Powder Aggregates Research Articles

Partial replacement of cement with marble powder and fine aggregate with copper slag

Concrete is the biggest utilized material around the world. With the expanding pace of populace development, framework to should be grown quickly to satisfy the necessities of individuals and for all these an enormous measure of assets are required. The significant one of them is total. In any case, the inordinate utilization of these assets will make an ecological awkwardness. Hence, we have chosen to supplant these significant element of the development business with marble powder and copper slag individually. As we know Concrete is the largest material after food and water. The main constituents of concrete are Cement and Fine aggregate. Many studies have been done to know the environmental impact of cement and concrete. Seeking the adverse effect of high production of cement on environment, we have thought of partial replacement of cement with marble dust and fine aggregate with copper slag in this research.

Characteristics of alkali-activated composites containing blast-furnace slag aggregate and ferronickel slag powder

The use of alkali-activated composites and alternative aggregates reduces the carbon dioxide emissions of the construction industry and mitigates the problem of aggregate depletion. However, published investigations into non-cement composites containing ferronickel slag powder (FSP) and blast-furnace slag fine aggregate (BSA) are limited. The aim of this study was thus to assess the mechanical properties and durability of non-cement composites containing FSP and BSA. The mix with 10% FSP and 25% BSA was found to have the highest 28-day compressive strength, of approximately 42.2 MPa. For the mixes with 5% FSP, the 28-day compressive strength increased with an increase in BSA content. Charge-passed tests revealed that, after 7 days, the sample with 5% FSP and 50% BSA exhibited a total charge of approximately 907 C, classifying it as ‘very low’ according to ASTM C1202. By 56 days, the total charge for this sample reached a value of approximately 120 C, close to ‘negligible’ as per ASTM C1202. It was thus concluded that an appropriate BSA content effectively enhances the mechanical properties and durability of non-cement composites.

Rod‐Like Microcrystal Scintillators Based on Organic–Inorganic Hybrid Copper Halides for X‐Ray Imaging

AbstractCopper‐based organic–inorganic hybrid halides (OIHHs) have garnered significant interest in X‐ray imaging due to their flexible structural adjustability, efficient light emission, strong X‐ray absorption, etc. Herein, four copper‐based OIHH crystals composed of the same organic ligands (isopropyl triphenylphosphonium cations, IPP+) and inorganic parts (Cu2I42−) are synthesized by varying the ratios of raw materials and types of reaction solvents. Although these crystals share identical structures, they exhibit different luminescent behaviors (blue, green, white, and yellow) attributed to vacancy defects originating from CuI. Notably, the novel copper‐based OIHH (CP2) with green emission shows the best luminescence efficiency (99.54%) and excellent scintillation performance (50675 photons MeV−1). The traditional technology of scintillation screens mixing scintillator powders and polymers often results in light scattering due to powder aggregation and inhomogeneity. To address this challenge, the dispersant polyvinyl pyrrolidone is introduced to prepare uniform rod‐like microcrystals of CP2. The scintillation screen based on CP2 microcrystals achieves a high spatial resolution of 16–18 lp mm−1, surpassing the resolution of most copper‐based OIHH scintillators. Furthermore, it is imaging capabilities are validated using a commercial X‐ray flat panel detector, demonstrating imaging performance comparable to that of commercial scintillators.

Study on the properties of recycled concrete mixed with coal gangue: Mechanics, workability and microstructure

Coal gangue is a by-product in the process of coal mining. Calcined coal gangue powder and coal gangue aggregate are used to prepare concrete, which can not only enhance the utilization rate of coal gangue, but also improve the performance of coal gangue concrete. In this study, calcined coal gangue powder (CCGP) was employed as an auxiliary cementation material, and coal gangue was employed as coarse concrete aggregate (CCA). Different mix proportions were designed to prepare 180 concrete specimens, and slump, cube compressive strength, splitting tensile strength and SEM test were carried out, respectively. The results show that after standing for 120min, the slump of CP0CA0 group is 53 mm, while the slump of CP30CA0 group is only 48 mm. CCGP can reduce the slump loss of concrete over time. The incorporation of CCGP into coal gangue concrete (CGC) can improve the late strength of concrete. When the substitution rate of CCA is constant, the CGC whose substitution rate of CCGP is 20 % will have the best mechanical properties: the compressive strength values are 49.67 MPa, 39.22 MPa and 27.35 MPa; the splitting tensile strength values are 2.92 MPa, 2.59 MPa and 1.92 MPa. In addition, how CCGP affects the mechanical properties of CGC was analyzed from the microscopic level in this paper. Through the regression analysis of the test data, the conversion relationship between the compressive strength and the splitting tensile strength of the concrete mixed with CCGP and CCA was obtained, which can be used to predict the splitting tensile strength. The results of this study can provide a new research idea for the efficient utilization of coal gangue.

