Powder Mass Ratio Research Articles

Research on the properties of brucite-based magnesium phosphate cement fire resistive coating for steel structures

Magnesium Phosphate Cement (MPC) exhibits high strength, exceptional high-temperature resistance, and outstanding adhesion properties at the steel interface, rendering it an ideal material for fire resistive coatings on steel structures. In this study, natural brucite powder was employed as the magnesium source, while hollow glass microspheres (HGM) were utilized as functional modifiers to formulate brucite-based MPC fire resistive coatings for steel structures. This research explored the influence of the mass ratio of brucite powder to ammonium dihydrogen phosphate (M/P), the brucite particle size, and the addition of HGM on the physical, mechanical, and fire-retardant properties of the coatings. The microstructure of the brucite-based MPC before and after fire testing was examined using SEM, XRD, TG-DTG, and X-CT. The results indicated that with an M/P ratio of 2.5:1 and a brucite particle size of 75–150 μm, the material exhibited optimal overall performance and was suitable as a matrix material for MPC. The incorporation of an appropriate amount of HGM increased the compressive strength of brucite-based MPC by 33.4 %, reduced the dry density by 20.5 %, extended the fire resistance of the structure, and decreased the thermal conductivity by 48.2 %. This can be attributed to: (i) HGM filling the pores in brucite-based MPC, creating a denser microstructure; (ii) HGM forming a closed porous structure with the MPC matrix, reducing thermal conductivity and increasing thermal resistance; (iii) The low thermal diffusivity of HGM/MPC impeded heat transfer, thereby decelerating thermal decomposition and flame propagation.

Combined preparation and application of geopolymer pavement materials from coal slurry-slag powder-fly ash mining solid waste: A case study

The solid waste treatment problem generated in the process of coal mining has always been an important factor restricting safe and environmentally friendly production, and the coal slurry from the coal mine road surface is a new type of mine solid waste, so it is of great significance to treat and efficiently utilize the coal slurry. Currently, a common method of solid waste utilization is to add modifying reagents to prepare functional materials. Select coal slurry, slag powder and fly ash as raw materials, and sodium sulfate and sodium hydroxide were used as alkali exciters to prepare coal slurry based geopolymer pavement material (CSGPM). Response surface methodology was used to establish regression equations between the design optimization objectives (coagulation time, compressive strength) and the variables (mass fraction, mass ratio of slag powder to fly ash, mass ratio of sodium sulfate to sodium hydroxide). The effects of two-by-two interactions of the factors on the optimization objective were explored, and the use of different raw materials was obtained. Under the optimal proportioning parameters, the coagulation time of CSGPM was 33 min and the compressive strength of 24 h of curing was 11.20 MPa. In addition, the generation mechanism of AFt and C-S-H gel substances inside the specimen was explained with the help of microscopic scanning. CSGPM showed good mechanical properties in both load-bearing numerical simulations and acoustic emission tests. Numerical simulation was used to establish the relationship between the design objective of the roadbed (maximum subsidence of the roadbed after bearing) and the design variable (thickness of CSGPM paving). Comparative analyses yielded an optimal subgrade surface layer design thickness of 5 cm, with a maximum subsidence of 0.0033 m after bearing vehicles. Synchronization of roadbed material and concrete damage in combined specimen acoustic emission tests with uniform load transfer. The final coal mine pavement was successfully paved and the total cost of CSGPMD is 63.2 per cent of C30 concrete. Those results are important for the preparation of new pavement functional materials.

