Bulk Density Tests Research Articles

Development of a high-fidelity digital twin using the discrete element method for a continuous direct compression process. Part 1. Calibration workflow

In this work, a high-fidelity digital twin was developed to support the design and testing of control strategies for drug product manufacturing via direct compression. The high-fidelity digital twin platform was based on typical pharmaceutical equipment, materials, and direct compression continuous processes. The paper describes in detail the material characterization, the Discrete Element Method (DEM) model and the DEM model parameter calibration approach and provides a comparison of the system’s response to the experimental results for stepwise changes in the API concentration at the mixer inlet. A calibration method for a cohesive DEM contact model parameter estimation was introduced. To assure a correct prediction for a wide range of processes, the calibration approach contained four characterization experiments using different stress states and different measurement principles, namely the bulk density test, compression with elastic recovery, the shear cell, and the rotating drum. To demonstrate the sensitivity of the DEM contact parameters to the process response, two powder characterization data sets with different powder flowability were applied. The results showed that the calibration method could differentiate between the different material batches of the same blend and that small-scale material characterization tests could be used to predict the residence time distribution in a continuous manufacturing process.

Effect of microwave sintering on density, microstructural and magnetic properties of pure strontium hexaferrite at low temperatures and heating rate

In recent decades, the rising demand for permanent magnetic materials has driven manufacturers to explore substitutes for rare earth elements in response to their fluctuating prices and negative environmental impact. M-type hexaferrites considered as good alternatives and studies have focused on enhancing their magnetic and structural properties through various approaches. In this study, new approach using low heating rate microwave sintering has been applied to investigate the changes on density, microstructure, and magnetic properties of strontium hexaferrite from core to surface. Sintering temperatures of 950 °C, 1000 °C, 1050 °C, and 1100 °C with 10 °C/minute heating rate were applied accordingly. The bulk density, FESEM, XRD and VSM tests were conducted to study materials’ properties. The outcomes of the study showed exponential relationship between density and sintering temperature reaching optimum value of 91.4 % at 1050 °C and then declined slightly at observed to analysis confirmed the magnetoplumbite structure P63/mmc in all samples and high crystallized structure at 1050 °C, with the occurrence of α-Fe2O3 at 1100 °C. Grain growth and crystallization observed to increase at higher sintering temperature with agglomeration while denser and melted boundaries at lower temperatures. Magnetic properties especially remanence magnetization Mr and saturation magnetization Ms fluctuated with sintering temperature achieving optimum values of 28.188 emu/g and 55.622 emu/g at 1000 °C respectively. Coercivity Hc and magnetic energy density BH max recorded optimum values at 1050 °C. The findings emphasize the critical role of microwave sintering in tailoring the properties of strontium hexaferrite for magnetic applications.

Study on Characteristics of Soil Profile Stability Indexes in Sakita

This research examines the suitability of soil as infrastructure which can help in the classification and identification of its properties for ideal engineering structures. Sakita, an area in Gesse III as a case study, is a virgin land, allocated for residential buildings. The need to investigate the soil profile in the report area prompted these studies as its physical properties are used for classifying its various engineering applications. These properties indicate qualitative behaviors of soil when subjected to various types of loads. Apart from physical/visual observation made of the soil, trial pits were dug to depths of 0.5m, 1.0m, 1.5m, 2.0m, and 2.5m respectively and disturbed soil samples were taken for tests. The disturbed soil samples obtained were analyzed for grading including mechanical sieve analysis, specific gravity, plastic limit, liquid limit, and bulk density tests. The resistances of the cone against penetration, compaction, consolidation, and permeability properties were also assessed. The detected geotechnical properties varied significantly with depth, except for specific gravity, which did not vary significantly at 0.5 m with depth. Soil samples from all pits consist mainly of poorly sorted gravel and sand with little fineness. They contain a medium- to coarse-grained fraction of sand on average above 85%. The puncture resistance obtained from the cone puncture test ranges from 100 knm2 to 950 knm2. The average safe bearing capacity estimated for the footing using a factor of safety of 3 at a depth of 1 m was not less than 473 km2 anywhere in the study area. The samples from the three locations generally have good compaction parameters, medium to high permeability, and low compressibility. The highest load-bearing capacity is associated with the lateralized basement ceiling. This means that the safety depth for placing infrastructure foundations in the prescribed research area (Sakita) is the depth where it meets the lateralized basement.

