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We describe a micron-sized ore powder production by propulsion and rapid unloading of high-pressure gas. The research consists of three parts. Firstly, we obtain the tensile strength parameters and permeability coefficient based on the experiment. Secondly, gas propulsion pressure and gas infiltration pressure of the powdering experiment are confirmed. Thirdly, the ore will be fragmented into micron-sized powder when rapid unloading occurs. The grain size analysis indicates that more particles with smaller sizes are obtained at a higher propulsion gas pressure. Particles less than 0.147 mm obtained at the 65 MPa gas propulsion pressure account for 63% of the sample. The critical gas propulsion pressure is determined to be 55 MPa when the volume ratio is 1:3. Powdering experiments show that this method is suitable for metallic and non-metallic ores.

Air penetration behavior plays a vital role in the performance of fibrous material in various industrial applications. Two parameters, the permeability coefficient and airflow resistivity, can describe the air penetration behavior of fibrous material. FX 3300 Textech Tester III and AFD300 AcoustiFlow devices were used to respectively characterize the permeability coefficient and airflow resistivity of nonwoven materials. Nonwoven samples were compressed due to the load from the test head of the FX 3300. Finite element analysis along with the mathematical method were implemented to recover the airflow permeability of samples at the uncompressed state. The effects of pressure drop on the airflow velocity and permeability coefficient were analyzed by the Ergun-type model. The determination of airflow resistivity based on the permeability coefficient is carried out via two approaches, that is, the direct method and the extrapolation method. The results show that the airflow velocity is not linearly related to the pressure drop, which differs from Darcy's law. This non-linear relation is mainly attributed to the influence of frictional loss. By comparing the relative error between assessed and measured airflow resistivity, most of the assessed values of the compressed samples are overestimated. The results also suggest that the direct and extrapolation methods are applicable to assess airflow resistivity on an airflow velocity (or air permeability) test device. Moreover, the Ergun-type model is also applicable to determine the permeability coefficient and airflow resistivity of nonwoven materials.

Porous asphalt pavement is mainly used for parking lots which able to let water to drain through the pavement surface into a stone recharge bed and infiltrate into soils under the pavement. This study is to investigate the performance of seashell in porous asphalt and determine the image analysis. The seashell used in this study is cockle shell. The strength of seashell was determined through the Aggregate Impact Value Test (AIV) and Aggregate Crushing Value Test (ACV). The grade of bitumen used was grade 60/70. The porous asphalt volumetric properties was determined through Marshall Stablity Test. The permeability coefficient of sample that contain seashell as aggregate replacement was determined through Permeability Test. Generally, the results shows that the seashell’s percentage loss (AIV and ACV) is suitable use for porous asphalt mixture, where the percentage of loss for AIV and ACV was 27.84% and 7.65% respectively. Based on the Marshall Test, porous asphalt that containing seashell as aggregate replacement shows a different result, where it had lower stability value and it can increase the bulk density of porous asphalt mixture. Furthermore, the permeability coefficient also increase. The surface of seashell able to bond with bitumen. Lastly, the trend of VFA and VTM value is effected by the surface and position of seashell in the porous asphalt sample.

Purpose The purpose of this paper is to form a numerical simulation method for permeability coefficient that can consider the characteristics of gravel gradation and further explore the effects of indoor test factors and gradation characteristics on the permeability coefficient of gravel. Design/methodology/approach The random point method is used to establish the polyhedral gravel particle model, the discrete element method (DEM) is used to construct the gravel permeability test sample with gradation characteristics and the finite element method is used to calculate the permeability coefficient to form a DEM-computational fluid dynamics combined method to simulate the gravel seepage characteristics. Then, verified by the indoor test results. Based on this method, the influence of sample size, treatment method of oversize particles and the content of fine particles on the permeability coefficient of gravel is studied. Findings For the gravel containing large particles, the larger size permeameter should be used as far as possible. When the permeameter size is limited, the equal weight substitution method is recommended for the treatment method of oversized particles. Compared with the porosity, the pore connectivity has a higher correlation with the permeability coefficient of the sample. Research limitations/implications Insufficient consideration of the movement of gravel particles in the seepage process is also an issue for further study. Originality/value The simulation method described in this paper is helpful for qualitative analysis, quantitative expression of pore size and makes up for the defect that the seepage characteristics in pores cannot be observed in laboratory tests.

