Hydraulic Mixtures Research Articles

Modelling hydraulic mixture movement along the extraction chamber bottom in case of hydraulic washout of the tuff-stone

This paper presents the research results of the pulp movement process along the extraction chamber bottom to the suction pipe of the pulp lifting device in case of downhole hydraulic mining the volcanic tuff-stone. The washout process and hydraulically operated transportation of the tuff-stone hydraulic mixture, when forming the extraction chamber, have been studied under various conditions and methods of exposure. As a result, the dominant parameters have been determined influencing the hydrodynamic washout technology as well as tuff-stone hydraulic mixture lifting to the alluviation map. The dependences have been substantiated of the washout process performance and transportation capacity of the hydraulic mixture flow on the determined parameters. To calculate the process of pulp flow-over along the extraction chamber bottom to the intaking hydraulic elevator headwall, the systems of equations have been determined based on the modelling the movement of tuff-stone hydraulic mixture along the extraction chamber bottom during hydraulic washout. The dependences of the contact strength of the tuff-stone samples mined by downhole method on the time spent in water are presented, resulting in determination of the tuff-stone weakening coefficient and the degree of its saturation with water.

ГИДРОСТРУЙНЫЙ ЭЖЕКЦИОННЫЙ ГИДРОМЕТАТЕЛЬ СЫПУЧИХ МАТЕРИАЛОВ. РАБОЧИЙ ПРОЦЕСС И ХАРАКТЕРИСТИКИ

Among hydrodynamic machines, jet pumps are among the most common. The high demand for this type of pump is due to their following features: the absence of moving parts and the simplicity of the device, small overall dimensions and weight, high self-priming ability, the ability to pump aggressive media and hydraulic mixtures containing solid impurities. In the hydromechanical method of developing deposits of building materials (sand, gravel, etc.), jet pumps – hydraulic elevators are used for underwater mining and transportation of bulk materials to the sorting plant, and after classification of the sand-gravel mixture – hydraulic transport of sand and gravel to dumps through pipelines. With this method of laying the finished product, the jet pump creates a static pressure of the hydraulic mixture, sufficient for its transport to the dump. However, another way of laying the finished product in dumps is also possible – through the air with a slurry stream. In this case, the jet pump performs the function of a hydrometer – a device for creating a high-speed slurry jet. A review of the literatureshowed that this mode of operation of the jet pump was not investigated. The effective operation of the jet pump-hydrometer depends on the ratio of the areas of the outlet section of the nozzle and the normal section of the mixing chamber, the relative density of the slurry in the input hopper. For each value of the relative density of the slurry, there is an optimal ratio of the areas of the nozzle and the chamber at which the specific energy consumption of the active stream will be minimal. The aim of this work is to determine and analyze the characteristics of an ejection hydrometer and to identify the most effective modes of its operation.

Theoretical analysis of hydromixture transport

This paper presents theoretical considerations and working parameters analyzes of hydrotransport during unstable flow. The variable flow of hydraulic mixture in installations causes unsteady operation and pipes spraying, pump damage, obturation in various sections of the pipeline, reduced capacity as well as higher operating costs. Using mathematical equations presented in this paper, such parameters of the hydraulic mixture, hydrotransport installation and control devices can be determined which protect system from possible clogging. Considering the fact that critical speed of hydraulic mixture depends on transported material grain size, mixture volume mass, diameter of pipeline and specific gravity of solid phase, it is possible to accurately analyze obturation in hydrotransport installations depending on those parameters. In order to prevent hydraulic impacts in hydrotransport installation pipelines, which value can be determined mathematically, it is necessary to adjust installation to hydromixture parameters and pump, or vice versa.