High performance illitic clay-based geopolymer: Influence of thermal/mechanical activation on strength development

The scientific community's interest in geopolymers keeps on growing under environmental and climate change pressures. Although most studies concern metakaolin or industrial by-products as aluminosilicate precursors, few are those concerning clay cuttings characterized by little or no kaolinite content. This study proposes a method to activate illitic clay in order to obtain a geopolymer with high mechanical performances. The tested illitic material contained 53 wt% of illite/muscovite, 22 wt% quartz, 7 wt% feldspars and low content of calcite. The innovation consists in coupling thermal and mechanical activations favoring both the clay dehydroxylation and the destruction of the clay crystalline structure. Such increase of amorphous rate in the precursor is required to make the material reactive. The evolution of the precursor material after activation was followed by ThermoGravimetric Analysis (TGA/DTG), X-Ray Diffraction (XRD), Fourier-Transform InfraRed spectroscopy (FTIR) and Scanning Electron Microscopy coupled to Energy Dispersive X-ray spectrometry (SEM-EDX). The impact of the variations of the mechanical activation duration and ball:powder mass ratio (b:p) were mainly explored, as well as the Liquid:Solid mass ratio (L:S) which is a key parameter of the geopolymerization. Finally, an optimized geopolymer with a mechanical compressive strength reaching 126 MPa after 28 days has been manufactured with a grinding duration of 240 min, a b:p = 15 and a L:S = 0.5. The demonstration was done that a geopolymer can be manufactured from 100% illitic clay precursor, in addition to a relatively low amount of alkaline solution (L:S mass ratio of 0.5) then lowering the cost and the environment impact of the final geopolymer material. The resulting illitic clay based geopolymers can display very high mechanical resistance (compressive strength up to 126 MPa after 28 days), fully competitive with conventional building materials.

Performance characterization and microscopic properties of asphalt modified with rapeseed heavy oil-activated waste rubber powder

To improve the waste rubber powder modified asphalt viscosity is high, poor storage stability, and other shortcomings, 40 mesh, 60 mesh, and 80 mesh are three kinds of mesh rubber powder using rapeseed heavy oil pre-swelling activation way to prepare modified asphalt, improve the waste rubber powder modified asphalt storage stability and reduce the viscosity. The optimum blending amount of rapeseed heavy oil-activated waste rubber powder was determined by setting three oil-rubber ratios, and the unactivated waste gum powder modified asphalt was set as a control group, and the physical, rheological, and microscopic properties of the asphalt were evaluated accordingly. The optimum preparation parameters under the premise of setting the total dosage of modifier as 20% were: the mass ratio of rubber powder to rapeseed oil was 2:1, and the mesh size of rubber powder was 80 mesh. Rapeseed heavy oil-activated waste rubber powder modified asphalt storage stability and low-temperature performance improved, viscosity decreased, but high-temperature performance decreased at the same time. Compared with the unactivated waste rubber powder modified asphalt, the softening point decreased by an average of 16%, the needle penetration increased by an average of 19%, the ductility increased by an average of 44%, the viscosity decreased by an average of 22%, and the softening point difference decreased by an average of 44%. In the high-temperature rheological performance test set temperature interval, the rutting coefficient G*/sinδ decline, creep stiffness Ѕ, and creep rate m have increased. Therefore, rapeseed heavy oil activation can effectively improve the overall stability of waste rubber powder-modified asphalt and can reduce the overall viscosity, which is conducive to the uniform dispersion of rubber powder in asphalt.

High performance epoxy soybean oil-based composite reinforced by wood powder

A novel bio-based composite, called the ESO-1,6-hexanediamine-ADP-wood (EHAW) composite, was created using epoxy soybean oil (ESO), 1,6-hexanediamine, and ammonium dihydrogen phosphate (ADP) co-condensed resin as matrix and wood powder as aggregate. The cross-linking was achieved through the ring opening polymerization of 1,6-hexanediamine and ESO, which was then esterified and condensed with ADP to form a network structure. The effects of mass ratio of wood powder to soybean oil-hexamethylene diamine-ammonium dihydrogen phosphate (EHA) resin on the performance of the composite were investigated. The mass ratio of wood powder to EHA resin was 0.25, 0.5 and 0.75, respectively. The results revealed that composite with the wood powder/EHA resin of 0.5 (EHAW2) had the best performance indicates by its smooth and uniform distribution under SEM observations. In addition, EHAW2 showed better Brinell hardness, compressive strength, UV resistance as well as water absorption properties than the other two ratios. It also showed better thermal conductivity and flame retardancy. The total heat released during combustion is low, and there are no collapse and shape change during the combustion process, making it an ideal material for building applications.

