The hydration reaction of each major mineral compound found in Portland cement, C3S, C2S, C3A and C4AF, is considered. ... the curing temperature increasing from 5 °C to 30 °C is helpful to ...
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These heat evolution results show that the addition of gypsum could shorten the induction period and promote to a higher hydration rate in the acceleration …
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In Portland cement, the combined amount of C 3 A and gypsum is only approximately 10 %, and the amount of C 3 S is about 50–60 %. Limestone powder is a common inert material that replaces silicate phases and simulate their interactions without accounting for hydration [53, 54].Therefore, the C 3 A-gypsum-CaCO 3 powder was …
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Bicine can improve the hydration of C 3 S as its dosage is 0.02% in this process (see Fig. 4b). The third exothermic peak is related to the secondary hydration of C 3 A and the transformation of ettringite to AFm phase. When adding bicine, the relevant hydration process would be promoted.
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It corresponds to the reaction between C3A and gypsum, yielding a pour crystalline AFm-phase that coats the C3A particles that are quickly masked by needle-like ettringite precipitates (Geng et al ...
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The hydration process of RFSAC can be divided into three stages: the initial stage of hydration, the accelerated stage of hydration, and the stable stage of hydration. The influence of gypsum is mainly reflected in the last two stages, which are the change in the formation rate of hydration products and the change in morphology.
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Ultrasonic results indicate gypsum hydration reaction consists of two stages: the dissolution of hemihydrate in the first st age …
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It was seen that PCs mainly shortened the induction stage of C₃A-gypsum hydration, and the amount of remaining gypsum was related to the duration of the induction stage. The second heat flow peak of the sample with PCs was higher than that of the blank. Moreover, PC intercalation occurred during the hydration.
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Learn how gypsum, hemihydrate and anhydrite react with water and change their crystal structure and solubility. See thermal analysis, dilatometry and …
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The second stage corresponds to the induction period, followed by the acceleration period corresponding to the alite peak (Figure 5a), which occurs at 4-4.5 h for all LC 3 systems, with higher ...
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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 …
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Hydration of C 3 A–gypsum systems with different gypsum additions was investigated in terms of the phase assemblage, kinetics and microstructural …
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2.2. Characterization methods2.2.1. Hydration heat. A TAM IV isothermal micro-calorimeter was used to measure the hydration kinetics of C 3 A with setting at a constant temperature of 20 ± 0.1 °C. A water/C 3 A ratio of 3 was adopted for this study. The deionized water or 0.5 % TA solution was mixed within the ampule for 1 min, following by sealed and then …
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In addition to the cation exchange, the formation of cementitious hydration products such as (CSH) and (CAH) has also been reported in gypsum-treated clays (Latifi et al., 2018; Zha et al., 2021).The CSH and CAH can be produced through the pozzolanic reaction if the calcium from gypsum reacts with soluble alumina and silica from clay in …
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The primary function of gypsum is to control the reaction of tricalcium aluminate (C 3 A) [11]. Without adding gypsum, the direct reaction of C 3 A with water …
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The second stage is propelled by the strengthening of CSH bridges, while the third stage involves reinforced CSH bridges and increased particle packing. It should …
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Gypsum, from either nature or industrial by-products, can be a lower-cost and cleaner alternative binder to Portland cement used in construction projects, such as affordable housing in developing countries. Although various building products have successfully used gypsum as the binder, some drawbacks of this material have still …
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Hydration heat. Figure 2 describes the hydration heat of cement samples with 0%, 0.00125%, 0.00250%, and 0.00500% DNA, and w/c ratios of 0.3 and 0.5 at age of 3 d. In general, the hydration process of each sample can be classified into five stages: dissolution stage, induction stage, acceleration stage, deceleration stage, and slow …
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Two distinct exothermic peaks appear following a short induction period: the second peak at approximately 1.15 and 1.16 h, and the third peak around 3.7 and 4.1 h. ... Therefore, at this stage, gypsum has only a marginal impact on the hydration process. ... Hydration reactions and stages of clinker composed mainly of stoichiometric ye'elimite ...
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C 3 A is the fastest hydrated mineral in ordinary Portland cement. Fig. 2 shows the hydration heat of Portland cement slurry with and without alkanolamine. It can be seen that in the first few minutes, alkanolamine accelerated the hydration of C 3 A (peak 1). Yaphary et al. [37] attributed the enhanced hydration of C 3 A to the chelation …
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The exothermic rate of hydration increased significantly in the dissolution-crystallization stage, the main reaction formula in this stage was formula (2). (2) C a 2 + + S O 4 2-+ 2 H 2 O → C a S O 4 ∙ 2 H 2 O. The third stage was the equilibrium stage, Ca 2+ and SO 4 2− concentration no longer decrease and the α-HH was basically ...
