Search Results (35)

This study presents a detailed and comprehensive investigation into the macro-scale performance, strength gain mechanisms, environment and economic performance of graphene oxide (GO)-enhanced low-emission concrete. A comprehensive experimental program evaluated fresh and hardened properties, including slump retention, bleeding, air content, compressive, flexural, and tensile strength, drying shrinkage, and elastic modulus. Scanning Electron Microscopy (SEM), energy-dispersive spectroscopy (EDS), Thermogravimetric analysis (TGA) and proton nuclear magnetic resonance (¹H-NMR) was employed to examine microstructural evolution and early age water retention, confirming GO’s role in accelerating cement hydration and promoting C-S-H formation. Optimal performance was achieved at 0.05% GO (by binder weight), resulting in a 25% increase in 28-day compressive strength without compromising workability. This outcome is attributed to a tailored, non-invasive mixing strategy, wherein GO was pre-dispersed during synthesis and subsequently blended without the use of invasive mixing methods such as high shear mixing or ultrasonication. Fourier-transform infrared (FTIR) spectroscopy further validated the chemical compatibility of GO and PCE and confirmed the compatibility and efficiency of the admixture. Sustainability metrics, including embodied carbon and strength-normalized cost indices (USD/MPa), indicated that, although GO increased material cost, the overall cost-performance ratio remained competitive at breakeven GO prices. Enhanced efficiency also led to lower net embodied CO₂ emissions. By integrating mechanical, microstructural, and environmental analyses, this study demonstrates GO’s multifunctional benefits and provides a robust basis for its industrial implementation in sustainable infrastructure. Full article

This study investigates the evolution of the macro- and micro-scale properties of foamed concrete under different saline environments, including sulfate, chloride, and composite salt conditions. The research focuses on the changes in compressive strength, pore structure, and hydration products of the material. Through full-immersion tests and compressive strength measurements, combined with microstructural characterization techniques such as mercury intrusion porosimetry (MIP) and thermogravimetric analysis (TG), the deterioration mechanisms of foamed concrete under salt attack are systematically explored. The results indicate that Sulfate ions exhibit the most aggressive erosion effect, and the presence of chloride ions can produce a “passivation” effect which partially mitigates the damage caused by sulfate ions. Moreover, increasing the material density and incorporation of mineral admixtures contributes to pore structure refinement, significantly enhancing resistance to salt attack. These findings provide a theoretical basis for the practical application of foamed concrete under a complex salt erosion environment. Full article

The pyrolysis of municipal solid waste (MSW) is an efficient, cost-effective, and environmentally beneficial thermochemical treatment method. A macro thermogravimetric analyzer (Macro TGA) was used to study the pyrolysis behavior of cedar and polyethylene (PE) at slow (10 K/min) and fast (700, 800, and 900 °C) heating rates. For cedar, the pyrolysis rate curve showed multi-peak characteristics at the slow heating rate and single-peak characteristics at the fast heating rate. Conversely, PE exhibited the opposite behavior. At fast heating rate of 700 °C, the pyrolysis rate for cedar increased from 0.685 to 0.847 min⁻¹ as the sample temperature rose by over 100 °C, from 351 to 455 °C. By contrast, for PE, the rate increased from 0.217 to 1.008 min⁻¹ with a smaller temperature rise of less than 30 °C, from 630 to 656 °C. According to the International Confederation for Thermal Analysis and Calorimetry (ICTAC) guidelines for analyzing pyrolysis thermogravimetric data, cedar pyrolysis primarily followed a single-step parallel reaction pathway, while PE exhibited some multi-step parallel reactions. A newly developed discrete distributed activation energy model (DDAEM), along with the traditional iso-conversional model (ICM) and distributed activation energy model (DAEM), were applied to predict pyrolysis characteristics at fast heating rates. For cedar, both DDAEM and ICM provide accurate predictions, with average activation energies calculated by these two models being 48.08 and 66.37 kJ/mol, respectively. For PE, DDAEM demonstrates significantly higher predictive accuracy than ICM, particularly when the conversion is below 0.2. As the pyrolysis conversion of PE increases from 0.25 to 0.65, the average activation energy calculated using ICM was found to be 58.32 kJ/mol. By contrast, for DDAEM, the activation energies for the first and second step reactions were 110 and 60 kJ/mol, respectively. This indicates that ICM can only calculate the activation energy for the final step and not for the rate-limiting step. For both cedar and PE, DAEM fails to provide accurate predictions due to the unsteady heating rate. Full article

