Natural Fines Research Articles

Mechanical Behaviour Slenderness Ratio of 13 Solid Wall Panels Under Uniformly Distributed Load

Recently, there has been a lot of research in the concrete industry on a sustainable approach using concrete waste as a substitute for natural aggregates. The reason for this is that the quantities of construction and demolition waste generated today pose a significant threat to the environment but can be used as a useful concrete material in the construction industry. The aim of this study is therefore to investigate the mechanical behaviour of solid concrete wall panels containing recycled concrete aggregates as a partial substitute for natural fine aggregates. Mortar cubes and wall panels with dimensions of 50 mm x 50 mm x 50 mm and 1000 mm x 300 mm x 75 mm, respectively, were produced. The wall panels were made from a 1:4 concrete mix consisting of 50% recycled concrete and 5% perlite (to reduce the weight of the concrete, and improve its workability), and 1% superplastizer, while the control wall was made with 100% natural fines. The wall panels were subjected to a compression test under uniformly distributed load. The cube samples were tested at 28 days of age. Mortar cubes with RCA achieved the highest compressive strength of 16.27 MPa compared to the control sample. The control wall panel has a higher ultimate load of 147.51 kN compared to the sample that contains RCA and perlite, which has an ultimate load of 128.68 kN. By 2030, our country needs to achieve sustainable management and efficient use of natural resources. By recycling this solid waste through separating, cleaning and crushing the concrete waste into small particles so that it can be used as a building material to replace sand. This shows that recycled concrete aggregate can be a potential material for making wall panels.

A novel high activity MnXFe3−XO4 spinel catalyst for selective catalytic reduction of NO using NH3 prepared by a short process from natural minerals for low-temperature sintering flue gas: Effect of X value on catalytic mechanism

The process of smelting and purifying the catalyst precursor salt from minerals is extremely complex, which directly leads to high catalyst costs and serious secondary pollution. In order to achieve energy saving and emission reduction in the catalyst preparation process, in-situ synthesis of catalyst materials from natural minerals is a new research direction. In this study, we firstly explored the optimal X value of MnXFe3-XO4 for the NH3 selective catalytic reduction of NO (NH3-SCR) reaction, i.e., the Mn, Fe ratio, and then prepared a novel highly active mineral-based pure phase MnXFe3-XO4 spinel NH3-SCR catalyst by natural ferromanganese ore fines with iron-red fines (Fe2O3) allotment through in situ solid-phase synthesis and magnetic separation methods according to this ratio. The results show that the X value of 1.5 (Mn1.5Fe1.5O4) is the best for NH3-SCR reaction. Mn1.5Fe1.5O4 nano-particles (201 nm) has nearly 100 % NO conversion (with 5 % H2O(g)) at 125–300 °C. The combination of characterizations and density functional theory (DFT) calculation shows that the catalytic process of Eley-Rideal (E-R) dehydrogenation is enhanced at both the active site Mn site and Fe site, which is a key factor in the acceleration of the NH3-SCR reaction with increasing X value at the MnXFe3-XO4 surface.

Comparative study on the effects of quarry dust and natural fines on performance of concrete blocks

Natural fine aggregates have been used in the construction industry to bind with cementing materials in the presence of water for building structures. Its use has led to increased daily demand with a subsequent rise in prices as the reserves get exhausted. Its overdependence has resulted in increasing scarcity because of over-harvesting from river beds causing an increase in demand. Moreover, uncontrolled sand harvesting has imposed dire impacts on the various environmental subcomponents of the river ecosystem such as water quality and quantity, bedforms, sediment milieu, flora and fauna, and socio-economic conditions of the people in the long run. This has led to the agitated search for an ecofriendly and less expensive substitute that can produce comparable compressive strength when used in concrete making. Quarry dust, a waste product of the quarry's grinding operation, is gaining momentum as a viable alternative to the conventional aggregates in concrete manufacturing due to its accessibility and lower cost. Quarry dust poses environmental pollution when dumped hence its use in the production of concrete will mitigate the pollution. This research was to determine the impacts of the addition of quarry dust in the performance of Concrete blocks (CB). This was achieved through the evaluation of the compressive strength of the CBs when quarry dust is used instead of natural fine aggregates. The concrete blocks were cast using molds of size 150 mm x 150 mm x 150 mm and then cured for seven days, fourteen days, and twenty- eight days. The size of particle distribution, the slump and workability test, and compressive strength was done respectively for the fresh and cured concrete blocks. The 28-day prepared CBs were subjected to alternate dry and wet cycles to assess their durability performance. A cost-benefit analysis of the use of quarry dust in place of fine aggregates in CB was also be conducted. The results obtained was be subjected to a T-test to study the significant difference in the performance between CB and the control.

