Calcium Aluminate Hydrate Research Articles

Macro–micro investigation on stabilization sludge as subgrade filler by the ternary blending of steel slag and fly ash and calcium carbide residue

This study investigates the efficacious utilization of sludge as a subgrade filler through in-situ shallow stabilization, employing cementitious industrial waste materials including steel slag (SS), fly ash (FA), and calcium carbide residue (CCR) as binding agents. The primary emphasis lies in the evaluation of the macro unconfined compression strength of stabilized sludge over a seven-day curing period, facilitated by a quadratic polynomial response surface model to determine the optimal composite stabilizer (WZ01) proportions. Furthermore, an array of meticulous microstructural analyses encompassing X-ray diffraction, X-ray fluorescence, scanning electron microscopy, and energy-dispersive spectroscopy were undertaken to elucidate the development of internal cementitious products and the intrinsic mechanisms underpinning sludge stabilization in tandem with WZ01. The findings ascertain that the optimum WZ01 composition stands at SS: FA: CCR = 32:28:40. Prominent mineralogical constituents within the stabilized sludge encompass amorphous calcium silicate hydrate, calcium aluminate hydrate, and crystalline ettringite. The amelioration in stabilized sludge properties stems from intricate processes involving ion exchange, hydration reactions, and pozzolanic activities. Significantly, the WZ01 curing agent demonstrates heightened cost-effectiveness and environmental merits compared to conventional Portland cement.

Ceramic-added lime and cement mortars: A review of applications in building products.

Ceramic-added air lime mortars have been used since ancient times owing to the pozzolanic effect provided by crushed ceramic particles that impart hydraulic properties. This work reviews the historical use, composition, reaction mechanisms, characterization techniques, and performance properties of ceramic-added air lime mortars. The fine ceramic powder composed of silica and alumina phases reacts with calcium hydroxide released during lime hydration to form calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH) via pozzolanic reaction. This provides hydraulicity and reduces setting time compared to pure air lime mortars. The coarser ceramic particles also serve as aggregate and refine the microstructure as filler. The reactivity depends on the ceramic composition, amorphous phase content, particle size distribution, and firing temperature. Optimal proportioning of the fine ceramic powder and coarse ceramic aggregate is necessary to achieve desired properties. Ceramic addition enhances the durability of air lime mortars against weathering while maintaining compatibility with lime-based masonry structures. Key novelties of this review include: (i) in-depth analysis of the influence of ceramic characteristics (mineralogy, particle size, pozzolanicity) and processing on reaction kinetics and phase evolution; (ii) systematic assessment of mechanical, physical and durability properties in comparison to conventional air lime mortars and cement-based grouts; (iii) elucidation of microstructural mechanisms governing performance using advanced characterization techniques; (iv) critical appraisal of test methods and standards for evaluation; and (v) rigorous discussion on potential applications in construction, conservation and repair, with case studies.

THE IMPACT OF THE C12A7/CA RATIO AND THE FLUORIDE CaF2 AND AlF3 ON THE PROCESS OF HYDRATION AND HARDENING OF ALUMINA CEMENT

The effect of the ratio CaO.Al2O3/12CaO.7Al2O3, AlF3 and CaF2 on the formation of the structure and phase composition of clinker minerals of aluminate cement during hydration has been studied. It is found that after 24 hours of hydration, the main hydraulic phases in the studied cement stones are CAH10, C2AH8, AH3. It has been shown that the introduction of AlF3 and CaF2 fluorides reduces the liquidus temperature of the systems and increases the rate of CA formation. Scanning electron microscopy has revealed that the process of hydration of calcium aluminates of cement at low temperatures can be considered as simultaneous reactions.

Experimental study of the mechanical and thermal properties of metakaolin based geopolymer stabilized soil during low temperature curing

