Hydration Products Research Articles

Preparation of High-Belite Calcium Sulfoaluminate Cement and Calcium Sulfoaluminate Cement from Industrial Solid Waste: A Review

To address the high carbon emissions and resource dependency associated with conventional ordinary Portland cement (OPC) production, this study systematically investigated the preparation processes, hydration mechanisms, and chemical properties of high-belite calcium sulfoaluminate (HBCSA) and calcium sulfoaluminate (CSA) cements based from industrial solid wastes. The results demonstrate that substituting natural raw materials (e.g., limestone and gypsum) with industrial solid wastes—including fly ash, phosphogypsum, steel slag, and red mud—not only reduces raw material costs but also mitigates land occupation and pollution caused by waste accumulation. Under optimized calcination regimes, clinkers containing key mineral phases (C4A3S− and C2S) were successfully synthesized. Hydration products, such as ettringite (AFt), aluminum hydroxide (AH3), and C-S-H gel, were identified, where AFt crystals form a three-dimensional framework through disordered growth, whereas AH3 and C-S-H fill the matrix to create a dense interfacial transition zone (ITZ), thereby increasing the mechanical strength. The incorporation of steel slag and granulated blast furnace slag was found to increase the setting time, with low reactivity contributing to reduced strength development in the hardened paste. In contrast, Solid-waste gypsum did not significantly differ from natural gypsum in stabilizing ettringite (AFt). Furthermore, this study clarified key roles of components in HBCSA/CSA systems; Fe2O3 serves as a flux but substitutes some Al2O3, reducing C4A3S− content. CaSO4 retards hydration while stabilizing strength via sustained AFt formation. CaCO3 provides nucleation sites and CaO but risks AFt expansion, degrading strength. These insights enable optimized clinker designs balancing reactivity, stability, and strength.

Microstructural Evolution and Mechanical Properties of Fly-Ash-Based Grouting Materials in Different Aqueous Environments

Grouting is widely used in the treatment works of goaf, which can enhance the foundation bearing capacity, reduce deformation, and ensure the stability of the construction of goaf. As the goaf is located below the water table line, the mechanical properties and microscopic changes of the stone body in the water-rich environment have not been revealed, which leads to the effect of grouting treatment in water-rich goaf being difficult to achieve in terms of the expected goal. This paper used uniaxial compression, electron microscopy (SEM), and X-ray diffraction (XRD) to study the mechanical properties and microscopic changes of the nodular body under natural, pure water, and tap water curing and revealed the deterioration mechanism of the nodular body’s mechanical properties under water curing. The research results show that under identical material proportions and curing durations, compared to naturally cured specimens, the specimens cured in purified water and tap water exhibited a significant increase in the content of unreacted fly ash, a reduction in the amount of hydration products such as C-S-H gel and ettringite, and a looser microstructure, resulting in average decreases in uniaxial compressive strength of 35.7% and 49.9%, respectively. In addition, the presence of chloride ions and Friedel’s induced decalcification of the C-S-H gel under tap water curing conditions led to a significant deterioration in the physical strength of the grouted stones.

Improvement in Early-Age Strength and Durability of Precast Concrete by Shrinkage-Reducing C-S-H

