting the colloidal theory is that of Fischer1, while still later Becherer and Fiedler2 have attributed the initial …
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However, the setting and hardening characteristics of the building gypsum are also affected to some extent by the composition, the time of delivery and the dampness of storage of the gypsum. The initial setting time of some gypsum is less than 5 min, and the final setting time of hemihydrate gypsum is just (6～30) minutes, operating time of ...
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Gypsum plasters were found to set in three stages: formation of the calcium sulphate dihydrate crystal matrix followed by relief of internal stress, and finally evaporation of …
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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 and contrasted with hemihydrate flue …
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Desulfurized building gypsum (DBG) has great application potential and can be used to produce lightweight plastering gypsum (LPG). In this work, DBG was modified by adding different proportions of sawdust, retarder, and hydroxypropyl methylcellulose (HPMC) water-retaining agent to prepare LPG. When the sawdust content is greater than 9% and less than …
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The effects of different dosages of gypsum on the hydration and hardening properties of AMCSA, such as setting time, hydration rate, compressive strength and hydration products, were studied. The results show that the mineral content of ye'elimite, C 2 S, C 3 S and iron phase in the calcined AMCSA clinker are 48.5 wt.%, 32.6 wt.%, 11.7 wt ...
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Samples are performed in rubber cone-shape molds of 40 mm of height and inner diameters of 65 and 75 mm. Setting times can be calculated with Equation (2) where T i is the setting time of the gypsum in min, t 1 is the time in minutes when Vicat Needle achieves 22 ± 2 mm of depth and t 0 is the time in minutes when water and gypsum are in ...
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It is shown that molasses solutions can be used to control the hardening time of the gypsum paste. DOI: 10.1134/S107042721306027X Gypsum plaster belongs to rapidly hardening air-setting binders. The hardening of a gypsum paste begins already in 3–5 min after its tempering with water. The gypsum setting time (GST) largely depends on the start-
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This research offers the mechanism of un hydration hardening of monomineral bindings, including gypsum. The mechanism is based on interaction of particles of the different size in the...
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This research offers the mechanism of un hydration hardening of monomineral bindings, including gypsum. The mechanism is based on interaction of particles of the different size in the …
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Difference between setting and hardening cement. Setting implies stiffening of the cement paste from fluid to a rigid form of material. In this process, the concrete cement gets its shape depending on the support inside, which converts from the plastic state to the amorphous form. During the setting stage, in case the external support that helps it stays in that position is …
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To further explore the strain hardening and water resistance mechanism, a series of analysis, including fiber-gypsum matrix interface bonding behavior, matrix fracture toughness and fiber bridging relationship, were made to investigate the properties of gypsum-based composites at microscopic, mesoscopic and macroscopic levels.
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Fresh state properties of gypsum include properties in fresh state (in liquid form) and during the hardening process so properties in fresh state define the workability of the material: setting …
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Effect of sodium gluconate addition on setting, hardening, and microstructure behaviour of hybrid alkaline mortar ... sodium gluconate forms complexes with dissolved Ca 2+ ions that assists in the formation of ettringite in the presence of gypsum present in OPC, thereby reducing Ca 2+ ion concentration. Further, ... Mechanism and environmental ...
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High-water rapid-setting material is a type of cement-based material, which is high water contained, rapid hardening and has early strength. Hydrating and hardening mechanism of this material have been studied by XRD and SEM, the influence of different curing time, gypsum lime content and water-cement ratio on the hydrating and hardening process was explored. The …
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The setting and hardening of cement is due to the formation of inter locking crystals reinforced by rigid gels formed by the hydration and hydrolysis of the constitutional compounds. Reactions involved in setting and hardening of cement:- When cement is mixed with water, the paste becomes rigid within a short time which is known as initial setting.
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A 4" long 1" diameter test bar is heated to austenitizing temperature. It Is then cooled with water at 75°F from the bottom. The nozzle for the water must be 0.5" inside diameter, the flow rate should produce a 2.5" vertical fountain the gap between the nozzle and specimen must be 0.5".
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Gypsum has been known to regulate cement setting since more than 100 years, whereas the understanding of the physio-chemical mechanism remains incomplete. Here, we investigated the influence of gypsum on elasticity evolution of fresh tricalcium silicate (C 3 S) paste through small amplitude oscillation shear method.
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The setting and hardening of building gypsum occur because water and semi-hydrate gypsum react mutually and then restore to dihydrate gypsum: CaSO 4 · 1 2 H 2 O + 1 1 2 H 2 O = …
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The setting process of gypsum plasters has been followed using strength testing, acoustic techniques and scanning electron microscopy. Gypsum plasters were found to set in three stages: formation of the calcium sulphate dihydrate crystal matrix followed by relief of internal stress, and finally evaporation of excess water. The α-calcium sulphate hemihydrate …
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Calcium sulphoaluminate cement (CSA) is considered a sustainable alternative to traditional Portland cement to reduce CO 2 emissions. To further improve the hardening properties and water resistance of CSA and advance its extensive special engineering application, nanoparticles including nano-SiO 2 (NS), nano-MgO (NM) and nano-Al 2 O 3 (NA) were used …
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B: The mechanism of cement hydration according to Michaëlis: After the dissolution of clinker and gypsum, crystalline calcium sulphoaluminate needles are formed from tricalcium aluminate and ...
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3. Key words : Gypsum : Calcium sulfate dihydrate ( CaSO4.2H2O) Models : A study purpose cast which has a positive likeness of an oral cavity or any other object Cast: Positive replica of on oral cavity or any …
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Due to the breadth of the question, some explanations will be necessarily brief. 1. Setting and Hardening of Cement: Step 1: Initial Setting. Cement particles react with water (hydration), forming calcium silicate hydrate (C-S-H) gel, the main binding agent. ... Compare the setting and hardening action of gypsum plaster with that of Portland ...
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Retarding action of various chemicals on setting and hardening characteristics of gypsum plaster at different pH. ... Introduction Gypsum is one of the oldest and most versatile building materials known. Gypsum is used in the manufacture of variety of plasters mainly hemihydrate, anhydrite, light weight premixed compositions etc. for use in ...
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Setting expansion of Gypsum - Download as a PDF or view online for free ... Setting expansion Mechanism Types (Linear and Hygroscopic) ... The dimensional increase that occurs concurrent with the hardening of various materials, such as plaster of paris, dental stone, die stone, and dental casting investment 8.
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The retardation mechanism of gypsum is: when cement is hydrated, gypsum reacts with C3A quickly to generate calcium sulfoaluminate hydrate which deposits and forms a protection film on the cement particles to hinder the hydration of C3A and delay the setting time of cement. ... Thus, the hydration will be quick, the setting and hardening will ...
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Tricalcium silicate (C 3 S) is the main phase in PC clinker. It is generally accepted that the hydration of C 3 S is responsible for the short-term properties of cement paste, including setting [11], [20], [21].The attraction between calcium silicate hydrates (C-S-H) is the key to the cohesion of early cement paste [21], [22], [23].Roussel et al. [4], [24] suggested that the …
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The setting times of the 0 % MK, 10 % MK, 20 % MK, and 30 % MK mixtures were about 387 s, 225 s, 240 s, and 300 s, respectively, at M/P = 4. The setting times of the MKPC mixtures with M/P = 6 were about 225 s, 148 s, 200 s and 200 s at otherwise identical settings. This is different from the findings of the studies mentioned above.
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