The results of studying the convective drying of cylindrical granules of a support for a nickel catalyst using mathematical modeling techniques have been presented. A mathematical model for intensive heat and mass transfer in a granule has been formulated that makes it possible to choose the efficient regimes of convective drying. The specific feature of the mathematical model is the analytical calculation of local mass transfer coefficients for a liquid taking into account the sorption properties of a material, a permeability coefficient, the local values of the moisture content, and temperature. Comparison of the results of mathematical modeling of heat and mass transfer in granules and the data of a laboratory experiment has shown that they are in satisfactory agreement.

The cement-plaster bonded rock-like material is one of the most commonly used materials to simulate different rocks in physical model tests. However, the applicability of this material in solid-fluid coupling model tests is not clear because there are few research studies on the water-physical properties of this material and its similarity to the actual rock is uncertain. This paper presents a systemic experimental study on the water-physical properties of the cement-plaster bonded rock-like materials. The parameters of rock-like materials, including water absorption, softening coefficient, and permeability coefficient, were compared with those of actual rocks to analyse the applicability of such material. Then, the influence of proportion on the water-physical properties of this material was discussed. By multiple regression analysis of the test results, empirical equations between the water-physical parameters and proportions were proposed. The equations can be used to estimate the water-physical properties of cement-plaster bonded rock-like materials with specific proportion and thus to select suitable materials in the solid-fluid coupling physical model tests.

The permeability property of a packed particles material has been caught much attention, it depends upon its pore characteristics caused by the particle accumulation, but the current empirical formulas and the permeable theory could not re-veal the effect of the particle accumulation thoroughly. In this paper, a theoretical formula is derived, and the fractal gradation spectrum is adopted to confirm the particle size distribution, furthermore, the pore feature is determined by the particle size and accumulation features, finally a permeability model of the packed particles material is established. In this model, the effect of particle size distribution on pore features is estimated more thoroughly than those in conventional models, and the calculated results are more accurate and verified experimentally.

In fracture or compaction grouting projects of sand layer, there exist many compacted sand regions on both sides of grout veins or around grout bulbs. It has an important effect on the final reinforcement effect of the sand layer that how much performance of the sand layer is improved after being compacted. Compression modulus, cohesion, and permeability coefficient are selected to be the performance indexes of the compaction reinforcement effect of sand. The relationship between the performance properties of sand and grouting pressure has been tested and analyzed. And influences of clay content and initial water ratio of sand on the compaction reinforcement effect have been studied. Results show that compaction can effectively improve the mechanical properties and impermeability properties of sand. Compression modulus of sand increases by 2∼18 times. The cohesion of sand increases from the scope of 9.4∼26 kPa to the scope of 40∼113.6 kPa. The permeability coefficient of sand decreases from the scope of 1.0 × 10−2∼ 8.33 × 10−4 cm/s to the scope of 2.19 × 10−4∼2.77 × 10−9 cm/s. When the clay content of sand is smaller than about 20%, sand cannot be reinforced effectively by compaction. Cohesion cannot be improved significantly and the permeability coefficient cannot be reduced markedly. A high initial water ratio of sand is beneficial to improve the compression modulus of compacted sand and goes against the improvement of cohesion of compacted sand. In addition, the initial water ratio has little effect on the permeability coefficient of compacted sand. In the end, fitting formulas have been developed to quantitatively describe the compaction reinforcement effect of sand by different grouting pressures.

Clogging effect surrounding prefabricated vertical drains (PVDs) is a typical problem when vacuum preloading is applied to a dredged fill foundation. A large-scale model test was designed to clarify the cause and mechanism of the clogging effect, and the basic physical and mechanical parameters of the soil in the clogging zone were tracked during the test. The results demonstrated that a clogging zone was formed around the PVD in the early stage of improvement with conventional vacuum preloading, and the boundary of the clogging zone was approximately 0.2–0.4 of the boundary radius. The clogging zone surrounding the PVD was formed because of the overall movement of the soil toward the PVD under the high vacuum pressure gradient, rather than fine particle migration. The soil in the clogging zone exhibited permeability anisotropy and equivalent ‘smear’ effect. The permeability ratio (kh/kv) was less than 1, and the ratio of horizontal permeability coefficients at the test distances of 45 cm and 10 cm were 9.6 at a depth of 20 cm and 8.9 at a depth of 80 cm. An analysis of the microstructure of the soil in the clogging zone demonstrated that the clay particles tended to be vertically oriented. The re-orientation of the clay particles reduced the horizontal permeability coefficient and led to the permeability anisotropy of the soil in the clogging zone. Thus, decrease in the horizontal permeability coefficient and equivalent ‘smear’ effect of the soil in the clogging zone affect the consolidation of dredged fill, which leads to the clogging effect. The permeability anisotropy also slightly affects consolidation.

