Particle Fineness Research Articles

Reaction kinetics of fly ash geopolymerization: Role of particle size controlled by using ball mill

Fly ash is milled for 0, 30 and 90 min and used to study the role of particle size on the kinetics of geopolymer formation. The increase in particle fineness is very prominent in the initial milling stage, and then slows down due to agglomeration effect of finer fraction. The fly ash geopolymerization kinetics and its mechanism is determined using heat of reaction data measured by isothermal conduction calorimeter. The improvement in reaction rate with milling is correlated with the median particle size of the fly ash. The apparent activation energy decreases with size reduction because finer fractions are more prone to alkali activation. Although the kinetics changes with particle fineness, but no alternation is detected in the reaction mechanism, governed by nucleation and growth. The apparent activation energy evaluated by rate method is showing three major steps of geopolymerization such as dissolution, gel formation and restructuring.

Effects of Grinding Process on the Properties of the Coal Bottom Ash and Cement Paste

The grinding process is necessary to convert original coal bottom ash (CBA) into a powder form. The aim of this study is to evaluate the grinding process effects on physical properties of CBA, it influences on consistency and setting time of cement paste and to predict it potentiality based on chemical characteristics to reduce the alkali-silica reaction (ASR) in concrete. The CBA is the by-product of coal based thermal power plant. Due to high production of electricity in Malaysia, the excess amount of CBA has been produced annually and it causes the environmental problems. Therefore, it is necessary to come up with advanced solutions for that pollution. This study considered the different grinding periods i.e. 2, 10, 20, and 40hrs as to produce different particle fineness. It was perceived through the laboratory findings that the more the grinding period, finer the particle sizes. Besides that, cement paste with 10, 20 and 30% of ground CBA as a substitute of ordinary portland cement (OPC) by weight was prepared, it was observed that the consistency of OPC paste increases with the addition of ground CBA. Moreover, initial and final setting time of cement paste containing ground CBA was observed higher than the OPC paste. Hence, based on experimental analysis and energy efficiency scenario, grinding period of 20hrs with specific surface area 3835.75 cm2/g is suggested for the future studies.

THE DEVELOPMENT AND VALIDATION OF THE METHOD TO QUANTIFY THE AMOUNT OF PHENOLIC ACIDS IN AERIAL PARTS OF ZIZIPHORA CLINOPODIOIDES LAM.

Development and validation of method for quantitative determination of the amount of phenolic acids in the aerial part of the Ziziphora clinopodioides Lam.
 Objective: to develop and conduct a validation assessment of the method for determining the content of the amount of phenolic acids in the Ziziphora clinopodioides.
 The method of quantification of phenolic acids equivalent to chlorogenic acid by direct spectrophotometry in aerial parts of the Ziziphora clinopodioides has been developed based on the study of the absorption spectrum of an aqueous-alcoholic extract. The influence of the following factors on the yield of phenolic acids was studied: the nature of the extractant, the ratio of raw material: extractant, the degree of particle fineness, the extraction multiplicity, the extraction temperature; their optimum values were established.
 The method of quantitative determination of the amount of phenolic acids in the aerial part of the Ziziphora clinopodioides is validated; it has been established that the proposed method is highly sensitive, correct, reproducible and suitable for use in an analytical laboratory based on the data obtained.

Performances of concrete containing coal bottom ash with different fineness as a supplementary cementitious material exposed to seawater

Concrete structures are seriously deteriorated under marine environment because marine water is aggressive in nature; it contains salts of sulphate and chloride and others. These salts deteriorate the plain and reinforced concrete structures. However, most of previous research was investigated on concrete performances exposed to single solution, such as sulphate or chloride attack, even though the actual conditions are the combination of both. Therefore, the object of this study is to evaluate the performances of concrete containing coal bottom ash (CBA) with different fineness as a supplementary cementitious material (SCM) exposed to seawater. This study considered 10% ground CBA as a SCM in concrete. The original CBA was ground in a ball mill for 20 and 30 h, to get different particle fineness. Initially all specimens were cured in normal water for 28 days as to achieve targeted strength and then half of the specimens were shifted into seawater for further 28, 56, 90 and 180 days and other specimens were kept in normal water. The particle fineness of CBA influence on the concrete performances was assessed in terms weight variations, compressive strength and chloride permeability. Experimental results demonstrated that concrete strength with CBA of fineness 3836 cm2/g (type-A) delivers around 11.9% and 8.5% higher than control mix in water and seawater respectively at 180 days. Subsequently, concrete strength with CBA fineness of 3895 cm2/g (type-B) brings about 12.7% and 5.8% greater than control mix in water and seawater respectively at 180 days. However, it was also detected that concrete with CBA-type-A and CBA-type-B exhibits around 45.4% and 42.4% reduction in chloride penetration as compared to control mix at 180 days. Hence, it was concluded the strength performances of CBA-type-B is superior than the control mix at 28 days. However, CBA-type-A gives the better performances at later ages of 90 and 180 days. Hence, CBA-type-A is suggested for the future studies, based on strength performances and resistance to chloride penetration. This study encourages the use of ground CBA in concrete as SCM in normal as well as in marine environment.

