Effect of Limestone Powder Mixing Methods on the Performance of Mass Concrete.

Using limestone powder (LP), the by-product of manufactured sand, to replace part of fly ash (FA) or manufactured sand could not only turn waste into treasure and decrease the price of concrete, but could also enhance the performance of concrete and reduce environmental pollution. However, the impact of various LP incorporation methods on the performance of mass concrete was inconsistent. In this paper, the effects of LP on the workability, compressive strength, constrained expansion rate, hydration temperature and impermeability of mass concrete were studied by replacing FA or manufactured sand alone and replacing FA and manufactured sand simultaneously. The results showed that the impact of LP on the performance of mass concrete was equal when it replaced FA alone and FA and manufactured sand at the same time. When the replacement amount was 20%, the workability, expansibility and early strength of concrete were improved, but the later strength and impermeability were slightly reduced. The workability, compressive strength, expansibility and impermeability of mass concrete were improved when manufactured sand was replaced alone, and the optimal dosage was 10%. The LP, moreover, reduced the hydration temperature peak of concrete in three kinds of mixing methods, but the temperature peak appeared earlier. At lower dosages, LP optimized pore structure and promoted the early hydration of cement through filler effects and nucleation effects. When LP replaced manufactured sand, the microstructure of concrete was more dense, so the replacement of manufactured sand had a better effect on the improvement of concrete properties. A reference value for the use of LP in mass concrete is provided in this study.

Mechanism of Acrylate Emulsion-Modified Cement-Based Materials.

Polymer-modified cement-based materials have been widely used in building materials. Polymers play a crucial role in improving the performance of cement-based materials. At the same time, different polymers are added according to specific special requirements to meet the needs of the industry. Therefore, this paper reviewed the research on the performance and mechanism of acrylic lotion in modifying cement-based materials. Firstly, the role of acrylate lotion in the improvement of the volume stability, mechanical properties, and durability of cement-based materials was discussed to explore the advantages and disadvantages further, optimize the application of polymer in cement-based materials according to the performance improvement, and amplify the advantages of polymer modification. Secondly, the physicochemical mechanism of acrylate-lotion-modified cement-based materials was discussed, and the products and reactants of acrylate lotion in the reaction process of cement-based materials, as well as the interaction mechanism of acrylic lotion and cement hydrates, were clarified. Cement hydration is a crucial step in exploring the mechanism of polymer-modified cement-based materials. Due to the acrylate lotion filled on the cement surface and the physical and chemical interaction between them, the cement hydration is delayed, resulting in the cement retarding phenomenon. This paper describes its mechanism. Finally, the improvement effect of acrylate lotion on the performance of cement-based materials was reviewed, the research methods of mechanism research on acrylate-lotion-modified cement-based materials were evaluated, and suggestions for future research methods were provided.

Exploration on the occurrence state of fluorine in cement hydration products mixed with high fluorine alkali free liquid accelerator.

If there was abundant fluorine in shotcrete, it might leach out and pollute the soil or migrate to corrode the reinforcement.Therefore, this research mainly investigated the basic properties of high-fluorine alkali free liquid accelerator (HF-AFA) and its occurrence forms in cement hydration products.The macro-test results showed that with the increase of HF-AFA dosage, it appeared excellent coagulation promoting property. However, when the HF-AFA dosage exceeded 7.0%, the 1d compressive strength of mortar was lower than 7.0 MPa. In addition, by measuring the early hydration heat of cement, C3A, C3S, C2S and C4AF pastes with and without HF-AFA, and combining XRD and SEM micro-analysis, the occurrence forms of fluorine in different clinker minerals were obtained.The final analysis results indicated that fluorine mainly existed in the form of CaF2, CaAlF5 and Ca2AlF7 crystals in C3A and C3S minerals, while only little CaF2 crystals appeared in C2S and C4AF minerals.

Study on the Influence of Shrinkage-Reducing Materials on the Volume Stability of Shotcrete with a Fluorine-Containing Alkali-Free Accelerator.