Effect of leachate on the geotechnical properties of soils at Gbagede Dumpsite Ilorin, Kwara State Nigeria

The increasing request for space for private buildings was brought about by the utilization of the previous dumpsites. If the issue of leachate infiltration into the soil isn't legitimately controlled it'll lead to future harm in construction works. The objectives are to compare the geotechnical properties of soil of the contaminated and uncontaminated regions region of the dump site and evaluate if the effect of leachate on the geotechnical properties of soil changes with depth. Laboratory soil tests were conducted on the soil samples obtained and compared the effect of these leachates at the dump site. These methods are Natural water content, Bulk Density, Specific Gravity, Shear strength, and Consolidation tests. The soil samples were obtained from the contaminated region, and the uncontaminated region (i.e. at 100 m away from the dumpsite). All soil samples were obtained at depths 0.5m, 1.0m, and 1.5m below the ground level, to know the effect of leachate on the soil at the dumpsite and also to know if the effects of leachate changes with depth as it goes down the soil. The results obtained show that samples at 0.5m and 1m depth have been affected by leachates but the effects are not so significant at 1.5m depth, thereby making the soil at depths 0.5m and 1m unfit for construction purposes. This result was useful to check the land requirement in urban areas and guide the geotechnical engineers when designing and constructing foundations for buildings and other related structures on these types of soils.

Development of red mud based sintered artificial aggregates with various industrial wastes

Red mud (RM) has drawn a lot of attention in the search for potential uses in the production of sintered artificial aggregate from industrial waste products. The main objective of the study is to produce an RM-based sintered artificial aggregate (SAA), with several blends (binary, ternary, and quaternary) using various industrial wastes. This study includes assessing the mechanical and physical properties of SAA as well as the sintering parameters in order to determine the appropriate material mix ratio. To achieve these objectives, a comprehensive experimental approach was adopted. A total of 35 different mixtures were formulated by incorporating various industrial wastes as binders and sintering additives. The green pellets were preheated at 105 °C for 24 h, and consecutively sintered at different temperatures, namely 700 °C, 900 °C, 1100 °C, and 1150 °C with a duration of 30 min. A compressive strength test was performed in order to find the mechanical property of SAA similarly water absorption and bulk density tests were conducted to find the physical properties of SAA. To characterize the SAA, scanning electron microscope analysis (SEM), X-ray diffraction (XRD) and energy dispersive x-ray analysis were conducted, and also data analysis was performed using Artificial Neural Network (ANN) tools, yielding accurate predictions. Successfully best compressive strength low water absorption SAA was produced. The best material weight mix ratio for the production of SAA was identified as (A18) RM: Fly Ash: Waste Glass Powder; 78:10:12. Out of all blends the ternary blend (A18) SAA exhibited impressive properties after 30 min of sintering at 1150 °C: high compressive strength of 22.92 MPa, water absorption of 4.26%, and bulk density of 1296.12 kg m−13. This was made possible by the high amount of Al2O3, SiO2, in the combination of fly ash, and waste glass powder with RM. SEM and XRD analysis also confirmed that the (A18) SAA achieved the best compressive strength, and low water absorption due to turning the surface and core area into a solid, reduced internal pores and formed quartz, and hematite phases. The findings of this study serve as a foundation for future work and pave the way for the development of sustainable construction materials.