Image interpretation for kaolinite detachment from solid substrate: Type curves, stochastic model

Kaolinite clays are the most widespread natural fines attached to the rock surface; they can be mobilised by the flow with further migration in porous spaces, straining in thin pore throats and causing significant decline in the rock permeability. We conducted mathematical and laboratory studies of kaolinite detachment from solid substrates in visualisation cells. The mechanical equilibrium of the attached particles in the creeping flow was described by the torque balance. For uniform particles and substrates, this model presents fines detachment using only two rates that correspond to particles in primary and secondary energy minima, i.e., the attached concentration versus velocity is a piecewise-constant function. To observe this maximum retention function, we saturated a single-channel micromodel visualisation cell with a transparent top with kaolinite particles; it was then subjected to a flow with a piecewise-constant increasing rate. Images of the remaining attached fines were filmed after each rate increase. All the tests exhibit gradual fines detachment. To explain the phenomenon, we assumed a probabilistic distribution of the properties of the particles and the substrate. For two-parametric probability distribution functions, it adds the standard deviations to the list of model parameters. The continuous fines detachment versus velocity was highly matched by the torque balance equation with probabilistically distributed coefficients. The match allowed restoring probabilistic distributions of the selected model parameters from the measured maximum retention function. The sensitivity of the detachment rate to properties follows a decreasing order: semi-major axis, aspect ratio, lever arm ratio, and zeta potential. This work fundamentally advances lab-based mathematical modelling of colloidal detachment from solid surfaces by developing stochastic torque-balance equation, where standard deviations of the model coefficients are tuning / matching parameters along with their mean values. This approach allows determining the probabilistic distributions of the model coefficients from the image processing, and also calculating the attached concentration variation within six standard deviations of each parameter, permitting placing the model parameters in the order of their effect on particle detachment.

Application of Soft Computing Techniques in Modelling of Soaked and Unsoaked California Bearing Ratio

In this study, author attempted to establish a correlation between soil physical parameters and California Bearing Ratio of lateritic soils using advanced mathematical techniques such as the Support Vector Machine (SVM), Random Forest (RF), M5 tree, multiple linear regression, and Artificial Neural Network. A total of 480 soil samples were collected and separated into a data set using training and validation of the generated models based on the main soil parameters of Liquid Limit (LL), Plastic Limit (PL), Natural moisture content (NMC), Specific gravity (GS), Fines (F), Gravel, and Sand. The Principal Component Analysis (PCA) was used to minimize the dataset's huge dimension, and the approximate sum of the first four principal components (PC) captured 88 percent of the variability in the response variable with just 12% information loss. The RMSE values of 21.6, 21.23, 295.67, 7.03, 14.54 and 24.43,24.59,326.49,8.63,17.71 are from the MLR, ANN, MS Tree, RF, and SVM models for SCBR and USCBR values, respectively. For SCBR and USCBR, random forest (RF) yielded the lowest values of 7.03 and 8.63, respectively. Similarly, the R values range from 0.1 to 0.94 and 0.01 to 0.92, indicating that the anticipated and real SCBR and USCBR are related. The Random Forest Model for SCBR and USCBR was shown to be the best by the correlation coefficient values, while the MS tree model for SCBR and USCBR was determined to have the lowest coefficient of determination R2. As a result, it can be concluded that Random Forest provided the best Soaked and Unsoaked CBR model based on the dataset, while MS tree provided the poorest model. The model is a valuable tool for evaluating the subsurface indices of a civil engineering site at the preliminary planning stage before final structural design for the substructures, as the anticipated soil parameter values are within permitted accuracy.