In contrast to ordinary concrete, shotcrete exhibits greater shrinkage deformation. The utilization of an aluminum fluoride alkali-free accelerator (AF) is prevalent in tunnel engineering, attributed to its economical nature and fast setting and hardening. Currently, there is a dearth of research on the volume stability of aluminum fluoride accelerators, and no relevant studies have been conducted on the application of shrinkage-reducing materials in shotcrete using an aluminum fluoride accelerator. With the use of an aluminum fluoride accelerator, the early strength of shotcrete is reduced, and the addition of a shrinkage-reducing agent (SRA) and super-absorbent polymer (SAP) can also lead to a further reduction in the early strength of concrete. Therefore, this study aims to investigate the influence of these two shrinkage-reducing materials (SRA and SAP) on the workability and mechanical properties of shotcrete. The primary focus of this research is to determine the better compensation effect of the two shrinkage-reducing materials. To accomplish this, the study focuses on assessing the setting time, compressive strength, and volume stability of shotcrete that has been mixed with an aluminum fluoride accelerator using SRA and SAP. Additionally, we also aim to explore the hydration and shrinkage compensation mechanism of these shrinkage-reducing materials on shotcrete by conducting a microscopic test analysis.

Review of the Influence of Acrylate Lotion on the Properties of Cement-Based Materials.

Polymer-modified cement-based materials have been widely used in the construction field. Acrylate lotion significantly improves durability, toughness, and bending resistance, especially durability, because the porosity of cement-based materials is reduced, preventing the entry of harmful ions and water. When acrylate lotion was at 20%, the resistance of cement-based materials to chloride ion penetration increased by 40%. At the same time, the fracture toughness of cement-based materials modified with acrylate lotion and carbon nanotubes increased by 10-15%. The flexural strength of cement-based materials modified by acrylate lotion and fiber increased by 29%. Additives such as TiO2 have a unique impact on the modification of cement-based materials, which has attracted the interest of researchers. This paper reviewed the performance of acrylate lotion-modified cement-based materials and the application of acrylate lotion in the field, which systematically increased the durability, mechanical properties, and waterproof properties of cement-based materials when acrylate lotion was modified, acrylate lotion was modified with nanomaterials, acrylate lotion was modified with other polymers, acrylate lotion was modified with fiber, and when acrylate lotion was modified with other additives. The shortcomings of acrylate lotion modification with different materials were reviewed and evaluated, and the comprehensive performance of cement-based materials modified by acrylate lotion was expected to achieve maximum strength improvement under the synergistic effect of various modifications.

Effect of Micro-Nano Bubble Water and Silica Fume on Properties of C60 Concrete.

Micro-nano bubble water (WNBW) in concrete is relatively uncommon due to its newness as a technology. This paper presents the preparation of C60 concrete with 35% fly ash (FA) through WNBW and varying amounts of silica fume (0%, 4%, 7%, and 10% SF). The study examines the impact of WNBW and SF on the working performance, compressive strength, and durability of concrete. The findings indicate that applying WNBW and SF independently or jointly deteriorates the working performance of fresh concrete. However, compared to regular mixing water, WNBW reduces the concrete passing time through the V-funnel, decreasing by 40%, 39.1%, 42.9%, and 50.5% for the four varying SF contents. Furthermore, using WNBW, SF, or both resulted in the increased compressive strength of concrete at 7 days and 28 days, with 7% SF content yielding a 12.2% and 6.6% increase, respectively. Using a combination of WNBW and SF has been shown to decrease the impermeability of concrete effectively. The addition of 4% SF results in the lowest electric flux when using regular mixing water, with a discernible decrease of 30.1% compared to the control group. Conversely, using WNBW as mixing water yields a decrease in electric flux at each SF content, with the maximum decrease being 39.7%. Furthermore, both the single and combined use of these materials can contribute to the reduction in the carbonation resistance of the concrete. C60 concrete mixed with 7% SF and 100% WNBW boasts enhanced frost resistance, as indicated by the mass loss and dynamic elastic modulus loss being the least following freeze-thaw under the same SF content. According to the findings of the tests, there is evidence that the incorporation of 7% SF and 100% WNBW into C60 concrete results in lowered viscosity, a highly advantageous attribute for actual construction. Additionally, this mixture displays impressive compressive strength and durability properties. These results provide technical support regarding the integration of WNBW and SF in C60 concrete.

Low Temperature Thermal Treatment of Incineration Fly Ash under Different Atmospheres and Its Recovery as Cement Admixture.

