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The preparation of cement-based supplementary cementitious materials is an important method for the efficient use of iron tailings and the reduction in CO2 emissions. The aim of this study is to improve the reactivity of iron tailings by mixing them with steel slag, slag, and fly ash through orthogonal tests to solve the problem that iron tailings cannot be utilised on a large scale. The compressive strength, hydration products, and microstructure of the iron tailings–cement-based supplementary cementitious materials were investigated using ICP-OES, XRD, TG, FTIR, and SEM. The results revealed that each solid waste raw material played a distinct role in the hydration reaction. In the iron tailings–cement-based supplementary cementitious materials system, steel slag provided Ca2+, OH−, and Si4+ ions, slag provided Ca2+ and Al3+ ions, fly ash contributed a significant amount of Ca2+ and Al3+ ions, and iron tailings offered more nucleation sites and some Si4+ ions for the hydration products. Moreover, there was a synergistic effect among these four materials, promoting the formation of hydration products such as ettringite, C-(A)-S-H gels, and others. When the proportion of IOTs:SS:FA:SL was 9:8:8:2, the highest 7 d compressive strength of cementitious material was 24.8 MPa. When the proportion of IOTs:SS:FA:SL was 9:6:8:4, the highest 28 d compressive strength of cementitious material was 35.0 MPa. This study provides a comprehensive solution for the utilisation of iron tailings and contributes to the high-value green utilisation of solid waste. [ABSTRACT FROM AUTHOR]

Utilizing a variety of solid wastes to prepare alkali-activated cementitious materials is one of the principal trends in the development of cementitious materials. Commonly used alkali activation precursors such as granulated blast furnace slag (GBFS) and fly ash (FA) will be less available due to resource pressures. Supply limitation is an important reason to research alternative precursors. To realize the high value-added utilization of copper–molybdenum tailings (CMTs), this study adopted the modified sodium silicate solution as an alkaline activator to activate GBFS-FA-CMTs cementitious system to prepare alkali-activated cementitious materials. The influence of CMTs content on the compressive strength of GBFS-FA-CMTs cementitious system was analyzed, and the mechanism of GBFS-FA-CMTs cementitious system was also analyzed through hydration product types, physical phase composition, and microscopic morphology. The results indicated that a paste with the incorporation of CMTs, S50F30C20 (50% GBFS, 30% FA, 20% CMTs), achieved the highest compressive strength of 79.14 MPa, which was due to the filling effect of the CMTs and the degree of participation in the reaction. Pastes with different contents of CMTs, while maintaining a constant CBFS content, exhibited similar strength development. Excessive amounts of CMTs could result in reduced compressive strength. Microstructural analysis revealed that the hydration products were structurally altered by the addition of CMTs. In addition to ettringite, quartz, C(-N)-S-H gel, and calcite, gaylussite was also formed; moreover, the mass of chemically bound water increased, and the microstructure of reaction products became denser. An excess of CMTs may restrict the growth of the hydration gel, leading to more microstructural defects. The study suggests that CMTs could enhance the compressive strength of hardened paste within an alkali-activated slag-fly ash system, possibly due to a filling effect and participation in the chemical reaction. This research confirms the feasibility of using CMTs in alkali-activated cementitious materials. [ABSTRACT FROM AUTHOR]

There are some limitations in the application of tuff powder as a supplementary cementitious material (SCM). Exploring its feasibility in new fields will consume a large amount of silica-alumina mine solid wastes. This study has investigated the mechanical properties and mechanism in contact-hardening of tuff powder with a method of compression molding. The compressive strength of specimens was tested, and the X-ray diffraction (XRD), thermogravimetric analysis (TG), scanning electron microscopy (SEM), and Mercury intrusion porosimetry (MIP) methods were used to reveal the mechanism of contact-hardening of tuff powder from a micro-perspective. The results indicated that the compressive strength of specimens was higher when activated by sodium hydroxide compared to calcium hydroxide. Compared to calcium hydroxide, the compressive strength of TFS20 and TFF20 activated by sodium hydroxide was improved by 20% and 23%, respectively. The hydration degree of tuff powder was very low, with a water–cement ratio (w/c) of 0.15, while the hydration degree of coal gangue powder was higher. The results of TGA and SEM indicated that the sodium hydroxide had a better activating effect on slag and fly ash. Therefore, more C-S-H gels were generated in those samples activated by sodium hydroxide. Furthermore, the structure of samples was more compacted, and there was a reduction of porosity by 10% and 11% for TFS20 and TFF20, respectively, especially the proportion of harmful pores. [ABSTRACT FROM AUTHOR]