To address the challenges associated with significant thermal disturbance and carbon emissions resulting from the conventional stabilization of frozen soil using cement, geopolymer material is used to replace cement to stabilize frozen soil. The unconfined compressive strength (UCS) of the geopolymer stabilized soil was investigated in relation to the proportions of metakaolin (MK), calcium carbide slag (CCS), curing temperature, and curing age. Microscopic analysis was conducted to unveil the stabilized mechanism. The UCS, shear strength, thermal conductivity, hydration products and microstructure of geopolymer stabilized soil and cement soil were compared in parallel. A total of 240 experiments were conducted in this study. The outcomes indicate that the optimal content of MK and CCS is 10% and 6% respectively. The UCS of samples with the optimal content after 28d of curing at 20 °C, −2 °C, and − 10 °C are 3.783 MPa, 1.164 MPa, and 0.901 MPa respectively. The primary causes of the rise in UCS of the geopolymer stabilized soil are the production of amorphous calcium silicate hydrate and calcium aluminate hydrate gel as a result of the stimulation of MK based geopolymer with CCS. The UCS of the geopolymer stabilized soil decreases with a decrease in curing temperature. In frozen conditions, the expansion of ice crystals in the soil creates voids and promotes crack growth, leading to a decrease in the efficiency of geopolymerization reactions. After 28d of curing at room temperature and low temperature, the geopolymer stabilized soil with the optimal content exhibits higher UCS, failure strain, shear strength, cohesion, and internal friction angle compared to the cement soil. At all curing temperatures and ages, the geopolymer stabilized soil has a lower thermal conductivity than the cement soil. The geopolymer stabilized soil is less susceptible to low temperature curing than cement soil, demonstrating a larger amount of hydration products and a denser microstructure, according to experimental results from XRD and SEM. The results of this work offer a theoretical foundation for using geopolymer in place of cement to stabilize soils in permafrost regions.

Chloride binding mechanism and free chloride reduction method of alkali-activated slag/fly ash mixed with seawater

The chloride binding mechanism of alkali-activated materials (AAM) under various granulated blast furnace slag (GBFS)/fly ash (FA) ratios is investigated in this work. Two types of layered double hydroxides (LDH), i.e., MgAl-LDH and CaAl-LDH, and active magnesium oxide (MgO) were added to reduce the concentration of free chloride in AAM. The results demonstrate that the ratio of GBFS to FA has non-negligible influence on the AAM’s ability to bind chloride. The content of bound chloride increased by 3.78%-17.42% as the FA content in seawater-based alkali-activated materials (SAAM) raised. The chloride binding forms of SAAM were mainly chemical binding by the hydrated calcium aluminate (AFm) phase and physical adsorption by calcium (alumino) silicate hydration (C-(A)-S-H) gels when the FA dosage is less than 20% in SAAM. When the FA mass ratio in SAAM was larger than 20%, the chloride binding form of SAAM was mainly the physical adsorption by calcium (sodium)alumino-silicatehydrate ((C,N)-A-S-H) gels. Among the three additive materials, CaAl-LDH was the most effective in reducing the free chlorine content by 11.34%. While for MgAl-LDH, the chloride binding capacity was compromised by the less strength loss. In this work, seawater was used as the mixing water to introduce chloride ions, the results of which could provide a reference for the application of seawater in future projects.

Effect of Hydrated Calcium Aluminate Cement on the Chloride Immobilization of Portland Cement Paste

Effect of Hydrated Calcium Aluminate Cement on the Chloride Immobilization of Portland Cement Paste

Electro-cementation of calcareous sand using colloidal silica (CS) nanoparticles and alumina powder

The research investigates the effectiveness of a ground improvement technique that involves the electro-cementation of an onshore calcareous sand containing 95.3% calcium carbonate through a series of laboratory experiments. Colloidal silica (CS) nanoparticles and alumina powder were introduced as pozzolanic materials in the sand, and a direct current (DC) was passed through the sand-silica-alumina mix inside an electrokinetic (EK) cell. The method resulted in the electro-cementation of the calcareous sand through the formation of calcium silicate hydrates (C–S–Hs) and calcium aluminate hydrates (C–A–Hs) as products of the pozzolanic reactions between Ca(OH)2, SiO2 and Al2O3 after electrolysis occurred. Iron-rich cements were also formed by the degradation of anodes. These newly formed compounds changed the nature of the treated soil from a granular material into a rock. Results show that the compressive strength of the resulting rock formation is significantly improved. The treatment can be considered as an artificial lithification process through which the nature of the treated soil was changed from a granular material into a rock formation. The electro-cementation achieved by the treatment was further assessed by spectroscopic analyses including FE-SEM, EDX and XRD, which confirmed the formation of cementing agents within the structure of the treated sand. Potential applications of the technique include caissons, highway construction projects, dune fixation and erosion control, in addition to liquefaction mitigation due to electrolysis of pore water and plugging the pores with cementitious materials.