Municipal solid waste incineration fly ash is classified as hazardous waste because it contains dioxins and a variety of heavy metals. It is not allowed to be directly landfilled without curing pretreatment, but the increasing production of fly ash and scarce land resources has triggered consideration of the rational disposal of fly ash. In this study, solidification treatment and resource utilization were combined, and the detoxified fly ash was used as cement admixture. The effects of thermal treatment in different atmospheres on the physical and chemical properties of fly ash and the effects of fly ash as admixture on cement properties were investigated. The results indicated that the mass of fly ash increased due to the capture of CO2 after thermal treatment in CO2 atmosphere. When the temperature was 500 °C, the weight gain reached the maximum. After thermal treatment (500 °C + 1 h) in air, CO2, and N2 atmospheres, the toxic equivalent quantities of dioxins in fly ash decreased to 17.12 ng TEQ/kg, 0.25 ng TEQ/kg, and 0.14 ng TEQ/kg, and the degradation rates were 69.95%, 99.56%, and 99.75%, respectively. The direct use of fly ash as admixture would increase the water consumption of standard consistency of cement and reduce the fluidity and 28 d strength of mortar. Thermal treatment in three atmospheres could inhibit the negative effect of fly ash, and the inhibition effect of thermal treatment in CO2 atmosphere was the best. The fly ash after thermal treatment in CO2 atmosphere had the possibility of being used as admixture for resource utilization. Because the dioxins in the fly ash were effectively degraded, the prepared cement did not have the risk of heavy metal leaching, and the performance of the cement also met the requirements.

Physical properties, chemical composition, and toxicity leaching of incineration fly ash by multistage water washing.

Incineration fly ash contains a large amount of chloride, which limits the scope of its resource utilization. Water washing effectively removes chlorides and soluble substances, increasing the ability to dispose of them. The properties of incineration fly ash after multi-level water washing have been studied, providing theoretical guidance for the safe disposal of water-washed ash at all levels. Taking a practical project as an example, this paper analyzed the impact of three-stage countercurrent water washing on the physicochemical properties and toxicity leaching of incineration fly ash with different washing grades by XRD, BET, XRF, SEM, and ICP-MS. The results showed that with the improvement of washing grade, the removal rate of chloride ions was more than 86.96%. However, due to the removal of soluble substances, dioxins enriched from 98 ng-TEQ/kg of raw ash to 359 ng-TEQ/kg of tertiary washed incineration fly ash. Cr, Cu, and Zn also increased from 40.35 mg/L, 356.55 mg/L, and 3290.58 mg/L of raw ash to 136.30 mg/L, 685.75 mg/L, and 5157.88 mg/L, respectively. Pozzolanic activity had increased from 40.56% of the raw ash to 74.12% of the tertiary-washed incineration fly ash. There was no risk of excessive heavy metal leaching, and the dioxin content was lower than the raw ash in the primary washed incineration fly ash. After multi-stage water washing, incineration fly ash accumulated heavy metals, so more attention must be paid to the issue of heavy metal content in the safe disposal process.

High performance sulfur/carbon cathode for Na-S battery enabled by electrocatalytic effect of Sn-doped In2S3.

Room-temperature sodium-sulfur (RT Na-S) batteries have been attracting enormous interests due to their low-cost, high capacity and environmental benignity. However, the shuttle effect and the sluggish electrochemical reaction activity of sodium polysulfides (NaPSs) seriously restrict their practical application. To solve these issues, we rationally designed an advanced Sn-doped In2S3/S/C cathode for RT Na-S batteries by magnetron sputtering in this work, which exhibited a high reversible capacity (1663.5 mAh g-1 at 0.1 A g-1) and excellent cycling performance (902.9 mAh g-1 after 50 cycles). The in situ electrochemical impedance spectroscopy indicated that the Sn-doped In2S3 coating can accelerate charge-transfer kinetics and facilitate the diffusion of Na+. Furthermore, theoretical calculation revealed that doping of Sn into In2S3 can reduce the energy band gap, thus accelerating the electron transfer and promoting the electrochemical conversion of active species. It is demonstrated that adjusting the electronic structure is a reliable method to improve the electrocatalytic effect of catalyst and significantly improve the performance of S cathode in RT Na-S batteries.

Imidazole Hydrochloride Promoted Synthesis of Nitriles from Aldehydes.