In recent years, highway infrastructure in the Ningxia region of China has rapidly advanced. Cement–loess is extensively utilized in the roadbed and foundation reinforcement. It is necessary to conduct micro–macro-analysis and model derivation of the electrical resistivity on Ningxia cement–loess, which are beneficial for both the practical application of electrical resistivity and the evaluation of the geotechnical properties of cement–loess. Therefore, a series of electrical resistivity measurements, microstructural observations (scanning electron microscopy), mineral analyses (thermogravimetric analysis), and theoretical analyses were adopted on the cement–loess. The following conclusions can be drawn: The electrical resistivity is negatively related to dry density and water content, while it is positively related to cement dosage and curing age. A cement dosage of 6% exhibits a lower hydration reaction potential compared to 12%, causing a slower increase in electrical resistivity. The formation of calcium silicate gel around particles results in particle clustering and pore filling, reducing the pore area and increasing electrical resistivity. Increased hydration also decreases microscopic orientation, contributing to a higher electrical resistivity of cement–loess. Finally, a new three-dimensional electrical resistivity model was created, finding that the electrical resistivity of Ningxia cement–loess was determined by the dry density, water content (ρ_d·w), cement dosage, and curing age (a_w·T) in an exponential function form. The new three-dimensional electrical resistivity model could be used in the high-efficiency evaluation of the cement–loess geotechnical parameter, offering valuable insights for the monitoring and maintenance of road infrastructure. Full article

Most of the therapeutic systems developed for managing chronic skin wounds lack adequate mechanical and hydration properties, primarily because they rely on a single component. This study addresses this issue by combining organic and inorganic materials to obtain hybrid films with enhanced mechanical behavior, adhesion, and fluid absorption properties. To that aim, chitosan/hydrolyzed collagen blends were mixed with halloysite/antimicrobial nanohybrids at 10% and 20% (w/w) using glycerin or glycerin/polyethylene glycol-1500 as plasticizers. The films were characterized through the use of Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and electron microscopy. The mechanical properties were evaluated macroscopically using tensile tests, and at a nanoscale through atomic force microscopy (AFM) and nanoindentation. Thermodynamic studies were conducted to assess their hydrophilic or hydrophobic character. Additionally, in vitro cytocompatibility tests were performed on human keratinocytes. Results from FTIR, TGA, AFM and electron microscopy confirmed the hybrid nature of the films. Both tensile tests and nanomechanical measurements postulated that the nanohybrids improved the films’ toughness and adhesion and optimized the nanoindentation properties. All nanohybrid-loaded films were hydrophilic and non-cytotoxic, showcasing their potential for skin wound applications given their enhanced performance at the macro- and nanoscale. Full article

Amphiphilic block copolymers of N-vinyl pyrrolidone (NVP) and various vinyl esters (VEs), PNVP-b-PVEs, namely vinyl butyrate (VBu), vinyl decanoate (VDc), and vinyl stearate (VSt), were synthesized through RAFT polymerization techniques. The sequential addition of the monomers methodology was employed starting from the polymerization of NVP followed by the polymerization of the Ves’ monomer. The polymerization of NVP was conducted at 60 °C in benzene solution using AIBN as the initiator and O-ethyl S-(phthalimidylmethyl) xanthate as the CTA. The resulting PNVP macro-CTA was further applied for the polymerization of the vinyl ester in dioxane solution at 80 °C using, again, AIBN as the initiator. The block copolymers were characterized through size-exclusion chromatography (SEC) and NMR spectroscopy. The thermal behavior of the copolymers was studied by Differential Scanning Calorimetry (DSC), whereas their thermal stability via Thermogravimetric Analysis (TGA) and Differential Thermogravimetry (DTG). Full article