Proposal for formulation of blocks to guarantee the sustainability of buildings in the Abidjan real estate park

A recurring fall of buildings in recent years (2013-2023) in the city of Abidjan has caused enormous material and human damage. This study was initiated in order to propose a formulation for the development of concrete blocks to guarantee the sustainability of buildings in the Abidjan real estate. The raw materials used are aggregates composed of sand, granite powder and a hydraulic binder (portland cement) then water for mixing. The aggregates were characterized before being used for the manufacture of the various FSB, FPS and FPG concrete blocks. The materials were subjected to physical and mechanical tests. The results showed that the sand and granite powder aggregates have a granular class of 0/1 and 0/2 respectively. Concerning concrete blocks, the density increases with the maturation time, namely 28 days maximum and when they are composed of both sand and granite powder (FPS). This significantly reduces the number of pores in the material. The compressive strength test showed that at 28 days of maturation, the FPS are more resistant than the FPG and FSB with respective values of 6.50 MPa; 5.31 MPa and 3.10 MPa. It appears that the addition of granite powder to the composition of the concrete blocks improves the density, porosity and compressive strength of the latter. The promotion of this formulation among concrete block manufacturers would make it possible to improve real estate construction, guarantee the durability of buildings in the Abidjan real estate park and thus avoid the possible fall of buildings.

On The Potential Use of Copper-Modified Geopolymer Incorporating Lead-Smelter Slag for Thermal Energy Storage

Thermal energy storage (TES) system has been widely employed in concentrated solar power (CSP) plants to ensure the system efficiency. With excellent thermal characteristics, electrolytic copper powder (ECP), graphene oxide (GO) and lead-smelter slag (LSS) aggregate – a mining waste material, have been utilised in this study, aiming to fabricate metallurgical geopolymer material as a storage medium in the TES system. This paper investigated the effect of ECP contents (0, 5%, 10%, 15%, 20%) on the strength, specific heat, thermal conductivity and thermal stability of GO-engineered geopolymer mixes incorporating LSS aggregate. With 10% ECP inclusion, the flow rate and compressive strength improved significantly. Increasing ECP content improved the thermal conductivity but reduce specific heat of geopolymers. The results revealed that ECP was a promising component to be incorporated into geopolymer to enhance its physio-mechanical characteristics and thermal stability. The combination of ECP, GO and LSS to produce geopolymer materials for TES system can provide an eco-friendly solution to the CSP plants and the industry waste recovery.

Rheology and buildability of sustainable 3D printed magnesium potassium phosphate cement composites incorporating MgO-SiO2-K2HPO4

MKPCs with unique advantage of superior strength, excellent durability and high thixotropy provides alternative binder for 3D printing. The acid-base reaction between dead burnt MgO and K2HPO4 is intense and the retarding effect is limited in practical cases. This paper presents the investigation of MKPCs incorporating MgO-SiO2-K2HPO4 binders prepared with dead burnt MgO, soluble phosphate (K2HPO4•3 H2O) and silica fume (SF). The effects of magnesium-to-phosphate (M/P) mass ratio, SF and slag ratios on rheological properties and the printability were tailored and setting time reached to 50 min by increasing the alkaline environment of the solution. In addition, the pozzolanic activity of SF and slag were synergistically motivated and thus promoted the precipitation of K-struvite, MgSiO3 and C-(A)-S-H hydrates. Two-stage Athix values were calculated to describe the structuration rate. It is confirmed excellent thixotropy was dominated by early-age physical re-flocculation and later-age cement hydration. Although the structure deformation increased significantly as SF content increased, the beneficial effect of SF content on the increase of strength is significantly important than that of adverse effect on the buildability. Slag powder and fine aggregate were incorporated to make the binders more “printable”. A cylinder with 16 layers on optimum mixture was printed without deformation.