The fraction of overlapping interphase around 2D and 3D polydisperse non-spherical particles: Theoretical and numerical models

The fraction of interphase is an important microstructure parameter in the prediction of macroscopic properties of particulate composites. Currently, some researchers have presented theoretical and numerical investigations on the interphase fraction for spherical particle systems, and even quantify the influence of interphase fraction on the overall elastic and transport properties of particulate composites. However, the overlapping interphase fraction in polydisperse non-spherical particle systems is still an open issue. In this work, a generic theoretical model is formulated to derive the overlapping interphase fraction for polydisperse 2D non-circular and 3D non-spherical particle systems by means of the statistical geometry of composites. In this model, the morphology of interphase coated onto the surface of non-spherical particles can be characterized by circularity and sphericity of particles that are important parameters to describe the shape of particles. On the other hand, numerical simulations for the one-point probability function of interphase are presented to verify the proposed theoretical framework. In the numerical simulations, a novel algorithm is developed by reducing the problem of identifying the precise location between an arbitrary spatial point and interphase to the basic issue of finding the distance from the point to the surface of particles. If the distance is less than the interphase thickness, the point definitely locates inside interphase. In addition, the algorithm can be further used to detect the overlap between adjacent ellipsoidal particles (2D ellipses). Moreover, a variety of particle shapes (such as regular polygons and ellipses with the same circularity, and regular polyhedrons and ellipsoids with the same sphericity) are taken into account to generate particle packing structures. Then, the fraction of overlapping interphase in each packing structure is statistically obtained. Results show that statistical values are consistent with their theoretical values under the same conditions. This validates the reliability of the theoretical framework. Finally, the effects of particle size distributions and interphase thicknesses on the interphase fraction are investigated. It can be found that the interphase fraction increases with the increase of particle volume fraction, particle fineness and interphase thickness.

Improving New Generation Concretes (NGCs) by Introducing Technogenic Materials

Currently, inclusion of technogenic materials as components of new generation concretes (NGC) attracts attention of researchers and engineers from various countries. Wide application of high-strength concretes with increased cement stone content, fineness of binder and aggregate particles, multi-component composition, facilitates improvement in concrete articles quality and further industrialization of the construction production. Due to that, it appears timely to study condition of structural formation of high-strength concrete, a role that technological factors play in this process and its substantial composition. The paper consider some aspects of designing a composition and a production technology for NGC articles, as well as their relevance in modern construction. Results of compositional and technological analysis of high-strength concretes produced with nanostructured modifiers having various chemical and mineral composition and genesis are given. Possibilities are found to reduce binder consumption by introducing technogenic and organic feed; to provide lower consumption of material resources and energy; to employ non-toxic, non-combustible and environmentally-friendly materials.

The Influence of Fine Particle Content (Cement Together with Sand Particles up to 0.25 mm) on Rheological Properties of Concrete Mixture

The influence of the fine particle content on the rheological properties of the fresh concrete mixture was studied. The change of cement together with sand particles up to 0.25 mm in mixture composition was taken into the consideration. The amount of fine particles in mixture composition varied in the range from 402 to 639 kg per one cubic meter of the concrete mixture. Technological properties of the concrete mixture were established according to the standardized requirements, rheological properties: yield stresses and viscosity of conventional concrete mixture were calculated based on analytical formulas. According to obtained test results, the increase of fine particle content from 481 to 520 kg in mixture reduced the yield stresses from about 557 to 132 Pa. Further increase of fine particle content from 600 to 639 kg showed the rise of yield stress by 3.87 times. On the other hand, the viscosity of concrete mixture gradually decreased (ca. 5.6 times). To sum up, the rheological properties of the concrete mixture were significantly influenced by the content, packing density, fineness, surface texture and particle size distribution of fine particles.

