Search Results (201)

This study investigates the effectiveness of geopolymer-based binders for the stabilization of silty sand, aiming to improve its strength and durability under cyclic environmental conditions. A composite binder consisting of Ground Granulated Blast-furnace Slag (GGBS) and Recycled Glass Powder (RGP), modified with nano poly aluminum silicate (PAS), was used to treat the soil. The long-term performance of the stabilized soil was evaluated under cyclic wetting–drying (W–D) conditions. The influence of PAS content on the mechanical strength, environmental safety, and durability of the stabilized soil was assessed through a series of laboratory tests. Key parameters, including unconfined compressive strength (UCS), mass retention, pH variation, ion leaching, and microstructural development, were analyzed using field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Results revealed that GGBS-stabilized specimens maintained over 90% of their original strength and mass after eight W–D cycles, indicating excellent durability. In contrast, RGP-stabilized samples exhibited early strength degradation, with up to an 80% reduction in UCS and 10% mass loss. Environmental evaluations confirmed that leachate concentrations remained within acceptable toxicity limits. Microstructural analysis further highlighted the critical role of PAS in enhancing the chemical stability and long-term performance of the stabilized soil matrix. Full article

In railways, problems in braking and traction can be caused by so-called low-adhesion conditions. Adhesion is increased by sanding, where sand grains are blasted towards the wheel–rail contact. Despite the successful use of sanding in practice and extensive experimental studies, the physical mechanisms of adhesion increase are poorly understood. This study combines experimental work with a DEM model to aim at a deeper understanding of adhesion increase during sanding. The experimentally observed processes during sanding involve repeated grain breakage, varying sand fragment spread, formation of clusters of crushed sand powders, plastic deformation of the steel surfaces due to the high load applied and shearing of the compressed sand fragments. The developed DEM model includes all these processes. Two types of rail sand are analysed, which differ in adhesion increase in High-Pressure Torsion tests under wet contact conditions. This study shows that higher adhesion is achieved when a larger proportion of the normal load is transferred through sand–steel contacts. This is strongly influenced by the coefficient of friction between sand and steel. Adhesion is higher for larger sand grains, higher sand fragment spread, and higher steel hardness, resulting in less indentation, all leading to larger areas covered by sand. Full article

In this study, we model a solution surface, with each point having nine components using artificial intelligence (AI), to optimise the effects of ground vibration during blasting operations in an open-pit diamond mine. This model has eight input parameters that can be adjusted by blasting engineers to arrive at a desired output value of ground vibration. It is built using the best performing artificial neural network architecture that best fits the blasting data from 100 blasting events provided by the Debswana diamond mine. Other AI algorithms used to compare the model’s performance were the k-nearest neighbour, support vector machine, and random forest—together with more traditional statistical approaches, i.e., multivariate and regression analyses. The input parameters were burden, spacing, stemming length, hole depth, hole diameter, distance from the blast face to the monitoring point, maximum charge per delay, and powder factor. The optimised model allows for variations in the input values, given the constraints, such that the output ground vibration will be within the minimum acceptable value. Through unconstrained optimisation, the minimum value of ground vibration is around 0.1 mm/s, which is within the vibration range caused by a passing vehicle. Full article

The use of recycled glass powder (RCGP) is investigated as a partial replacement for ground granulated blast furnace slag in blended CEM II/A-LL cements using thermodynamic modelling to simulate cement paste hydration at a water-to-cement (w/c) ratio of 0.5. This study allows a rapid means of examining the likely evolution of these materials over the first two to three years, allowing experimental work to focus on promising formulations. A comparison is made between the evolving solid phase and solution chemistries of four materials: a standard Portland-limestone (CEM II/A-LL), a ‘control’ blend, comprising equal quantities of CEM II/A-LL with GGBS and two novel blended cements containing RCGP. These represent 15% replacement (by mass) of GGBS by RCGP blended with either 40% or 60% CEM II/A-LL. The simulations were performed using the code HYDCEM, a cement hydration simulator, which calls on the thermodynamic model PHREEQC to sequentially simulate the evolution of the four cements. The results suggest that partial replacement of GGBS by 15% RCGP results in no significant change in system chemistry. The partial replacement of cementitious slag by waste container glass provides a route by which this material can be diverted from the landfill inventory, and the mass-balance and energy balance implications will be reported elsewhere. Full article