The process technological parameters of forming a film composite for making heat-protective clothing have been developed. The peculiarities of its application in sewing production are taken into account. The effect of the initial polymer compositions formulation on the formed composites physical-mechanical and technological properties was studied. It has been found that the use of the composite film material developed reduces the compounds permeability of protective clothing.

The strength and permeability of tailing-waste rock mixtures directly affect deposits’ stability for an alternative co-disposal technique. In the mixed co-disposal method, the void of the waste rock is filled with tailings, while the waste rock forms the particle skeleton. This method does not only improve deposits stability but also potentially reduces acid pollution. In this study, the rock percentage influence on the shear strength and permeability of tailing-waste rock mixtures was investigated by carrying out large triaxial tests and permeability tests. The shear strength, enhanced strength mechanism, and mixture permeability were analyzed. The results indicate that the shear strength and internal friction angle of the tailing-waste rock mixtures gently increased until the rock percentage reached 30% and then rapidly increased with the further increase of the rock percentage. The permeability coefficient of the mixtures slowly increased until the rock percentage reached 50% and then rapidly increased with the further increase of the rock percentage. The tailings washed out of the waste rock skeleton when the permeability was large. In this paper, 50% of waste rock is recommended for building mixture deposits.

To investigate the influence of confining pressures and temperatures on the seepage characteristics of fractured rocks, seepage tests were conducted on a fractured silty mudstone using a self-developed experimental system, and the effects of different factors on coefficient of permeability were discussed. The results showed that the increasing confining pressure will gradually decrease the coefficient of permeability, and this process is divided into two stages: 1) the fast decrease stage, which corresponds to a confining pressure less than 30 kPa, and 2) the slow decrease stage, which corresponds to a confining pressure larger than 30 kPa. Unlike confining pressure, an increase in temperature will increase the coefficient of permeability. It is noted that fracture surface roughness will also affect the variation of coefficient of permeability to a certain extent. Among the three examined factors, the effect of confining pressure increases is dominant on fracture permeability coefficient. The relationship between the confining pressure and coefficient of permeability can be quantified by an exponential function.

A polyoxadiazole polymer POz-CF3 was prepared and complete gas permeation properties were investigated on its corresponding membrane using pure-, and multicomponent mixed-gas feeds. The POz-CF3 mem...

Column leaching experiments with ion adsorption-type rare earth ores for different lixiviant concentrations and different column heights were carried out. A mathematical model of column leaching was constructed based on the experimental data. Two parameters (a and b) in the model were determined according to the following methodology: the ore column was divided into several units; each unit was treated with multiple leaching steps. The leaching process was simulated as a series of batch leaching experiments. Parameter a of the model was determined based on the selectivity coefficient of the balanced batch leaching experiment. Further, the influences of ammonium sulfate concentration, rare earth grade, column height, permeability coefficient, and hydrodynamic dispersion coefficient on the extraction were analyzed. Relationships between parameter b, the ammonium sulfate concentration, and the physical and mechanical properties of the ore column, were examined using dimensional analysis. It was determined that the optimal ammonium sulfate concentration for different column heights (2.5, 5.0, 7.5, and 10.0 cm) using the mathematical model were 5.9, 6.2, 7.3, and 7.7 g/L, respectively. The mathematical model can be used to estimate the breakthrough curve, leaching rate, and leaching period of rare earth ores, to achieve optimal extraction.

