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This paper mainly discusses the mechanical characteristics of steel-reinforced reactive powder concrete (SRRPC) columns with different geometrical dimensions after high-temperature treatment. The bearing capacity, axial stiffness, and ductility of 35 SRRPC column specimens after high-temperature treatment are investigated, considering two parameters: concrete cover thickness (30–100 mm) and slenderness ratio (3–50). The findings indicate that (1) the ultimate bearing capacity increases by 26.0–135.7% as the concrete cover thickness increases and decreases by 1.5–92.0% as the slenderness ratio increases. (2) The axial stiffness increases by 18.9–92.5% as the concrete cover thickness increases and sharply decreases by 31.9–92.6% as slenderness ratio increases, and change degree decreases. (3) As concrete cover thickness and slenderness ratio increase, the displacement ductility coefficient declines, and degree of decrease in displacement ductility coefficient becomes progressively smaller. (4) The bearing capacity, stiffness, and ductility are extremely sensitive to concrete cover thickness, followed by slenderness ratio. Considering confining effect of stirrups and section steel on concrete in the core area, methods for calculating bearing capacity after high-temperature treatment are proposed. From the perspectives of preventing buckling instability and cracking of components after high temperature, two methods for determining the critical concrete cover thickness are given. Finally, the calculation formula of the stability coefficient corresponding to various slenderness ratios after high-temperature exposure is provided, which provides a reference for postfire evaluation and reinforcement of SRRPC structure.

The three-dimensional nonlinear finite element model of steel reinforced reactive powder concrete (SRRPC) column was created to analyze mechanical properties after high temperature. Effect of temperature on mechanical behaviors of RPC, section steel and steel bars were taken into account in model. Accuracy of the temperature distribution and the prediction of eccentric bearing capacity after high temperature was verified by comparing experimental results with numerical results. Effects of eccentricity, loading angle, RPC strength, section steel strength and steel ratio on eccentric bearing capacity after high temperature were analyzed. Findings indicate that: there are two typical failure modes of SRRPC columns after high temperature under different eccentric loads, including small and large eccentric compression failure. As eccentricity has increased, residual bearing capacity declines obviously. Increase of RPC strength will greatly increase residual bearing capacity, and improve ductility to a certain extent. Increase of section steel strength and steel ratio can improve residual bearing capacity to a certain extent. Residual bearing capacity is mostly unaffected by the loading angle. Finally, the calculation formula of normal section bearing capacity of SRRPC bias column after high temperature was established based on limit state design method, which has high accuracy and can provide reference for identifying and strengthening composite structures following fire.

With the continuous development of building structures and the increasing demand for use, the composite structure of steel reinforced reactive powder concrete (SRRPC) with excellent bearing capacity, stiffness, ductility, fire resistance and seismic performance was proposed. In this paper, the SRRPC column model was established by finite element software ABAQUS to investigate mechanical characteristics, and consistency within the model and the test results were verified from the aspects of failure phenomenon, load-displacement curve and bearing capacity. On this basis, the influence of calculated length, section steel strength, reinforcing bar strength, stirrup ratio and concrete strength on the mechanical characteristics of SRRPC columns was investigated. The consequences show that: (1) The bearing capacity rose with the rise of concrete strength, section steel strength, reinforcing bar strength and stirrup ratio, and decreased with the rise of calculated length. (2) On the basis of sensitivity analysis of parameters, bearing capacity is highly sensitive to concrete strength and section steel strength, generally to stirrup ratio and calculated length, and minimally to reinforcing bar strength. (3) The load entering the elastic-plastic stage increased with the rise of concrete strength, section steel strength and stirrup ratio, and decreased with the increase of calculated length. (4) The stiffness increased in each phase with the rise of concrete strength, section steel strength, reinforcing bar strength and stirrup ratio, and changed the most in phase C (0.5–0.75 Pu). The stiffness in each phase decreased with the increase of the calculated length, and changed the most in phase B (0.25∼0.5 Pu). Finally, the calculation method of bearing capacity was proposed.

Organic acid is prevalent in underground environments and, against the backdrop of biogeochemical cycles on Earth, holds significant importance in the degradation of contaminants by redox-active minerals. While earlier studies on the role of organic acid in the generation of reactive oxygen species (ROS) primarily concentrated on electron shuttle or ligand effects, this study delves into the combined impacts of organic acid decomposition and Mackinawite (FeS) oxidation in contaminant transformation under dark aerobic conditions. Using bisphenol A (BPA) as a model, our findings showed that oxalic acid (OA) notably outperforms other acids in enhancing BPA removal, attaining a rate constant of 0.69 h–1. Mass spectrometry characterizations, coupled with anaerobic treatments, advocate for molecule-O2activation as the principal mechanism behind pollutant transformation. Comprehensive results unveiled that carbon center radicals, initiated by hydroxyl radical (•OH) attack, serve as the primary agents in pollutant oxidation, accounting for at least 93.6% of the total •OH generation. This dynamic, driven by the decomposition of organic acids and the concurrent formation of carbon-centered radicals, ensures a steady supply of electrons for ROS generation. The obtained information highlights the importance of OA decomposition in the natural attenuation of pollutants and offers innovative strategies for FeS and organic acid-coupled decontamination.