High-viscosity modified asphalt binder (HVMA) is used widely as a polymer-modified binder in porous asphalt pavement because it can improve the cohesiveness of the asphalt mixture. However, because of the high voidage in the mixture, HVMA is vulnerable to aging induced by temperature, oxygen, water, sunlight, and other climatic conditions, which degrades the performance of pavement. The properties of asphalt binder are affected adversely by the effects of hygrothermal environments in megathermal and rainy areas. Therefore, it is essential to study the aging characteristics of HVMA under the influence of hygrothermal environments to promote its application as a high-viscosity modifier. A hygrothermal cycle aging test (HCAT) was designed to simulate the aging of HVMA when rainwater was kept inside of the pavement after rainfall in megathermal areas. One kind of base bitumen and three kinds of HVMA (referred to as SBS, A, and B, respectively) were selected in this study. Short-term aging tests, hygrothermal cycling aging tests, and long-term aging tests were performed on the base bitumen and three kinds of modified asphalt binder. Fourier-transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), and dynamic shear rheological (DSR) tests were used to evaluate the properties of the binders on the micro and macro scales. By comparing the index variations of the four binders before and after aging, the effects of the hygrothermal environment on the properties of HVMA were studied. It was found that the effects of the hygrothermal environment expedited the decomposition of the polymer and the formation of carbonyl groups compared with the TFOT and PAV test, which TGA confirmed further. Moreover, the thermal stability of the samples was improved after HCAT. In addition, the master curves of the complex modulus showed that hygrothermal cycles made the high-temperature rutting resistance of asphalt binder increase significantly. All of the results above verified that the effect of hygrothermal cycling could accelerate the aging of HVMA and shorten its service life. Full article

For the first time, new sorbents based on polyacrylonitrile (PAN) fiber and transition metal ferrocyanides were obtained. The main difference between the obtained sorbents and the existing ones is the stage of preliminary preparation of the initial support by converting it into the forms PAN-Fe(OH)₃ or PAN-MnO₂, due to which additional ion exchange groups (carboxyl, carbonyl, etc.) are formed, which increases the amount of ferrocyanide fixed to the support. The best components and conditions for the synthesis of new sorbents were determined (concentration (0.1–0.2 mol/L), as well as pH (1 for sorbents based on PAN-Fe(OH)₃, and 1–5—PAN-MnO₂) of potassium ferrocyanide solution, concentration of transition metal salts (0.02 mol/L), temperature conditions). The influence of the studied solution composition (pH, concentration of Na⁺, K⁺, NH₄⁺ ions) on the cesium distribution coefficients during its recovery by the obtained sorbents was assessed. The possibility of cesium recovery from solutions with pH 1–9 containing macro quantities of cations was demonstrated. The sorbents derived were characterized by modern structural methods such as infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy with EDS analysis. A study of the trace amount sorption of ¹³⁷Cs was carried out in comparison with commercially available highly efficient sorbents (FNS-10 and Termoksid-35), and it was shown that the resulting sorbents are not inferior to industrial ferrocyanide sorbents and can be used for ¹³⁷Cs selective sorption from technological solutions and natural waters. Full article

Fiber-reinforced composites are widely used in industrial development due to their excellent performance, and the study of basalt fiber-reinforced resin (BFRP) as a new type of economical and environmentally friendly material is highly valued, since harsh environments can affect the durability of bonded joints. In this paper, the Araldite^® 2015 adhesive for BFRP–BFRP single lap joints (SLJs) was selected as the subject of study and the joints were analyzed in aging experiments in three environments: deionized water (DW), 3.5% NaCl solution, and 5% NaCl solution at 80 °C for 0 days (no aging), 10 days, 20 days, and 30 days. Using Fick’s second law to describe water absorption in joints and materials, the comparison shows that the water absorption in the joints occurs primarily in the adhesive. Differential scanning calorimetry (DSC) was used to characterize the decrease in the glass transition temperature (Tg) of the adhesive at each failure point, and the thermogravimetric analysis (TGA) tests showed that moisture and heat led to the degradation of the polymer material in the joint. The failure strength of the joints in quasi-static tensile tests was positively correlated with the moisture content of the solution, and the changes in the absorption peaks of the functional groups of the adhesive after aging were observed. The comprehensive macro-micro failed section analysis showed that the water molecules damage the chemical properties of the adhesive, meaning that the adhesive and BFRP binding ability is decreased. The proportion of failure section tear decreased with the extension of the aging time, and a high temperature induced water evaporation and an adhesive post-curing reaction. The change in the failure mode is a result of the combined effect of the post-curing effect and hydrolysis reaction, which is validated by the results of the Fourier infrared spectroscopy (FTIR). This study contributes to an in-depth understanding of the effect of moisture and heat on the residual properties of bonded joints. Full article

