Search Results (3,133)

In this study, the rapidly setting and hardening high-belite sulfoaluminate cement (HBSAC) is used as the cementitious material, with natural river sand as the fine aggregate, and a high-performance repair mortar is prepared through the synergistic use of different polymers and admixtures. The influences of two polymers (VAE and HPMC) on the working performance, mechanical properties, and hydration characteristics of HBSAC mortars are systematically studied. The results showed that the two polymers had a significant improvement effect on the setting time, mortar flowability, and water retention rate of HBSAC mortar. Among them, VAE had a significant effect on the mortar flowability, and a 5% content could increase the flowability of HBSAC mortar by 29.8%. HPMC has a significant improvement effect on setting time and water retention rate; at 0.1% content, it can delay the initial setting time by 6.5 min and achieve a water retention rate of over 90%. As the polymer to binder ratio increases, both polymers, except for 2.5% VAE, which can slightly improve the flexural strength of mortar, will reduce the flexural and compressive strength of mortar, with VAE causing greater damage to strength. On the contrary, the polymer significantly enhanced the bond strength of the mortar. Compared with the cement control group, the 28 d bond strength of 5% VAE and 0.1% HPMC groups increased by 56.7% and 15.1%, respectively. Moreover, the addition of polymers delayed the occurrence of the exothermic peaks of HBSAC dissolution and ettringite formation, but the total amount of hydration heat released within 48 h was higher than that of pure cement. The diffraction peaks of AFt in the hydration products of VAE-HBSAC paste at 3d and 28d showed significant enhancement, and the peak intensity increased with higher doping levels, while the diffraction peak intensity of C₂S showed a certain decrease. The polymer significantly increased the weight loss peak intensity and mass loss after heating of AFt, AH₃, AFm, and C-S-H gel. The SEM images indicate that VAE can form a mesh on the surface of hydration products and refine the crystal size of AFt; HPMC wraps more flocculent substances around the hydration products, thereby improving the compactness of paste. This study can provide scientific reference for improving the performance and promoting the practical application of high-performance rapid repair mortar for concrete structure damage. Full article

The development of sustainable grouting materials is essential for enhancing underground strata stability while reducing the environmental impact associated with ordinary Portland cement (OPC). This review summarizes previously published studies on alkali-activated grouting materials (AAGMs) prepared using fly ash (FA) and ground granulated blast furnace slag (GGBFS), activated by sodium hydroxide and sodium silicate solutions. A comprehensive literature-based analysis was conducted to evaluate both fresh and hardened properties, including fluidity, setting time, yield stress, compressive strength, and durability-related performance. Particular attention was given to the influence of FA-GGBFS proportions and activator composition on rheological behaviour, mechanical performance, and engineering applicability. The reviewed studies indicate that increasing GGBFS content significantly accelerates geo-polymerization and setting behaviour and enhances early-age strength development due to its higher calcium reactivity. In contrast, FA contributes to improved workability and flowability, attributed owing to its spherical particle morphology and slower reaction kinetics. The reviewed literature further suggests that balanced FA–GGBFS alkali-activated systems can provide a favourable combination of fluidity, injectability, setting behaviour, and mechanical performance, making them particularly suitable for underground grouting and rock mass reinforcement applications. Compared with conventional OPC-based grouts, AAGMs demonstrate superior mechanical performance together reduced environmental impact through the utilization of industrial by-products and reduced clinker consumption. However, several critical challenges still hinder the large-scale implementation of alkali-activated grouting materials in underground mining, particularly with respect to field-scale validation, shrinkage mitigation, safe handling of alkaline activators, and the current lack of standardized specifications and design guidelines for underground grouting applications. These findings provide a robust scientific basis for the design and application of eco-efficient grouting materials in deep underground mining environments and support the advancement of sustainable practices in underground engineering. Full article