BACKGROUND AND OBJECTIVE: As a key pharmacophore, the cyano group widely exists in a variety of biologically active compounds. Besides, nitriles are also valuable intermediates for many common functional groups. In this current work, a new synthesis strategy was developed to obtain nitriles from aldehydes. METHODS: Using commercially available aldehydes as raw materials, and hydroxylamine and hydrochloride as nitrogen sources, the corresponding nitrile compounds were successfully synthesized by the one-pot method through the promotion of imidazole hydrochloride. And it was characterized by 1H NMR, 13C NMR, and mass spectrometry. RESULTS: Various reaction conditions were applied in order to find an optimum and convenient procedure for the formation of nitriles. The highest yields (95%) were achieved using sulfolane as a solvent, and imidazole hydrochloride as a promoter. CONCLUSION: In conclusion, we developed a new synthetic method for nitrile compounds from aldehydes. Twenty seven examples of functionalized nitrile compounds have been synthesized in good to excellent yields. This methodology features that an environmentally benign imidazole hydrochloride replaces transition metal catalysts and oxidants required in conventional strategies to convert aldehydes into nitriles with good functional group tolerability. Further exploration of imidazole hydrochloride is ongoing in our laboratory.

Influence of magnetized water on molybdenite flotation and its mechanism.

Through the flotation test of pure molybdenite and analyses of surface tension, XPS spectrum, zeta potential and contact angle, the influence of magnetized water on the flotation efficiency of pure molybdenite and its mechanism was investigated. The results showed that the recovery of coarse fraction was much higher than that of fine fraction, the magnetized water could significantly decrease the optimum dosages of collector and frother, simultaneously improve the recovery of molybdenite flotation, and the increase of fine fraction was obviously more than that of coarse fraction. The magnetization had little effect on the surface tension and dissolved oxygen of water, but obviously decreased the conductivity of water and pulp, which was beneficial to restrain molybdenite edge oxidation in water. The XPS test showed that the oxidation degree of molybdenite in magnetized water was obviously lower than that in unmagnetized water, which illustrated that the magnetized water could keep the natural floatability of molybdenite. The absolute value of the zeta potential and the contact angle of the molybdenite were increased after the treatment of magnetized water, which further verified that the magnetized water could help to inhibit molybdenite edge oxidation in water and improve the flotation efficiency of molybdenite.

Leaching behavior and environmental safety evaluation of fluorine ions from shotcrete with high-fluorine alkali-free liquid accelerator.

High-fluorine alkali-free liquid accelerator (AF-hf, F- concentration was about 2.31g/L) was still used in engineering because of its low cost, excellent stability, and coagulation-promoting effect. The main purpose of this study was to explore the leaching behavior of fluorine ions in shotcrete for tunnel lining with high-fluorine alkali-free liquid accelerator and whether there was fluoride pollution. The setting time and mechanical properties of cement paste and mortar with AF-hf were tested. Under different environmental conditions, F- leaching concentration from sprayed concrete was studied comparatively. Moreover, XRD and SEM were used to analyze the crystal composition and micro morphology of hydration products. The experimental results showed that with the increase of AF-hf dosage, the setting time of cement paste was greatly shortened, and later strength of mortar and shotcrete could meet the construction requirements. In addition, when the leaching solution type (including Na2CO3, Na3PO4, Na2SO4, and NaNO3) and testing conditions (particle size, soaking temperature, leaching solutions) were different, F- leaching concentration changed regularly, and the minimum value was more than 20 mg/L, which might cause fluorine pollution to groundwater and soil. After shotcrete samples were soaked, the CaF2 peaks' intensity was relatively weaker and Ca(OH)2 decreased obviously. Meanwhile, cement hydration products became looser and abundant of flaky C-S-H gel transformed into fibrous and chained structure.

Potential of preparing cement clinker by adding the fluorine-containing sludge into raw meal.

Fluorine-containing sludge from semiconductor industries were one kind of hazardous wastes, there was hardly effective treatment to realize its safe disposal and utilization. This paper evaluated the potential of preparing cement clinker by adding the sludge into raw meal by a series of experiments. The results revealed 2.0 % addition of the sludge markedly improved the burnability of the produced clinker, and promoted the formation of alite with more amounts and smaller size, but the 5.0 % addition of the sludge resulted in the abundant formation of interstitial phases to inhibit the formation of alite and belite. The better workability was gained with the addition of 2.0 %, and the optimal 28 d compressive strength was 50.76 MPa. The distribution of fluorine was higher in silicate phases, and it was mainly accumulated in the interfaces of silicate phases. Fluorine in the sludge was immobilized by calcium to form the binding forms of calcium fluoride in produced clinker and hydration products. The immobilization ratios of fluorine, copper, zinc and nickel were more than 99.5 %, and the addition of the sludge (≤5.0 %) into raw meal could not induce further environment hazards.