Complex Effect of Portland Cement Modified with Natural Zeolite and Ground Glass Mixture on Durability Properties of Concrete

This article analyses the combined effect of a mixture of natural zeolite and ground soda lime silicate glass on the durability properties of concrete. The specimens were prepared by replacing 25% of the cement with a mixture of zeolite and glass at different proportions with zeolite particles of two different sizes and cured for 28 and 90 days. Chloride migration, the depth of water penetration under pressure, and freeze–thaw cycle tests were performed, and compressive strength was determined. The combined effect of the mixture on the composition and microstructure of the cement matrix was studied by analysing the results of XRD, TGA, SEM-BSE, and porosity tests. The test results showed that irrespective of the cement “dilution” effect, the mixture of additives had a beneficial combined effect: increased durability of concrete, a denser structure of the cement matrix, the formation of calcium aluminate hydrates, faster rate, and higher degree of hydration.

Multi-Response Optimization on Hydrated Calcium Aluminate Rich Ternary Binders Using Taguchi Design of Experiments and Principal Component Analysis

This study investigates the influence of various factors on the performance of ternary binders, utilizing statistical approaches. The research focuses on the influence of varying compositions of Portland Cement-Calcium Aluminate Cement-Calcium Sulphate (PC-CAC-CŜ), types and amounts of mineral powders, and chemical admixtures in ternary binders. Using the Taguchi design, the study required a limited number of experimental trials, utilizing a standard orthogonal array of seven factors across three levels. These factors encompassed binder composition (C1-C2-C3), mineral powder types (limestone, quartz, slag), replacement ratio (0%, 25%, 50%), retarder (0%, 0.1%, 0.2%), superplasticizer, viscosity modifying agent (stabilizer) and accelerator (0%, 0.05%, 0.1%). Measurements on hydration kinetics, dimensional stability, compressive strength, and microstructural analyses like X-ray diffraction were conducted. Principal Component Analysis (PCA) was employed to interpret the continuous data derived from heat of hydration curves, length change curves and X-ray diffraction (XRD) patterns. Results indicated that retarder quantity and binder type significantly impacted paste workability. Higher powder content led to reduced strength, whereas increased accelerator improved strength. A strong correlation was observed between accelerator content and the dimensional stability. The primary hydration product’s formation was predominantly influenced by the PC-CAC-CŜ ratio, accelerator, and cement substitutions.

Effects of Fly Ash Composition to Mitigate Conversion of Calcium Aluminate Cement Composites

Calcium aluminate cement (CAC) is one of the alternative cements that is widely used for special applications. However, during the hydration process degradation of CAC microstructure, the so-called hydrate conversion process, hexagonal calcium aluminate hydrate (CAH10) transforms into a cubic (C3AH6) phase, resulting in increased porosity and reduced strengths. It is known that alternative means for stabilizing the CAC conversion are conducted by introducing fly ash (FA) in CAC, where its microstructure is attributed to aluminosilicates. However, no study has yet been conducted on different FA compositions influencing CAC performance. This study aims to evaluate the effects of different compositions of FA on CACs’ fresh and hardened characteristics. Results revealed that the microstructure was denser when CAC was mixed with FA. Regarding reactivity, CAC with calcium-rich FA systems is 13% faster than the silica-rich one. The higher the density and the lower the porosity of calcium-rich FA mixtures were found compared with silica-rich FA in both micro- and macro-structures. As seen in the microscopic structure, this is due to the calcium-rich phase formation.

Experimental study of mixtures soil-industrial waste using simplex design for application in paving

The large amount of solid waste generated by industry is a concern for society. A possible solution is to incorporate these wastes into soils to improve their properties and contribute to sustainable development. The objective of this research was to conduct an experimental study on the chemical stabilization of two samples of tropical soils using two industrial wastes, electric arc furnace slag (EAFS) and fly ash (FA), using a design of experiments (DoE) of mixtures in a simplex centroid network. Seven mixtures were determined from the DoE for each soil sample. Using specimens of these mixes prepared at optimum moisture content, after a curing period of 7 days in a humid chamber, the properties were evaluated: unconfined compressive strength (UCS), California Bearing Ratio (CBR), and resilient modulus (RM). An improvement in the evaluated mechanical properties was observed with the addition of waste, especially with the addition of EAFS. The statistical software Minitab 18 allowed to obtain response surfaces for each mechanical property studied as a function of the pseudo-components of the mixtures. To determine the proportion of components that optimized the soil-waste mixtures, the desirability function was used, which resulted in the proportions of 80% soil, 20% EAFS, and 0% FA for both soil samples. Based on SEM and XRD tests, it was found that calcium silicate hydrate (C–S–H), calcium aluminate silicate hydrate (C-A-S-H), and calcium aluminate hydrate (C-A-H) were formed, which were responsible for improving the mechanical strength. The use of industrial waste to stabilize tropical soils with low bearing capacity proved to be a technically and environmentally viable alternative.