In this study, a type of fly ash and iron tailing powder were used as a binary supplementary cementitious material (SCM) and two different mechanically activated procedures, named coalescent activation and separated activation, were carried out to improve the pozzolanic reactivity. Then, three binary supplementary cementitious materials were used to replace 30 wt% of ordinary Portland cement to develop cemented mortars, and the compressive strength, hydration products, and micro-structure were studied. The experimental results indicated that the activated supplementary cementitious materials increased the compressive strengths of the mortars by 5.4% and 13.2%, negligibly changed the hydration product types, and impacted the quantity only. The application of SCMs also prolonged the setting time and decreased the hydration rate, profiting the application. Simultaneously, the micro-pore structure was ameliorated, and the porosity decreased. Therefore, comprehensively considering the improved mechanical behavior and inexpensive cost, the activated binary SCM can be considered an ecological and economical admixture, especially for the coalescent activation procedure. [ABSTRACT FROM AUTHOR]

How to realize the resource utilization of by-product lithium slag has become an urgent problem with the rise of lithium batteries. This study investigates the feasibility of using lithium slag as a supplementary siliceous material for the preparation of autoclaved aerated concrete. The effect of replacement method and substitution level on the physical properties of lithium slag based autoclaved aerated concrete were evaluated. In addition, the matching relationship between hydration products and physical properties was investigated by utilizing multiple microscopic tests. The results showed that the incorporation of lithium slag contributed to the enhancement of system reactivity at the chemical level. In contrast to quartz sand, lithium slag introduced reactive Al 2 O 3 to the system, leading to the generation of Al-substituted tobermorite and katoite. The suitable level of substitution promoted the generation of hydration products. The composition of the elements and the morphology of hydration products were made closer to the desirable state, which contributed to strength development. Considering the comprehensive impact of lithium slag incorporation on physical properties and microstructures, specimens prepared utilizing lithium slag with a substitution rate of 50 %-75 % by the material quality control method possessed better application prospects. • Lithium slag was utilized as siliceous material to produce autoclaved aerated concrete. • In contrast to quartz sand, lithium slag introduced more reactive Al 2 O 3 to the system. • Appropriate proportions of lithium slag supported the generation of tobermorite. • The incorporation of lithium slag rendered the shape of tobermorite more acicular. [ABSTRACT FROM AUTHOR]

In order to control energy consumption and reduce pollution, the use of supplementary cementitious materials (SCMs) instead of cement to produce green cementitious materials can save energy, reduce emissions and achieve sustainable development. This study demonstrates the possibility of developing SCMs with iron tailings (IOTs), fly ash (FA) and ceramic powder (CP) ternary system, as well as the optimization and improvement scheme of gelation activation. The effects of activator dosage, mix ratio and substitution rate on mechanical properties of ternary SCMs system were investigated. The formation and evolution of hydration products were analyzed by differential thermogravimetric analysis (DTA) and scanning electron microscopy (SEM). The results of the study show that there is synergy in the system. The results show that there is synergy in the system and the hydration reaction is sufficient. At the substitution rate of 30%, the doping ratio of IOTs, CP and FA is 1:2:2 and the Ca(OH)2 is 0.6%, the strength reaches 39.9 MPa and the activity index is 91.5%, which can provide a basis for the application and more in-depth study of IOTs multi SCMs. [ABSTRACT FROM AUTHOR]

This study investigates the synergistic effect of steel slag (SS) and metakaolin (MK) on cementitious systems. The compressive strength, flowability, packing properties, hydration products, and microstructure of composite cementitious materials containing SS and MK are investigated using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope with energy-dispersive X-ray spectroscopy, mercury intrusion porosimetry, and surface fractal analysis. The results show that the incorporation of MK into the SS-cement system increases the wet packing density and generates calcium silicate hydrate with low Ca/Si and high Al/Ca ratios, thus increasing the compressive strength. In addition, the pore structure is refined. This study facilitates the sustainable and high-value utilization of SS and MK. • The packing density and PSD were used to evaluate physical synergies. • The synergistic effect of SS and MK can produce produced C-S-H with low Ca/Si. • SS and MK replacement cement can reduce costs and carbon emissions. [ABSTRACT FROM AUTHOR]