Development of eco-friendly engineered cementitious composites (ECC) with both waste glass powder and aggregate: A comprehensive investigation

This study investigated the micro-macro properties of engineered cementitious composites (ECC) with both waste glass powder (WGP) and waste glass aggregate (WGA) as substitutes for binder and silica sand, aiming to achieve sustainable ECC materials and recycle waste glass in a high-value approach. The results indicate that a high volume of WGP used as a replacement for cement leads to a loose microstructure in ECC, whereas ECC prepared with 100 % WGA replacing silica sand exhibit a better microstructure compared to the reference ECC. Replacing cement with a high volume of WGP reduces the compressive and flexural strengths, but replacing silica sand with WGA increases the compressive and flexural strengths of ECC. Under tensile loading, both WGP replacing binders and WGA replacing silica sand enhance the strain capacity of ECC at substitution rates not exceeding 25 %. As the substitution rate increases, replacing 50 % of cement with WGP reduces the strain capacity and ultimate tensile strength of ECC by 18 % and 32.5 %, respectively. Nevertheless, substituting WGA for silica sand can enhance the strain capacity of ECC. Substituting WGP for the binders increases the transport properties and water-permeable porosity of blended ECC, while the replacement of silica sand with a moderate dosage of WGA reduces the water transport properties and water-permeable porosity. The simultaneous substitution of binder and silica sand with WGP and WGA, respectively, enables the production of sustainable ECC with desirable micro-macro properties. The complete replacement of silica sand and fly ash with WGA and WGP, respectively, is feasible, whereas the substitution of cement with a high-volume WGP should be limited.

Prediction of alkali–silica reaction expansions of mortars containing glass waste

The majority of existing findings regarding expansion (EXP) risks in concretes containing waste glass stem from experimental studies. There is a need for rapid assessment methods to ensure safer recycling of glass waste in cementitious composites. In this study, an artificial neural network (ANN) model was developed to accurately predict alkali–silica reaction EXP/mitigation resulting from the integration of glass waste in mortars. The analysis considered glass incorporation either separately as waste glass powder (WGP) and waste glass aggregates (WGAs), or in combination, at contents of up to 100% for WGA and 30% for WGP. A set of 175 mixtures was analysed, considering five distinct variables, which encompassed different mix proportions, involving varying components of cement, natural aggregates, WGP and WGA, in addition to the duration of environmental exposure. The results show that the EXP of WGA mortars decreased with the increased incorporation of WGP. The EXP values obtained from validation and experience confirm the high accuracy of the developed ANN model, with validation coefficients reaching up to 98.061% and a small value of the mean square error.

Plasma-solution synthesis of cobalt oxides

The production of nanosized oxide materials is an important practical problem. This is due to the fact that many of these substances are intensively used as catalysts, microelectronic devices, medical applications, etc. Among the various methods for their production, methods based on the use of gas-discharge plasma are the least studied. But these methods, compared to others, have a number of significant advantages. Among them, the main ones are high process rates and the absence of additional reagents. Therefore, in this work the regularities of the processes of formation of insoluble compounds under the action of a direct current discharge of atmospheric pressure in air on aqueous solutions of cobalt (II) nitrate have been studied. The solutions served as the cathode and anode of the discharge. The discharge was excited by applying a high voltage to two pointed titanium electrodes placed above the liquid anode and liquid cathode in the H-shaped cell. The range of discharge currents was (20–80) mA, and the range of concentrations was (20–60) mmol l−1. It was discovered that when a discharge acts on a liquid anode, a colloidal solution is formed in it, the destruction of which leads to the formation of precipitates. Based on measurements of the kinetics of consumption of Co2+ ions (spectrophotometric method) and the power inputted in the discharge, the rates of this process, effective rate constants, as well as the degree of conversion of Co2+ ions and energy yields of conversion were determined. These parameters depended on the discharge current and the initial concentration of the solution. The values of the constants were ∼(0.2–6) × 10−1 s−1, the energy yields were ∼(0.2–0.5) ions per 100 eV, and the degrees of conversion were ∼(0.1–0.5). The resulting powders were analyzed by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS). The sizes of the powder aggregates were estimated from the results of scanning electron microscopy (SEM), transmission electron microscope (TEM) and Scherrer’s relation. It turned out that the resulting precipitates were a mixture of amorphous Co2+ and Co3+ hydroxides. Their calcination in air led, depending on the temperature, to the formation of predominantly cubic either CoO or Co3O4. The size of the aggregates of the calcined samples was ∼500 nm. The specific surface area of the powders, determined by the Brunauer–Emmett–Teller (BET) method, was ∼53 m2 g−1. The average pore volume and their size was ∼17 cm3 g−1 and ∼240 Å. The advantages of the proposed method over other methods are high process rates (process time ∼10 min) and the absence of any additional reagents.