Effect of Variable Synthesis Conditions on the Formation of Ye'elimite-Aluminate-Calcium (YAC) Cement and Its Hydration in the Presence of Portland Cement (OPC) and Several Accessory Additives.

In the presented study, ye'elimite-aluminate-calcium (YAC) cement was synthesized. Complete synthesis of crystalline phases was achieved at a temperature of 1300 °C, which is 150 °C lower than the temperature standardly used in the processes of obtaining calcium aluminate cements (CAC). The greatest amount of ye'elimite phase (Klein complex), roughly 87% by mass, was acquired utilizing a sulphur ion transporter derived from artificial dihydrate gypsum obtained in the flue gas desulphurization process (variation I). In the case of anhydrite, the amount of synthesized crystalline ye'elimite in the clinker was 67% by weight (variant II). Depending on the synthesis conditions in the clinkers, the quantity of obtained calcium aluminates (C12A7, CA, and CA2) ranged from 20 to 40% by weight. Studies on the hydration process of YAC cement samples showed that the main products are hydrated calcium aluminates and dodecahydrate calcium alumino-sulphate. In sinters of YAC and OPC, no crystalline ettringite was observed. Hydration analysis of Chinese cement revealed the presence of crystalline ettringite and dodecahydrate calcium alumino-sulphate, as well as hydrated calcium silicates of the CSH type accompanied with pseudo-crystalline Al(OH)3. The obtained clinkers from variants I and II constitute a special binder, which, due to its phase composition after hydration, can be used in the construction of reactors for biogas production in eco-energy applications.

Study on the Corrosion Behavior of Cemented Organic Soil in Dianchi Lake, China.

To study the corrosion behavior of cement soil in peat soil, the experiment involves the preparation of peat soil by incorporating humic acid into cohesive soil with a lower organic matter content. Cement soil samples are then prepared by adding cement to the mixture. These samples are subjected to immersion in fulvic acid solution and deionized water to simulate different working environments of cement soil. The experiment considers immersion time as the variable factor. It conducts observations of apparent phenomena, ion leaching tests, and unconfined compression strength tests on the cement soil. The experiment results are as follows: (1) With increasing immersion time, the surface of the cement soil in the peat soil environment experiences the disappearance of Ca(OH)2 and calcium aluminate hydrate. Additionally, large amounts of bird dropping crystals precipitate on the surface and within the specimen. The cement soil undergoes localized disintegration due to extensive erosion caused by swelling forces. (2) In the peat soil environment, fulvic acid reacts with the hydration products of cement, resulting in partial leaching of ions such as Ca2+, Mg2+, Al3+, and Fe3+ into the immersion solution. The lower the pH of the fulvic acid immersion (indicating higher concentration), the more significant the ion leaching. Increasing the ratio of humic acid to cement can slow down the leaching of ions. The cement soil undergoes dissolutive erosion in the peat soil environment. (3) The peat soil environment exerts both strengthening and corrosive effects on the cement soil. Cement soil without humic acid exhibits noticeable corrosion in the peat soil environment, gradually decreasing strength as immersion time increases. The strength decreases by 83% from 28 to 365 days. In contrast, cement soil with humic acid experiences an initial period of strengthening, leading to a significant increase in strength in the short term (34% increase from 28 to 90 days). However, the corrosive effects gradually dominate, resulting in a decrease in strength over time. The strength decreases by 80% from 90 to 365 days. This study also explores the strengthening effects of peat soil on cement soil. It identifies phenomena such as extensive erosion and new substance precipitation in cement soil.

Shear strength and durability against wetting and drying cycles of lime-stabilised laterite soil as subgrade

Laterite soil is commonly used as a fill or pavement material. However, it tends to lose its natural bonding and experiences large deformation when subjected to cyclic rainy (wet) and hot (dry) seasons. This leads to cracking and deflection of road pavement. It has long been known that lime stabilisation can improve the engineering properties of laterite soils. Unconfined Compressive Strength (UCS) tests at different curing periods (0, 3, 7, 14, and 28 days) were conducted with various percentages of lime (3%, 5%, 7%, and 9%). The durability of stabilised soil against wet and dry cycles was also evaluated. In addition, the variation of shear strength parameters during the Consolidated Undrained (CU) triaxial test under different confining pressures has been presented. Microstructural analyses showed an increased soil strength due to the formation of calcium silicate hydrate (CSH) and calcium aluminate hydrate (CAH).