Permeable pavement is generally considered as one of the most effective prac-tices of rainwater management. This paper analyses the defects of current permeable pavement. Inspired by the honeycomb bionic structure which has superior mechanical properties and structural efficiency, an innovative “honeycomb-like” model of permeable brick measuring 190 × 100 × 60 mm in size was proposed and constructed. The mechanical strength and permeability performance of the honeycomb permeable brick were experimentally assessed by universal testing machine and artificial rainfall equipment, respectively. Ex-periment results demonstrated an excellent performance in compressive toler-ance and permeability. The critical damage load (Fc) and compressive strength (Ec) of honeycomb brick were 336.46 KN and 17.70 MPa, which were 18.06% and 11.04% higher than that of ordinary solid permeable bricks, respectively, compared with the conventional permeable bricks. The honeycomb brick is capable of increasing the permeability coefficient by 19.2% and 11.96% under rainfall repetition period of 20 and 30 years respectively. These results demon-strated that the permeable brick with honeycomb-like structure can provide a new paving strategy for the construction of sponge city.

Methods and instruments the characteristics of porosity and permeability of solids and materials are described, which are part of the improved GET 210-2014. The metrological characteristics of the GET 210-2014 are compared and after its improvement the GET 210-2019. Certified reference materials of approved types based on micro-, meso- and macroporous solids are considered. The results of international comparisons, confirmed measuring and calibration capabilities, as well as a comparison of the metrological characteristics of the GET 210-2019 with the standards of foreign countries are presented.

One of the main means of reducing aerodynamic noise is the use of silencers, which can be made of various porous materials, depending on the specific operating conditions. The aim of the work is to study the dependence of the noise reduction on the characteristics of porous permeable materials (PPM) obtained by vibration molding from metal powders. Such PPMs have a wide range of porosity, high permeability, mechanical strength, provide the ability to work in a wide temperature range, high corrosion resistance, and therefore find more and more widespread application in practice. When designing silencers, their pore size, permeability, mechanical strength, cost, and the chemical composition of the material are taken into account. Basic research methods – determination of noise level, powder particle size, permeability coefficient, pore size. Vibration molding of PPM samples for experimental studies was carried out on a ВЭДС 10-1А vibration bench with vibration parameters that ensured the maximum bulk density of the powder in the mold (acceleration 10 m/s2, frequency 500 Hz). Main results – the dependence of the noise reduction value on the PPM characteristics obtained by the method of vibration molding of metal powders of various grades of various particle size distribution was studied. It has been shown that the most effective damping is provided by PPM from spherical bronze powder of the БрОФ10-1 grade with particle sizes of 350–400 microns, which provides at the same time a combination of a high level of noise reduction and high permeability to air or gas. It was found that the thickness of the muff significantly affects the efficiency of noise suppression, while the minimum thickness of the muff, which provides a sufficiently high degree of noise reduction, is about 3.5 mm, therefore it is not practical to increase the thickness of the muffler material above this value.

Sand boiling is a type of hydraulic failure occurring the downstream of dams with huge damages. In this study, the reinforcement effect of Firuzkuh sand with bulk continuous filament (BCF) fibers and geotextile (woven and nonwoven) on the resistance to boiling is examined on a laboratory scale. For this purpose, an upward seepage apparatus was designed and fabricated. In reinforcement with BCF fibers, with increasing the weight percentage of fibers, soil strength increased and the permeability coefficient was changed. In soil reinforcement with geotextile, two types of woven and nonwoven geotextiles were used in two modes of one and two layers. Based on the results of the performed tests on these samples, the reinforced samples have shown more resistance to boiling than the natural samples. Also, the increase in critical hydraulic gradient and seepage force (to sand boiling) was found to be a function of the type and number of geotextile layers. Moreover, in this research, the effect of the relative compaction of the sample on permeability and critical hydraulic gradient of samples (reinforced and unreinforced) was investigated. According to the results, in denser samples, the boiling is delayed and soil improvement (a reinforcement with fibers and geotextile) is significantly effective.

To study the influence of admixtures, including blast furnace slag, quicklime, and fly ash, on the properties of solidified uranium mill tailings, the mechanical strength, permeability coefficient, and radon exhalation rate of solidified samples were measured after curing and storage for 28 days. The results showed that, with increased admixture dosage, the curing degree of the solidified body improved, mechanical strength increased, and permeability coefficient and radon exhalation rate decreased. At the same dosage of the three additives, the optimized curing degree in the blast furnace slag samples with 25% dosage had the properties of blast furnace slag samples, which was in accordance with China GB 14569.1-2011 standards that provide theoretical reference and decision evidence for the future management of uranium tailing impoundment/decommissioning treatment.