Lateritic clay is widely distributed in southern China, and its strength is greatly affected by water content. The elevated moisture content in lateritic clay during monsoon periods frequently results in insufficient shear strength for standard engineering applications. Large quantities of solid waste, including steel slag, fly ash, and granulated blast furnace slag, are produced as industrial by-products. This paper is based on the backfilling resource utilization of steel slag, fly ash, and ground-granulated blast-furnace slag as lateritic clay improvement admixtures, along with the stress–strain behavior, strength characteristics, and microstructure of steel-slag-modified lateritic clay, fly-ash-modified lateritic clay, and ground-granulated blast-furnace slag-modified lateritic clay, by combining uniaxial compression tests, straight shear tests, and scanning electron microscopy observation. The experimental results were analyzed to determine the appropriate dosages of three kinds of solid waste and their mechanisms in lateritic clay modification. The results indicate that the unconfined compressive strength of SS-modified lateritic clay exhibited an increase with an increase in SS dosage in the range of 1–7%, the unconfined compressive strength of FA-modified lateritic clay showed an increase with an increase in FA dosage in the range of 1–5%, and the unconfined compressive strength of GGBFS-modified lateritic clay increased with an increase in the use of GGBFS in the range of 1–5%. Under the condition of a 7-day curing age, the unconfined compressive strength of lateritic clay modified with 7% SS increased by approximately 397%, while that modified with 5% FA and 5% GGBFS exhibited increases of about 187% and 185%, respectively. The stress–strain relationship of fly-ash and blast-furnace slag-modified lateritic clays showed elastic–plastic deformation. But the stress–strain behavior of steel-slag-modified lateritic clay at a steel slag dose greater than 5% and a maintenance age greater than 7 days showed elastic deformation. Analyzing the SEM images shows that the more hydration products are generated, the relatively higher the unconfined compressive strength of modified lateritic clay is, and the form of deformation of modified lateritic clay is closer to elastic deformation. Through comparative analysis of modified lateritic clay samples, this study elucidates the property-altering mechanisms of waste powder additives, guiding their engineering utilization. Full article

Alkali-activated slag-like powder (AASP) materials are a novel type of binder prepared by activating slag-like powder (SP) with alkaline activators, providing a sustainable alternative to traditional cement for construction in remote mountainous regions, as well as on islands and reefs far from the inland, reducing transportation costs, shortening construction timelines, and minimizing energy consumption. SP is locally produced from siliceous and calcareous materials through calcining, water quenching, and grinding, exhibiting reactivity similar to that of ground granulated blast-furnace slag. In this study, siliceous sand and ground calcium carbonate powder were utilized to produce SP, with sodium carbonate (Na₂CO₃), sodium hydroxide (NaOH), and their mixture serving as activators. The results indicated that the Ca/Si ratio in SP, along with the dosage of Na₂CO₃ (D_sc) and Na₂O content (N_c) in the activator, significantly affected the compressive strength of AASP materials at both early and late stages. The 28-day compressive strength reached up to 78.95 MPa, comparable to that of alkali-activated slag (AAS) materials. The optimum mix ratio for Na₂CO₃-NaOH based AASP materials was also determined to be 80% D_sc and 8% N_c (C8N2-8). Microscopic analyses were employed to investigate the changes in the macroscopic properties of AASP materials driven by hydration products, chemical group composition, and microstructure. Full article

This study analyzes the impact of powder-blasted surface modification on the performance of non-imaging solar concentrators and evaluates a ray-tracing simulation approach to virtual solar power measurements. Powder blasting was applied to poly(methyl methacrylate) (PMMA) sheets to create a rough, Lambertian-like scattering surface, enhancing light trapping and total internal reflection. The effects of this modification were systematically assessed using optical transmission spectroscopy, angular scattering measurements, and solar cell efficiency characterization under standard AM1.5 illumination. The results show that surface roughening significantly improves light redirection toward the concentrator’s edge, enhancing solar cell performance. OptisWorks ray-tracing simulations were employed to model the concentrator’s optical behavior, demonstrating strong agreement (within 5–10% deviation) with experimental data. These findings confirm that surface modification is crucial in optimizing concentrator efficiency and establishing ray tracing as a reliable tool for virtual performance evaluation in photovoltaic applications. Full article