Review of the Properties of Sustainable Cementitious Systems Incorporating Ceramic Waste

Global carbon dioxide emissions can be attributed to Portland cement production; thus, an alternative cementitious system is essential to reduce cement demand. Ceramic waste powder (CWP), which contains high proportions of silica and alumina, has emerged as a promising alternative because of its chemical composition. This review discusses the potential of CWP as an alternative cementitious system and its effects on the physical, mechanical, and durability properties of cementitious systems. The findings revealed that the utilization of CWP in cementitious systems has positive effects on their physical, mechanical, and durability properties owing to the chemical composition of CWP, which can act as a filler material or contribute to the pozzolanic reaction. A pozzolanic reaction occurs between the silica and alumina in the CWP and calcium hydroxide in the cement, resulting in the production of additional cementitious materials such as calcium silicate hydrates and calcium aluminate hydrates. These additional materials can improve the strength and durability of cementitious systems. Various studies have demonstrated that CWP can be effectively used as a partial replacement for cement in cementitious systems. This can reduce the carbon footprint of construction activities by reducing the demand for Portland cement. However, the optimal amount and particle size of CWP have not been fully determined, and further research is required to optimize its use in cementitious systems. In addition, the technical and economic challenges associated with the use of CWP in construction must be further investigated to ensure its effective implementation.

Sustainable incorporation of Plaster of Paris kiln dust for stabilization of dispersive soil: A potential solution for construction industry

The presence of dispersive soils in the region of Khushab, Pakistan, has been recognized as a significant element causative to numerous challenges in construction. This research intended to examine the efficacy of Plaster of Paris kiln dust (PKD) as a cost-effective and eco-friendly material in stabilizing the strength properties and dispersion potential (DP) of dispersive soil at optimal curing period. Different contents of PKD (from 0.5% to 3%) were added to the soil. A series of tests have been carried out over various curing times (0, 7, 14, 28, and 60 days) to evaluate the effectiveness of PKD as a stabilizing agent. The tests included a double hydrometer, Atterberg limits, specific gravity, compaction, unconfined compression strength (UCS), consolidation, physiochemical properties (pH, Electrical conductivity), and chemical analysis (percentage sodium, sodium adsorption ratio). The results illustrated that DP decreased from 74.12% to 8.57% while the increase in UCS value was observed from 124.3 kPa to 1212.5 kPa (an increase of 875%) by increasing PKD up to 3% after curing for 60 days. The X-ray diffraction and scanning electron microscopy exhibited the development of cementitious products (Calcium silicate hydrate, Calcium aluminate hydrate) due to the pozzolanic reaction with 3% PKD after a curing time of 28 days, which is responsible for the increment in strength. PKD exhibits both favorable economic and environmentally friendly characteristics, as it has the lowest cost among several additives used previously and provides a significant portion of the treated area (92.6%) free from pollution and landfill. PKD improved the stability and strength of dispersive soil and provided a sustainable waste management solution, making it a highly viable option for soil improvement applications in the construction industry.

The competitive hydration of [formula omitted] and Cl− in alkali-activated slag cementitious materials

This article presents a study on alkali-activated slag cementitious materials that were doped with varying levels of calcium chloride and calcium sulfate. The article delves into the hydration products and mechanisms of the cementitious material, utilizing pH values, X-ray diffraction (XRD), thermogravimetric (TG), and scanning electron microscopy (SEM). The results show that under the condition of Ca2+ dosage less than 2.5%, CaCl2 is more advantageous than CaSO4 in improving compressive strength. Under the condition of Ca2+ dosage of 2%, adding CaCl2 to the cement paste increased the compressive strength of the test block by 230% at 3 curing days and by 190% at 28 curing days compared to the sample with calcium oxide. After calcium chloride replaced calcium sulfate, the compressive strength was improved. At a Ca2+(CaCl2)-Ca2+(CaSO4) ratio of 1:1, the strength was increased by 44% and 18% at 3 days and 28 days, respectively, compared with the addition of calcium sulfate alone. SO42- can promote the formation of ettringite (AFt), while Cl− can promote the formation of Friedel's salt (3CaO·Al2O3·CaCl2·10H2O, F’s). The contribution of hydrated Friedel's salt to compressive strength is greater than that of AFt. As Cl− is added to the alkali-activated slag cementitious materials stimulated by SO42-, Cl− is dominant in the hydration process, and form Friedel's salt with hydrated calcium aluminate and calcium hydroxide, while promoting the increase of C-S-H gel quantity, thus improving the compressive strength of the material.