An analysis is made of application of Kozeny approach for estimating air permeability of nonwoven needle-punched fabrics based on fibres with 0.33 and 1.7 tex linear densities and a blend of these fibres as well as of treated materials based on polyester and bicomponent fibres. The inverse problem, which boils down to calculation of the Kozeny constant using experimentally derived permeability coefficient of fabrics and materials is solved. The Kozeny constant depends on the composition of the fabrics and materials and diminishes with transition from fabrics made with fibres of different linear densities to treated materials.

To make steel slag being reasonably used in geotechnical backfilling projects or soft foundation treatment projects, three kinds of steel slag such as fine, coarse, and gravel steel slag were studied through particle analysis tests, relative density tests, and specific gravity tests to obtain basic physical parameters. Considering the influence of relative density, gradation, and other factors, constant head permeability tests of pure steel slag and variable head permeability tests of modified silt soil with different mixing contents of steel slag were carried out to test permeability coefficients under various working conditions. Prediction formulas on the permeability coefficients of the three kinds of pure steel slag and steel slag-treated silt soil were, respectively, deduced. It was concluded that the permeability coefficient of pure steel slag was greatly influenced by particle size and relative density, similar to the case of permeability coefficients of fly ash and fine sand in their dense states, and the larger the relative density was, the smaller the permeability coefficient was. The permeability coefficient of steel slag-treated silt soil increased with increasing of mixing content of steel slag, showing that steel slag can obviously improve the permeability performance of silt soil. Research results provide reference for design and construction on the application of steel slag in roadbed backfill, steel slag modifying silt soil, and other projects.

An exposure test in a natural tidal environment was conducted to measure the gas permeability coefficient and micro-structural parameters of concrete at different ages. The time-dependent micro-structural parameters and gas permeability coefficient of test concrete and their correlation have been analyzed. Besides, an indicator of age reduction factor (mg) has been proposed to investigate the decreasing of gas permeability over time. Results indicate that, the total porosity and gas permeability of test concrete both decrease with time. There is a positive linear correlation between gas permeability coefficient and total porosity (R2 = 0.872) as well as contributive porosity. Moreover, the correlation coefficient of gas permeability coefficient fitting by two micro-structural parameters (porosity and contributive porosity of pore size within 100–1000 nm) is higher than that by using a single micro-structural parameter, which can provide a more accurate basis for predicting gas permeability coefficient of concrete.

The use of pervious concrete to minimize the effects caused by the impermeability of the soil as a result of increasing urbanization is an alternative that still requires further studies regarding its design and implementation. From this perspective, this paper presents a study of the characteristics of pervious concrete, including its tensile strength, compressive strength, flexural strength and the permeability coefficient, through the development of various mixtures to adjust the characteristics of the local aggregates. Eight mixtures were studied based on a reference mixture, five of which were related to the pervious concrete with the addition of finer aggregates than the reference mixture without these aggregates. Subsequently, three mixtures were studied with the inclusion of polypropylene fibers in order to analyze the effects of the addition of fibers on the properties of the pervious concrete. It is concluded that the presence of fibers changed the characteristics of the concrete, increasing its strengths while achieving a good permeability in its mixtures. An improvement in the flexural strength of the pervious concrete was observed, which is the main property to be considered for its use in pavements, without harming the permeability, which raises the possibility for its application. Resumo Utilizar concreto permeável para minimizar os efeitos causados pela impermeabilidade do solo causado pela crescente urbanização é uma alternativa que ainda necessita de estudos quanto à sua concepção e aplicação. Seguindo esta linha, o presente artigo apresenta um estudo das características do concreto drenante, tal como a resistência à tração, resistência à compressão, resistência à tração na flexão e coeficiente de permeabilidade, através do desenvolvimento de varios traços, para ajustar às características dos agregados locais. A partir de um traço referência, foram estudados oito traços, sendo cinco referentes ao concreto drenante com adição de agregados mais finos ao traço referência sem estes agregados. Posteriormente estudou-se três traços com a inclusão de fibras de polipropileno, com o objetivo de analisar os efeitos que a adição de fibras causa nas propriedades do concreto drenante. Concluiu-se então, que a presença das fibras alterou as características do concreto, levando o mesmo a atingir maiores resistências, aliadas a uma boa permeabilidade em seus traços, verificando-se assim a melhoria de capacidade de resistência à tração na flexão do concreto drenante, principal propriedade para uso em pavimentos, sem prejudicar a permeabilidade e avaliando a possibilidade de aplicação do mesmo.