Driven by its accessibility, extensive availability, and growing environmental consciousness, solid biomass has emerged as a viable alternative to enhance the diversity of renewable energy sources for electricity generation. To understand the phenomena involved in solid biomass conversion, it is necessary not only to understand the stages of the biomass combustion process but also to understand specifically the kinetics of the reaction and the release of the volatiles. The present work presents an overview of the existing literature on several topics related to the biomass combustion process, its characterization, as well as strategies to develop simple and effective models to describe biomass conversion with a view to the future development of numerical simulation models. Since the focus of most of the investigations is the development of a numerical model, a summary and identification of the different model assumptions and problems involved in thermal analysis experiments are presented. This literature review establishes the significance and credibility of the research, providing the main concepts and assumptions with a critique on their validity. Hence, this work provides specific contributions from a multi-scale perspective which can further be extended to provide insights into the design and optimization of biomass combustion technologies, such as boilers and furnaces. Full article

Pyrolysis is a promising technology used to recycle both the energy and chemicals in plastics. Three types of plastics, polyethylene plastic (PE), polypropylene plastic (PP) and polystyrene plastic (PS) were investigated using thermogravimetry–mass spectrometry (TG–MS) and reactive force field molecular dynamics (ReaxFF-MD) simulation. The thermogravimetric analysis showed that all three plastics lost weight during the pyrolysis in one step. The thermal decomposition stability is PS < PP < PE. The activation energies and reaction mechanism function of the three plastics were determined by the Kissinger and CR methods. Meanwhile, the ReaxFF-MD combined with density functional theory (DFT) was used to calculate the kinetics, as well as explore the pyrolysis mechanism. The calculated kinetic results agree well with the experimental methods. The common pyrolysis reaction process follows the dissociation sequence of the polymer to polymeric monomer and, then, to the gas molecules. Based on the bond length between the monomers and the bond dissociation energy for different plastics, the required energy for polymer dissociation is PS < PP < PE, which microscopically explains the macro-activation energy sequence and thermal stability. Moreover, due to the retention of aromatic rings in its monomers, PS almost completely converts into oil. Full article

Boiler cinder is a kind of mining waste that may cause environmental pollution. Based on this reason, a processing method needs to be carried out. In this study, the influence of CO₂-cured boiler cinder on the compressive and flexural strengths of reactive powder cement concrete (RPC) under NaCl actions is investigated. The mass loss rates (MLR) and the relative dynamic modulus of elasticity (RDME) are measured to reflect the resistance of NaCl erosion. The thermogravimetric analysis (TGA), scanning electron microscope (SEM), and X-ray diffraction (XRD) spectrum are obtained for revealing the mechanism of the macro performance. Results show that the relationship between the MLR and the mass ratio of CO₂-cured boiler cinder fits the quadratic function with NaCl erosion. Meanwhile, the MLR during NaCl action are decreased by increasing the amount of CO₂-cured boiler cinder. The MLR range from 0% to 5.3% during NaCl action, and the decreasing rate of MLR by CO₂ curing on boiler cinder is 0%–51.3%. The function of RDME and the mass ratio of CO₂-cured boiler cinder accords with the positive correlation quadratic function. The mechanical strengths decrease when NaCl erosion is encountered. The mechanical strengths’ decreasing rates of RPC are elevated with the increasing number of NaCl freeze–thaw cycles and the NaCl dry–wet alternations. The increasing rates of flexural and compressive strengths of RPC by 13.1%–36.3% and 11.2%–50.4% are achieved by adding CO₂-cured boiler cinder. As observed from the TGA and SEM’s results, the addition of CO₂-cured boiler cinder can increase the thermogravimetric value and the compactness of hydration products. Full article