Flotation of calcite from apatite of a uranium-carbonate phosphate ore using carbon dioxide

The most common method to concentrate apatite from carbonate phosphate ore is reverse configuration using fatty acids as collectors and inorganic acids as apatite depressants, such as H2SO4 and H3PO4. This work evaluates the process based on the separation between apatite and calcite by flotation, in bench and pilot scale, using carbon dioxide injected through the bubble generation system with the use of saponified coconut fatty acid as a collector, as an alternative to the inorganic acids as apatite depressants in the process circuit developed to treat a uranium-carbonate phosphate ore (Santa Quitéria, Brazil). Moreover, the discharge of natural slimes only was evaluated, without the removal of the grinding slimes, which is not observed in apatite flotation plants for weathered material, where the removal of both kinds of slimes is necessary. The circuit proposed in this study provided significant gains in P2O5 recovery. In calcite flotation studies using carbon dioxide, in RG/CL/RCL mechanical cell circuit configuration, considering the overall performance obtained (grinding product + natural fines), the overall P2O5 recovery was approximately 91% and the P2O5, SiO2 and Al2O3 grades were 29%, 11% and 13%, respectively. The results obtained in this study indicated that the process circuit proposed by discharging only natural slimes increases the global P2O5 recovery, and the flotation process based on the injection of carbon dioxide is a potential alternative to concentrate apatite from the Santa Quitéria ore. Furthermore, previous studies have indicated that the use of carbon dioxide instead of inorganic acids as apatite depressants causes less ion accumulation in the process water, which is a major issue mainly in areas with scarce water supply such as the Santa Quitéria region.

Fines migration in aquifers: Production history treatment and well behaviour prediction

Migration of natural reservoir fines mobilised by water production may cause significant well productivity decline. The aim of this work is long-term productivity forecast from the production history under fines migration. We derive an exact solution of the radial inflow problem for suspension with size-distributed particles. The exact solution allows for detailed analysis of the structure of the flow domain and for an implicit formulae for well impedance. Six model coefficients are determined from the history of well production and fines concentration in the produced fluid. 23 field cases have been matched by the analytical model. Close agreement between the field and modelling data and common variation intervals for the tuned model parameters validate the model proposed. The analytical model allows determining the size of the damaged zone during water production under fines migration, which is important for well stimulation planning and design.

Cost Anatomy of A Vessel Spill Response

The focus of this paper is to highlight cost issues that have arisen during actual spill responses in the United States including issues related to a Responsible Party's (RP) named Spill Management Team (SMT), its named Oil Spill Response Organization (OSRO), the USCG, the National Pollution Fund Center (NPFC), and state/local government agencies. In addition, there will be a brief discussion related to third party claim costs and management. The author's sincere hope is that this paper will generate meaningful discussion concerning the issues raised that, in turn, will lead to reasoned changes resulting in lower, and more palatable response costs. The purpose of this paper is to highlight issues, not to criticize or embarrass individuals or entities. Accordingly, no company or individuals will be identified. This paper is not all inclusive and does not include costs related to Natural Resource Damage Assessment (NRDA), fines, or legal fees. In addition, while recognizing that entities other than vessels are covered under OPA 90, this paper, as noted in the title, concerns only spills from vessels. All opinions expressed in this paper are solely those of the author.

Use of recycled coarse and fine aggregates in structural eco-concretes. Physical and mechanical properties and CO2 emissions

This study analysed the effect of simultaneously replacing 0% to 100% natural with recycled concrete coarse aggregate and natural fines with 50% recycled concrete or mixed CDW fines. Characterisation of these new secondary raw materials is followed by an analysis of the effect of their use on the fresh and hardened state properties of the resulting eco-concretes. The implications for the mechanical requirements laid down in the existing legislation are determined and proposals put forward for new expressions for calculating splitting tensile and flexural strength. The CO2 emitted (global warming potential, GWP) by the new formulations is also explored and eco-efficiency, defined as the ratio between strength and CO2 emissions, is assessed. The findings show declines of no >17% in compressive and tensile strength with these new aggregates and in flexural strength of <15%. Emissions analysis reveals that eco-efficiency is enhanced with the separate or joint use of recycled coarse and fine aggregates, due to the CO2 emissions abatement ensuing.