Study on phase transformation and reaction behavior of alumina extraction process by calcification of aluminum dross

The aluminum dross generated during the aluminum alloy processing and regeneration process contains a large amount of harmful highly reactive aluminum nitride and salts, which can cause environmental pollution. A novel method for preparing calcium aluminate by dry calcification of aluminum dross is proposed in this paper to extract valuable aluminum resources while achieving efficient detoxification. Detection methods such as XRD, XRF, and standard dissolution procedures have been applied to characterize the phase transition and reaction behavior of the aluminum extraction process. The results indicate that calcium additives can react with aluminum components in aluminum dross to generate 12CaO·7Al2O3 (C12A7), which is soluble in sodium carbonate solution, thereby separating it from other impurities. Under the optimal roasting conditions, the leaching rate of alumina is 87.89%, and the removal rate of nitrogen, chlorine, and soluble fluorine elements exceeds 99%.Excessive sodium carbonate is required to ensure that the hydrolysis product of C12A7 is calcium carbonate, avoiding the formation of hydrated calcium aluminate precipitates. The optimal leaching conditions are sodium carbonate concentration of 80 g L−1, caustic soda concentration of 5 g L−1, liquid-solid ratio of 8 mL g−1, and leaching time of 30 min. The leaching reaction of calcium aluminate conforms to the unreacted core model controlled by internal diffusion, and the apparent activation energy of the reaction is 18.05 kJ mol−1.

Mineralogical study of a binder based on alkali-activated coal gangue

The activation of materials, including those derived from mining waste, has garnered growing interest among researchers and industrialists seeking to produce eco-friendly binders. Activation can be achieved through various methods, with mechanical grinding and chemical alkaline activation using substances like NaOH being the most commonly employed. This study specifically investigates the properties of alkali-activated coal gangue-lime (AACG-L) using techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM-EDS). Lime (CaO) is acknowledged as an effective cementing agent that enhances the reactivity of raw coal gangue. The synthesis of AACG-L involves two successive stages: grinding and reducing grain size with 5% lime incorporation, followed by activation using 5 M NaOH and subsequent 28-day curing. XRD, FTIR, and SEM-EDS analyses confirm that the resulting AACG-L product primarily comprises hydrated calcium aluminate silicate (C-A-S-H), hydrated alkaline aluminate silicate (N-A-S-H), and portlandite Ca(OH)2.

Features of the formation of crystalline hydrosulfoaluminates during hydration of stoichiometric mixtures of calcium aluminates with calcium sulfate

Calcium aluminates as mineral binders allow to produce cements and concretes with high early strength, low porosity, increased heat resistance, frost resistance and corrosion resistance compared to materials based on Portland cement. An important structure-forming process in aluminate cements is formation of hydrosulfoaluminate phases (ettringite, monosulfoaluminate). Finding out the parameters that allow to control this process is of exceptional importance for construction practice. Hydration of various calcium aluminates C3A, C12A7, CA, and CA2 in the presence of stoichiometric amounts of various forms of calcium sulfate (CaSO4⋅2H2O, α-CaSO4⋅0.5H2O, anhydrite) was studied in order to determine the comparative ratio and the peculiarities of nucleation and growth of the hydrosulfoaluminate phase crystals. It was found that the highest yield of ettringite (∼100 wt% by 28 days) is achieved during hydration hardening of the composition C3A + 3CS¯H2, the yield is reduced in the series C12A7–CA–CA2. Monosulfoaluminate is not formed as the predominant product, its yield reaches 25 wt% during hydration of low-base aluminates. Ettringite crystals can form as a highly dispersed mass (from C3A) or prismatic (fibrous) crystals (from other aluminates). It was clearly shown for the first time that the origin and growth of ettringite crystals occurs in the matrix of aluminum hydroxide gel formed during hydration of calcium aluminates. Varying the pH of aluminate-sulfate mixtures changes the morphology, size and number of primary ettringite crystals. Lamellar hexagonal crystals of monosulfoaluminate are formed from hydroaluminates of type C4AH13-19 at low availability of calcium sulfate. The explanation of the experimental data was carried out using thermodynamic calculations. The results obtained can be used in practice to control the content, ratio and morphology of hydrosulfoaluminate phases in cement stone.