The reformulation of cookies using alternative flours and structured lipid systems represents a promising strategy for improving their nutritional profile. The present study characterized the dough properties, baking behavior, compositional attributes, and 48-day storage physicochemical and textural stability of cookie formulations combining mesquite or wheat flour with varying proportions of shortening and monoglyceride-based oleogel. A multifaceted modeling and temporal analysis approach was employed to assess the impact of flour type, fat blend, and storage duration on critical physicochemical variables. The findings of the study indicated that the type of flour was the predominant factor influencing moisture retention, ash content, and the rate of bake loss. In contrast, the fat blend was found to regulate oil migration and dough mechanical parameters. Oleogel-rich systems demonstrated superior stability over time, as evidenced by a diminished color change and a decelerated textural hardening process in comparison to conventional shortening controls. Concurrently, these systems maintained water activity levels below the established microbiological safety thresholds. Sensory analysis demonstrated that oleogels effectively replicated the mouthfeel and acceptability of conventional fats, exhibiting comparable hardness and crunchiness to traditional formulations. However, mesquite flour-rich formulations exhibited higher bitterness and lower adhesiveness. These findings demonstrate that oleogel incorporation provides a viable strategy for mitigating textural staling and improving lipid profiles of cookies. Full article

Heterogeneous grain structured design has emerged as an effective strategy to overcome the limitations of mechanical properties in structural materials. Core–shell heterogeneous grain structured materials exhibit a good strength-ductility synergy owing to their continuously networked grain topology. However, controlling the grain size and fraction in core–shell structures through mechanical milling and powder metallurgy remains challenging. Therefore, the effects of grain structure topology on mechanical behavior remain unclear. This study establishes a crystal plastic finite element (CPFE) model of a core–shell structure and discusses the effects of core–shell topological characteristics, i.e., core–shell fraction (S_f = 15% to 65%), the core–shell interface gradient (θ = 63° to 90°), and the coarse grain/ultrafine grain size ratio (CG/UFG = 8/2 to 8/1), on tensile strength and hetero-deformation induced (HDI) hardening. The results indicate that the tensile strength is strongly correlated with the core–shell fraction and CG/UFG size ratio. The tensile strength is enhanced with increasing core–shell fraction and CG/UFG size ratio, which can be attributed to the increased fraction of ultrafine grains and their reduced grain size. The tensile strength increases by approximately 30% when the core–shell fraction increases from 15% to 65%, and increases by approximately 12% when the CG/UFG size ratio changes from 8/2 to 8/1. However, these two parameters exhibit a negligible influence on HDI hardening. In contrast, compared to θ = 63°, the HDI hardening at θ = 90° increases by approximately 20%, thus it indicates the sharp core–shell interface gradient markedly promotes HDI hardening, thereby improving the tensile strength through an increased hardening rate. Collectively, this study provides useful information for the microstructure design of core–shell heterogeneous grain structured materials. Full article

This study systematically investigated the effects of air-cooled pre-hardening and oil-quenched quenching-and-tempering processes on the microstructure, mechanical properties, and polishing performance of P20 plastic mold steel. Increasing the austenitizing temperature from 820 °C to 940 °C resulted in a more uniform carbide distribution, a slight improvement in hardness, and enhanced polishing performance for both processes. However, grain coarsening at 940 °C reduced the impact toughness from 157.6 J to 111.7 J. After tempering at 650 °C, both processes yielded a tempered sorbite microstructure. However, in the air-cooled samples, the carbides were aligned along the bainite lath direction, whereas in the oil-quenched samples, they exhibited an equiaxed, non-directional distribution owing to the complete recovery of the matrix. Austenitizing at 940 °C followed by air cooling and tempering at 550 °C provides the optimal balance of hardness, toughness, and polishing performance. Mitigating elemental segregation and narrowing the segregation bands represent key strategies for further enhancing polishing performance. Full article

The article presents the results of experimental studies on the possibility of predicting the efficiency of CO₂ mineralization using metallurgical wastes (MWs) from the perspective of chemical thermodynamics and on identifying, accordingly, promising MWs for the production of construction materials and products. The study examined MWs from major Russian iron and steel producers, namely: blast furnace, electric steelmaking, ferroalloy, converter steelmaking slag, as well as nepheline slag, a by-product of nepheline ore processing for alumina. The CO₂ binding capacity of MWs was determined using experimental samples fabricated by semi-dry pressing of MW powders, followed by curing them in a gas atmosphere with an CO₂ concentration of 80% vol. It was found that the investigated MWs are capable of absorbing and binding CO₂, thereby improving their physical and mechanical properties. Experimental samples made from nepheline slag bind 11.3 to 12.0 wt.% of CO₂; samples from steelmaking slags: up to 9 wt.% or more; and samples from blast furnace dump slag: approximately 5.5 wt.% At the same time, the compressive strength of samples from steelmaking slags exceeds 100 MPa, that of samples from nepheline slag approaches 80 MPa, and that of samples from blast furnace dump slag exceeds 50 MPa. It has been established that predicting the efficiency of CO₂ mineralization by metallurgical wastes based solely on chemical thermodynamics is not entirely accurate. To develop a preliminary forecasting model for the carbonate hardening potential of various MWs, further studies are needed to identify additional key factors influencing the carbonate hardening process of MWs. Full article