Using mechanical drilling to obtain energy resources stored in deep and hard rock layers is becoming increasingly challenging. Therefore, laser irradiation has emerged as a new and promising drilling method. In this study, the effects of immersion conditions on rock-breaking by laser irradiation on the temperature, hole size, rock-breaking efficiency, and macro-fracture after laser irradiation were investigated. Furthermore, the mineral changes and thermogravimetric analysis of rocks were studied. As indicated by the results, the temperature area over 100 °C increases with the increase of irradiation time, and the temperature range of between 2.27 cm² and 13.20 cm² varies with the change of laser power at between 90 W and 135 W. The hole-diameter value of the soaked sample was smaller than that of the dried sample. In addition, the hole depth of the soaked sample reduced by 15% at a power of 90 W and 45% at a power of 135 W, compared with that of the dried sample. The value of the modified specific energy of the soaked sample increased, which was particularly noticeable at low power. The soaked sample had a larger effect on the rate of perforation at high power and a smaller effect at low power. The cracks on the surface of the rock samples became larger after being placed for one month. Fracture length increased from 0.61 to 5.09 mm for dried samples and from 2.24 to 8.7 mm for soaked samples at a laser power of 90 W. Fracture length increased from 6.30 to 9.85 mm for dried samples and from 9.04 to 11.38 mm for soaked samples at a laser power of 135 W. The soaked sample began to show differences when heated at 100 °C, which was caused by the evaporation of some free water molecules in the rock. The main weight loss temperatures of the samples occurred in the range of 640 °C to 900 °C. Full article

Due to the energy crisis that some countries are facing nowadays, the gasification process appears to be a good alternative to produce some energy from solid materials. Increasingly, gasification involves using wastes as a solid fuel, making the process green and reusing some materials that otherwise could end up in a landfill. However, the process of finding the best gasification parameters of a sample can be very expensive and time-consuming. In this sense, a refuse-derived fuel (RDF) char produced from an original RDF under 30 min at 400 °C was tested on a small-scale reactor using macro thermogravimetric analysis (TGA), as presented in this paper. The goal was to study and evaluate the devolatilization and residual carbon rate of the sample under several conditions and, at the same time, quantify and analyze the released gas. In the first round of tests, 5, 10, and 20 g of samples were tested at 750 °C with an excess of air coefficient (λ) = 0 and 0.2. It was possible to conclude that the lower the mass, the higher the devolatilization rate. The λ only had an influence on the devolatilization rate with a 20 g sample. Regarding the gas, CO, CO₂, and H₂ had no variation in the sample mass in contrast to CH₄, which increased with the increase in the sample mass. The second round of tests was performed with samples of 10 g of mass at temperatures of 700, 800, and 900 °C and λ values of 0.15, 0.2, and 0.25. The tests indicated that the temperature influenced the devolatilization rate but not the residual carbon combustion rate. Regarding the gas composition, CH₄, CO₂, and CO followed the same trend, decreasing the concentration with the increase in temperature; in contrast, H₂ increased in concentration with an increase in temperature. The heating value of the gas followed the same behavior as CH₄. Full article

Various genetic and morphological types of voids in carbonate reservoirs make it difficult to diagnose them, which can be seen in the determination of reservoir properties in the northern marginal shear zone of the Caspian Syneclise. A macro- and microscopic study of rocks was carried out by staining carbonates in thin sections with alizarin (determination of the mineral composition, structure, texture, void and fracture spaces, rock genesis). Instrumental methods (X-ray, DTA—differential thermal analysis, TGA—thermo-gravimetric analysis, and probe microanalysis) established the composition of rocks, the nature of their diagenetic transformations, and the formation of void space. The elemental and oxide composition of a number of samples was carried out using the X-ray probe microanalysis method, and mineral formations with intermediate thermochemical properties were found. The results of X-ray, DTA, and TGA measurements and the data of probe microanalysis made it possible to reveal thermally inert formations of oxides of calcium, magnesium, silicon, iron, and other compounds in the composition of carbonates. A relatively low-cost express method was used to determine the material composition and the nature of epigenetic changes and to obtain data on the void space as a result of the development of tectonic fracturing and diagenetic processes of leaching and secondary mineral formation in bedded carbonate reservoirs. Full article