Fabrication of green anti-microbial and anti-static cement building bricks

The design cement mix of grade 350 was created in accordance with Egyptian Standards by partially substituting the fine aggregate with WPVC waste in various weight percentages (10, 20, 30, 40, 50, 75, and 100%). A control mix with 0% replacement was also prepared. The W/C ratio was about 0.5 for all mixes. Compressive, flexure strength, bulk density, and absorption tests were studied. For WPVC replacement, until 30%, compressive strength and flexure strength are acceptable with respect to standerds. Thermal treatment at 200 °C improves the compressive strength, flexure strength and water absorption for 20% WPVC only. The dielectric properties of all cement paste mixes before and after heat treatment, over a frequency range (0.1–106 Hz), were measured as a function of frequency. For dielectric properties and conductivity, an improvement was obtained until 30% WPVC. After this percentage, the dielectric properties and the conductivity got worse. So, cement paste with 30% WPVC as replacement of sand is the optimum ratio with conductivity in range of 10−12 S/cm, which is a good choice for antistatic cement paste applications (10−10–10−12 S/cm). The antimicrobial efficacy of the prepared cement samples of WPVC concentrations (0, 20 and 30) % were studied, the number of grown microbial colonies decreased for all the samples compared to control tap water and decreased by introducing WPVC into the cement paste sample. So, it is recommended to use these samples in places that should be carefully shielded from bacterial infections and static electric charge dangers.

Co-densification of rice straw and cow dung in different food-to-microorganism ratios for biogas production

Agricultural residues such as rice straw (RS) are desirable raw materials for biogas generation. However, the recalcitrant nature of RS hinders biogas production, and its low bulk density increases storage space requirements, transportation needs, and overall costs. These challenges could be resolved by pretreatment and pelletization. In this study, various thermal pretreatments were performed, and the best conditions (temperature and time) were identified. Also, rice straw and cow dung pellets (RCP) at different food-to-microorganism (F/M) ratios (0.5–2.5) were prepared. Parameters such as bulk density, moisture absorption, and drop shatter tests were conducted to evaluate the physical properties. Finally, the biochemical methane potential (BMP) study of the best RCP with varying total solids (TS: 4–12%) content was investigated. The results indicate that hot air oven pretreatment (for 60 min at 120 °C) resulted in maximum solubilization. In physical characteristics, RCP with an F/M ratio of 2.5 pellets was ideal. The bulk density of RCP 2.5 was found to be around 25 times that of the raw. Also, the TS 8% yielded maximum biomethane (279 mL/g-VSconsumed) as compared to other TS contents. Overall, this study will propel the growth of bioenergy while simultaneously tackling the pressing issues related to RS management.

The Effects of Particle Packing and Inter-particle Force on Rheological Behaviors of Binary Cement Paste

This article aims to study the effects of particle packing and inter-particle force on the rheological behaviors of binary cement paste. Fly ash (FA), ground granulated blast furnace slag (GGBFS), and limestone powder (LP) were added by 10 – 40% of cement weight to prepare the binary binder. The particle packing of each binary binder was analyzed based on the close packing theory and bulk density test. Atomic force microscopy and direct shear method were used to investigate the Hamaker constant and friction coefficient of different binders. Fresh pastes of every binder were prepared with variable solid volume fractions (w/b is 0.50, 0.55, and 0.60), and the rheology was measured by a rotary rheometer. Eventually, two empirical models were proposed to predict the yield stress and plastic viscosity of paste based on the porosity, friction coefficient, and w/b obtained from the experiments, and the accuracy of these new models was verified by ANOVA and p-value approach. The results show that particle packing and inter-particle force play a collaborative role in determining the rheological behavior of paste. Increasing particle packing or reducing inter-particle force (i.e., decreasing porosity or friction coefficient) benefits the enhancement of paste rheology. Moreover, an increase in the Hamaker constant leads to higher friction coefficients for binders. Comparisons between the predicted and experimental results demonstrated that these empirical models accurately capture the rheological behaviors of fresh pastes.