Effect of Mineral Admixtures on the Sulfate Resistance of High-Strength Piles Mortar.

Pre-stressed high-strength concrete piles (PHCP) are widely used in the building industry in China. The main aim of our research was to investigate the utilization of quartz powder, fly ash, and blast furnace slag as mineral additives to prepare PHCP mortar. The samples were prepared using steam and autoclaving steaming. The influence of minerals on the sulfate resistance of mortar was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) tests. The results showed that when compared to single doped quartz powder samples, samples prepared using fly ash or blast furnace slag improved the sulfate resistance of the PHCP mortar. Furthermore, the resistance to sulfate attack of samples with dual doped quartz powder, fly ash, and blast furnace slag also improved. MIP tests showed that mineral additives can change the pore size distribution after autoclave curing. However, the number of aching holes increased after mixing with 20% quartz powder and caused a decrease in the sulfate resistance.

Electrocatalytic Assisted Performance Enhancement for the Na-S Battery in Nitrogen-Doped Carbon Nanospheres Loaded with Fe.

Room temperature sodium-sulfur batteries have been considered to be potential candidates for future energy storage devices because of their low cost, abundance, and high performance. The sluggish sulfur reaction and the "shuttle effect" are among the main problems that hinder the commercial utilization of room temperature sodium-sulfur batteries. In this study, the performance of a hybrid that was based on nitrogen (N)-doped carbon nanospheres loaded with a meagre amount of Fe ions (0.14 at.%) was investigated in the sodium-sulfur battery. The Fe ions accelerated the conversion of polysulfides and provided a stronger interaction with soluble polysulfides. The Fe-carbon nanospheres hybrid delivered a reversible capacity of 359 mAh·g-1 at a current density of 0.1 A·g-1 and retained a capacity of 180 mAh·g-1 at 1 A·g-1, after 200 cycles. These results, combined with the excellent rate performance, suggest that Fe ions, even at low loading, are able to improve the electrocatalytic effect of carbon nanostructures significantly. In addition to Na-S batteries, the new hybrid is anticipated to be a strong candidate for other energy storage and conversion applications such as other metal-sulfur batteries and metal-air batteries.

Biomass-Derived Carbons for Sodium-Ion Batteries and Sodium-Ion Capacitors.

In the past decade, the rapid development of portable electronic devices, electric vehicles, and electrical devices has stimulated extensive interest in fundamental research and the commercialization of electrochemical energy-storage systems. Biomass-derived carbon has garnered significant research attention as an efficient, inexpensive, and eco-friendly active material for energy-storage systems. Therefore, high-performance carbonaceous materials, derived from renewable sources, have been utilized as electrode materials in sodium-ion batteries and sodium-ion capacitors. Herein, the charge-storage mechanism and utilization of biomass-derived carbon for sodium storage in batteries and capacitors are summarized. In particular, the structure-performance relationship of biomass-derived carbon for sodium storage in the form of batteries and capacitors is discussed. Despite the fact that further research is required to optimize the process and application of biomass-derived carbon in energy-storage devices, the current review demonstrates the potential of carbonaceous materials for next-generation sodium-related energy-storage applications.

Mesoporous NiCo2O4 networks with enhanced performance as counter electrodes for dye-sensitized solar cells.

The performance of a dye-sensitized solar cell (DSSC) is strongly influenced by the catalytic performance of its counter electrode (CE) materials. Platinum (Pt) is conventionally used as the CE for DSSCs, but it is precious and is readily corroded by the iodide/triiodide electrolyte. Herein, mesoporous NiCo2O4 networks with different types of building blocks were prepared by electrospinning of a composite solution followed by annealing in air, and their performances as CEs in DSSCs were investigated. The honeycomb-like NiCo2O4 exhibited better performance than the nanotube ones, showing a photoelectric conversion efficiency of 7.09% which is higher than that of a standard Pt CE (7.05%) under the same conditions. The enhanced electrode performance was attributed to the relatively larger surface area and higher conductivity. The preparation methods demonstrated in this study are scalable and would pave the way for practical applications of Pt-free DSSCs.