Preparation of h‐BN/PMMA composites by in situ polymerization and research on their structure and properties

AbstractInorganic fillers like hexagonal boron nitride (h‐BN) have the potential to enhance the thermal conductivity of polymer mixtures. However, it has been restricted due to poor dispersion of particles in polymer matrices by melt mixing process. The addition of inorganic powders into sticky prepolymer is expected to alleviate the aggregation of powders. In this paper, h‐BN/polymethyl methacrylate (PMMA) composites were prepared by in situ polymerization of methyl methacrylate (MMA) with 5 and 20 μm of h‐BN particle as fillers respectively, for even distribution of fillers with in composites. The structures and properties of composites were characterized by FT‐IR, DSC, TGA, SEM, laser thermal conductivity meter and universal electronic tester. By SEM, it can be seen that a highly uniform dispersion of h‐BN in PMMA. When the mass fraction of h‐BN is 20 wt%, the thermal conductivity of the composites is increased by 107% for 5 μm h‐BN and 189% for 20 μm h‐BN, respectively. With the mass constituting of 5 wt% h‐BN, majority of mechanical characteristics of the composite, such as tensile strength, tensile modulus, along with impact strength, are enhanced, alongside a decrease in bending strength. This work would provide a filling strategy of h‐BN into the polymer matrices to achieve uniform dispersion, and enhance both the thermoconductivity and mechanical strength of thermoplastic composites.Highlights A technique for creating h‐BN/PMMA composites using in suit redox polymerization. Ehancing the thermal conductivity of these composites is achievable through the even distribution of h‐BN flakes within the PMMA matrix. It provides a reference for the design of future h‐BN/PMMA composites with favorable the thermal conductivity which achieves a good balance between performance and cost.

Preparation and Evaluation of Inhalable Microparticles with Improved Aerodynamic Performance and Dispersibility Using L-Leucine and Hot-Melt Extrusion.

Dry-powder inhalers (DPIs) are valued for their stability but formulating them is challenging due to powder aggregation and limited flowability, which affects drug delivery and uniformity. In this study, the incorporation of L-leucine (LEU) into hot-melt extrusion (HME) was proposed to enhance dispersibility while simultaneously maintaining the high aerodynamic performance of inhalable microparticles. This study explored using LEU in HME to improve dispersibility and maintain the high aerodynamic performance of inhalable microparticles. Formulations with crystalline itraconazole (ITZ) and LEU were made via co-jet milling and HME followed by jet milling. The LEU ratio varied, comparing solubility, homogenization, and aerodynamic performance enhancements. In HME, ITZ solubility increased, and crystallinity decreased. Higher LEU ratios in HME formulations reduced the contact angle, enhancing mass median aerodynamic diameter (MMAD) size and aerodynamic performance synergistically. Achieving a maximum extra fine particle fraction of 33.68 ± 1.31% enabled stable deep lung delivery. This study shows that HME combined with LEU effectively produces inhalable particles, which is promising for improved drug dispersion and delivery.

Experimental study of Compressive Strength of Concrete by Partial Replacement of Cement with Egg Shell Powder and Fine Aggregate with Copper Slag

Experimental study of Compressive Strength of Concrete by Partial Replacement of Cement with Egg Shell Powder and Fine Aggregate with Copper Slag

Improving flow dynamics and storage longevity of a low-cost phosphorescent fingerprint powder.

