Hydration behavior, microstructural evolution, and mechanical performance of tailings-based solid waste cemented backfill under high-temperature conditions

From waste to wellbore reinforcement: Assessment of quartz tailings functionalization in oil well cement under simulated HTHP conditions.

Sustainable application of waste residue from coal gasification process in low-carbon cement: multiscale evaluation, hydration behavior, mechanical performance, and environmental assessment.

The hydration of Portland cement involves initial dissolution of CaO, CaSO4.1H20 or CaSO4-2H20, alkaline contents and aluminate phases etc. This is followed by the reaction of C3S and C2S with free water and formation of C-S-H, calcium hydroxide (CH), ettringite and other minor compounds, which bridge the individual particles and fill up the capillary pores. These reactions promote formation of a rigid microstructure and strength development. The stability of C-S-H depends on the variation of environmental conditions as evidenced by changes in morphology, interfacial regions, pore structure and intrinsic strength. These characteristics can be studied by means of impedance or conductance measurements. Electrical methods are considered as a nondestructive, rapid way to determine the physical properties, such as strength, porosity and permeability. Electrical conductivity measurement (ECM) [14] and a.c. impedance spectroscopy (ACIS) [5-15] have been used in cement and concrete hydration investigations. Information on hydration behaviour and microstructural development was obtained. These studies indicated that certain parameters obtained from ECM and ACIS are very sensitive to microstructural characteristics of cement paste and concrete. Dielectric constant measurement (DCM) is one of the most popular methods of characterizing solid materials because it is easier to apply than chemical analysis techniques. The electrical, as well as physical and structural, characteristics of hydrated cement systems can be evaluated. There is a paucity of data [16-20] reported on the dielectric properties of cement and concrete, especially at RF frequencies. In this study, the dielectric properties of hardened cement paste at various water/cement ratios were investigated over the frequency range from 1 MHz to 1 GHz. This preliminary work revealed that the dielectric constant value of hydrated cement paste varies indirectly with original water/cement ratio. Type 10 Portland cement was used. The chemical composition (wt%) was as follows: SiO 2 19.83; CaO 61.21; Fe203 3.20; A1203 4.18; MgO 4.09; SO3 3.93; Na20 0.45; K20 0.82. Fresh cement was mixed at various water/cement ratios from 0.3 to 0.7 and cast in cylindrical moulds, 3 cm diameter × 6 cm. The samples were cured in 100% relative humidity environment for 24 h and subsequently immersed in saturated lime solution for 1 year. Cement paste samples were sliced to form 3 mm thick discs and

Effect of hydrogen on the microstructural evolution and local mechanical properties of 430 ferritic stainless steel at high-temperature conditions

This study focuses on the calcined coal gangue (CCG)-blended cements containing Stöber nano-SiO2 (SNS) particles. The effects of SNS particles on the workability, hydration behaviour, mechanical properties and microstructure evolution of the blended cements were comprehensively investigated at curing ages ranging from 1 to 28 d. The hydration behaviour was studied via isothermal calorimetry test, X-ray diffraction (XRD) and thermogravimetric (TG) tests. The microstructural evolution was studied using mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). The results show that the incorporation of SNS led to a significant reduction in fluidity, particularly at an SNS content of 3%. The SNS significantly increased the compressive strength of the CCG-blended cement at all curing ages, and the optimum SNS content was found to be 2%. SNS significantly accelerated not only the early cement hydration but also the pozzolanic reaction of CCG at later curing ages, resulting in a decrease in portlandite, as evidenced by the isothermal calorimetry, XRD and TG analysis. Microstructural analysis shows that the incorporation of SNS effectively refined the pore structure of the CCG-blended cement, resulting in the formation of a dense microstructure. All these beneficial effects of SNS provides advantages in the development of the compressive strength of the CCG-blended cement at all curing ages.