Microbial community shifts in streams receiving treated wastewater effluent

Wastewater treatment plant (WWTP) effluents release not only chemical constituents in watersheds, but also contain microorganisms. Thus, an understanding of what microorganisms are released and how they change microbial communities within natural streams is needed. To characterize the community shifts in streams receiving WWTP effluent, we sampled water-column microorganisms from upstream, downstream, and the effluent of WWTPs located on 23 headwater streams in which no other effluent was released upstream. We characterized the bacterial community by sequencing the V3-V4 region of the 16S rRNA gene. We hypothesized that the downstream community profile would be a hydraulic mixture between the two sources (i.e., upstream and effluent). In ordination analyses, the downstream bacterial community profile was a mixture between the upstream and effluent. For 14 of the sites, the main contribution (>50%) to the downstream community originated from bacteria in the WWTP effluent and significant shifts in relative abundance of specific sequence variants were detected. These shifts in sequence variants may serve as general bioindicators of wastewater-effluent influenced streams, with a human-gut related Ruminococcus genus displaying the highest shift (30-fold higher abundances downstream). However, not all taxa composition changes were predicted based on hydraulic mixing alone. Specifically, the decrease of Cyanobacteria/Chloroplast reads was not adequately described by hydraulic mixing. The potential alteration of stream microbial communities via a high inflow of human-gut related bacteria and a decrease in autotrophic functional groups resulting from WWTP effluent creates the potential for general shifts in stream ecosystem function.

Possibilities of Processing of Slag Aggregate from Heap Koněv

The aim of this work is to find out whether the slag aggregates from heap Koněv can be used in hydraulic mixtures based on traditional Portland cement as well as in alternative binders based on alkali activated blast furnace slag.In the experiment the basic physical-mechanical parameters of prepared mixtures were determined and the durability properties of these composites were verified. The composition of the aggregate extract and its influence on the properties of the prepared mixtures and the subsequent determination of the alkaline ions in slag aggregates were also verified.

The Role of Alkalis in Hydraulic Mixtures

Alkali substances are present in cements used as a binder in concrete only in a minimum content. The most known process that alkali causes is the alkali-silica reaction. In this reaction, the alkali contained in the cement or supplied from the outside with an inappropriately selected aggregate containing amorphous SiO2. This reaction results in the development of hydration products, resulting in an increase in the volume of the original components, which can cause a breakage of the concrete structure and subsequent disintegration. The range of alkali-silica reaction can be reduced by the use of a suitable aggregate or the use of Type II admixtures which are characterized by pozzolanic or latently hydraulic activity. These admixtures react with alkali and then no longer react with the amorphous SiO2 contained in the aggregate. Alkalis also affect other properties of concrete such as basic physical-mechanical properties, frost resistance and pH.In the experimental part the pH values were compared between mixtures of Portland cement and alkaline activated blast furnace slag using slag aggregate from the heap Koněv.

The non-linear regression - the Levenberg-Marquardt algorithm for assumption the energy losses of hydraulic transport in a case of the mine "Trepca"

The main problem of hydraulic transport is the resistance generated during the mixture transport through the pipe-line. Testing the flow characteristics of mixtures, shown in this paper, are based on the principles of determining the unit energy losses by a mathematical calculation using the non-linear regression ? the Levenberg-Marquardt algorithm. Such obtained results allow determining a transport rate in the horizontal pipe-line, depending on the mixture bulk density and pipe-line diameter. The flotation tailings is mainly used as a filling material in the mine ?Trepca? - Stari Trg. According to the grain size distribution, it is a fine-grained material of a size of 0.074 mm to 1.2 mm. It is a multicomponent material containing pyrite, pyrrhotine and other heavy metals, and therefore, has a high bulk mass. The average rate of the hydromixture, in which the energy losses reach the minimum value, depends on the pipe-line diameter and kinetic bulk density of the mixture. For the test interval of change in the pipe-line diameter, shown in this paper (0.168 mm, 0.176 mm, 0.193 mm, and 0.225 mm), and kinetic bulk density of the hydraulic mixture (1-1.6 kg/m3), this rate ranges from 3-5.5 m/s. The increase of the energy losses in the hydraulic mixture transport increases proportionality with the increase of its kinetic bulk density. The results, presented in this paper, show that the required bulk density of 1.6 kg/m3 should be accepted as a limit from a point of view of the hydraulic transport cost-efficiency.