Effect of CeO2-Y2O3 sintering aids on the microstructure and properties of corundum-based composite ceramics

ABSTRACT Reducing the preparation cost of alumina ceramics has received significant attention, as alumina is one of the most widely used structural ceramics. In this study, corundum-based composite ceramics with a white corundum-to-zircon powder mass ratio of 7:3 were selected as the matrix. CeO2 and Y2O3 doped corundum-based composite ceramics were prepared via pressureless sintering. The total content of CeO2-Y2O3 was set at 10 wt% to study the effects of different temperatures and CeO2-Y2O3 ratios on the properties of the corundum-based composite ceramics. Physical phase and microstructural analyses of the corundum-based composite ceramics were performed using X-ray diffraction and scanning electron microscopy, respectively. The results showed that the sintering temperature of the corundum-based composite ceramics could be effectively reduced by using a solid solution of CeO2 and Y2O3. The best sintering temperature was 1400°C, and the best composition was 5 wt% CeO2-5 wt% Y2O3. The physical properties of the corundum-based composite ceramics prepared under these technological conditions include a flexural strength of 386.2 MPa, hardness of 13.5 GPa, density of 3.9128 g/cm3, linear shrinkage of 16.31% and an apparent porosity of 0.62%.

Design Strategies for Perovskite-Type High-Entropy Oxides with Applications in Optics.

It is essential and challenging to develop advanced ceramic materials with thermal stability and high reflectivity for optical fields. Encouragingly, recent breakthroughs and significant advances in high-entropy ceramics have made high-entropy oxides a potential candidate material for optical applications. Therefore, in this study, we analyzed the effect of lattice distortion on the design of high-reflectivity, high-entropy oxides using first-principles calculations and aberration-corrected microscopy. In order to optimize the optical properties of the materials, a series of novel perovskite-type high-entropy oxides, (LaxK0.4-xCa0.2Sr0.2Ba0.2)TiO3+δ (x = 0.1, 0.15, 0.2, 0.25, 0.3), were designed and synthesized using solid-state sintering based on the charge conservation principle and bond energy principle. When the content of La in the A-site element was 30%, the optical reflectivity reached 94% by suppressing the oxygen vacancy. Furthermore, we have successfully prepared a series of coatings by air spraying based on the regulation of the mass ratio of resin and powder. Compared to the uncoated substrate, the backside temperature can be reduced by 41%. This work provides a feasible design route with the first clear guidelines for highly reflective high-entropy ceramic materials and enables highly stable material design in multielement spaces.

Process-property correlations for spherical composite Al·Ti powders prepared by emulsion-assisted milling

Spherical composite powders desired in many applications can be produced using emulsion-assisted milling. This study is focused on finding correlations between the milling process parameters and characteristics of the produced spherical powders. A composite Al·Ti powder served as the test material system. Spherical powders were prepared using a planetary mill and using an emulsion formed by hexane and acetonitrile as continuous and droplet phases, respectively. Milling conditions including the ratio of immiscible liquids (LR), ball to powder mass ratio (BPR), rotation rate (RPM) and milling time were varied. Optical microscopy images of the powders produced served to recover descriptors of the product particle shapes and sizes. Analysis of the generated image-based data enabled classification of the produced powders, separating spherical and nonspherical particles. This made it possible to recover characteristics of spherical particles, which were correlated with the milling conditions. The quality of the produced spherical powders was assessed using a parameter, Q, maximized when a large fraction of spherical particles with the narrowest size distribution was produced. A correlation was found between Q and a compounded milling process parameter taken as product of grouped parameters: X=BPR∙RPM∙time, Y=BPR∙RPM∙LR, and Z=RPM/BPR, each raised in a separate power, x, y, and z, respectively. The correlation formed a maximum around the conditions leading to formation of the spherical powders with the best quality (highest Q). For the same milling conditions, for which the highest quality spheres were formed, the refinement of the material was maximized, based on the smallest crystallite sizes for both Al and Ti.