Evaluation of the Technological Properties of Artificial Agglomerated Stones in Epoxy Resin and Castor Oil-Based Vegetable Polyurethane Matrix

Objective: The aim of this study was to produce and evaluate the technological properties of artificial agglomerated stone slabs produced using the waste from the stone commercially known as "Preto São Gabriel," using epoxy resin and castor oil-based polyurethane. Theoretical framework: Ornamental stones are widely used in the construction sector and are of great economic importance to the country. During the production stages, a significant amount of waste is generated. The production process generates a substantial amount of waste from the extraction and processing processes that have no economic value, accounting for approximately 40 to 60% of the production during mining, and during the cutting stage, about 30 to 35% is generated. Method: To manufacture the artificial stone slabs, the waste was crushed in a jaw crusher and ceramic plate mill and screened into three particle size ranges. The slabs were produced using the vacuum vibro-compression method. Technological characterization tests were conducted, including bulk density, apparent porosity, water absorption, and three-point strength tests. Results and conclusions: It is concluded that slabs produced with both resins can be applied in locations requiring good flexural strength. For use in areas with water presence, those produced with epoxy resin are recommended, as they exhibited lower porosity and water absorption. Research implications: Utilizing waste from ornamental stones, which amounts to millions of tons and is disposed of in landfills or storage facilities, to manufacture agglomerated stones represents a significant contribution to environmental impact reduction, aligning with the principles of ESG (Environmental, Social, and Corporate Governance). Originality/value: The evaluation of the technological properties of artificial agglomerated stones produced from ornamental stone waste is of fundamental importance for the correct and safe application of these sustainable materials in civil construction.

Effect of heavy-weight recycled materials on radiation shielding and properties of high-strength concrete with CEM III

This research aims to study the effect of replacing up to 100% of recycled coarse aggregates with heavyweight aggregates. In addition to the effect of adding heavyweight aggregate slag on the efficiency of shielding against radiation and on the mechanical physical properties and elevated temperature of heavyweight high-strength concrete (HWHSC). In this investigation, HWHSC mixtures incorporate lead slag (LS), copper slag (CS), and steel slag (SS) as coarse aggregate. Recycled heavyweight coarse aggregates are added to concrete mixtures at volume ratios of 0%, 25%, 50%, 75%, and 100%. Slump test, compressive strength, flexural strength, tensile strength, elastic modulus, and bulk density tests were carried out. Three different gamma-ray energies at 137Cs 662, 60Co 1173, and 60Co 1332 (keV) sources were used to evaluate the mass attenuation coefficient, linear attenuation coefficient, half and tenth-value layer, and mean free path. To evaluate the impact of elevated temperature on density, compressive strength, and radiation shielding properties, concrete mixtures were exposed to 22 °C, 300 °C, 500 °C, and 800 °C. Compared to basalt-based concrete, heavy-weight concrete (HWC) incorporating LS, CS, and SS coarse aggregate has a significantly higher density. The results show a good effect of recycled heavyweight coarse aggregates on fresh, mechanical, and radiation-shielding properties. The density of the developed high-strength concrete (HSC) mixes ranges between 2400 and 3370 kg/m3, and the increase in recycled heavyweight coarse aggregates replacement ratio up to 75% increased all mechanical characteristics of HWC mixtures. Using LS as a replacement of basalt by 75% resulted in the highest compressive strength, splitting tensile strength, flexural strength, and elastic modulus of 105.8 MPa, 14.2 MPa, 19.5 MPa, and 45.76 GPa, respectively. Compared to basalt, LS, CS, and SS eliminate the impact of elevated temperatures on HSHWC strength. The best radiation protection properties were achieved with the complete replacement of basalt by LS.