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The reaction of C 3 A in the presence of gypsum can be divided into three stages, as depicted in Fig. 1 by the rate of heat evolution as function of hydration time. Stage 1 corresponds to the reaction between C 3 A and gypsum and in calorimetric measurements, it results in an initial dissolution peak followed by a stage of low heat …
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In the high-temperature and low water vapor pressure region, gypsum dehydrates to form γ-CaSO 4 in a single-step process (CaSO 4 ·2H 2 O → γ-CaSO 4); …
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Heat and rate of hydration are often reduced, and the duration of hydration is extended. • Cold weather construction may increase these effects. In mixtures using PLC, note the following: • Setting time may slightly increase. • The heat of hydration may be higher in the early stages of hydration but equal or lower at later stages of ...
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The hydration of the cement minerals C 3 S (3CaO·SiO 2), C 2 S (2CaO·SiO 2), C 3 A (3CaO·Al 2 O 3) and C 4 AF (4CaO·Al 2 O 3 ·Fe 2 O 3) is an exothermal chemical process.At early ages, the generated heat can be monitored by isothermal (conduction) calorimetry and five stages can be distinguished, as mentioned …
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Section snippets Kinetics model for hydration. To study the hydration kinetics of a calcination activated tailings-lime-gypsum ternary system, the hydration kinetics equation, which was used in the study related to the hydration reaction of the pozzolanic reaction of metakaolin [22],can be borrowed, as shown in Eq.
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In a recent study, Bullerjahn et al. [89] identified five stages for the hydration of pure C4A3$, which can be summarized as follows: stage I (initial period), stage II (dormant period), stage III ...
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The reaction time of each stage was shortened at elevated curing temperatures, thereby increasing the compressive strength of the material more quickly. ... The AUP with the highest activity index ...
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The results show that the hydration reaction between FGDG and OPC can be synergistic with each other, and C-A-H further generates AFt under the action of SO42−, and at the same time, it plays the role of alkali-salt joint excitation for FA–GGBS, generates a large amount of cementitious materials, fills up the pores of the gypsum crystal ...
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This indicates that the water released slowly by the biochar makes the hydration reaction more complete. The pre-soaked saturated biochar mortar has less water evaporation …
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It can be seen that gypsum does not participate in the hydration reaction in the early-ages and reduces the content of hydration products, which obviously inhibits the reaction progress of MOCP. On the other hand, for gypsum-modified MOCP, the main reason for its strength reduction is the reduction in hydration product (5-phase).
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In the presence of calcium sulfates, a rapid reaction of C 3 A, C$, and H 2 O to ettringite as the only stable hydration product during this stage of C 3 A hydration occurs initially [19, 29 ...
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According to Pourchet et al. [89] the type of sulfate can interfere with C 3 A hydration reactions. Hydration of C 3 A with gypsum carried out in a saturated solution of calcium hydroxide leads to the precipitation of hydroxy-AFm and ettringite, while hydration of C 3 A in the presence of hemihydrate prevents the more soluble hydroxy-AFm from ...
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Their experimental results reveal that gypsum dehydration proceeds through only a single CaSO 4 ·2H 2 O → γ-CaSO 4 step when the ambient water vapor pressure …
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Ultrasonic results indicate gypsum hydration reaction consists of two stages: the dissolution of hemihydrate in the first st age and the nucleation and precipitation of dihydrate in the second stage.
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Hydration of C 3 A–gypsum systems with different gypsum additions was investigated in terms of the phase assemblage, kinetics and microstructural development. The second stage of the reaction, which begins after the depletion of gypsum, was of particular interest. From in-situ X-ray diffraction results, it was seen that the dissolution …
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Influence of polycarboxylate superplasticizers (PCs) with different functional units on the hydration heat and hydration products of C3A-gypsum was investigated. Three kinds of PCs with different monomers were discussed. It was seen that PCs mainly shortened the induction stage of C3A-gypsum hydration, and the amount of …
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The reaction time of each stage was shortened at elevated curing temperatures, thereby increasing the compressive strength of the material more quickly. ... Through the analysis of properties, SS contains dicalcium silicate (C 2 S) and tricalcium silicate (C 3 S) that can undergo hydration reaction, which makes it have a certain self …
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Gypsum plays a crucial role in cement. Though it is used in a small quantity, in the range of 2.5-3.0 percent in terms of SO3, gypsum's role in cement is significant, more predominantly at early ages.
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