Optimization of Grinding Parameters for the Mechanochemical Activation of Kaolin with the Addition of Trass

At present, to achieve further reductions in CO2 emissions in the cement industry, it is essential to improve the efficiency of grinding processes and reduce the energy demand. This study examined the effects of various grinding parameters (addition of trass, ball to powder mass ratio (BPR), material of grinding bodies and jars, rotational speed, and mill type) to minimize the energy consumption of the mechanochemical activation of kaolinite. X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectroscopy, scanning electron microscopy, and specific surface area measurements were used to examine the influence of grinding parameters. It was found that the addition of as little as 25% (mass percent) trass reduced the specific energy demand for the complete amorphization of kaolinite by 56%. The application of steel grinding bodies (instead of ZrO2 ones) had a slight influence on the amorphization kinetics of kaolinite, but it could mechanochemically activate 30% more samples at the same BPR and specific energy demand. The use of the four-pot milling instead of the one-pot could considerably decrease the specific energy demand of the complete and incomplete (α = 0.9) amorphization of kaolinite. Overall, a 94% reduction was achieved in specific energy demand with steel grinding material, 14:1 BPR, four-pot milling, and the incomplete amorphization of kaolinite.

Experimental Study on the Strength and Hydration Products of Cement Mortar with Hybrid Recycled Powders Based Industrial-Construction Residue Cement Stabilization of Crushed Aggregate.

The strength-formation mechanism for industrial-construction residue cement stabilization of crushed aggregate (IRCSCA) is not clear. To expand the application range for recycled micro-powders in road engineering, the dosages of eco-friendly hybrid recycled powders (HRPs) with different proportions of RBP and RCP affecting the strengths of cement-fly ash mortar at different ages, and the strength-formation mechanism, were studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the early strength of the mortar was 2.62 times higher than that of the reference specimen when a 3/2 mass ratio of brick powder and concrete powder was mixed to form the HRP and replace some of the cement. With increasing HRP content substituted for fly ash, the strength of the cement mortar first increased and then decreased. When the HRP content was 35%, the compressive strength of the mortar was 1.56 times higher than that of the reference specimen, and the flexural strength was 1.51 times higher; XRD and SEM studies of the hydrated cement mixed with HRP showed that the amount of CH in the cement paste was reduced by the pozzolanic reaction of HRP at later hydration ages, and it was very useful in improving the compactness of the mortar. The XRD spectrum of the cement paste made with HRP indicated that the CH crystal plane orientation index R, with a diffraction angle peak of approximately 34.0, was consistent with the cement slurry strength evolution law, and this research provides a reference for the application of HRP to produce IRCSCA.

A mechanically durable induction heating coating with desirable anti-/de-icing performance

ABSTRACT The anti-/de-icing technology based on induction heating offers significant advantages regarding fast heating, high efficiency, safety and environmental protection. However, the reported methods require the modification of base materials, which lacks universal applicability. Here, a universal and facile anti-/de-icing method is proposed based on induction heating. The durable induction heating coating was prepared by one-step spin coating with micron-sized nickel powder, epoxy resin and silicone resin. The induction heating ability of this coating was investigated by adjusting the proportion of composition, particle size and thickness. An optimal induction heating ability was achieved with the mass ratio of nickel powder and resin, particle size of nickel powder and coating thickness being 1.5, 7 μm and 1070 μm, respectively. We further show this coating can be applied for anti-/de-icing, demonstrated by its excellent de-/anti-icing performances. Finally, the mechanical durability of the coating was verified by the tape peel and sandpaper friction.

Antifouling Coatings Fabricated by Laser Cladding

Laser surface treatment is a very useful technology for the fabrication of functional surfaces. In this study, novel antifouling surfaces are fabricated by laser cladding of TC4 and Ni60 mixed materials in various mass ratios on the surfaces of 316L stainless steel substrates. Parametric studies are carried out to investigate the effects of the mixed powder mass ratios and laser cladding parameters on the antifouling performance of the laser clad coatings (LCCs). The antifouling mechanism of the LCCs is investigated by using the water contact angle/surface energy measurement, scanning electron microscope (SEM) surface observation, and phase composition analysis via XRD (X-ray diffractometer) testing. The experimental results show that the LCCs with Ni60/TC4 mass ratio of 3/7 has better antifouling performance in this study. The antifouling performance of the LCC decreases with the increase in laser scanning speed. Surface energy and surface topography have a significant effect on the antifouling performance of LCCs. In order to get the optimal antifouling performance of LCCs, the Ni60/TC4 mass ratio and laser cladding parameters should be optimized.