Wire drawing is a key processing method for producing ultrahigh-strength stainless steel wires. In metastable austenitic steels, the strain-induced martensitic transformation is known to govern strain hardening. However, the transformation mechanism and kinetics behavior under wire drawing remain unclear due to the distinct deformation conditions compared to those of conventional loading modes. In this work, the microstructural evolution, transformation kinetics and strengthening behavior of the 304 stainless steel during cold wire drawing are systematically analyzed. The results show that the transformation is dominated by the austenite → twin→ α′-martensite pathway, with the ε-martensite effectively suppressed. The martensite fraction follows a sigmoidal evolution with the equivalent drawing strain and could be well described by the Olson–Cohen model. The yield strength is increased from 320 MPa to 2 GPa and exhibits a linear relationship with the martensite fraction, indicating a dominant composite strengthening mechanism. These findings clarify the deformation-mode-dependent transformation mechanism and its role in governing mechanical properties during wire drawing. Full article

The increasing generation of ceramic waste from manufacturing defects, construction activities, and demolition operations poses significant environmental and waste management challenges worldwide. This study presents a preliminary investigation into the incorporation of ceramic waste aggregates (CW) as partial and full replacement for natural coarse aggregates in fly ash-based geopolymer concrete (GPC) under water-curing conditions. Five mix compositions were prepared with ceramic waste aggregate replacement levels of 0%, 20%, 40%, 60%, and 100%. Fresh and hardened properties were evaluated using flow table and early-age compressive strength tests at 7 and 14 days. The 20% replacement mix achieved the best compressive strength value of 5.52 MPa at 14 days, slightly exceeding the control GPC mix (5.09 MPa) among the limited mixtures investigated in this preliminary study. However, higher replacement levels resulted in reduced compressive strength, which may be associated with increased porosity, weaker aggregate–matrix bonding, and limitations related to the adopted water-curing regime. Workability remained within acceptable flow ranges for most mixes, although reduced flowability was observed for the 40% replacement. The comparatively low strength values obtained across all mixtures may largely be associated with the absence of heat curing and the inclusion of additional water to improve workability, both of which likely limited the geopolymerization efficiency. Based on the comparatively low compressive strength values obtained, the investigated mixtures, in their current form, are only suitable for low-strength or non-structural applications rather than structural concrete applications. Overall, this study provides preliminary insights into the influence of ceramic waste coarse aggregates on the workability and early-age compressive strength behavior of fly ash-based geopolymer concrete under the adopted experimental conditions. Further optimization of the curing regimes, mix design parameters, and long-term mechanical and durability performance is necessary before broader engineering applicability can be established. Full article

This study investigates the effect of mineral additives of different natures, namely blast-furnace slag, fly ash, and bentonite, on structure formation, phase composition, microstructure, and physicomechanical properties of cement matrices. The analysis included measurements of mass change and linear shrinkage during hardening, determination of density and microhardness, X-ray phase analysis, and microstructural examination by scanning electron microscopy. It was found that the introduction of mineral additives reduced linear shrinkage from 6.06 mm for the control composition to 0.25 mm for the composition with blast-furnace slag, 2.31 mm for the composition with fly ash, and 1.01 mm for the composition with bentonite. The maximum density and microhardness values were obtained for the matrix with blast-furnace slag and amounted to 1.99 ± 0.03 g/cm³ and 39.95 ± 1.12 HV1, respectively, whereas the overall range of values for the investigated compositions was 1.52–1.99 g/cm³ and 30.2–39.95 HV1. X-ray phase analysis showed that the amorphous component varied from 61 to 78%, reaching its maximum value in the composition with blast-furnace slag, which is associated with the formation of poorly crystalline C–S–H and aluminosilicate phases. According to the SEM data, the average size of visible pore-like defects was 2.4 μm for the control composition, 1.4 μm for the composition with blast-furnace slag, 1.3 μm for the composition with fly ash, and 1.7 μm for the composition with bentonite. The most favorable combination of high density, microhardness, developed amorphous component, and homogeneous microstructure was established for the composition with blast-furnace slag. The obtained results can be used as a materials-science basis for the development of cement matrices intended for further studies on the immobilization of solid radioactive waste. Full article