In order to improve early-age strength, steam curing is mostly used for railway prefabricated components, which consumes a lot of energy and affects the durability of concrete. Synthetic calcium silicate hydrate (C-S-H) has an excellent early-age strength effect, which can improve the early-age strength of concrete and help to reduce the energy consumption of steam curing, but C-S-H will increase the shrinkage of concrete and affect the durability of concrete. In this work, C-S-H/SRPCA was synthesized using a shrinkage-reducing polycarboxylate superplasticizer (SRPCA) in order to increase the early-age strength and decrease the shrinkage of concrete. The effects of 0.5%, 4.0%, and 8.0% C-S-H/SRPCA on the shrinkage and strength of concrete were studied. Meanwhile, the internal mechanism was also explored through cement hydration, the physical aggregation morphology of hydration products, pore structure and classification, and the chemical properties of pore solution. The results suggest that C-S-H/SRPCA can shorten the setting time and accelerate cement hydration. Specifically, when the dosage of C-S-H/SRPCA is 4.0%, the initial setting time of concrete is shortened by 2.5 h and the final setting time is shortened by 6.2 h compared with the control group. As a result, the 1-day compressive strength is effectively increased by 29.5%, and the plastic shrinkage is reduced. In the stage of plastic shrinkage, the plastic shrinkage time of the concrete with 4.0% C-S-H/SRPCA is 4.1 h, which is 6.1 h shorter than that of the control group. In addition, C-S-H/SRPCA decreases the porosity. When the dosage is 4.0%, the porosity of the hardened cement paste at 28 days is reduced by 15% compared with the control group. It lessens the content of the capillary pores at 10–50 nm. At 24 h, the content of 10–50 nm capillary pores in the paste with 4.0% C-S-H/SRPCA is 40% lower than that of the control group. It also reduces the surface tension of the pore solution. The surface tension of the simulated pore solution with 4.0% C-S-H/SRPCA is 34 mN/m, which is 53% of that of the control group, and it inhibits the volatilization of the pore solution. At 28 days, the evaporation rate of the pore solution in the paste with 4.0% C-S-H/SRPCA is 40% lower than that of the control group. Thus, the drying shrinkage of concrete is inhibited. Given the above, at the optimum content of 4.0%, C-S-H/SRPCA improves the 1-day compressive strength of concrete by 29.5%, reduces the 28-day total shrinkage by 21.7%, and restrains the development of microcracks.

The Effect of Mineral Fillers on the Rheological and Performance Properties of Self-Compacting Concretes in the Production of Reinforced Concrete Products

This study investigates the impact of widely used mineral fillers in self-compacting concrete compositions applied in vibration-free reinforced concrete production technology, as a means of enhancing rheological characteristics and cost-effectiveness. Three distinct types of mineral fillers, including the well-studied fillers microsilica and metakaolin, as well as the lesser-explored filler Kazakhstani natural opal-chalcedony opoka, are examined in this research. In addition to the evaluation of conventional rheological and performance properties of concretes containing these fillers, the internal processes within the cement–filler matrix are analyzed. This includes X-ray phase analysis and microstructural examination of cement hydration products in combination with a superplasticizer and each of the three minerals. The findings confirm the potential for optimizing the rheological parameters of the concrete mixture by substituting up to 15% of the cement with mineral fillers, achieving optimal viscosity and workability. It is established that compositions with the addition of microsilica and metakaolin have a more homogeneous structure, mainly represented by low-basicity calcium hydrosilicates of the CSH(B) type, along with an increase in compressive strength of up to 10%. The addition of these mineral fillers to C30/35 strength class self-compacting concrete resulted in improved frost resistance up to F300, a reduction in volumetric water absorption by up to 30%, and a decrease in shrinkage deformations by 32%. The developed SCC compositions have successfully passed production testing and are recommended for implementation in the operational processes of reinforced concrete product manufacturing plants.

Preparation of green concrete using recycled aggregate in alkali-activated concrete

To promote industrial solid waste recycling and sustainable development, this study prepared alkali-activated recycled aggregate concrete (AARAC) using ground granulated blast-furnace slag and recycled coarse aggregate. The effects of alkali content and recycled aggregate replacement ratio on AARAC performance were examined. Results indicated that while recycled aggregate can impair concrete properties, an optimal alkali content of 6% significantly mitigates these effects, improving physical properties, mechanical stability, and compactness. Microstructural analysis showed enhanced hydration product formation and a denser interfacial transition zone at this alkali level. Entropy weight-TOPSIS evaluation confirmed that 6% alkali content provided the best overall performance with low sensitivity to aggregate variation. Additionally, carbon emission analysis revealed that AARAC reduced CO2 emissions by approximately 45% compared to conventional recycled concrete. These findings suggest that alkali-activated recycled aggregate systems offer a promising approach to developing low-carbon, sustainable construction materials.