A facile hydrous mechano-synthesis of magnesium hydroxide [Hy-Mg(OH)2] nano fillers for flame-retardant polyester composites

Scrap metals are a cost-effective secondary resource for producing functional metal oxides/hydroxides. Developing such functional hydroxides from scrap Mg via a low-energy, chemical-free process has high technological importance in the current scenario, as it emphasizes the ‘waste to wealth’ and green motives of production. This study presents an aqueous mechanical milling technique as a facile approach to yield functional grade nano Mg(OH)2 from industrial Mg crumbs. Formation of fiber-like nano Hy-Mg(OH)2 was confirmed on milling of waste metal scraps, by carefully controlling the mechanical parameters viz. the ball to powder mass ratio, milling medium, milling time, and milling speed. The optimized production of Hy-Mg(OH)2 was obtained after 90 h of milling, the evolution was confirmed using standard characterization techniques like XRD, TEM, and EDS. Flame retardant polyester/nano Hy-Mg(OH)2 composites were developed using casting technique. The developed polyester/nano Hy-Mg(OH)2 composites showed good flame retardancy, an oxygen index of ∼ 33% was obtained with 0.3 wf of nano Hy-Mg(OH)2 addition.

Development and optimization of high–performance nano–biochar for efficient removal Cd in aqueous: Absorption performance and interaction mechanisms

Cadmium (Cd) pollution has aroused wide public attention due its high mobility, bioaccumulation and carcinogenic properties, and biochar has been proven as an efficient adsorbent for removal of Cd due to its environmentally friendly and economic approach. In this study, three variables (grinding time, rotational speed, and mass ratio of ball–to–powder) were established through response surface methodology and Box–Behnken design, and the preparation process of ball–milled biochar (BMBC) was successfully optimized. The results indicated that the impact factors on Cd removal by BMBC were in the order of milling speed > grinding time > ball to powder mass ratio, and the optimum parameters for Cd removal were found to be: milling time = 16 h, speed = 448 rpm, and ball to powder mass ratio = 1.5:100. BMBC (300 nm) has a dramatically larger specific surface area and pore volume by 22 and 15 times, respectively, and was companied with richer oxygen–containing functional groups. The adsorption of Cd2+ on BMBC conformed to the pseudo–second–order kinetic model and the Langmuir model. The maximum adsorption capacity of Cd2+ was 3 times that of BC. Precipitation and complexation were the main mechanisms for the adsorption of Cd. Therefore, BMBC was a promising and effective adsorbent for the removal of Cd, which has potential application value.

Green facile synthesis of biowaste-converted Cu-Cu2O/BPC for non-enzymatic hydrogen peroxide sensing

Despite the rapid development of non-enzyme sensors, there is an urgent need for a sensor that can produce sensing materials without the use of reducing agents. Herein，a green biowaste conversion strategy is elaborately developed to fabricate advanced Cu-based sensing material, in which the Cu-Cu 2 O/BPC-1 was obtained by facilely carbonizing the bamboo powder soaked with Cu (NO 3 ) 2 without using any reduction agents. Particularly, the Cu-Cu 2 O particles were uniformly anchored on the mesoporous carbon plate. Profited from the synergistic effect between biomass carbon plate and Cu-Cu 2 O particles, electrochemical measurements showed that the prepared Cu-Cu 2 O/BPC-Y/GCE sensor demonstrated prominent catalytic activity for H 2 O 2 . In particular, the Cu-Cu 2 O/BPC-1/GCE sensor displayed a wide linear range (1–8330 μM), a low detection limit (0.35 μM) (S/N = 3), and excellent selectivity, reproducibility and stability. This work provides a cost-effective and environmentally friendly strategy to fabricate the non-enzymatic H 2 O 2 sensor. • Cu-CuO/BPC-1 was obtained by adjusting the mass ratio of bamboo powder to copper nitrate. • Non-enzyme H 2 O 2 sensors were prepared from waste biomass materials without using any reducing agents. • The as-prepared sensor displayed a wide linear range and a low detection limit.