Quality assessment of bricks produced in Chitwan District, central Nepal

Based on the physical, mechanical, and mineralogical properties of fire clay bricks from different brick industries of the Chitwan District, the quality of bricks was determined. The specific objective of this study was to assess the characteristics and comparison of bricks produced from different kilns. Both desk study and field study was carried out for this purpose. Parameters such as dimension, hardness, soundness, and impact were studied in the field for twenty brick samples obtained from each brick industry. Water absorption, apparent porosity, bulk density, and compressive strength tests were carried out in the laboratory, encompassing high and low quality of samples. Additionally, seven types of bricks were manually crafted using clay from those industries. For mineralogical analysis, XRD was carried out on seven brick samples each from seven different brick industries. IS standard was followed for various testing. The dimension test results showed that none of the samples meet the standard. Similarly, the laboratory test result showed that the bulk density of each brick sample increased with increasing compressive strength and decreasing water absorption capacity and apparent porosity. XRD analysis has identified mineral phases like quartz, hematite, and berlinite. Thus, this research tries to provide valuable insights into brick quality, strength and potential applications.

Ellipsoidal seed modeling and simulation parameter selection based on the discrete element method

At present, there are still some issues in the discrete element modeling of non-spherical agricultural materials. For example, it is still necessary to enrich and optimize the particle model of non-spherical granular materials and study their simulation parameters. Therefore, in this paper, ellipsoidal seeds, such as those of soybeans, red beans, and kidney beans, were taken as the research object, and their dimensions and shapes were analyzed. The results showed that the dispersion in size could be approximated by a normal distribution. An approach for modeling ellipsoidal seeds as particles based on the multi-sphere (MS) method was proposed. Moreover, the Plackett–Burman (PB) test and the path of the steepest ascent method were both adopted to calibrate the simulation parameters, which were obtained with difficulty through experiments, and simulations of the piling test and the rotating hub test for calibration to ensure the rationality of the parameter selection. In addition, to improve the reliability of the calibration test, the automatic filling function in EDEM software was adopted for particle modeling, where the smoothness was 2. A 122-sphere model for the soybean seed, a 114-sphere model for the red bean seed, and a 242-sphere model for the kidney bean seed were established, and the three models were applied for the calibration of the simulations of the tests. The results showed that the coefficients of rolling friction between seeds had a significant influence on the simulation results for the three varieties of seeds. Finally, the manual filling models and the automatic filling models were further verified by using simulations of bulk density tests. Comparing the simulation and experiment results showed that when the number of filling spheres increased, the simulation results were closer to those obtained experimentally. Better simulation accuracy could be obtained with fewer filling spheres. These results could provide a reasonable discrete element model and simulation parameters for further simulation and optimization of designs of seeding machinery for ellipsoidal seeds.

From by-product to sustainable building material: Reusing phosphate washing sludge for eco-friendly red brick production

Brick production is a major contributor to the construction industry, but the process requires a significant amount of non-renewable clay. To address this, researchers have explored incorporating waste materials into clay bricks. This study investigates phosphate-washing sludge (PS-K) as an additive in clay bricks and evaluates its impact on physical, mechanical, and thermal properties. Laboratory and pilot-scale experiments were conducted to determine the optimal quantity of PS-K for waste reduction. Five compositions with PS-K percentages ranging from 0% to 50% were prepared in the laboratory based on the raw materials' chemical composition. The bricks were shaped using a humic method, underwent drying and cooking processes, and underwent physical analysis, including bulk density, apparent porosity, and water absorption tests. Microstructural analysis was performed using a scanning electron microscope, while thermal conductivity and compressive strength were evaluated.Results showed that increasing PS-K content led to higher open porosity and water absorption in the bricks. At 50% waste content, the open porosity reached 52%, and water absorption reached 32%. The relationship between waste content and porosity/water absorption was nonlinear, with greater increases observed at higher waste contents. Incorporating up to 30% sludge met standard brick requirements.Pilot-scale experiments using the optimal 30% PS-K content demonstrated similar porosity and water absorption trends as observed in the laboratory samples. The bricks' extrusion shaping process and final appearance after drying were successfully demonstrated.This research provides valuable insights into utilizing phosphate-washing sludge in clay bricks, offering a potential waste management solution and reducing clay consumption in brick production. The findings demonstrate the feasibility of incorporating PS-K into bricks while meeting industry standards, contributing to sustainable practices in the construction sector.