Cutaneous biophysical factors related to age and body location

The biophysical properties of human skin, such as hydration, elasticity, sebum content, and transepidermal water loss (TEWL), are influenced by both age and body location. These factors play a critical role in dermatological health and the efficacy of skincare products. Aging is generally associated with decreased hydration, elasticity, and sebum production, while TEWL increases, indicating a decline in skin barrier function. Additionally, different anatomical locations exhibit distinct biophysical characteristics due to varying densities of sebaceous glands and exposure to environmental factors. For instance, sebaceous gland-rich areas like the forehead show higher sebum content, while the palms exhibit lower hydration levels. This review presents a comprehensive analysis of current research on the effects of age and body location on skin biophysical properties to guide future dermatological studies and skincare product development.

The Effect of Industrial Byproducts Fly Ash and Quartz Powder on Cement Properties and Environmental Benefits Analysis

Using industrial byproducts to replace cement is an important way to reduce carbon emissions from the cement industry. In this study, the effects of two industrial byproducts, fly ash (FA) and quartz powder (QZ), as supplementary cementitious materials (SCMs) on the macroscopic properties and microstructure of cement-based materials were experimentally investigated. The results of the compressive strength and ultrasonic pulse velocity experiments showed that QZ significantly mitigated the decrease in strength and ultrasonic pulse velocity caused by the reduction in cement dosage in the early stage. Moreover, the 28-day compressive strength of the FA group was comparable to that of the control group, and regression analysis indicated a negligible effect of FA addition on 28-day compressive strength. X-ray diffraction and Fourier transform infrared spectroscopy experiments showed that QZ can promote the hydration reaction in the early stage. Scanning electron microscopy images revealed that a layer of hydration products can form on the surface of FA after 28 days of hydration. Hydration heat experiments indicated that FA significantly reduces the release of hydration heat, while QZ promotes the formation of ettringite through nucleation effects in the early stage of hydration, thereby accelerating the release of hydration heat. Thermogravimetric analysis after 28 days showed that the amount of hydration products and calcium hydroxide produced decreased with the addition of cementitious materials. Finally, the use of FA and QZ was analyzed for carbon emissions and energy consumption. The results showed that using these two cementitious materials significantly reduces carbon dioxide emissions and energy consumption.

Capillary Water Absorption Characteristics of Steel Fiber-Reinforced Concrete

The water absorption behavior of concrete is a critical indicator of its durability, and a comprehensive understanding of water transport characteristics can significantly enhance concrete performance. This study investigates the capillary water absorption properties of steel fiber-reinforced concrete across various strength grades by combining mercury intrusion porosimetry (MIP) and 1H low-field nuclear magnetic resonance (1H low-field NMR) techniques. Key findings reveal that the capillary water absorption of steel fiber-reinforced concretes occurs in the following two distinct stages: an initial rapid absorption phase (0 min to 6 h) and a subsequent slow absorption phase (1 day to 12 days). Modifications to the concrete matrix composition substantially reduce capillary water absorption rates, with ultra-high-performance concrete (UHPC) exhibiting exceptionally low absorption levels (the cumulative capillary water absorption of UHPC accounts for only 4.5–5.7% of that of C30 concrete). Additionally, for higher-strength concrete and extended absorption durations, the capillary water absorption rate deviates from the linear relationship with the square root of time. This deviation is attributed to the interaction of gel pore water with unhydrated cement particles, generating more hydration products, which refine the pore structure, reduce capillary pore connectivity, and increase pore tortuosity. Furthermore, steel fibers influence water transport through the following two primary mechanisms: interfacial interactions between the fibers and the matrix and a physical blocking effect that impedes water movement.