• The SS and LS shows a synergist effect on the hydration of the cement pastes. • A large amount of C-(A)-S-H is produced with the addition of SS and LS. • The addition of LS to the cement-SS system refines the pore structure. Replacement of cement with solid waste is an important method for conserving natural resources and reducing CO 2 emissions. In this study, steel slag and lithium slag were used to replace cement to address the low activity of steel slag, which limits its large-scale utilization. The compressive strength, flow properties, dissolution characteristics, hydration products, and microstructure of composite cementitious materials containing steel slag and lithium slag were investigated by ICP-OES, XRD, TG, FTIR, SEM and MIP. The results showed that the addition of lithium slag into the cementitious material with steel slag improved the compressive strength. The lithium slag consumed a large amount of portlandite and promoted hydration of the steel slag to produce more C-(A)-S-H. Furthermore, the porosity and pore size distribution were optimized, the most probable pore size was reduced, and the pore complexity was increased. This research provides a solution for comprehensive use of steel slag, which contributes to high-value green utilization of solid waste. [ABSTRACT FROM AUTHOR]

In this paper iron tailing sand (TS) are used as aggerate to develop ultra high-performance concrete (UHPC). The mix proportion of UHPC is designed and TS were added by 25%, 50%, 75% and 100% (wt.%, i.e., weight percentage) to replace natural river sand. Firstly, the influence of TS on the slurry behavior was carried out. The experimental result indicates that with the continuously increasing content of TS, the workability of slurry decreases, while the air content increases. Considering the workability, the optimal replacing dosage of TS should be less than 50%. Then, tests for the hardened specimens were taken. The compressive behavior and micro-porosity deteriorate with increasing content of TS, and the compressive strength had a positive linear relationship with the workability, which indicated that the decline the compressive behavior is mainly due to the loss of flowability. Finally, autogenous shrinkages of UHPC with different TS dosage were also tested. At the same time, the micro-structure of specimens was discussed, which was deteriorate with the increasing dosage of TS. Therefore, comprehensively considering the compressive behavior, micro-structure and shrinkage behavior, as much as 50% of the aggregate could be replaced by TS when developing UHPC. [ABSTRACT FROM AUTHOR]

In order to effectively improve the flexural strength and fracture toughness of ceramics, two methods can be used to control the growth rate of grain during sintering of ceramic materials by adding a certain amount of (W,Ti)C material. Therefore, on the one hand, the paper simulates the composite ceramic materials based on cellular automata (CA) to optimize the ratio of two formulations. On the other hand, in order to optimize sintering process, CA modeling is also carried out for the sintering process of composite ceramics. Finally, in order to detect the temperature of the firing zone of the ceramic kiln by using the characteristics of the flame image of the firing zone, the K-means clustering method is used for the color segmentation of the flame image of the firing zone of the ceramic kiln. The experimental results show that the size of the grains is in accordance with the actual situation of the simulation and the microstructure evolution of the composites can be simulated well by using the CA theory to simulate the composites; with the increase of simulation time, the grain size distribution is basically unchanged, which accords with the normal distribution, and the simulation process of grain growth is very stable. Based on the K-mean clustering segmentation method, the segmentation of the flame image of ceramic kiln firing zone is realized. This method also provides a good technical means for feature extraction of flame image in ceramic kiln firing zone. [ABSTRACT FROM AUTHOR]