Evaluation of methods for improving the efficiency of the hydro-technical systems functioning at mineral-metallurgical combines

Purpose. Justification of hydraulic systems management methods of mining and metallurgical plants, taking into account indicators and comparative analysis and on the basis of pipelines rational parameters and slurry concentrates.. Methodology. Analysis of modern methods for assessing the efficiency of operation of hydraulic systems of enterprises in the mining and metallurgical industry allowed us to determine the promising directions for the use of various chemical reagents in order to reduce hydraulic resistance during transportation of hydraulic mixtures in mineral processing technologies. Findings. The rational parameters of the operation of hydraulic systems of mining and smelting plants, namely: the diameter of the pipeline and the concentration of the slurry for a given amount of transportation to ensure a minimum of reduced costs for the evaluation period and taking into account the usage of chemicals which were used to improve the efficiency of pipeline transport. Originality. Based on the analysis of methods for assessing the effectiveness of mineral processing technologies. It is determined that the most rational in the totality of technologies to improve the efficiency and reliability of the hydrotransport complex is the use of polyethylene pipes, as well as additives to the carrier fluid of hydrodynamically active substances. Practical value. It consists in the improvement of methods for calculating rational parameters and modes of operation of hydraulic systems, allowing to determine the value of the velocity and concentration of the slurry, providing a minimum of reduced costs for the estimated period. These methods are adapted for the case of using polyethylene pipes, taking into account additives to the carrier fluid of hydrodynamically active substances, taking into account the reduction of reduced costs due to diagnosing the technical condition of the equipment, as well as allowing to optimize maintenance costs.

Investigation of anisotropic flow in asphalt mixtures using the X-ray image technique: pore structure effect

The importance of moisture flow as the main contributor to premature deterioration of asphalt pavements has long been recognised. However, a precise quantification of anisotropic flow and their relationships to complex pore structures in asphalt mixtures are yet to be determined. The objective of this study was to (1) quantify the anisotropic flow in asphalt mixtures and (2) investigate the pore structure effect on anisotropic flow. Three asphalt mixtures with contrasting pore structures were selected for this study. A custom-made permeameter in accordance with the UNI EN 12697/19 procedure was used to analyse the anisotropic flow in asphalt pavement. Results illustrated that the vertical flow rate is quantitatively smaller, even much smaller, than that of the horizontal flow rate which is influenced strongly by the hydraulic gradient and mixture type. Within the same mixture type, the flow under a high hydraulic gradient always has a lower anisotropy than that under a low hydraulic gradient. Within the same hydraulic gradient, stone mastic asphalt mixtures display a higher overall anisotropy than open-graded friction courses and asphalt concrete. Then, the pore structure of asphalt mixtures was quantified by X-ray computed tomography. The analysis of variance indicated that pore distribution characteristics, including air voids content, void diameter and tortuosity, contribute slightly to anisotropic flow, while the anisotropy of pore connectivity, such as connective void content/ratio, is the main factor influencing the anisotropic flow in asphalt mixtures.

Environmental Protection Agency Assessing Utility of Toxic Substances Control Act to Obtain Information on Hydraulic Fracturing Chemical Substances and Mixtures

Environmental Protection Agency Assessing Utility of Toxic Substances Control Act to Obtain Information on Hydraulic Fracturing Chemical Substances and Mixtures

Experimental analysis of hydraulically bound mixtures made with waste foundry sand and steel slag