High‐strength concrete based on ternary binder with high pozzolan content

Several high‐strength concrete mixes containing ternary binders composed of Portland cement, silica fume, and waste brick powder are designed. Taking into account the functional properties of hardened mixes, together with their supposed environmental qualities and economic benefits, the practical limits of pozzolan content in the binder are analyzed. Based on a wide set of material characterization experiments including mercury intrusion porosimetry, scanning electron microscopy, and X‐ray diffraction analysis, complemented with a series of measurements of basic physical properties, mechanical parameters, and water and water vapor transport properties, the binder consisting of 57% Portland cement, 18.5% silica fume, and 24.5% brick powder is identified as the optimum in the studied system. The excellent functional properties of the mix with such a high pozzolan content are achieved due to the synergetic effects of the combination of silica fume and waste brick powder on concrete properties. The fineness of brick particles, together with the dual character of the applied brick powder acting as active pozzolan and microfiller at the same time, is found to magnify the ability of silica fume to fill the intergranular space through the improvement of the granulometry curve.

Laboratory tests for studying the performance of grouted micro-fine cement

In geological engineering, grouting with Portland cement is a common technique for ground improvement, during which micro-fine cement is applied as a slurry, such that it intrudes into soil voids and decreases soil porosity. To determine the utility and behavior of cements with different Blaine values (index of cement particle fineness) for stabilization of fine sand, non-destructive and destructive tests were employed, such as laser-ray determination of grain size distribution, and sedimentation, permeability, and compressive strength tests. The results of the experimental study demonstrated a suitable mix design for the upper and lower regions of the cement-grading curve that are important for grouting and stabilization. Increasing the fineness of the cement decreased the permeability and increased the compressive strength of grouted sand samples considerably after two weeks. Moreover, relative to finer (higher Blaine value) or coarser (lower Blaine value) cements, cement with a Blaine value of 5,100 cm2/g was optimal for void reduction in a grouted soil mass. Overall, study results indicate that cement with an optimum Blaine value can be used to satisfy the designed geotechnical criteria.

Strength activity and microstructure of blended ultra-fine coal bottom ash-cement mortar

Replacing Portland cement with reutilized coal combustion products can have substantial benefits to the environment as well as infrastructure. In this study, a sub-bituminous coal bottom ash is re-utilized as a cement replacement. The bottom ash was pulverized using a high energy vibratory ball mill at two different milling times to achieve a particle fineness approximately two and three-times finer, respectively, than type I cement. The workability and final setting time were found to increase by 21% and 14%, respectively, and the highest strength activity was observed to be 120% at 90days. After normalization for particle fineness, age, and binder replacement using a general linear regression model, the data suggested the bottom ash blended cement mortar had 6.8% less strength activity than a comparative fly ash blended cement mortar. Blended bottom ash-cement paste samples were observed to have densely packed CSH product composed of relatively lower Ca/Si ratio (1.37) compared to that of fly ash blended cement paste (1.43) and the control (2.27). The CH content was also observed to be significantly lower in the bottom ash blended cement paste (19.1%) when compared against the control (27.2%) and fly ash blended paste (23.3%). Within the range of experimental conditions considered here, the results suggest that a coal bottom ash can be pulverized with a high energy ball mill to produce a re-utilizable pozzolan that, depending on the powder fineness, can significantly increase the strength activity, improve the microstructure of cement mortar, and increase the cement replacement tolerances without significant reduction to compressive strength activity.

Micropetrography of Hydrothermal Sediment and Synergy of Microorganisms in the Geological Environment

In the Jurihe area of Inner Mongolia, lamellar hydrothermal sediment of Permian was recognized. These rocks were inter-bedded with volcanic rocks, altered by hot water (hydrothermal fkuid) during the synsedimentary and quasi-synsedimentary stage. The lithogeochemistry of the rock components differ from typical sedimentary rocks. The particles and mineralogical components cannot be identified by microscope. By scanning electronic microscopy (SEM) observation and the rock mineral micro-district analysis (QEMSCAN), we found the mineralogical components of rocks are mainly illite and quartz, plagioclase and alkali feldspar, biotite, montmorillonite, chlorite, glauconite, apatite, hornblende, kaolinite and pyrite, zoisite, and there is a small amount of dolomite, calcite, rutile, gypsum/anhydrite, diopside, zircon, sphene, pyrophyllite, muscovite, epidote, siderite, ilmenite, sphalerite, paragonite, etc. Amongst these, biotite, epidote, zoisite are hydrothermalized alteration minerals. Total organic carbon (TOC) within sedimentary rocks is 0.41~0.27%. Crystalline minerals are generally of micro and nano-size. Amorphous minerals account for a large portion. Fineness of particles in the rock results from heat inhibiting crystallization,?regulation of organic molecules and macromolecular (Microbe-mediated mineralization). Oriented large granules are silicified organic matter from a hydrothermal source. Another form of organic matter taking shapes of clouds or clumps, distributed in layers, and rich in heavy elements, contains filamentous carbon-containing material. It is associated with microbiological activity. If, as postulated above, there are two types of organic matter, the theory of petroleum formation can be enriched to a certain extent.