Based on the characteristics of alkali-activated materials (AAMs) in energy saving and emission reduction, as well as giving full play to the complementary advantages of multi-component solid waste. In this study, a new type of AAMs was prepared from oil shale residue (OSR), ground granulated blast furnace slag (GGBFS), and fly ash (FA). Compressive and flexural strength tests, fluidity experiments, setting time, heat of hydration, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS), and Thermo-gravimetric analysis (DTG-TG) were used to analyse the mechanical properties, workability, mineral composition, microstructure, and hydration products of the AAMs. The results showed that the microstructure of AAMs was dense, with high early strength, good mechanical and working properties, and no tendency for retrogressive strength with an increase in the age of maintenance. Under the action of NaOH/Na 2 SiO 3 , there is a synergistic hydration of the water-hard and volcanic ash materials, and the three raw materials have synergistic hydration properties and indispensable coupling mechanisms. Meanwhile, the effect of the activator content on AAMs is bidirectional. The OSR, GGBFS, and FA in the AAMs exhibited faster hydration reactions under the action of NaOH/Na 2 SiO 3 and abundant hydration products, which mainly included C-S-H, C-A-S-H, N-A-S-H, and small amounts of CaCO 3 , hydrotalcite (HT), and Ettringite (AFt). The specimens all met the requirements of the 42.5-grade composite silicate cement, and some specimens reached the strength requirements of the 62.5-grade silicate cement or above. OSR has great potential as a silicate-aluminate material, and this study provides a solid foundation for its further development and utilisation. • Oil shale residue was added into to blended slag/fly ash alkali activated binder system. • There is a synergistic effect of OSR-GGBFS-FA. • All specimens are comparable with Portland cement 42.5, even to Portland cement 62.5. • The hydration products are C-S-H, C-A-S-H, N-A-S-H gels, calcite, hydrotalcite, and AFt. [ABSTRACT FROM AUTHOR]

Herein, the relationship between oxygen reduction reaction (ORR) catalytic activities of N-doped hollow graphene spheres (N-HGSs) and their morphologies, microstructures, and nitrogen doping configuration is deeply investigated. Based on all detection results it can be concluded that all of the level and configuration of doped-N atoms, the surface area, the mesopore structure of fabricated hollow graphene spheres related to the exposure of edges and vacancies correlating with the active sites, will ultimately affect the ORR catalytic performance of N-HGSs. Therefore, the optimized synthesis of N-HGSs can produce efficient electrocatalyst for ORR, which is better than the noble-metal Pt/C catalysts and most highly active graphene-based ORR catalysts reported to date. Additionally, the optimized synthesis of N-HGSs also exhibit excellent performance in sodium-ion storage. Because the large specific surface area, the well-connected hollow spherical and mesopore structures and the increased hydrophilicity induced by the doped-N atoms facilitate a ready transfer of charges and adsorption, diffusion and desorption of Na+ ions in and out of the active material, which could enhance sodium ion storage capacity. Additionally, expect the storage of Na+ ions by surface electro-adsorption/desorption, the insertion/extraction of Na+ through the thinner graphene shell makes a significant contribution to the improvement of sodium-ion storage capacity. Image 1 • N-doping configuration, surface area, microstructure affect ORR performance. • The mesopore structure is correlating with the ORR active sites. • The optimized N-HGSs exhibit excellent performance in ORR and sodium ion storage. • Hollow spherical and mesopore structures enhance sodium ion storage capacity. • Insertion/extraction of Na+ through thinner graphene shell enhances performance. [ABSTRACT FROM AUTHOR]

Limited electrode size with high electrochemical performance and reliability of modified materials are two of the main concerns for flexible neural electrodes in recent years. Here, an effective fabrication method of enhanced micro-scale wrinkles based on oil-pretreated hyperelastic substrates (PDMS and Ecoflex) is proposed for the application of microelectrode biosensors. Compared to pre-stretching or compressing methods, this approach has better advantages including compatibility with MEMS processes on wafer and easy replication. Wrinkled gold microelectrodes exhibit superior electrochemical properties than the flat one, and no crack or delamination occurs after electroplating PEDOT:PSS and platinum black on wrinkled microelectrodes. Cyclic voltammetry (CV) scanning for 2500 times is performed to investigate adhesion and stability of modified materials. For the modified microelectrodes, no significant change is observed in charge storage capacity (CSC) and impedance at 1 kHz, whereas PEDOT:PSS coated flat microelectrodes appears delamination. Ultrasonication and cycling forces are also conducted on modified microelectrodes, which demonstrates little influence on the wrinkled ones. Flexible wrinkled microelectrodes are further verified by in-vivo ECoG recordings combined with optogenetics in mice. These results highlight the importance of micro-structure in neural electrode design and tremendous application potentials in flexible electronics. • A novel fabrication method of microelectrode biosensors with enhanced micro-scale wrinkles was proposed for the first time. • The modified enhanced wrinkled microelectrodes exhibited stronger stability than the flat ones, especially for PEDOT:PSS. • In-vivo ECoG signals combined with optogenetics in mice showed reliable recording ability of the proposed microelectrodes. [ABSTRACT FROM AUTHOR]