Cr(VI), a common wastewater pollutant discharged from metallurgical, electroplating and other industries poses a threat to human health and the ecological environment. Layered double hydroxides (LDHs), which have a strong anion exchange capacity and memory effect, are excellent adsorbents that are widely used for heavy metal adsorption. In this this study, we found that Mg-Al-Fe ternary metal oxides (MAF-LDOs) obtained by the calcination of Mg-Al-Fe hydrotalcite-like compounds (MAF-LDHs) had great potential for the treatment of Cr(VI)-containing wastewater. The influences of the adsorption time, Cr(VI) concentrations, pH value and coexisting metal ions were also considered. By using batch adsorption experiments and various characterization tools, it was found that the mechanism of Cr(VI) adsorbed by MAF-LDO involved the use of a memory effect that involved HCrO4-in the reconstruction of laminates. In addition, some laminate -OH groups were protonated to electrostatically attract HCrO4-. The -OH groups in the laminate acted as electron donors to reduce Cr(VI) to Cr(III) that then underwent complexation for the effective removal of Cr(VI). The maximum theoretical adsorption capacity of MAF/LDOs for Cr(VI) was 122.85mg/g at 20°C. Furthermore, the MAF-LDO demonstrated excellent stability and reusability. In conclusion, the MAF-LDO exhibited a simple synthesis process, superior adsorption capacity with a short contact time, and a wide pH range of application. Hence, it is well-suited for industrial wastewater treatment and provides new insights for treating Cr(VI)-containing wastewater.

Aimed to solve the problems of low adsorption capacity, complex preparation and difficult recovery for reported cesium ion adsorbents, a novel high-efficiency Cs+adsorbent of vermiculite/zinc hexacyanoferrate (II) (VMT/ZnHCF) composite was prepared via in situ synthetic method. The structure and properties of this composite were comprehensively characterized using XRD, FTIR, SEM, TEM, and TG-DTA. The maximum Cs+adsorption capacity was recorded to be 378.79mg/g, and this value was significantly higher than the values recorded for other absorbents. This spontaneous and exothermic adsorption behavior could be explained by the Langmuir isotherm model and the pseudo-second-order kinetic model. In addition, this composite exhibited excellent selective adsorption ability towards Cs+even in solutions containing high concentrations of Na+, K+, Ca2+, and Mg2+. The Cs+adsorption mechanism was analyzed by conducting ion exchange experiments and using XRD, SEM, and XPS techniques. The Cs+adsorption of the VMT/ZnHCF composite was synergistically achieved through the ion exchange of Na+in vermiculite interlayers and Zn2+in zinc hexacyanoferrate (II) lattices. A high-efficiency and simple preparation of cesium ion adsorbent has been developed in application of cesium ion wastewater treatment. This work can provide theoretical guidance to realize the non-hazardous treatment of radioactive wastewater.

In this paper, the SHapley Additive exPlanation (SHAP) is utilized in conjunction with the ensemble machine learning (EML) model to study the creep behaviors of recycled aggregate concrete (RAC) for the first time. Five typical EML models, such as Random Forest (RF), Adaptive Boost Machine (AdaBoost), Gradient Boosting Decision Tree (GBDT), Extreme Gradient Boosting Machine (XGBoost), and Light Gradient Boosting Machine (LGBM) are considered. The proposed method can sort the contributions of input features for creep behaviors and interpret the prediction results of the best EML model. The findings show that the existing empirical models fibModel Code 2010 and JTG 3362-2018 cannot satisfy the requirements for RAC creep behavior prediction because the impact of RAC aggregate ratio and other factors are ignored. Moreover, the water-cement ratio and loading age are the two most significant factors. Therefore, this study has the potential to provide insight into the performance of RAC structures and help engineers adjust RAC mechanical behaviors.

Microwave-assisted pyrolysis of Chlorella vulgariswas carried out under compound additives, which contained catalyst (ZSM-5) and microwave absorbent (graphite). The effects of three independent variables (Si/Al ratio of ZSM-5, additives amount and catalyst ratio) on the weight loss characteristics, product yield and energy consumption were investigated. Response Surface Methodology (RSM) coupled with Box-Behnken Design (BBD) was used to optimize pyrolysis time (Ts) and bio-oil yield (Bo) of Chlorella vulgarispyrolysis under three independent variables. The results showed that compound additives can promoted the pyrolysis progress and increased the bio-oil yield. Besides, compound additives can also reduce the energy consumption of bio-oil production in most cases. The predicted results showed that optimal Tsand Bowere 3550s and 22.70%, respectively. GC-MS analysis further revealed that compound additive has stronger effect on denitrogenating than single additive, which is of great significance in alleviating nitrogen oxide pollution caused by bio-oil with high nitrogen content.