Redispersion of Nanoparticle‐Loaded Orodispersible Films: Preservation of Particle Fineness

AbstractThe application of orodispersible films (ODFs) as carrier for drug nanoparticles was discovered a few years ago. Poorly water‐soluble drugs are milled to nanosuspensions to improve their bioavailability. During the manufacturing process they are embedded into a polymer matrix or loaded on the surface of drug‐free ODF templates. The particle size of the particles released from the ODF was measured when redispersed in water. A preservation of the drug particle sizes could be achieved for both investigated ODF types when an adequate amount of matrix material is added to prevent agglomeration during the drying process.

Soil erosion and deposition in the new shorelines of the Three Gorges Reservoir

During the last few decades, the construction of storage reservoirs worldwide has led to the formation of many new shorelines in former upland areas. After the formation of such shorelines, a dynamic phase of soil erosion and deposition follows. We explored the factors regulating soil dynamics in the shorelines of the Three Gorges Reservoir (TGR) on the Yangtze River in China. We selected four study sites on the main stem and three on the tributaries in the upstream parts of the reservoir, and evaluated whether the sites close to the backwater tail (the point at which the river meets the reservoir) had more soil deposition than the sites far from the backwater tail. We also tested whether soil erosion differed between the main stem and the tributaries and across shorelines. We found that soil deposition in the new shorelines was higher close to the backwater tail and decreased downstream. Soil erosion was higher in the main stem than in the tributaries and higher at lower compared to higher shoreline altitudes. In the tributaries, erosion did not differ between higher and lower shoreline levels. Erosion increased with increasing fetch length, inundation duration and distance from the backwater tail, and decreased with increasing soil particle fineness. Our results provide a basis for identifying shorelines in need of restorative or protective measures.

アルミナ粉砕によるMMAのメカノケミカル重合反応に及ぼす溶媒の影響

Mechanochemical polymerization of methyl methacrylate (MMA) monomer was carried out by grinding alumina powder that had high thermal conductivity. A planetary ball mill with high grinding ability was used because alumina has high hardness. The experiments were conducted using different monomer concentrations and different types of solvents. In addition, the effects of grinding conditions on the fineness of alumina particles and the amount of generated polymer were examined. It was found that the amount of polymer could be controlled by the MMA concentration and that the rate of mechanochemical polymerization was highest in aqueous solution. The polymerization occurred in alcohol solvents, but to a limited extent because of inhibition of radical initiation.

Evaluation of slag characteristics on the reaction kinetics and mechanical properties of Na2CO3 activated slag

This paper evaluates the slag characteristics on the reaction kinetics, reaction products and mechanical properties of sodium carbonate activated slag (SCAS). The results show that, by reducing the slag particle size, the precipitation of strength-giving phase of SCAS can be dramatically accelerated, and the time to reach the reaction peak (TRRP) can be accelerated from 86h to 23h and a 3d-compressive strength of about 34MPa is achieved. The fresh behaviour of pastes is affected by the initial precipitation of calcium carbonate and the formation of gaylussite is also accelerated when reducing the particle sizes of slags. It is observed that the early strength development of samples is largely controlled by the fineness of slag particles, while the later strength firstly increases with the reduction of slag particles until reaching a turning point and then decreases. Furthermore, the influential factors including the alkali activator dosage and slag characteristics on the reaction kinetics of Na2CO3 activated slag are discussed.

Covering ability of aluminum pigments prepared by milling processes

This paper deals with the influence of milling regimes on the development of a lamellar structure of aluminum pigment particles. A group of parameters describing the degree of fineness and morphology of the pigment particles were monitored simultaneously. The experiments were carried out using a semi-pilot milling plant with a vibrating mill and a ball mill. Based on the experiments, a criterial non-dimensional relationship was outlined. The relationship generalizes the influence of milling process conditions on the lamellar structure of pigment particles. At the same time, an equation which limits milling time used for the milling process was outlined. This equation solves the problem posed by the risk of destroying the lamellar structure of the particles over time. The theory of metal working was applied as an analogical base for establishing the efficiency of the milling process with respect to energy demand. In addition to basic process parameters, the significant influence of surface active agents on pigment lamellar structure was studied.