To address the slow early-age strength development of conventional engineered cementitious composites (ECCs), which limits their applicability in rapid-hardening engineering, and to promote the efficient resource utilization of construction and demolition waste, this study proposes a recycled high-ductility early-strength ECC (RHE-ECC) prepared using an ordinary Portland cement (OPC)–sulfoaluminate cement (SAC) composite binder, with recycled fine aggregate (RFA) fully replacing natural fine aggregate (NFA) and PVA fibers incorporated. The effects of the SAC replacement level and water–binder ratio (W/B) on the workability and mechanical properties of RHE-ECC were systematically investigated. The mechanical performance differences between RFA and NFA systems under the SAC–OPC composite binder were compared, and the micro-mechanisms by which RFA regulates the multiple-cracking behavior of ECC were elucidated through XRD and SEM analyses. The results indicate that at a SAC replacement level of 25%, the RHE-ECC achieves a 1 d compressive strength of 19.3 MPa while maintaining a 28 d compressive strength of 47.9 MPa, establishing a favorable balance between rapid early-age strength gain and sustained long-term development. At a W/B of 0.27, the RHE-ECC attains a 28 d ultimate tensile strain of 3.13%. This study systematically investigates, for the first time, the synergistic effects of the OPC-SAC composite cementitious system and full RFA replacement on the strain-hardening behavior of ECC, revealing that the porous old mortar layer of RFA weakens the ITZ, thereby reducing matrix fracture toughness and promoting multiple cracking, which enhances tensile strain capacity. These findings provide a theoretical foundation and technical support for the application of green, high-ductility cementitious composites in rapid-hardening engineering. Full article

High-Mn twinning-induced plasticity (TWIP) steels are renowned for their exceptional strength-ductility synergy. However, their practical applications are severely constrained by inadequate yield strength and poor corrosion resistance. In this study, an N-alloyed TWIP steel (Fe-25Mn-12Cr-0.3C-0.3N, wt.%, designated as TWIP-2) was developed, using an N-free counterpart (Fe-25Mn-12Cr-0.3C, TWIP-1) as a reference. Both steels underwent hot forging (HF) followed by solution treatment (ST). The synergistic effects of N alloying and thermomechanical processing on the microstructural evolution, mechanical properties, and corrosion behavior were systematically investigated. Results indicate that all samples retain a single-phase FCC austenitic structure. N alloying increased the yield strength of the hot-forged TWIP steel from 488.1 MPa to 802.9 MPa while maintaining an elongation after fracture around 40%. Solution treatment markedly improved corrosion resistance, changing the corrosion mode from intergranular attack to pitting. The TWIP-2-ST specimen exhibited the lowest corrosion current density of 2.88 × 10⁻⁵ A/cm² and demonstrated the best overall performance. This comprehensive improvement in mechanical and corrosion performance is primarily attributed to the elevated work-hardening capacity, a higher fraction of low-energy grain boundaries, and the beneficial role of interstitial N in suppressing pitting nucleation and propagation. Full article

The use of iron tailing powder (ITP) and granulated blast-furnace slag (GBFS) offers a feasible route for preparing low-cement mortar while recycling industrial by-products. In this study, seven cement mortar mixtures were designed to investigate the influence of the ITP–GBFS ratio on mechanical properties, microstructure, hydration products, and chloride ion penetration resistance. The mixtures included plain cement mortar (A0), mortar with 50% ITP (A1), mortar with 50% GBFS (A2), and four composite mixtures (A3–A6) in which ITP and GBFS jointly replaced 50% of cement at different ratios. The results showed that the mixture containing 20% ITP and 30% GBFS (A4) exhibited the best overall performance among the composite mixtures. At 28 d, A4 reached a compressive strength of 51.3 MPa and a flexural strength of 11.0 MPa, exceeding those of the plain cement control. SEM and XRD analyses suggested that the optimized ITP–GBFS combination promoted the formation of poorly crystalline hydration products, such as C–S–H/C–A–S–H gels, and refined the pore structure, resulting in a denser hardened matrix. The rapid chloride migration test showed that the chloride migration coefficient of A4 was 15.47 × 10⁻¹² m²/s, only slightly higher than that of A0, indicating that the optimized composite binder maintained chloride penetration resistance close to that of plain cement mortar while replacing 50% of cement. The results indicate that a properly proportioned ITP–GBFS binder can maintain acceptable strength and chloride resistance while reducing cement consumption. Full article