Conversion of obsolete keyboard plastics mixed with egg shells and fly ash into concrete brick cubes

Plastic waste is a menace due to its non-degradable properties and chemical composition. Owing to inefficient recycling methods, around 90% of the E-waste plastics are landfilled every year. Burning of E-waste plastics results into the release of dioxins and furans which create severe environmental threats and health hazards. Several studies have been conducted on the utilization of plastics like soda bottles, plastic bags, etc. comprising of single polymers. However, the sustainable utilization of E-waste plastics is limited because E-waste along with plastics is also comprised of another key ingredients that are critical to recycle. US EPA (2012) study reported that approximately 94% of non-metallic fractions (Plastics) in E-waste are landfilled every year. Also, the plastic in E-waste forms a more complex polymer blend, and hence the initiative toward its safe recycling is limited.This article presents an endeavor towards transforming obsolete keyboard plastics into concrete brick cubes mixed with fly ash and eggshell. FTIR test was conducted to screen the polymers present in E-waste plastics. Qualitative and quantitative tests, such as water absorption, bulk density, compressive strength, hardness, and soundness tests were performed to compare different sets A, B, C, D, and E of the brick cubes. The heavy metals in the plastics were found to be within the permissible limit as per RoHS Standard, US EPA, 1989. The obtained peak of the FTIR test revealed (ABS, TBBA, and PC) polymers which were found to be efficient materials for the preparation of concrete brick cubes. The comprehensive strength (15.25 N/mm2) of brick cube D, comprising keyboard plastic, eggshell, and fly ash as 3.12%, 3.12%, and 6.25%, respectively, was found to be almost similar to the second-class bricks. The experimental approach directs that the conversion of E-waste plastics into concrete brick cubes is a better way to obtrude unusual pressure on the environment.

Development of refractories for the pyro-processing (heat-based) industry in Nigeria through the evaluation of mixtures of Enugu Iva-Pottery clay, Nsu-clay and palm kernel shell waste

The energy demand is on the global increase as the world economy is increasing steadily. Hence, the need to develop energy-saving technology with local raw materials and abundant waste materials becomes paramount. The mixtures of Enugu Iva-pottery clay, Nsu clay and PKS were evaluated to improve the quality of locally produced refractory for pyro-processing industries. The chemical and mineralogical composition of the PKS and the clay were determined. Eight recipes were made by varying PKS with quartz from 5 to 35% and produced by the wet pressing technique, then fired to 1200 °C and 1300°C respectively. The mechanical properties were determined by the Modulus of Rupture test, also, the bulk density, linear shrinkage, total shrinkage, apparent porosity, water absorption and thermal efficiency tests of the produced refractories were ascertained.The recipe with 15% PKS sintered well at 1300°C and gave the best optimum results of 1.76g/cm3 bulk density, 6.49% linear shrinkage, 21.384% apparent porosity, 20 cycles of spalling tests at 1300 °C. The results comply well with the standards of refractory properties. The PKS additives have shown significant improvement in the properties of the locally produced refractories and waste control; hence, can promote sustainable development of the local pyro-processing industry.