The influence of physico-chemical properties of fly ash and CKD on strength generation of high-volume fly ash concrete

This paper presents a laboratory study on the use of cement kiln dust (CKD) as an activator of fly ash when used in high volumes within concrete. Two separate batches of fly ash and CKD were tested to assess the effect of material variability on binder properties and compressive strength gain. Ternary blends of fly ash (55–65%), CEM 1 (30%) and CKD (5–15%) and quaternary blends that included moderate amounts (15–18·5%) of ground granulated blast-furnace slag (GGBS) were prepared. Physico-chemical properties of individual binder materials were compared and concrete compressive strength was measured at 2 d, 7 d and 28 d. Ternary blends of 60% fly ash, 30% cement and 10% CKD resulted in moderate early age and 28 d strength and addition of GGBS enhanced strength significantly due to increased ettringite formation. Particle fineness, water demand and loss on ignition content of fly ash, and calcium oxide and sulfur trioxide content of CKD were found to be the main physico-chemical factors that influence compressive strength gain.

Mass flow and particle size monitoring of pulverised fuel vertical spindle mills

Abstract The first step towards condition based maintenance of the milling plant is the implementation of online condition monitoring of the mill. The following paper presents and analyses methods of monitoring the key performance factors of a vertical spindle mill that is suited for implementation on older power stations, i.e. the quantity (mass flow rate) and quality (particle fineness) of the pulverised fuel produced by the mill. It is shown herein that the mill throughput can be monitored on-line using a simple mill energy balance that successfully predicts the coal throughput within 2.33% as compared to a calibrated coal feeder. A sensitivity analysis reveals that the coal moisture is a critical measurement for this method to be adopted as an on-line mass flow monitoring tool. A laser based particle size analyser tool was tested for use in the power plant environment as an online monitoring solution to measure pulverised fuel fineness. It was revealed that several factors around the set-up and operation of the instrument have an influence on the perceived results. Although the instrument showed good precision and repeatability of results, these factors must be taken into account in order to improve the accuracy of the reported results before the instrument can be commissioned as an on-line monitoring solution.

Thermal Conductivity of Binary Sand Mixtures Evaluated through Full Water Content Range

Core Ideas Thermal conductivity and water content relationship based upon mixtures are distinct. Systematic change in particle fine fraction directly affects thermal conductivity. Strong correlation between density and thermal conductivity Campbell model well predicts thermal conductivity with all four parameters calibrated. Lu and Dong model well predicts thermal conductivity with both parameters calibrated. A soil's grain‐size distribution affects its physical and hydraulic properties; however, little is known about its effect on soil thermal properties. To better understand how grain‐size distribution affects soil thermal properties, specifically the effective thermal conductivity, a set of laboratory experiments was performed using binary mixtures of two uniform sands tightly packed with seven different mixing fractions over the full range of saturation. For each binary mixture, the effective thermal conductivity, λ, capillary pressure, hc, and volumetric water content, θ, were measured. Results demonstrated that the λ–θ relationship exhibited distinct characteristics based on the percentage of fine‐ and coarse‐grained sands. We further compared measured λ–θ properties with independent estimates from two semi‐empirical models (Campbell Model and Lu and Dong Model) to evaluate the models' applicability in relation to physically based parameters associated with changes in soil mixing (e.g., porosity and grain size). Both models were able to fit experimental data but to varying degrees based on the number of physically based parameters used. In general, model improvements are needed to capture the λ–θ relationship solely on physically based parameters.

Research in the Field of Preparing Molded and Unmolded Refractories Based on High-Alumina HCBS. Part 2. Properties of Starting Components and Castings Based on Composite Composition HCBS. Study of the Initial Stage of Sintering and Mullitization1

The initial stages of sintering and mullite formation are studied for specimens based on HCBS of complex composition prepared by combined wet milling of high-alumina bauxite and fuzed quartz. The starting materials have a different ratio of components and solid phase particle fineness. The initial sintering stage is in the range 900 – 950°C, and mullite formation 1100 – 1150°C. In the range 1150 – 1200°C there are simultaneously both sintering and mullite formation. Depending on fineness and fuzed quartz HCBS content the maximum amount of shrinkage is 0.35 – 0.60%. An increase in firing temperature to above 1200°C is accompanied by specimen growth and an increase in porosity. Even with an insignificant level of the proportion of sintering pores (0.09 – 0.11) materials have an ultimate strength in bending of 100 – 130 MPa and open porosity of 14 – 16%.