Cemented soil impermeable projects directly or indirectly contact an underground corrosive environment in most cases, which could cause reduced impermeability and malfunction of the cemented soil. Laboratory simulation permeability tests of cemented soil were conducted under different cement ratios in acidic and alkali environments. The variation in the permeability coefficient of the cemented soil was studied under different curing times, pH, and cement contents. Using scanning electron microscopy (SEM) and energy spectrum analysis, the permeability of cemented soil in acidic and alkali environments was studied at the microstructure level. The test results show that an acidic environment has a major effect on the permeability coefficient of cemented soil with a low cement content, and a greater cement content offers increased resistance to acid erosion. In an alkali environment of pH 9-13, the permeability coefficient of the cemented soil gradually decreases as the curing time increases. The research results provide technical parameters for the impermeability and durability design and application of cemented soil in impermeable projects, which has important engineering implications.

Compressive stress and tensile stress were applied to concrete specimens using test rigs designed by RILEM TC 246-TDC. Ultrasonic wave velocity and autoclam permeability system were used to characterize the damage variable and gas permeability coefficient of concrete, respectively. The experimental results show that the strain value of concrete increases with the increasing of stress level and loading time. The damage variable and gas permeability coefficient of concrete under compressive stress decrease at first and increase after a threshold value between 0 and 0.6. When the concrete is under tensile load, the damage variable and gas permeability coefficient increase with tensile stress, with a significant increase from 0.3 to 0.6 tensile stress. There is a strong linear relationship between the damage variable and the gas permeability coefficient, suggesting both as good indicators to characterize the damage of concrete under stress.

This study examines the use of cement treatment in improving the lead immobilization properties of a compacted clay liner for sanitary landfill applications. The compaction and strength characteristics of the cement treated clay at cement contents of 0%, 3%, 6%, 9%, 12%, 15% and 18% by weight of dry soil are studied via standard compaction and unconfined compressive strength tests. The lead immobilization characteristics of the cement treated clay are also investigated using atomic absorption spectroscopy. The cement contents of 6% and 9% significantly affect the permeability coefficient and lead absorption of the clay. The permeability coefficient of the cement treated clay meets the requirement for a waterproof material in landfill, i.e., Clay-liner, Landfill, Lead, Unconfined compressive strength, Immobilization, Soil cement, Ground improvement.

The construction of sponge city is a major green innovation to implement the concept of sustainable development. In this study, the road performance of permeable asphalt concrete (PAC), which displays pronounced water permeability and noise reduction that are favorable for sponge cities, has been improved with a two-fold modification using styrene–butadiene–styrene (SBS) and crumb rubber (CR). Four percent SBS and three different ratios (10%, 15%, and 20%) of CR have been used to modify the virgin asphalt binder. The Marshall design has been followed to produce PAC samples. To evaluate the asphalt binder performance, multiple-stress creep-recovery (MSCR) test, linear amplitude sweep (LAS) test, and engineering property test programs including softening point test, penetration test, and rotational viscosity test have been conducted. Freeze–thaw splitting test, Hamburg wheel-tracking test, resilient modulus test, and permeability coefficient test have been performed to evaluate the asphalt mixture performance. The test results show that the addition of SBS and CR reduces the permeability coefficient, but significantly improves the high temperature performance, fatigue performance, and rutting resistance as well as the resilient modulus. However, the optimum rubber content should not exceed 15%. Meanwhile, after adding CR and SBS modifier, the indirect tensile strength (ITS) and tensile strength ratio (TSR) increase. It indicates that the moisture stability and crack resistance have been improved by the composite modification effect.

