This way, James (1992) noted that in very hot climates gypsum can dehydrate to anhydrite when it is exposed at the surface, above 42 • C, or where high salinity is present. ...
The influences of aluminum sulfate (AS) introduction and dosage on setting time, hydration heat evolution, hydration product type and pore structure of Portland cement were studied, and the influence of AS on concrete strength was investigated also. The results indicate that AS can effectively accelerate setting time of Portland cement …
In this paper, we present our Hydration Control additive (HyCon® B) which fundamentally alters the hydration process by shifting the main reactions of C4AF and C3A before the …
For exploring the cause of this problem, the hydration characteristics of the tricalcium aluminate–anhydrite system in the saturated calcium hydroxide solution with and without CL were ...
1. Introduction. The addition of CaCO 3 and CaSO 4 to Portland cement clinker influences the setting behaviour, the progress of hydration and the strength …
five step mechanism of hydration via solution-precipitation: i) rapid initial partial dissolution of CaSO 4 and adsorption of hydrated Ca2+ and SO 4 2-ions at the surface of anhydrite; …
Here we show a hydration control additive that selectively modifies the hydration kinetics, thereby facilitating enhanced dissolution of aluminates (calcium …
The hydration of OPC can be divided into several stages based on the reactivity [12], most often analyzed based on the heat flow measured in isothermal heat flow calorimetry (Fig. 1).The stages of OPC hydration are frequently described as the initial period of fast reaction, which only lasts for several minutes (I), the induction period with …
It was found that pure syngenite promotes the hydration of anhydrite more strongly than equimolar amounts of K₂SO₄, leading to a high degree of hydration, reduced setting times, significantly increased compressive strength and overall improved …
We studied composite binders of hemihydrate or anhydrite and blast-furnace slag.. The main hydration products are gypsum, amorphous C–S–H and ettringite.. Gypsum from anhydrite is less porous than the gypsum matrix from the hemihydrate. • Excellent dimensional stability is observed when silica fume and fly ash are used.. …
Results illustrate that the hydration of prepared CSA cement is highly dependent on the curing regimes and anhydrite dosage. The addition of anhydrite …
anhydrite rocks, and forms along cracks and grain boundaries (Jaworska, 2012; Warren, 2016). Leininger et al. (1957) studied the effect of acids, bases, and salts, particularly alkali sulphates, and showed that cations serve as activators and accelerate the hydration of gypsum, whereas anions decelerate the reaction.
The influences of aluminum sulfate (AS) introduction and dosage on setting time, hydration heat evolution, hydration product type and pore structure of Portland cement were studied, and the influence of AS on concrete strength was investigated also. The results indicate that AS can effectively accelerate setting time of Portland cement …
The hydration of an anhydrite of gypsum (CaSO4.II) in a ball mill was studied as a function of time and temperature. The amount of gypsum formed at different intervals of time was determined by ...
Hydration characteristics and mechanical properties of calcium sulphoaluminate (CSA) cement with different contents of CaCO3 and gypsum under NaCl solutions were studied, using the testing methods of isothermal calorimetry, X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), linear shrinkage, and compressive strength. …
The hydration of an anhydrite of gypsum ... this process, known as setting, is very slow. The reactivity can be enhanced considerably by grinding the anhydrite to fine powders and also adding certain activators. ... and accelerate the hydration process of fluorogypsum. The optimum contents of K 2 CO 3 and KHCO 3 were found to be 1% …
As a hydration proceeds, the C 3 S particles shrink and are replaced by a layer of inner hydration product and the product layer thickness buildup leading to a …
The influence of sodium sulfate on the anhydrite hydration process and the crystal morphology of its dihydrate products were studied by the determination of the hydration rate, hydration temperature and the ion concentration in liquid phase, in combina-tion with the investigation of the microstructure of the hardened anhydrite paste. Moreover, the …
In this article the progress of the research on cement hydration mechanisms is critically reviewed, starting with the work of Le Chatelier and Michaelis during the late nineteenth century. Proposed mechanisms are discussed in the light of experimental data to highlight the role of new or improved analytical techniques. The focus of this article lies …
Effect of CL on SO 4 2 − concentration during the hydration of the C 3 A–anhydrite system is shown in Fig. 2.SO 4 2 − concentration in the liquid phase without CL increases obviously with the increase of hydration time from 1 min to 30 min, and then gradually decreases. This result suggests that the amount of SO 4 2 − generated from …
Hydration characteristics and mechanical properties of calcium sulphoaluminate (CSA) cement with different contents of CaCO 3 and gypsum under NaCl solutions were studied, using the testing methods of isothermal calorimetry, X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), linear shrinkage, and compressive strength. …
The hydration properties of hemihydrate gypsum and anhydrite affect the quality of MPPG-based materials. Anhydrite has a much slower hydration rate and strength development than hemihydrate gypsum, and is commonly blended with cement, strong alkali or alkali sulfate to increase its hydration activity [15–17].
At the same time, anhydrite will combine with Al 2 O 3 in slag to form ettringite [11] and CSH [12] to improve hydration and hardening characteristics of anhydrite-based cementitious material. International researchers have previously conducted on the relationship model between pore structure and compressive strength, …
The cement clinker was homogenized with 15 wt% of ground limestone and different quantities of natural anhydrite (2.5, 3.5 and 4.5 wt%) to give Portland ... of very fine seedings was observed, capturing 7.09 wt% CO 2 of the total cement used. These seedings also acted as nucleation sites to accelerate further cement hydration, which …
The addition of Na2C2O4 increased the hydration rate of anhydrite, concentrated the hydration heat, shortened the hydration latency period, and accelerated the hydration process, accordingly ...
Wolf et al. [41] found that when the lithium carbonate content is less than 0.45 wt.% of the cement, the total hydration heat released from ternary CSA-OPC-anhydrite mixtures can be improved in ...
The lower peak of the acceleration zone in SCC-7.5% indicates a lower hydration reaction of C 3 S, less calcium silicate hydrate phase formation, and a lower strength gain than SCC-0%.
Abstract The influences of aluminum sulfate (AS) introduction and dosage on setting time, hydration heat evolution, hydration product type and pore structure of Portland cement were studied, and the influence of AS on concrete strength was investigated also. The results indicate that AS can effectively accelerate setting time of …
The mechanisms governing the hydration of calcium silicate are usually discussed in terms of the heat evolution curve, Fig. 1.Although this curve has been divided into up to 7 regions, it is more straightforward to discuss 3 periods: I - up to the end of the induction period; II - the main hydration peak; III - hydration after the main peak.
The hydration of belite in CSAB cement usually is very slow, most often occurring after 28 days, and it contributes to long-term properties [18]. ... differences from the way they inhibit cement ...