Preparation and performance characterization of steel slag-based thermal storage composites for waste recycling and thermal energy storage

ABSTRACT At present, the steel industry produces a large amount of steel slag during the smelting process, which causes serious pollution to the environment and land. Therefore, new technologies must be used to deal with steel slag. In this study, the steel slag powder refined by the wet grinding technology is used as the matrix material, MgO as material additive, and the clay is used as the binder to prepare a new type of composite heat storage material. The results indicate that the mass ratio of wet grinding steel slag powder, MgO powder and clay is 6:3:1, the composite heat storage material can have a strong compressive strength of 70.9 MPa. The thermal conductivity of the heat storage material is 0.98 W/m⋅K and can reach 1.27 J/g⋅K at 720 ℃, which has good thermal conductivity and long service life. When the heat storage material rises to 900 ℃, the heat storage density can reach 905 J/g, with good heat storage performance and thermal cycle stability. The objective is to develop sustainable and low-cost thermal energy storage material for industry waste heat recovery and in renewable energy applications. At the same time, this valuable market for slag in the energy field provide a new way to directly utilize steel slag with extraordinary economic and environmental benefits.

The Influence of CaO and MgO on the Mechanical Properties of Alkali-Activated Blast Furnace Slag Powder.

CaO and MgO are both reported as effective activators for blast furnace slag. However, the synergistic effect of these two components on the mechanical properties of alkali-activated blast furnace slag remains unclear. In this study, the flexural and compressive strengths of alkali-activated blast furnace slag powder with MgO and CaO range from 0% to 30% by the mass ratio of alkali-activated blast furnace slag powder are investigated. Moreover, the dry shrinkage rate of alkali-activated blast furnace slag powder is measured. One percent refractory fibers by volume of binder materials are added in the alkali-activated blast furnace slag. Some refractory fibers are treated with water flushing, meanwhile, some refractory fibers are directly used without any treatment. Finally, the scanning electron microscope, the thermogravimetric analysis curves and the XRD diffraction spectrums are obtained to reflect the inner mechanism of the alkali-activated blast furnace slag powder’s mechanical properties. The water-binder ratios of the alkali-activated blast furnace slag powder are 0.35 and 0.42. The curing ages are 3 d, 7 d and 28 d. The measuring temperature for the specimens ranges from 20 °C to 800 °C. Results show that the flexural and compressive strengths increase with the increased curing age, the decreased water-binder ratio and the addition of refractory fibers. The water-treated refractory fibers can improve the mechanical strengths. The mechanical strengths increase in the form of a quadratic function with the mass ratio of MgO and CaO, when the curing age is 3 d, the increasing effect is the most obvious. A higher water-binder ratio leads to an increasing the drying shrinkage rate. The activated blast furnace slag powder with CaO shows a higher drying shrinkage rate. The mechanical strengths decrease with the increasing testing temperature.

Recycling of granite powder and waste marble produced from stone processing for the preparation of architectural glass–ceramic