In China, Gaomiaozi (GMZ) bentonite is recognized as a barrier material for isolating nuclear waste. Different chemical solutions may change the hydraulic conductivity and swelling capacity of bentonite. Consequently, a series of swelling pressure and permeability experiments was carried out on bentonite-sand mixtures with various dry densities and infiltrating solutions. X-ray diffraction (XRD) and the field emission scanning electron microscope (FESEM) were carried out on the samples experiencing the tests to identify the influence of chemistry pore solutions upon the mineralogical and microstructure changes. The results show that the swelling pressure experienced rapid swelling, slow expansion, and the stable expansion stage for the specimens of infiltrating solutions except for NaOH. For the specimens infiltrated with NaOH solutions, the swelling pressure experienced rapid increases, slow decreases, and a stable development stage. With hyper-alkaline and hyper-salinity infiltration, the swelling pressure decreased, and the permeability increased. In addition, swelling pressure attained stability more quickly on contact with hyper-alkaline and hyper-salinity solutions. Comparing the test results, the results indicate that the influence of NaOH on the expansion and permeability was higher than NaCl-Na2SO4 at the same concentration.

The effect of silica fume on the performance, mechanical properties, durability and air tightness of airtight concrete was studied. The results showed that with the increase of silica fume content, the concrete performance will decrease, the compressive strength of airtight concrete will increase first, and reach the highest when the silica fume content was 8%, and then it will decrease gradually. With the increase of silica fume content, the corrosion resistance coefficient of concrete increased gradually, then decreased. The permeability coefficient of concrete decreases with the increase of silica fume content, and the air tightness of concrete was improved obviously; In the project, it was advisable to use silica fume to prepare airtight concrete, and the amount of silica fume should be controlled at 4% - 8%.

This paper proposes an economical thermal cycle of the production of ceramic articles from submicronic powders of aluminum oxide, titanium oxide, and manganese oxide. The implementation of a given cycle involves the introduction of a special aluminophosphate bond into the charge in order to reduce the temperature of firing. The optimal composition of the material for a foam-ceramic filter with the highest physical and mechanical properties has been determined; the optimal method for preparing the original charge and the baking mode have been selected. According to the results of tests under industrial conditions, the manufactured alumina filters became a decent alternative to known analogs used in aluminum metallurgy for the purification of liquid metal. The application and rational dosage of titanium dioxides, manganese, and aluminum aluminophosphate in porous ceramic compositions on an alumina base have made it possible to significantly reduce the time and, consequently, improve the productivity, of firing. The results obtained were evaluated by the level of maximum temperature in the cycle of heat treatment according to known technologies. Compared to those technologies, the developed technology ensures the growth of firing productivity when implementing the proposed solution by about 220%. It was found that the high true density of ceramic powder requires large dispersion as the relatively large powder particles are significantly worse retained in foam films and settle. At medium (intermediate) temperatures, a large weight loss occurs at a heating rate of 10°C/h. In this case, the decomposition progress changes in proportion to the heating speed. Changing the heating speed with temperature is the most effective technique for deparaffinization in the air. The heating time from the ambient temperature to 200°C significantly decreases. At a certain temperature, prior to the thermal decomposition, the bond would transfer from a strongly viscous state to a liquid state

Gamma radiation shielding and liquid permeability coefficient of baked and unbaked kaolin powder were experimentally and theoretically investigated. A NaI(Tl) detector was used to measure attenuation properties of the samples. The experimental values for the linear coefficient were validated by theoretical values using WinXCOM software. The results established that unbaked kaolin with density 2.65 g/cm3 yielded highest mass attenuation coefficients of 0.0736 cm2/g, 0.0561 cm2/g and 0.0527 cm2/g for 661.7, 1173.2 and 1332.5 keV respectively and liquid permeability coefficient of 2.33 x 10 -12 m/s. The study concludes that compacted unbaked kaolin be considered a valid alternative for radiation shielding due to its low liquid permeability coefficient for liquid radioactive waste management.