Process mineralogy of rare earths from deeply weathered alkali-carbonatite deposits in Brazil

Brazil has the second largest rare earths mineral (REM) resource in the world, mainly associated with the weathered portion of carbonatite complexes. This paper reports process mineralogy studies performed for 10 samples collected from the deeply weathered portion of different relevant Brazilian deposits, having a soil appearance and varied grain sizes with a significant content of natural fines (below 20μm). The results indicate that REM are mainly composed of light rare earth elements and present a fine-grained nature and intricate associations with gangue minerals. Monazite is by far the most relevant REM; cerianite and bastnaesite are typical of only one of the studied deposits. The complexity of the occurrence of the rare earths challenges the development of mineral processing routes. A scandium phosphate mineral identified as a trace in one of the studied deposits has not yet been reported in the Brazilian alkaline complexes.

Effect of mix proportion on the structural and functional properties of pervious concrete paving mixtures

In recent years, pervious concrete pavement (PCP) is emerging as a novel pavement technology that is gaining a lot of attention amongst academicians due to its storm water runoff capabilities and mitigating urban heat island. This pavement technology consists of special types of concrete which has little amount of fines or no fines and interconnected voids. The different types of aggregate gradation, water-to-cement (w/c) and cement-to-aggregate, and compaction techniques with variations in efforts plays an important role in providing an optimum balance in the mixture designing of PCP mixtures. Therefore, the present study is an attempt to explore the possibility of variation of different aggregate gradation types with different proportion of w/c ratios for the production of PCP mixtures. Also, to study the effect of these mix properties on structural, functional as well as durable properties of PCP mixtures. Five aggregate gradation types and variability in w/c ratios were adopted in the present study viz. G1, G2, G3, G4 and G5, respectively. G1 and G2 consisted of larger-sized and well graded aggregates, while, G4 and G5 consisted of natural fines in proportion of 5% and 10%. Meanwhile, G3 consisted of binary blended single-sized aggregates: 30% of 10 mm and 70% of 4.75 mm. The above considered gradations were studied for porosity, density, permeability, compressive strength, flexural strength, and resistance to sulphate attack, at varied w/c ratios 0.30, 0.35, and 0.38, respectively. From an extensive laboratory investigation, it was observed that the G3 mix showed the best-balanced relation between all the afore-stated parameters, required for PCP mixtures. Hence, it can be recommended that the utilization of binary blended single-sized aggregates at a w/c ratio of 0.35 would provide an optimal solution keeping in mind the desired parameters of pervious concrete pavement mixtures are met.

The relation between the state indices and the characteristic features of undrained behaviour of silty sand

The characteristic features of a series of isotropically and K0-consolidated undrained triaxial compression behaviour of a silty sand were investigated for a range of initial void ratio (e) and mean effective confining stress (p′). The silty sand used in this study contained about 10% natural fines. The critical state line (CSL) of K0-consolidated specimens, K0U was slightly lower than the CSL for isotropically consolidated specimens, CIU. The respective CSLs for K0U and CIU were used to define state indices, such as state parameter (ψ), state index (Is), state pressure index (Ip) and modified state parameter (ψm), within critical state soil mechanics (CSSM) framework. It was found that each state index exhibit a unique relation with liquefaction potential, irrespective of consolidation type, however different relationships were observed between state indices and the stress ratio at the triggering of liquefaction, ηIS or the liquefaction resistance, qIS. The correlation of characteristic features of undrained shearing (i.e., liquefaction potential, ηIS and qIS) and drained shearing (maximum rate of volume change, dεv/dεamax) with state indices were compared statistically in terms of root mean square deviations (RMSD). All characteristic features of undrained shearing generally showed the best correlation with Ip in term of RMSDs, however ψ showed comparatively wider scatter for the specimens showing flow and limited flow behaviour.