Laterite soil powder as cementing material for the production of high-performance mortar

Cement has a substantial environmental impact, particularly carbon dioxide (CO2) emissions, which occur mostly during the production stage, as it is anticipated that nearly 4–5% of the world’s total CO2 emissions result from cement production. To address these environmental concerns, future scenarios will require alternative raw materials for clinker production and the usage of supplemental cementitious materials (SCMs). Hence, the current study correspondingly sought to assess the applicability of Laterite soil powder (LSP) for manufacturing High performance Mortar (HPM) and its influence on fresh, hard, and microstructure qualities with varied replacement levels. A series of experiments—including slump flow, compressive strength, chemical resistance, water absorption, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) were conducted. The results indicate that while a superplasticizer maintained adequate flow, the addition of LSP reduced mortar flowability; for example, a 20% replacement resulted in a 23% decrease in flowability. In contrast, a 10% replacement level did not significantly affect the mechanical or durability properties over all curing periods. A one-way ANOVA (p = 0.62) confirmed that there was no statistically significant difference (p > 0.05) in compressive strength between the control mix LSP-0 and the LSP-10 mix. Furthermore, FTIR analysis indicated that a 10% LSP content exerted only a modest influence on the hydration products, as the wavenumbers, curves, peaks, and valleys observed in the spectra of the LSP-0 and LSP-10 mortar samples were nearly identical. In general, analysis of various properties indicates that a 10% LSP replacement is optimal, as it maintains performance without significant adverse effects.

A semi-analytical model considering two-phase flow and full thermal–hydraulic–mechanical (THM) coupling for the mechanical response of formation in hydrate production

A semi-analytical model considering two-phase flow and full thermal–hydraulic–mechanical (THM) coupling for the mechanical response of formation in hydrate production

Effect of triethanolamine on the properties and hydration of fly ash-based geopolymer foam.

Effect of triethanolamine on the properties and hydration of fly ash-based geopolymer foam.

Impact of Alkali-Activated Tannery Sludge-Derived Geopolymer Gel on Cement Properties: Workability, Hydration Process, and Compressive Strength

The utilization of tannery sludge (TS) in construction materials not only effectively reduces pollution and resource consumption associated with waste disposal, but also promotes low carbon transformation in the building materials sector, further advancing sustainable development of green construction. This study aims to investigate the impact of sludge-based geopolymer gel on cementitious material performance, revealing the evolution mechanisms of material fluidity, setting time, hydration process, and compressive strength under the coupled effects of tannery sludge and alkali activation, thereby providing a reusable technical pathway to address the resource utilization challenges of similar special solid wastes. A series of alkali-activated composite cementitious materials (AACC) were prepared in the study by partially substituting cement with alkaline activators, TS, and fly ash (FA), through adjustments in TS–FA ratios and alkali equivalent (AE) variations. The workability, hydration process, and compressive strength evolution of AACC were systematically investigated. The experimental results indicated that as the TS content increased from 0% to 100%, the fluidity of fresh AACC decreased from 147 mm to 87 mm, while the initial and final setting times exhibited an exponential upward trend. The incorporation of TS was found to inhibit cement hydration, though this adverse effect could be mitigated by alkaline activation. Notably, 20–40% sludge dosages (SD) enhanced early-age compressive strength. Specifically, the compressive strength of the 0% TS group at 3 d age was 24.3 MPa, that of the 20% TS group was 25.9 MPa (an increase rate of 6.58%), and that of the 40% TS group was 24.5 MPa (an increase rate of 0.82%), whereas excessive additions resulted in the reduction of hydration products content and diminished later stage strength development. Furthermore, the investigation into AE effects revealed that maximum compressive strength (37.4 MPa) was achieved at 9% AE. These findings provide critical data support for realizing effective utilization of industrial solid wastes.

Graphene oxide/carbon nanotubes harmonize to enhance the initial hydration products and mechanical properties of cement mortar

Graphene oxide/carbon nanotubes harmonize to enhance the initial hydration products and mechanical properties of cement mortar

Effect of hydration products composition on high temperature resistance of geopolymers

Effect of hydration products composition on high temperature resistance of geopolymers

Abrasion resistance mechanism of high-ferrite Portland cement: Insights into the microstructure of hydration products and interfacial transition zone

Abrasion resistance mechanism of high-ferrite Portland cement: Insights into the microstructure of hydration products and interfacial transition zone

In-situ polymerization of acrylamide in limestone calcined clay concrete(LC3) for toughness: Hydration products bonding and interface transition zone(ITZ) strengthening

In-situ polymerization of acrylamide in limestone calcined clay concrete(LC3) for toughness: Hydration products bonding and interface transition zone(ITZ) strengthening