To address the demands of the low-carbon era, this study proposed a solution by using eggshell powder (ESP), fly ash, and ground granulated blast furnace slag together with alkaline solution in the preparation of lightweight geopolymer foam concrete (LWGFC). The aim of this study is to investigate the influence of replacing precursor materials with 5–20% ESP on the expansion behavior, physical, mechanical characteristics, and thermal conductivity of LWGFC. Additionally, the study examines the effect of varying the silicate modulus (SiO₂/Na₂O ratios of 1.0, 1.25, and 1.5) on the properties of LWGFC. Incorporating ESP from 5% to 20% with a constant SiO₂/Na₂O ratio reduced the initial setting time, while a high SiO₂/Na₂O ratio controlled the setting time and expansion volume. The high SiO₂/Na₂O ratio decreased the porosity and enhanced the compressive strength of the LWGFC but increased the thermal conductivity. The inclusion of more than 10% ESP content negatively affected compressive strength; however, a high SiO₂/Na₂O ratio can mitigate this detrimental effect. The thermal conductivity of optimal-content ESP mixtures with a SiO₂/Na₂O ratio of 1.0 was about 0.84 W/m·K, which is 2.1% lower than mixtures with a ratio of 1.25 and 18.6% lower than those with a ratio of 1.5. High-content ESP mixtures had a density of 1707 kg/m³, 0.97 W/m·K, and a compressive strength of 18.9 MPa at a low SiO₂/Na₂O ratio. Finally, the inclusion of ESP in the LWGFC, along with the use of an appropriate silicate modulus, resulted in improved strength development while decreasing porosity. Full article

With the rapid development of big data and artificial intelligence technologies, the era of Industry 4.0 has driven large open-pit mines towards digital and intelligent transformation. This is particularly true in mature mining areas such as the Yanshan Iron Mine, where the depletion of shallow proven reserves and the increasing issues of mixed surrounding rocks with shallow ore bodies make it increasingly important to build intelligent mines and implement green and sustainable development strategies. However, previous mineralization predictions for the Yanshan Iron Mine largely relied on traditional geological data (such as blasting rock powder, borehole profiles, etc.) exploration reports or three-dimensional explicit ore body models, which lacked precision and were insufficient to meet the requirements for intelligent mine construction. Therefore, this study, based on artificial intelligence technology, focuses on geoscience big data mining and quantitative prediction, with the goal of achieving multi-scale, multi-dimensional, and multi-modal precise positioning of the Yanshan Iron Mine and establishing its intelligent mine technology system. The specific research contents and results are as follows: (1) This study collected and organized multi-source geoscience data for the Yanshan Iron Mine, including geological, geophysical, and remote sensing data, such as mine drilling data, centimeter-level drone image data, and high-spectral data of rocks and minerals, establishing a rich mine big data set. (2) SOM clustering analysis was performed on the elemental data of rock and mineral samples, identifying key elements positively correlated with iron as Mg, Al, Si, S, K, Ca, and Mn. TSG was used to interpret shortwave and thermal infrared hyperspectral data of the samples, identifying the main alteration mineral types in the mining area. Combined with spectral and elemental analysis, the universality of alteration features such as chloritization and carbonation, which are closely related to the mineralization process, was further verified. (3) Based on the spectral and elemental grade data of rock and mineral samples, a training model for ore grade–spectrum correlation was constructed using Random Forests, Support Vector Machines, and other algorithms, with the SMOTE algorithm applied to balance positive and negative samples. This model was then applied to centimeter-level drone images, achieving high-precision intelligent identification of magnetite in the mining area. Combined with LiDAR image elevation data, a real-time three-dimensional surface mineral monitoring model for the mining area was built. (4) The Bagged Positive Label Unlabeled Learning (BPUL) method was adopted to integrate five evidence maps—carbonate alteration, chloritization, mixed rockization, fault zones, and magnetic anomalies—to conduct three-dimensional mineralization prediction analysis for the mining area. The locations of key target areas were delineated. The SHAP index and three-dimensional explicit geological models were used to conduct an in-depth analysis of the contributions of different feature variables in the mineralization process of the Yanshan Iron Mine. In conclusion, this study successfully constructed the technical framework for intelligent mine construction at the Yanshan Iron Mine, providing important theoretical and practical support for mineralization prediction and intelligent exploration in the mining area. Full article