An inexpensive, commercially available doped strontium aluminate phosphor with long-lived afterglow was prepared as a luminescent fingerprint dusting powder suited for challenging, highly patterned substrates; however, prolonged exposure to humidity was found to reduce that powder's affinity for fingermarks. Here, an enhanced preparation for synthesizing that fingerprint dusting powder is presented that prevents powder aggregation and loss of function upon exposure to humid environments. This was achieved by introducing a flow regulator during synthesis: hydrophobic silica SIPERNAT® D10 or SIPERNAT® D17. Increasing the hydrophobicity of the powder prevents aggregation by inhibiting the uptake of water, thereby improving the material's flow dynamics and transfer behavior from brush to fingermark. The angle of repose and flow characteristics made by the modified powders were quantified, with excellent affinity for fingermarks observed, even after being stored under 85% (±5%) humidity for 4 weeks. A preliminary comparison of the performance of the modified hydrophobic powders relative to the unmodified precursor revealed that more of the SIPERNAT® treated powder typically adhered to fingermarks while simultaneously imparting less background development. In addition, fewer clumps of particulate were observed in the developed fingermarks after addition of a hydrophobic flow regulator. This technical report outlines the updated method for synthesizing the fingerprint powder, with summarized flow performance results, and a demonstration of the modified powder's affinity for simulated fingermark evidence.

Coal gangue in asphalt pavement: A review of applications and performance influence

The comprehensive utilization of coal gangue is low, and this causes serious environment problems and security risks. The physical and chemical properties of coal gangue were analyzed in this paper, and the estimated value of different chemical components of coal gangue was counted. The physical properties of coal gangue aggregate were analyzed, and performance and its influencing factors of base course mixture with coal gangue aggregate were studied. The influence of coal gangue powder and coal gangue aggregate on performance of asphalt mortar and asphalt mixture was analyzed, and possible influencing factors and function mechanism were discussed. The results showed that heavy metal elements of coal gangue applied into asphalt pavement is not seeped out. The crushing value, water absorption and flat elongated particles content of coal gangue aggregate are generally high, but the compressive strength of base course with coal gangue aggregate is verified to meet the strength requirement. The performance, volume stability and durability of base course with coal gangue aggregate are closely related to aggregate gradation, the type and dosage of cementations materials and aggregate. The high temperature performance, temperature susceptibility and viscosity of asphalt mortar are improved by the addition of different coal gangue powder, and improvement effect of activated coal gangue powder on asphalt mortar performance is better. The low temperature performance and adhesion property of asphalt mortar with chemical activated coal gangue powder are improved. The physical reaction between asphalt and different coal gangue powder is only taken place. The temperature stability of asphalt mixture with coal gangue coarse aggregate has achieved the specification requirement. The water stability and low temperature fracture performance of asphalt mixture with fine aggregate replaced by coal gangue are improved. However, the high temperature performance of above mixture is lower than conventional hot mix asphalt mixture. The research results will provide reference for coal gangue applied into asphalt pavement.

Ultra-high performance concrete with metal mine tailings and its properties: a review

Abstract Metal mine tailings (MMT) are a kind of industrial solid waste, with an increasing accumulation year by year, which has seriously damaged the ecological environment. Incorporating MMT in ultra-high performance concrete (UHPC) is an effective means to achieve green sustainable development, which can not only make wastes be resources and prevent pollution but also save raw material costs and reduce energy consumption. However, metal mine tailings contain complex and diverse metal oxides and other chemical substance and even contain certain radioactive elements and heavy metal ions. These factors can affect the corrosion resistance of UHPC, accelerate its aging and damage, and in addition may have serious impacts on the environment and human health. This paper summarizes the material properties of MMT and its application in UHPC; analyzes the effects of MMT as powder or fine aggregate on the workability, mechanical properties, durability, and leaching toxicity of UHPC; and elaborates the hydration products, interfacial transition zone, and pore structure of UHPC incorporating MMT (MMT-UHPC). Based on previous research results, the relationship between flowability, flexural strength, porosity, and compressive strength of MMT-UHPC is established.