This paper presents the results of a laboratory study aimed at verifying the suitability of two types of industrial waste, foundry sand and steel slag, to be recycled in the aggregate skeleton of hydraulically bound mixtures for road foundations. The investigation involved a preliminary study of the leaching, physical and mechanical properties of the by-products and then the formulation of the hydraulic mixtures, in terms of Proctor, compressive and indirect tensile strength (ITS) tests, at various curing periods. In order to obtain a better mechanical characterization, the elastic modulus of the mixtures has been evaluated through static and dynamic tests, at different curing times. The results were completely satisfactory for all the mixtures designed, especially for that characterized by 80 % of steel slag and 20 % of foundry sand; it showed a compressive and ITS, at 7 days, up to 5.6 and 0.72 MPa respectively, depending on the mix and the cement content. Since the requisites for acceptance in the Italian Specifications and Standards have been satisfied and given the positive mechanical performance, it has been verified the possibility to use industrial by-products as integral substitutes of the natural aggregate in the production of cement bound granular materials for road foundations.

The Study of Stabilization of Hydraulic Fill Sand and Silt Mixture in Coastal Area

In this paper, relevant experiments had been conducted on the stabilized mixture of hydraulic fill sand and silt in coastal areas, include the study of optimum mixing ratio of hydraulic fill sand and silt and the appropriate curing agent; as well as the change law for the strength of solidified sediment mixture with different curing agent content. The results show that strength of the stabilized mixture showed the highest when mass ratio of hydraulic fill sand and silt was 60% :40%, and using G2 as the curing agent. Strength of stabilized sediment mixture all increased in different degrees as the mixing amount of curing agent increased.

Giant Die Forging Press Machine Main Circuit Electromechanical Hydraulic Servo Control System Modeling and Simulation

This paper research on an electromechanical hydraulic mixture control system used in large scale die-forging press, based on the national major science and technology project (2009ZX04005-011). This mixture control system used in press machine accomplishes pressing, pressure-keeping, return. The control system uses hydraulic oil to control three-position five-path slide valve as hydraulic system main valve, for drive system of giant die forging press is characteristic of ultrahigh pressure and large flow, high power. This control system consists of two parts: firstly, establishing electromechanical hydraulic mixture control model by adding electronics and feedback section to servo slide system. Secondly, combining existing slide control hydraulic cylinder model and server slide system form main circuit closed-loop control system. The last but not least, Computer simulation was conducted by matlab got the ideal control curve.

Modelling of Mechanical Properties of Cement Concrete Incorporating Reclaimed Asphalt Pavement

ABSTRACT In many countries there is a trend to recycle wastes obtained during pavement maintenance or reconstruction, and to forbid the landfill of these products. Thus, in some circumstances it can be tempting to use reclaimed asphalt pavement (RAP) in new hydraulic concrete mixtures. This paper presents experimental data and modelling about the effect of RAP incorporation on cement concrete mechanical properties (compressive strength, tensile strengths and E-modulus). All these properties tend to decrease with the rate of RAP dosage, and with temperature. Then attempts are made to adapt LCPC mix-design models to these innovative concretes. Two alternative hypotheses are evaluated. In the first one, RAP aggregate is viewed as composite particles playing the role of an homogenous aggregate having lower bond, strength and E-modulus as compared to normal aggregate. In the second one, the bitumen phase is assumed to be finely dispersed within the cement paste, acting as a supplementary dosage of water (or air). According to the simulations, the second hypothesis is the best one. This finding extends the scope of application of modern mix-design methods, and will help in using RAP in cement concrete, for the technical, economical and environmental benefit of the road community.

Résistance à la traction et module d’élasticité des bétons calcaires: application à des mélanges tunisiens

This article presents the results of the tensile strength and the elastic modulus obtained between one day and a year on a vast set of mortars, micro-concretes and concretes carried out with limestone aggregates out coming from five Tunisian careers. For the tensile strength, the results were compared with the compression strength measured on the same mixtures. The obtained evolutions do not coincide with the power-laws generally adopted for the predicted tensile strength. An approach, where the law parameters (coefficient, exponent) can be adjusted, gives better results. The resort to another more precise model, described by a hyperbolic law, makes it possible to provide a physical interpretation to the tensile strength behavior of the hydraulic mixtures. Its parameters are linked to the aggregate strength and cohesion in the paste-aggregate transition zone. For the elastic modulus, the use of a model taking into account the properties of the granular phase and the binding phase made it possible to reach the elastic modulus of the aggregates.