To address the limitations in determining the amount of activator and optimizing the mix proportion during the preparation of bauxite tailings (BX)-based alkali-activated materials (AAMs), as well as the insufficient research on the interactions of multiple factors, this study aims to synthesize and optimize composite cementitious materials with BX and granulated blast furnace slag (GGBFS) as precursors via response surface methodology and central composite design (RSM-CCD). The optimal alkali activator proportion and slag content for alkali-activated, bauxite tailing, powder slag cementitious materials were investigated. A series of tests, including XRD, FTIR, TG-DSC, and SEM–EDS, were used for analysis to further investigate the effects of the alkali activator dosage on the mechanical properties and the influence of the slag content on the hydration products and microstructure. The results show that the optimal composition of alkali-activated bauxite tailings-based cementitious material is 35% slag content, 4% alkali content, a water glass modulus of 1.3, and a water–solid ratio of 0.32. The relationship model between the activator parameters and compressive strength fits well, with model determination coefficients of 0.9803 for f_3c and 0.9789 for f_28c. The identified hydration products were mainly C-S-H and C-(N)-A-S-H gels in the form of SiQ₃ and SiQ₄ tetrahedra. The SEM–EDS results show that the incorporation of slag changes the silicon–aluminum ratio of the system, promoting an increase in the content of hydration products and increasing the complexity and density of the structure. GGBFS also has a micro-aggregate filling effect and a nucleation effect, which improve the distribution of hydration products. This study demonstrates the significant potential of BX in the preparation of cementitious materials, which contributes to the sustainable development of the construction industry. Full article

Geopolymer-based grouting materials often have a higher early strength, better durability, and lower environmental impact than those of traditional cement-based grouts. However, existing geopolymer grouts face common challenges such as rapid setting and low compatibility with treated substrates. This study develops a new grouting material using industrial byproducts to overcome these limitations while optimizing performance for reinforcing silty mudstone slopes. The base materials used were ground granulated blast furnace slag (GGBFS) and zeolite powder, with calcium lignosulphonate (CL) serving as the retarding agent and NaOH as the alkali activator. The investigation focused on the effects of the mix ratio and water–binder ratio on the setting time, flowability, bleeding rate, concretion rate, and compressive strength of the new grouting material. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were employed to examine the action mechanism of the material components in the slurry. The one-factor standard deviation method and Grey Relational Analysis (GRA) were used to assess the influence of each material component on the slurry performance indices and the correlation between each performance index and its optimal mix ratio. Subsequently, the optimal mix ratio of the new grouting material was ascertained. The results indicate that the setting time is positively correlated with the zeolite powder and CL dosages and the water–binder ratio, while it is inversely related to the NaOH dosage. The flowability is significantly enhanced with increasing zeolite powder and NaOH dosages, but decreases at a higher CL dosage and water–binder ratio. This insight is crucial for optimizing the workability of the grouting material under various conditions. The optimal ratio of the grout is zeolite powder:GGBFS:CL:NaOH = 30:70:5:7, with a water–binder ratio of 0.6. Compared to existing commercial grouting materials, the compressive strength of this new grout is comparable to that of silty mudstone. This significantly reduces the problem of stress concentration at the grout–rock interface due to strength differences, thus effectively reducing the risk of secondary cracking at the interface. These findings provide a new material solution for grouting and repairing fractured silty mudstone slopes. Full article

Steel slag is a common solid waste, but it has good microwave absorbing ability. The poor microwave sensitivity of asphalt mixture limits the development of microwave maintenance for asphalt pavement. Therefore, it is significant to apply steel slag to asphalt pavement. This study analyzes the difference in the microwave sensitivity and performance between the asphalt mastics with blast furnace slag powder (BFSP), converter slag powder (CSP), refined slag powder (RSP), and limestone powder (LP). First, the chemical composition of BFSP, CSP, RSP, and LP is analyzed by X-ray diffractometer (XRD) and X-ray fluorescence (XRF) tests. Then, the micromorphology characteristics of the asphalt mastic with BFSP, that with CSP, that with RSP, and that with LP are studied using atomic force microscope (AFM) tests. Finally, the rheological properties of the four asphalt mastics are investigated through dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. The results show that steel slag powder can effectively improve the microwave sensitivity of asphalt mastic. RSP and CSP can improve the anti-deformation ability of asphalt mastic. In addition, steel slag powders have an adverse effect on the low-temperature cracking resistance of asphalt mastic, but the creep strength and creep rate of asphalt mastic with steel slag powder are within a reasonable range. In general, steel slag powder as filler has great application potential in road engineering. However, it has a certain influence on the performance of asphalt mastic. It is necessary to carry out targeted selection in practical engineering. Full article