Study on Verification Approach and Multicontact Points Issue When Modeling Cyperus esculentus Seeds Based on DEM

In this paper, the Multisphere (MS) models of three varieties of Cyperus esculentus seeds are modeled based on DEM. In addition, for comparison, other particle models based on automatic filing in EDEM software are also introduced. Then, the direct shear test, piling test, bulk density test, and rotating hub test are used to verify the feasibility of particle models of Cyperus esculentus seeds that we proposed. By comparing the simulated results and experimental results, combined with the CPU computation time, the proposed particle models achieved better simulation accuracy with fewer filing spheres. According to simulation results, some limitation was present when using one single verification test; varieties of verification tests used could improve the verification reliability, and a more appropriate particle model could be selected. Additionally, the issue of multicontact points in the MS model was studied. The Hertz Mindlin (no slip) (HM) model and Hertz Mindlin new restitution (HMNR) model were both considered in simulations for comparison. The rotating hub test and particle–wall impact test were used, and the influences of multiple contact points on the motion behavior of individual particles and particle assemblies were analyzed. Simulation results showed that the multiple contact points affected the motion behavior of individual particles; in contrast, the influence of multiple contact points on the motion behavior of the particle assembly was insignificant. Moreover, the relationships between moisture content of seeds and Young’s modulus, Young’s modulus, and the number of contact points were also considered. Young’s modulus decreased with increasing moisture content. The number of contact points increased with a decreasing Young’s modulus.

Preparation and characterization of mortar specimens based on municipal solid waste incineration fly ash-activated slag

Municipal solid waste incineration fly ash (MSWIFA) contains a large amount of heavy metals, inhibiting resource utilization. This study used MSWIFA as an alkali activator and ground-granulated blast-furnace slag (GGBS) as a precursor to prepare the MSWIFA GGBS binder. Based on this, used the iron tailing sand instead of natural river sand as fine aggregate prepared mortar specimens by cooperative compression molding. Compressive strength, bulk density, water absorption, and heavy metal leaching tests were conducted and combined with micro XRD, FTIR, and SEM examinations to characterize the mortar specimens. The results show that the optimal MSWIFA: GGBS was 2:8. It was also found that increasing the molding pressure was beneficial to strength development. Compared to the specimens without the application of molding pressure, the 3 d and 28 d strength values increased by 148.6 and 122.2%, respectively, after the application of 35 MPa molding pressure. The reason is that the pressure effect can increase the cohesion of the particles, promote the hydration reaction to proceed, and the hydration products increase to fill the pores, increase the structural compactness and promote strength development. The resource utilization of MSWIFA must be guaranteed not to produce environmental pollution simultaneously. For this reason, the heavy metal leaching test was conducted on 28 d mortar specimens, and the results showed that the leaching rates of Zn, Pb, Cu, Cr, and Ni met the requirements of the Chinese Standard (GB16889-2008). The research results can provide a theoretical basis for the large-scale recycling of MSWIFA.

Evaluation of particle models of corn kernels for discrete element method simulation of shelled corn mass flow

Bulk handling behavior of grains can be studied experimentally, but large-scale investigations of grain flow especially at the commercial scale are expensive, time consuming, and are therefore limited in the treatment factors that can be evaluated in any one study. Recent research has demonstrated the potential of discrete element method (DEM) in simulating grain flow in handling operations. However, application of DEM for simulating grain flow, requires development of appropriate particle models for each grain type. In this study, particle models comprised of one to four overlapping spheres were developed for shelled corn and tested. With these models, measurement of bulk properties, namely bulk density and angle of repose, both involving bulk flow were simulated using EDEM™ software with published data of material and interaction properties of shelled corn as inputs associated with each particle shape. Predicted time for the complete outflow from the bulk density test hopper (hopper emptying time), designated as simulation time in the study, was also recorded as another discriminant for model selection. Variable inputs into the simulation modeling were material properties particle shape, particle size distribution, Poisson's ratio, shear modulus, and density and interaction properties particle coefficients of restitution, static friction, and rolling friction. Computation time is critical in DEM modeling so single sphere particle models were emphasized over multi-sphere particles in the research even though multi-sphere particles represent the corn kernel shape more precisely because their simplicity can provide markedly reduced computation times to complete simulations. Predicted results for hopper emptying time, bulk density, and angle of repose were compared to experimental results or published data to select the most appropriate particle models for simulating bulk behavior of corn kernels in free-flowing grain applications using DEM. From the study, the most appropriate particle model (particle shape/physical properties combination) for corn kernels involved a single-sphere shape particle shape with a particle coefficient of restitution of 0.30, particle coefficients of static friction of 0.30 for corn-corn contact and 0.20 for corn-steel contact, particle coefficient of rolling friction of 0.05, normal particle size distribution with a standard deviation factor of 0.4, and particle shear modulus of 20 MPa.