Contribution des fillers calcaires à l’adhérence pâte-granulat. Exemples tunisiens

This article presents compressive test results carried out on a series of hydraulic concrete mixes without admixtures based on Tunisian limestones aggregates. Their estimated strength was calculated with the French model of LCPC (Laboratoire Central des Ponts et Chaussees), which takes into account the effect of bond to the paste and the ceiling effect of the aggregates. To check the experimental values, the parameter of bond had to be associated the content of fillers aggregates, because the performances predicted by the model are lower than the measurements, at least beyond 10% of fillers. The assumption is that the presence of these fine elements, of comparable nature that the aggregates, improves adherence or linking between paste and aggregate, thanks to bringing together the properties of rigidity of the two materials and to a better homogeneity of the system. The relationship found between the calcareous filler ratio and the bond coefficient then makes it possible to extend the forecasts of the model to the hydraulic mixtures containing aggregates crushed limestones, naturally rich in fillers.

The risk of cracking of fine hydraulic mixtures

The hydraulic mixtures studied in this two-part article are destined for the fabrication of fine reconstituted sandstones. They were obtained from two sands whose size does not exceed 1 mm, white cement, water, and for some, from mineral additions, fibers, and superplasticizer or antishrinkage admixtures. During the elaboration, the method of fabrication created significant vertical variations in the water content, especially in the thick blocks from which were cut the 4×4×70 cm test pieces used in the shrinkage measurements. The first part of the article presented in detail the materials, the formula adjustments, estimates of the rates of hydration and carbonation, and the various measurements. This second part is devoted the models retained for the description of the evolution of the characteristics of these products as well as simulation involving a likely cracking index.

Physical and mechanical properties of fine hydraulic mixtures

This two-part article deals with the problem of the fissuring of sandstones reconstituted from fine hydraulic mixtures packed and vacuum dried according to a patented procedure. During more than two years, the dimensional variations of these products were measured on slender test pieces reconstituted according to several models proposed for hydraulic concretes. In this part, we present the materials, the procedures used to mould the stones along with the calculations developed to obtain the exact composition of the test pieces. We also give densities, the mechanical strength and recorded time evolution of the deformations for different conservation modes which are representative of the possibilities of the envisaged production. In the second part, we present the method for describing the dimensional variations and the adaptations leading to the introduction of a crack index in choice of the formulas.

Characterization of structural byzantine mortars by thermogravimetric analysis

The mortars and `cocciopesto' plasters were largely used in the historic buildings, as waterproof coverings and in the preparation of mortars, especially in horizontal structures. In recent years, the necessity of restoration interventions with materials which are compatible with the masonry structure requires a detailed study on these materials. In this study, the composition of a significative number of mortars of the Byzantine period in the Hagia Sophia Basilica are investigated. They were made of `cocciopesto' (crushed ceramic) and probably have a bearing function in the masonry structure. The samples are examined by particle size, infrared spectroscopy (FT-IR) and thermogravimetric analyses (TG-DTG), both on the total sample and on the finer fraction (<63 μm) which mostly constituted of binder. The results indicate slightly hydraulic mixtures made with a binder/aggregate ratio variable in volume between 1/2 and 1/4. The mixture morphology and heterogeneity seem to imply the use of hot lime technology that would lend themselves to the bearing function of the mortar.

Hydraulic filling of tailings with a limited sand content

1. In the case of a limited content of sand in tailings (<30%) hydraulic filling of a tailings dump with the formation of a sand beach of sufficient length is possible, provided that the maximum bulk density of the hydraulic mixture is not exceeded (not above≥70% sand deposition for the investigated tailings dumps). 2. The results obtained are applicable under conditions similar to those which were investigated and can be used in the case of hydraulic filling of earth.