Transforming AOD slag toward a highly reactive mineral admixture with appreciable CO2 sequestration: Hydration behavior, microstructure evolution, and CO2 footprint

Microstructure evolution and thermostability of bondline based on Cu@Sn core-shell structured microparticles under high-temperature conditions

Multi-ring side groups copolymer as an effective filtration control additive for water-based drilling fluids under high temperature and salt contamination

An investigation into the microstructural evolution and shrinkage control in internally cured mortars with milkweed fibres

Electrolytic manganese residue (EMR) is a solid waste with a main mineralogical composition of gypsum. It is generated in the production of metal manganese by the electrolysis process. In this research, EMR, fly ash, and clinker were blended to make fly ash-based cementitious material (FAC) to investigate the effect of EMR on strength properties, hydration behavior, microstructure, and environmental performance of FAC. XRD, TG, and SEM studied the hydration behavior of FAC. The pore structure and [SiO4] polymerization degree were characterized by MIP and 29Si NMR, respectively. The experimental results indicate that FAC shows excellent mechanical properties when the EMR dosage is 10%. Moderate content of sulfate provided by EMR can promote hydration reaction of FAC, and it shows a denser pore structure and higher [SiO4] polymerization degree in this case. Heavy metal ions derived from EMR can be adsorbed in the hydration products of FAC to obtain better environmental properties. This paper presents an AFt covering model for the case of excessive EMR in FAC, and it importantly provides theoretical support for the recycling of EMR in cementitious materials.

Synergistic alkali activation of cement kiln dust and ground granulated blast furnace slag: Material performance and reaction kinetics.

Large quantities of agricultural waste, particularly rice husk ash (RHA), are generated worldwide each year, and the lack of rational, value-added disposal pathways poses both environmental and resource-utilization challenges. To address this practical problem while improving the freeze–thaw (F–T) durability of cement-based materials in cold regions, this study investigates the effects of replacing silica fume (SF) with finely milled RHA on the hydration behavior, mechanical performance, and durability of cement mortar. From a scientific perspective, the freeze–thaw behavior of RHA-modified cementitious materials and the underlying relationships among hydration kinetics, microstructural evolution, and durability remain insufficiently understood. Mortars with different RHA–SF blending ratios were prepared at a constant water-to-binder ratio. Compressive strength was measured before and after F–T cycling, and the underlying mechanisms were investigated using isothermal calorimetry, water absorption tests, and scanning electron microscopy. Results show that SF significantly enhances pre-F–T compressive strength, with the SF-only mixture reaching 56.8 MPa at 28 d, approximately 28.7% higher than the control. With increasing RHA replacement, pre-F–T strength decreased with a non-monotonic variation (40.1–51.5 MPa). F–T cycling caused severe degradation in the reference mortar, with a strength loss rate of 31.75%, whereas RHA- or SF-modified mortars exhibited substantially lower loss rates (6.30–21.54%). Notably, high-RHA mixtures retained residual strengths of 36.0–38.3 MPa after F–T cycling. Although RHA delayed early hydration and increased water absorption, freeze–thaw resistance was not proportionally reduced. These results demonstrate that freeze–thaw durability is governed primarily by long-term microstructural stability rather than early-age strength, and they provide mechanistic evidence supporting the rational utilization of finely milled RHA as a low-carbon supplementary cementitious material for cold-region applications.

High-entropy alloys, since their development, have demonstrated great potential for applications in extreme temperatures. This article reviews recent progress in their mechanical performance, microstructural evolution, and deformation mechanisms at low and high temperatures. Under low-temperature conditions, the focus is on alloys with face-centered cubic, body-centered cubic, and multi-phase structures. Special attention is given to their strength, toughness, strain-hardening capacity, and plastic-toughening mechanisms in cold environments. The key roles of lattice distortion, nanoscale twin formation, and deformation-induced martensitic transformation in enhancing low-temperature performance are highlighted. Dynamic mechanical behavior, microstructural evolution, and deformation characteristics at various strain rates under cold conditions are also summarized. Research progress on transition metal-based and refractory high-entropy alloys is reviewed for high-temperature environments, emphasizing their thermal stability, oxidation resistance, and frictional properties. The discussion reveals the importance of precipitation strengthening and multi-phase microstructure design in improving high-temperature strength and elasticity. Advanced fabrication methods, including additive manufacturing and high-pressure torsion, are examined to optimize microstructures and improve service performance. Finally, this review suggests that future research should focus on understanding low-temperature toughening mechanisms and enhancing high-temperature creep resistance. Further work on cost-effective alloy design, dynamic mechanical behavior exploration, and innovative fabrication methods will be essential. These efforts will help meet engineering demands in extreme environments.

Influence of Mo and Ru additions on the creep behavior of Ni-based single crystal superalloys at 1100 °C

Failure mechanism of single-crystal superalloy NiAlReRu components with film cooling holes under the coupling high-speed rotating and high temperature condition