Adiabatic behavior of gas wells due to natural reservoir fines migration: analytical model and CFD study

The adiabatic behavior of natural gas production well is frequently neglected in the reservoir formation damage study. The temperature of surrounding formation contributes to the smooth flow of natural gas in the wellbore. The heat transfer from the formation and geothermal gradient plays vital role in the efficient transport of gas in the subsurface formation and wellbore. But, fine particles which are attached to the rock surface migrate and are trapped in the pore throats, and as a result, there is deterioration in the permeability. The detachment of fines occurs due to high reservoir temperature and gas internal energy and temperature. Therefore, this paper conducts theoretical and numerical investigations on the adiabatic behavior of natural gas production well due to in situ reservoir fines migration. Firstly, an analytical model is developed and then, numerical models were constructed using CFD simulation tool to study the adiabatic nature of a gas well. A total of 24 cases were run in simulation, and input temperatures such as 200 °C, 250 °C, 300 °C, 350 °C, 400 °C and 450 °C were given for modeling. The results revealed that there was no sign of heat transfer from the wellbore to the surroundings. There was a heat circulation only within the wellbore. During the adiabatic state, the pressure in the central zone of the gas well is moderate, but rises linearly on the radial sides.

The effect of plastic fines on the shear modulus and damping ratio of silty sands

The dynamic behavior of soil material is of importance in construction and geotechnical engineering. This study focuses on the dynamic properties of silty sands, particularly on the effect of plastic fines content (FC) on the shear modulus and damping ratio. Natural sand (Taiyuan sand) and fines (Taiyuan loess) were collected from an engineering site in China. Fujian standard sand, kaolin, and stone powder were also used for comparison. Fines plasticity, FC, effective confining pressure, and relative density were considered. A series of tests were conducted using a Stokoe-type resonant column apparatus manufactured by GDS Instruments, UK. The small strain shear modulus (Gmax) of the samples were investigated under various test conditions. Hardin’s function was used to fit the experimental data. The results indicate that the shear modulus changes non-linearly with increasing FC. The shear modulus of various mixtures initially decreases and then increases. The threshold FC (FCth) of Taiyuan and Fujian sand mixtures is 30% and 20%, respectively, which indicates that the FCth is related to the host sand. The addition of plastic fines will decrease the shear modulus. The effect of non-plastic fines on the shear modulus of sand–fines mixtures is dependent on FC. The damping ratio of various mixtures initially increases and then decreases with increasing FC. The addition of fines will increase the damping ratio. Moreover, the damping ratio of plastic fines mixtures is higher than that of non-plastic fines mixtures. The values of the fitting constant, namely, A, n, and d, are related to fines plasticity. The findings of this study can provide a reference for engineering designers.

Injectivity decline during low-salinity waterflooding due to fines migration

Injectivity damage by fines migration during low-salinity water injection can highly affect field-scale waterflooding projects. In this paper, we develop novel analytical models for one-dimensional linear and radial suspension-colloidal flows accounting for detachment, mobilisation, migration, and straining of natural reservoir fines. We also perform laboratory corefloods by water with piecewise constant decreasing salinity, and with monitoring the breakthrough particle concentration and pressure drop across the core. The analytical model for linear flows matches the laboratory data with high accuracy, and tuned model coefficients belong to the common-value intervals for those coefficients. The analytical model for radial flows predicts well behaviour; the experimental-data-tuned coefficients are used for reliable laboratory-based prediction of injectivity index decline. The calculations show a significant decline of injection-well index due to fines migration during low-salinity water injection.

Injectivity formation damage due to fines migration

Formation damage by fines migration during low-salinity water injection can greatly affect field-scale waterflooding projects. In this paper, we present the basic governing equations for single-phase flow with detachment, migration and straining of natural reservoir fines. We perform laboratory corefloods with low-salinity water injections and monitor the breakthrough particle concentration and pressure drop across the core. The analytical model for linear flow matches the laboratory data with high accuracy. The analytical model for radial flow predicts well behaviour from laboratory-tuned coefficients. The calculations show that fines migration during low-salinity water injection causes significant injectivity decline. For typical values of fines-migration model coefficients, injectivity index declines 2–8 times during 10−3 pore volumes injected and the radius of the damaged zone does not exceed a few metres. We present two field cases on waterflooding and low-salinity water injection. The radial model presents good agreement with well injectivity field data.