Modeling and experimental validation of carbonation mechanism of ye’elimite-gypsum-water system

Calcium sulfoaluminate cement is a promising low-carbon alternative to Portland cement, and the carbonation of its hydration products influences its mechanical performance. However, a comprehensive theoretical model describing its carbonation mechanism remains elusive. This paper established a theoretical reaction range, including different zones and boundaries for ye’elimite (C4A3S̅)-gypsum (CS̅H2)-water (H2O)-carbon dioxide (CO2) system via priority-based theoretical calculations of chemical reactions. The reactions and product evolution within each boundary and zone were summarized. A theoretical database was obtained, including the change of Gibbs energy and enthalpy, solid volume and chemical volume, and the theoretical carbon absorption. Calculation results reveal that the reactions of each zone and boundary occur spontaneously and exothermically. The solid volume increases, while the chemical volume decreases conversely. The maximum carbon absorption of 1 mol C4A3S̅ is 3 mol theoretically regardless of the amount of gypsum. The modeling obtained by Gibbs Energy Minimization software (GEMS-PSI) and experimental verification were carried out to validate the fidelity of the established theoretical reaction range, which demonstrate that the evolution of carbonation products in each zone and boundary was in line with the theoretical calculations. Compared with GEMS modeling, the theoretical reaction range can distinguish the source of ettringite in detail, and provide a more direct and insightful representation of carbonation process.

A new approach for constructing UHPC conductive pathways: Oriented deposition of conductive hydration products

A new approach for constructing UHPC conductive pathways: Oriented deposition of conductive hydration products

Natural gas hydrate production using the corona electric discharge treated carbon nanotubes

In this research, methane gas hydrate production using the corona electric discharge treated carbon nanotubes is investigated for the first time. The findings indicate that when an optimal quantity of corona discharge-treated multi-walled carbon nanotubes (MWCNTs) is present, the gas to hydrate (GTH) conversion rate can increase by as much as 780% compared to the case of untreated MWCNTs. The corona technique introduced here significantly outperforms traditional chemical treatment methods, as it does not involve the introduction of harmful or toxic chemicals into the aqueous phase. Furthermore, a mechanistic kinetic model is introduced, exhibiting an average absolute deviation (AAD) of 1.5%, which facilitates precise predictions of gas hydrate production process. The proposed innovative corona technique presents a strong and eco-friendly alternative to usual functionalization methods, with the potential to markedly improve the performance of gas hydrate production in petroleum industry.

Strength, Durability, and Microscopic Analysis of Silt Solidified with Two-Phase Phosphogypsum and Cement Fiber

The accumulation of silty soils and industrial solid waste not only results in a significant waste of land resources but also causes environmental pollution. Phosphogypsum and cement are commonly utilized as binding agents for the solidification of silt in engineering applications. However, the use of PG and cement alone may lead to issues such as insufficient strength, crack formation, and poor durability. Therefore, this research considered and employed a two-phase stabilization method using phosphogypsum and cement to solidify silt. Additionally, to further enhance the durability of the stabilized silt, polypropylene fiber (PP) and sodium sulfate (Na2SO4, NS) were incorporated. The effects of two-phase phosphogypsum and the proportion of hemihydrate phosphogypsum (BHPG) in the two-phase phosphogypsum on the strength characteristics of the stabilized silt were investigated through unconfined compressive strength tests and durability tests. The results show that when the content of two-phase phosphogypsum is 5%, and the proportion of BHPG in the two-phase phosphogypsum is 20%, the 28-day unconfined compressive strength of the stabilized silt reaches 1.42 MPa, and the deformation modulus is 95.5 MPa. After incorporating sodium sulfate (NS), the water and frost resistance of the stabilized silt significantly improved. The microstructural analysis shows that NS promotes the formation of ettringite. Furthermore, an excessively high proportion of hemihydrate phosphogypsum (BHPG) in the two-phase phosphogypsum content can lead to dihydrate phosphogypsum (2HPG) not being encapsulated by hydration products, which results in a less dense structure of the solidified silt and a decline in performance.