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 …
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 …
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 …
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.
The mixture then sent to final grinding process. For ordinary Portland cement it remains between 3 to 4% and in case of Quick setting cement it can be reduced up to 2.5%. Role of Gypsum in Cement The main purpose of adding gypsum in the cement is to slow down the hydration process of cement once it is mixed with water.
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 …
After the induction period, the behavior changes and gypsum enhance the C 3 S hydration [6,8,18,19,[51][52][53][54][55] [56] [57]; see Fig. 4. Yamashita et al. [58] have observed that increasing ...
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 …
In this stage, reactions including Eq. (1), Eq. (3) and Eq. (4) may take place. It may also include the transformation of AFt that is achieved from early stage hydration to AFm as in Eq. (6) [10]. This stage is highly correlated with the setting and hardening of CSA cement [5]. The heat flow slows down thereafter after 150 min.
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 ...
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 …
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 …
Ultrasonic results indicate gypsum hydration reaction consists of two stages: the dissolution of hemihydrate in the first st age …
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 ...
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.
Fig. 1 displays the concrete samples' evolution rate and cumulative heat of hydration over the first 10 days of ageing. Fig. 1 illustrates how each sample's hydration heat may be broken down into five stages: diffusion, induction, acceleration, deceleration, and dissolution. These findings are in line with earlier studies' findings [31], [32].The cement …
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.
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 ...
Gypsum is one of the most important minerals on earth, and its dehydration product, plaster of paris, is mainly used as a building material. Furthermore, there are abundant deposits of gypsum mineral in nature; moreover, recent studies have indicated that Mars also has an abundance of gypsum mineral as well as other mineral calcium …
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 ...
Hydration of C 3 A–gypsum systems with different gypsum additions was investigated in terms of the phase assemblage, kinetics and microstructural …
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); …
In a recent study, Bullerjahn et al. [89] identified five stages for the hydration of pure C4A3$, which can be summarized as follows: stage I (initial period), stage II (dormant period), stage III ...
In addition to the cation exchange, the formation of cementitious hydration products such as (CSH) and (CAH) has also been reported in gypsum-treated clays (Latifi et al., 2018; Zha et al., 2021).The CSH and CAH can be produced through the pozzolanic reaction if the calcium from gypsum reacts with soluble alumina and silica from clay in …
The primary function of gypsum is to control the reaction of tricalcium aluminate (C 3 A) [11]. Without adding gypsum, the direct reaction of C 3 A with water …
The second stage corresponds to the induction period, followed by the acceleration period corresponding to the alite peak (Figure 5a), which occurs at 4-4.5 h for all LC 3 systems, with higher ...
In Portland cement, the combined amount of C 3 A and gypsum is only approximately 10 %, and the amount of C 3 S is about 50–60 %. Limestone powder is a common inert material that replaces silicate phases and simulate their interactions without accounting for hydration [53, 54].Therefore, the C 3 A-gypsum-CaCO 3 powder was …
The reaction time of each stage was shortened at elevated curing temperatures, thereby increasing the compressive strength of the material more quickly. ... Through the analysis of properties, SS contains dicalcium silicate (C 2 S) and tricalcium silicate (C 3 S) that can undergo hydration reaction, which makes it have a certain self …
The results show that the hydration reaction between FGDG and OPC can be synergistic with each other, and C-A-H further generates AFt under the action of SO42−, and at the same time, it plays the role of alkali-salt joint excitation for FA–GGBS, generates a large amount of cementitious materials, fills up the pores of the gypsum crystal ...
In the presence of calcium sulfates, a rapid reaction of C 3 A, C$, and H 2 O to ettringite as the only stable hydration product during this stage of C 3 A hydration occurs initially [19, 29 ...
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 ...
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.
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 …
The second one is an intense exothermic peak (with a maximum centered in the very first minutes) attributable to the initial hydration reactions involving C 3 S, C 3 A, and gypsum (Figure 5, step 2). The third one corresponds to the induction (dormant) period, and it is associated with a minimum of the heat of hydration ( Figure 5, step 3).
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.
Learn how gypsum, hemihydrate and anhydrite react with water and change their crystal structure and solubility. See thermal analysis, dilatometry and …