Non-monotonic permeability variation during colloidal transport: Governing equations and analytical model

Permeability decline associated with the migration of natural reservoir fines impairs the well index of injection and production wells in aquifers and oilfields. In this study, we perform laboratory corefloods using aqueous solutions with different salinities in engineered rocks with different kaolinite content, yielding fines migration and permeability alteration. Unusual permeability growth has been observed at high salinities in rocks with low kaolinite concentrations. This has been attributed to permeability increase during particle detachment and re-attachment of already mobilised fines by electrostatic attraction to the rock in stagnant zones of the porous space. We refine the traditional model for fines migration by adding mathematical expressions for the particle re-attachment rate, particle detachment with delay relative to salinity decrease, and the attached-concentration-dependency of permeability. A one-dimensional flow problem that accounts for those three effects allows for an exact analytical solution. The modified model captures the observed effect of permeability increase at high water salinities in rocks with low kaolinite concentrations. The developed model matches the coreflooding data with high accuracy, and the obtained model coefficients vary within their usual intervals.

Exact Solutions for Nonlinear High Retention-Concentration Fines Migration

The paper discusses migration of natural reservoir fines lifted by high-rate or low-salinity water injection. The previous papers used linear analytical model, which is valid for low retention of mobilised fine particles in order to determine the model parameters from breakthrough fines concentration and pressure drop across the core during laboratory corefloods. The current work derives exact analytical solutions for the nonlinear case of high retention-concentration fines migration. The solution exhibits uniform profiles of suspended and retained concentrations ahead of the particle front and steady-state retained concentration behind the front. The obtained type curves allow distinguishing between linear and nonlinear fines migration. The laboratory data exhibit close agreement with the nonlinear model predictions, whereas the linear model poorly matches the laboratory data.

Effects of two sorbents applied to mercury-contaminated river sediments on bioaccumulation in and detrital processing by Hyalella azteca

Mercury (Hg) released into the environment often accumulates to high concentrations in sediments, creating a potential risk to aquatic wildlife. The in situ application of sorbents such as activated carbon is one promising option for reducing the bioavailability of sediment-bound Hg. The present study evaluates the influence of contact time of two sorbents (Sedimite® and Cowboy® biochar) applied to sediment taken downstream and upstream of a historic Hg discharge into the South River (Virginia, USA) on bioaccumulation in and detrital processing by Hyalella azteca. Hg bioaccumulation decreased when sediments were mixed with both sorbents, but their respective efficiency depended on their initial particle size and contact time. Hyalella showed a slight increase in detrital processing and substantial increase in Hg bioaccumulation when exposed to contaminated relative to uncontaminated sediment. Sedimite® adversely affected detrital processing but reduced Hg bioaccumulation. In contrast, Cowboy® biochar did not impact detrital processing but appeared to decrease bioaccumulation less effectively than Sedimite®. This difference in sorbent efficacy lessened with duration. It remains unclear whether the Sedimite®-induced reduction in detrital processing is substantially worse than that associated with natural fines settling on detritus in depositional reaches of rivers. The differences in efficacy of the two materials in reducing bioavailability suggest the need for further studies addressing both the mechanisms causing the reduction in Hg bioavailability as well as associated ecological risks prior to field application of these materials at the larger scale.

Laboratory-based mathematical modelling of graded proppant injection in CBM reservoirs

The graded proppant injection into a connected cleat system of coal bed methane (CBM) reservoir allows deeper particle penetration and straining in the remote open cleats yielding higher well productivity index. The analytical model for axisymmetric flow has been derived for exponential stress–permeability relationship and accounting for permeability variation outside the stimulated zone. Laboratory proppant injections into coal cores have been performed for different proppant sizes and water salinities. It is shown that the proppant suspension based on low salinity water prevents the particle–particle and particle–coal attraction with the consequent core inlet plugging and external cake formation. However, low salinity of the injected water may cause mobilisation, migration and straining of the natural reservoir fines resulting in high formation damage. The interval where salinity is low enough for the rock inlet not to be plugged by the injected proppant, and is high enough for large formation damage due to fine migration not to occur, is proposed for the cores under investigation. The analytical model is tuned from the laboratory data and used for well index prediction. Ignoring the model matching by the laboratory results causes the overestimation of the incremental productivity index, as achieved by the graded proppant injection into coal beds below the fracturing pressure.