Multistep kinetics in self-induced sol–gel process of amorphous anhydride formation during thermal dehydration of potassium tetraborate tetrahydrate

AbstractThe physico-geometrical mechanism and kinetics of the multistep thermal dehydration of potassium tetraborate tetrahydrate was investigated as a model reaction to produce amorphous anhydrate via the self-induced sol–gel process. The thermal dehydration is composed of three consecutive dehydration steps: (1) a surface reaction in the solid-state accompanied by crack formation; (2) a rapid mass loss process accompanied by liquefaction to form the aggregate of the gel powders; and (3) the dehydration of gel powder aggregate to form a glassy anhydride. The changes in the contribution of the individual dehydration steps to the overall process according to the sample particle size and the heating rate (β) were identified as specific features of the multistep dehydration, which was characterized quantitatively using mathematical deconvolution analysis with log-normal four-parameter functions. The difficulty in determining the apparent activation energy (Ea) of the individual dehydration steps using isoconversional analysis due to the changes in the contribution depending on β values was addressed using modulated temperature thermogravimetry. Using the contributions and the apparent Ea of the individual dehydration steps as initial values, the kinetic description of the multistep thermal dehydration was refined through a kinetic deconvolution analysis using the cumulative kinetic equation. As a result, the individual dehydration steps were kinetically characterized as: (1) a surface reaction described by the first-order rate law with Ea,1 of approximately 68 kJ mol−1; (2) a reaction accompanied by liquefaction controlled by an autocatalytic rate behavior with Ea,2 of approximately 123 kJ mol−1; (3) a diffusion-controlled dehydration of gel powder with Ea,3 of approximately 82 kJ mol−1.

Thermal and mechanical properties of a sustainable bio-flax fibre-based lightweight aggregate concrete

A novel lightweight aggregate concrete (LWAC) or lightweight concrete (LWC) is developed using expanded perlite powder and lightweight expanded clay aggregate as a replacement for conventional fine and coarse aggregates, respectively. Furthermore, the natural plant-based flax fibre in treated form was added to the LWC mix at three different volume fractions. The mechanical and thermal characterisation of LWC was carried out using the compressive strength test, split tensile test, modulus of rupture, thermal conductivity and thermal resistance test. Moreover, the microstructural and durability properties were obtained using scanning electron microscopy/energy dispersive X-ray spectrum analysis, rapid chloride penetration test, sorptivity test and water absorption test. Test results reveal that the addition of 2.0% flax fibre resulted in improved mechanical, thermal and durability properties when compared to LWC with no fibres. Moreover, the microstructural analysis using SEM revealed the formation of ettringite which is responsible for the strength development in the LWAC mix.

Ceramic-added lime and cement mortars: A review of applications in building products.

Ceramic-added air lime mortars have been used since ancient times owing to the pozzolanic effect provided by crushed ceramic particles that impart hydraulic properties. This work reviews the historical use, composition, reaction mechanisms, characterization techniques, and performance properties of ceramic-added air lime mortars. The fine ceramic powder composed of silica and alumina phases reacts with calcium hydroxide released during lime hydration to form calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH) via pozzolanic reaction. This provides hydraulicity and reduces setting time compared to pure air lime mortars. The coarser ceramic particles also serve as aggregate and refine the microstructure as filler. The reactivity depends on the ceramic composition, amorphous phase content, particle size distribution, and firing temperature. Optimal proportioning of the fine ceramic powder and coarse ceramic aggregate is necessary to achieve desired properties. Ceramic addition enhances the durability of air lime mortars against weathering while maintaining compatibility with lime-based masonry structures. Key novelties of this review include: (i) in-depth analysis of the influence of ceramic characteristics (mineralogy, particle size, pozzolanicity) and processing on reaction kinetics and phase evolution; (ii) systematic assessment of mechanical, physical and durability properties in comparison to conventional air lime mortars and cement-based grouts; (iii) elucidation of microstructural mechanisms governing performance using advanced characterization techniques; (iv) critical appraisal of test methods and standards for evaluation; and (v) rigorous discussion on potential applications in construction, conservation and repair, with case studies.

Preparation of pavement base material by using steel slag powder and steel slag aggregate

Preparation of pavement base material by using steel slag powder and steel slag aggregate