• Glass-ceramic was prepared using granite powder and waste marble by melting-sintering method. • The addition of MgO changes the main crystalline phase of the glass–ceramic from wollastonite to augite. • The acid resistance of glass-ceramics is weakened with the increase of basic oxide content in the chemical composition. • The glass–ceramic with flexural strength of 146.95 MPa and Vickers hardness of 10.24 GPa can be achieved. A large amount of solid waste is generated during the stone processing, and a serious environmental issues has arisen from the accumulation of these wastes. In this work, granite powder and waste marble are used to prepare architectural glass–ceramic. The mechanical properties, microstructure, and acid resistance of glass-ceramics designed with different compositions were investigated. With the increase of waste marble content, the main crystalline phase of glass–ceramic changed from anorthite to wollastonite, and the flexural strength of glass–ceramic was also enhanced. When the mass ratio of granite powder to waste marble is 40:60, a CaO-Al 2 O 3 -SiO 2 (CAS) glass–ceramic with a flexural strength of 109.33 MPa and a Vickers hardness of 6.61 GPa is obtained. After the addition of MgO, the main crystalline phase of the glass–ceramic is augite. Under the addition of 5 wt% MgO, the flexural strength and Vickers hardness of CaO-MgO-Al 2 O 3 -SiO 2 (CMAS) glass–ceramic reached the maximum, which are 146.95 MPa and 10.24 GPa, respectively. The mechanical properties of these two types of glass-ceramics developed from granite powder and waste marble can meet the requirements of building materials. From the acid resistance test results, it was found that the higher the content of MgO and CaO in the chemical composition of glass–ceramic, the worse the acid resistance. Therefore, the basic oxide content should be carefully controlled in the composition design of glass–ceramic. This technology of converting granite powder and waste marble into value-added glass–ceramic provides a promising method for the utilization of solid waste from stone processing, which can greatly improve the sustainability of the stone industry.

Influence of mineral admixtures on high performance concrete

Taking high performance concrete (HPC) in hydraulic engineering as an example, this paper discusses the influence of different mixing methods of slag powder and fly ash on its frost resistance and chloride ion permeability. The results show that the compressive strength decreases with the addition of HPC; Proper addition of mineral admixtures is beneficial to improve the anti chloride ion permeability of HPC and reduce the electric flux; The HPC flux of 28d and 90 reaches 680C and 280C, when the mass ratio of slag powder to fly ash is 15:35 and the content of mineral admixture is 35 %; The frost resistance of HPC gradually deteriorates with the increase of mineral admixture under the condition of constant air content and water binder ratio. The frost resistance grade of HPC without mineral admixture reaches F200, and its frost resistance is the best.

3D-printed Mg-1Ca/polycaprolactone composite scaffolds with promoted bone regeneration

In bone tissue engineering, polycaprolactone (PCL) is a promising material with good biocompatibility, but its poor degradation rate, mechanical strength, and osteogenic properties limit its application. In this study, we developed an Mg-1Ca/polycaprolactone (Mg-1Ca/PCL) composite scaffolds to overcome these limitations. We used a melt blending method to prepare Mg-1Ca/PCL composites with Mg-1Ca alloy powder mass ratios of 5, 10, and 20 wt%. Porous scaffolds with controlled macro- and microstructure were printed using the fused deposition modeling method. We explored the mechanical strength, biocompatibility, osteogenesis performance, and molecular mechanism of the Mg-1Ca/PCL composites. The 5 and 10 wt% Mg-1Ca/PCL composites were found to have good biocompatibility. Moreover, they promoted the mechanical strength, proliferation, adhesion, and osteogenic differentiation of human bone marrow stem cells (hBMSCs) of pure PCL. In vitro degradation experiments revealed that the composite material stably released Mg2+ ions for a long period; it formed an apatite layer on the surface of the scaffold that facilitated cell adhesion and growth. Microcomputed tomography and histological analysis showed that both 5 and 10 wt% Mg-1Ca/PCL composite scaffolds promoted bone regeneration bone defects. Our results indicated that the Wnt/β-catenin pathway was involved in the osteogenic effect. Therefore, Mg-1Ca/PCL composite scaffolds are expected to be a promising bone regeneration material for clinical application. Statement of significanceBone tissue engineering scaffolds have promising applications in the regeneration of critical-sized bone defects. However, there remain many limitations in the materials and manufacturing methods used to fabricate scaffolds. This study shows that the developed Ma-1Ca/PCL composites provides scaffolds with suitable degradation rates and enhanced boneformation capabilities. Furthermore, the fused deposition modeling method allows precise control of the macroscopic morphology and microscopic porosity of the scaffold. The obtained porous scaffolds can significantly promote the regeneration of bone defects.