Potential utilization of regional cashew nutshell ash wastes as a cementitious replacement on the performance and environmental impact of eco-friendly mortar

Globally, agro-waste ashes are increasing significantly due to the rapid implementation of biomass-based power plants. In the present trend, agro-wastes are disposed of in an unsustainable manner. The recycling of agro-waste has significantly contributed to sustainable goals. In the construction sector, it is possible to dispose of waste more efficiently. However, the efficiency of locally available agro-residual waste in cementitious composites is not well understood. In the present investigation, the practicability of using agro-residual ash obtained from the burning of cashew nutshells on the properties of eco-friendly blended cement paste and mortars is explored. Blended cement mixtures containing cashew nutshell ash (CNSA) were prepared at five replacement levels, 5, 10, 15, 20, and 25%, relative to the weight of the cement. To understand the characteristics of CNSA, microstructure investigations such as X-ray diffraction, thermogravimetric analysis (TGA), scanning electron microscopy, and energy-dispersive spectroscopy analyses were performed. Paste properties of CNSA-based cement are observed through consistency, setting time, mini-slump flow, and expansion tests. For the CNSA-based mortars flow table, compressive strength, ultrasonic pulse velocity (UPV), electrical resistivity (ER), water absorption, bulk density, and porosity tests were performed to understand its efficiency. The strength indices of mortars were used to quantify the pozzolanic effect of CNSA. With the incorporation of CNSA, water demand increased by 57%, initial and final setting time decreased by 90% and 83%, respectively. Results showed that CNSA-based mortars absorbed more water and had higher porosity, which reduced compressive strength, UPV, and ER values. CNSA blended mortar is more suitable for applications that do not require high compressive strength. Results indicated that the compressive strength, UPV, and ER are within the limit specified. Strength indices indicated that CNSA has a positive and negative pozzolanic effect during early and later ages, respectively. Further, the sustainable assessment showed that the introduction of CNSA in mortar could substantially reduce embodied carbon, embodied energy, and strength efficiency over the control mortar. The inadequate amount of SiO2, Fe2O3, and Al2O3 in CNSA makes it an unsuitable pozzolanic material. However, it can be utilized in smaller amounts as a fractional replacement of cement and is found to be promising for specific desired properties of cement as a cost-effective accelerator.

Potential use of recycled cork as aggregates for lightweight self-compacting concrete production

This work questions the possibility of using expanded black cork aggregates (EBCA), for the production of lightweight self-compacting concrete. Five concrete mixtures were tested: concrete made entirely with natural aggregate as a control concrete and four concrete mixtures made with cork recycled aggregate (5, 25, 50 and 75% replacement in volume of natural aggregate). The estimation of the success of the formulations was judged by studying the properties of concrete in the fresh state by the slump flow, T500, L-box and the sieve stability tests. In the hardened state, the properties of the concrete produced have been determined by compressive and flexural strengths and bulk density tests. The experimental results showed that as the replacement level of natural aggregates by EBCA increased, the flowability of the concrete decreased. However, a good flowability was obtained for concrete mixtures containing EBCA until 50%, satisfying the recommendations of self-compacting concrete given by EFNARC 2002. The obtained results indicate the possible use of EBCA for the production of lightweight self-compacting concrete, the replacement of 50% of natural aggregates by EBCA allows obtaining a formulation which corresponds to a lightweight self-compacting concrete with a density of 1750kg/m3 and a compressive strength of 8MPa.