This study aims to assess the mechanical tensile properties of Polyamide produced via selective laser sintering (SLS). The research focuses on the effects of post-processing, positional dependency, anisotropy, and the repeatability of SLS print jobs on material properties. Understanding this anisotropy is crucial for reliable component simulation. A design-appropriate simulation method is developed. A total of 27 identical specimens were fabricated in various orientations and positions within the build chamber, repeated across three print jobs, alongside standard specimens for different post-processing treatments and tempering durations. The mechanical tensile properties were evaluated through tensile tests and compared with simulation outcomes. A new material modeling concept was formulated in the finite element (FE) program ANSYS, employing an orthotropic approach based on linear elastic initial deformation. The Hill Yield Criterion was utilized to model the transition to the plastic region, characterized by a nonlinear strain hardening curve. The print direction was integrated into the FE simulation mesh via a local material coordinate system. Surface treatment via glass bead blasting resulted in slight increases in mechanical response, while tempering had a minor influence. Significant anisotropy was observed, with only the z-position in the build chamber affecting mechanical properties. Successful mapping of anisotropy in structural simulations was achieved. This research did not address optimization of the printing process, recyclate effects, powder aging, or fatigue. The findings provide a comprehensive analysis of the mechanical behavior of SLS-printed specimens, serving as a foundation for treatment methodologies and simulation strategy development. Full article

This study evaluates the influence of multiwall carbon nanotubes (MWCNTs), reduced graphene oxide (rGO), and magnesium oxide (MgO) on the thermal conductivity of alkali-activated engineered composites (AAECs). Thirty-two ambient-cured AAECs consisting of two types of powdered-form reagents/activators (type 1—calcium hydroxide: sodium meta silicate = 1:2.5; type 2—calcium hydroxide: sodium sulfate 2.5:1), two dosages of MgO (0 and 0.5%) of MgO, three percentages (0, 0.3%, and 0.6%) of MWCNTs/rGO, and binary (45% ground granulated blast furnace slag ‘GGBFS’ and 55% Class C fly ash ‘FA-C’) and ternary combinations (40% GGBFS, 25% FA-C and 35% class F fly ash ‘FA-F’) of industrial-waste-based source materials, silica sand, and polyvinyl alcohol (PVA) fiber were developed using the ‘one-part dry mix’ technique. Problems associated with the dispersion and agglomeration of nanomaterials during production were avoided through the use of defined ultra-sonication with a high-shear mixing protocol. The impact of the combination of source materials, activators, and MgO/MWCNT/rGO dosages and their combinations on the thermal properties of AAECs is evaluated and discussed based on temperature–time history and thermal conductivity/diffusivity properties along with micro-structural characteristics. It was found that the change in temperature of the AAECs decreased during testing with the addition of MWCNTs/rGO/MgO. The thermal conductivity and diffusivity of AAECs increased with the increase in MWCNT/rGO/MgO contents due to the formation of additional crystalline reaction products, improved matrix connectivity, and high conductivity of nanomaterials. MWCNT AAECs showed the highest thermal conductivity of 0.91–1.26 W/mK with 49% enhancement compared to control AAECs followed by rGO AAECs. The study confirmed the viability of producing MgO/MWCNT/rGO-incorporated AAECs with enhanced thermal properties. Full article

Steel slag powder (SS), ground granulated blast-furnace slag (GGBS), and flue gas desulfurization gypsum (FDG) are environmentally friendly and cost-effective substitute materials for ordinary Portland cement (OPC). This study investigated the use of industrial solid wastes, including SS, GGBS, and FDG, as auxiliary materials in OPC to stabilize pretreated recycled concrete aggregate (pretreated RCA). The use of pretreated RCA, mixed cementitious materials, and water at the optimum content created a mixture designated recycled cement-stabilized macadam (RCSM). A series of mechanical tests were conducted to clarify the performance of the RCSM, and microscopic tests were performed to elucidate the microcharacteristics of the mixed cementitious materials. With a curing time from 3 days to 28 days, the unconfined compression strength (UCS) of the mixed cementitious materials (A4) composed of SS, GGBS, FDG, and OPC increased by 5.94–10.79% compared with that of the cementitious material of OPC (A0). The UCS of the mixture composed (C4) of SS, GGBS, FDG, OPC, and pretreated RCA was greater than that of the mixture composed (C0) of OPC and RCA from 7 days to 90 days, increasing by 4.26–8.35%. The total drying shrinkage coefficient of C4 was lower than that of C0, whereas the temperature shrinkage coefficient of C4 was higher than that of C0, indicating that the use of A4 can effectively reduce drying shrinkage cracking in C4. The hydration products of A4 primarily consisted of flocculent calcium silicate hydrate (C-S-H) gel, fibrous calcium aluminate hydrate gel, and needle-like ettringite crystals. The interlocked growth of C-S-H gel and ettringite crystals continued and promoted an increase in the UCS of the cementitious system. The test results provide a reference for the application of similar materials. Full article