The study presents an approach to the synthesis of micro- and nano-sized biosilica from rice husk ash (RHA) and describes its effective incorporation into cementitious composites for 3D concrete printing (3DCP). It is demonstrated that the calcination of rice husk at 700 °C, followed by sonochemical treatment, leads to the formation of a nanoscale silica phase with high pozzolanic reactivity. X-ray powder diffraction (XRD), infrared spectroscopy (IR), differential thermogravimetric analysis (DTG), and scanning electron microscopy (SEM) show that the incorporation of nano-biosilica (NBS) into the cementitious composites accelerates the hydration process through a nucleation effect and pozzolanic reaction. This, in turn, densifies the hardened cement microstructure and improves compressive strength significantly. Laboratory 3D concrete printing tests demonstrate that adding 1.72 wt.% NBS improves shape retention, decreases layer slump, and improves interlayer bond strength. The results indicate the viability of rice husk ash-derived biosilica as a supplementary cementitious material (SCM) in 3DCP due to its positive influence on the concrete mortar properties and parameters. Full article

In this study, a UV surface modification method was applied to polyamide (PA) fibers, and its effect on certain fresh and hardened properties of fiber-reinforced cementitious systems was investigated. Within the scope of the study, the individual and interactive effects of fiber volume fraction and UV surface modification time were optimized using the Response Surface Methodology (RSM) based on Central Composite Design (CCD). The optimal performance parameters with CCD were identified at 0.50% fiber content and 18 min of UV exposure. Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) were utilized to analyze the fibers and examine the impacts of surface modification. Three different sample groups were prepared to test the effect of UV treatment after optimization: a control cement mortar without fibers, a polyamide fiber-reinforced mortar without UV treatment, and a polyamide fiber-reinforced mortar with UV surface modification. The tensile, flexural, and compressive strength values of the specimens were determined. The results indicated that UV surface modification led to changes in fiber roughness and an increase in oxygen-containing functional groups on the fiber surface. The data revealed that the mechanical performance of fiber-reinforced composites subjected to surface modification improved (with a 27.4% increase in flexural strength and an 11.3% increase in compressive strength compared to the control samples). The findings indicate that UV surface modification improves the fiber–matrix bond in cement-based systems reinforced with polyamide fibers. UV surface modification emerges as an effective and environmentally friendly method for enhancing the performance properties of fiber-reinforced cement-based systems. Full article

Cement is widely used worldwide but contributes to environmental issues due to its reliance on non-renewable resources and high CO₂ emissions. Incorporating waste materials, such as eggshell ash (ESA) and granite waste powder (GWP), as partial cement replacements offers a sustainable approach to reducing the environmental impact of mortar production. This study investigated the effects of replacing cement with a blended eggshell ash–granite waste powder (ESAGWP) mixture at 0%, 5%, 10%, 15%, 20%, 25%, and 30% by weight. Experimental tests evaluated fresh, hardened, and microstructural properties, including workability, compressive strength, bulk density, water absorption, porosity, ultrasonic pulse velocity (UPV), and resistance to sulfate attack at curing ages of 3, 7, 28, 56, and 91 days. The results showed that a 15% replacement of cement with ESAGWP provided optimal performance, maximizing compressive strength, bulk density, and UPV, particularly at later curing ages. At this optimal level, compressive strength reached 35.00 MPa, 36.77 MPa, and 37.58 MPa at 28, 56, and 91 days, respectively, representing improvements of approximately 28.0%, 28.8%, and 26.6% over the plain cement control mix at the corresponding ages. Replacements beyond 15% led to reduced strength, increased porosity, and higher water absorption due to unreacted particles. Microstructural analysis revealed that the ESAGWP15 mix achieved a dense and well-packed matrix, correlating with improved mechanical and durability properties. Overall, the study demonstrates that ESAGWP can serve as an effective supplementary cementitious material (SCM), with 15% replacement recommended for balanced performance and sustainability in mortar production. Full article