This study presents a flow pump technique usually used for evaluating the permeability of soils, which was, for first time, applied to measure the water permeability of concrete. Additionally, a new easy-to-apply method to determine permeability is proposed, based on a modification of Valenta&rsquo, s formula. In the calculations, the apparent air content of concrete mixes was taken into account. An additional purpose of the conducted research was to determine the influence of a new generation of polycarboxylate superplasticizer and chemically active admixtures on the permeability, compressive strength, and other properties of concrete. The following four types of concrete were tested: concrete without admixtures, concrete with an admixture to increase the compressive strength, concrete with a superplasticizer, and concrete containing two admixtures simultaneously. The results showed that the proposed method allows to obtain reliable measurements within a very short period of time. The obtained results confirmed that new method may be very useful in engineering practice, particularly in terms of the watertightness of hydrotechnical concretes and the properties of the concretes used in bridge construction, underground parts of office buildings, or sealed tanks.

3D multicellular tumor spheroids (MCTSs) have recently emerged as a landmark for cancer research due to their inherent traits that are physiologically relevant to primary tumor microenvironments. A facile approach–laser‐ablated micro U‐wells–has been widely adopted in the past decade. However, the differentiation of microwell uniformities and the construction of arrays have all remained elusive. Herein, an improved laser‐ablated microwell array technique is proposed that can not only achieve arrayed MCTSs with identical sizes but can also perform high‐throughput drug assessments in situ. Three critical laser ablation parameters, including frequency, duty cycle, and pulse number, are investigated to generate microwells flexibly with a range from 170 to 400 μm. The choice of microwells is optimally arranged into an array via precise control of horizontal spacing (d x) and vertical spacing (d y) amenable of cell‐loss‐free culture during cell seeding. Harvested T24, A549 and Huh‐7 MCTSs from the microwell array correspond to approximately 75 to 140 μm in diameter. Anticancer drug screening of cisplatin validated IC50 values in 2D and MCTS conditions are 3.5 versus 9.1 μM (T24), 11.8 versus 277.7 μM (A549) and 33.5 versus 52.8 μM (Huh‐7), and the permeability is measured to range from 0.042 to 0.58 μm min−1., A facile and highly reproducible laser‐ablated micro U‐well with optimal array arrangement is demonstrated. Cell‐loss free formation of multicellular tumor spheroids is performed in 96‐well plates for high‐throughput drug screening of cisplatin. Dose‐response assays are investigated on T24, A549, and Huh‐7 in both 2D and MCTS conditions. The permeability dynamics of each type of MCTS are examined.

Microbial induced calcite precipitation (MICP) has shown great potential to reduce the permeability of fractured rock, but its permeability reduction characteristic, affected by cementing solution concentration and geometric morphology of fractured rock, has not been presented. In this paper, a self-designed device for experimental MICP grouting and seepage performance was used to study the effects of factors including urea and calcium chloride concentration, fracture roughness and aperture on the permeability reduction of MICP on fractured rock. During the experiment, the same total volume of cement solution was injected into each sample with the same injection times. Based on the experimental results, the Darcy permeability coefficient of MICP grouted fractured rock was reduced to 3–5 × 10–5 m/s by four orders of magnitude smaller than that of non-grouted fractured rock. An increase in fracture roughness, urea and calcium chloride concentrations, as well as a decrease of fracture aperture, caused the MICP grouting ratio in fractured rocks to decrease, as well as a decrease of the Darcy permeability coefficient. In addition, the permeability reduction of MICP on fractured rock increased with the decrement of the above four factors. The permeability coefficient of grouted fractured rock and the permeability reduction of MICP were excessively sensitive to urea concentration. Furthermore, the permeability reduction was fitted well by power function. The research results could provide important guidance and reference significance for MICP grouting application in rock engineering.

The high degree of uncertainty and conflicting literature data on the value of the permeability coefficient (also known as the mushy zone constant), which aims to dampen fluid velocities in the mushy zone and suppress them in solid regions, is a critical drawback when using the fixed-grid enthalpy-porosity technique for modelling non-isothermal phase-change processes. In the present study, the sensitivity of numerical predictions to the value of this coefficient was scrutinised. Using finite-volume based numerical simulations of isothermal and non-isothermal melting and solidification problems, the causes of increased sensitivity were identified. It was found that depending on the mushy-zone thickness and the velocity field, the solid-liquid interface morphology and the rate of phase-change are sensitive to the permeability coefficient. It is demonstrated that numerical predictions of an isothermal phase-change problem are independent of the permeability coefficient for sufficiently fine meshes. It is also shown that sensitivity to the choice of permeability coefficient can be assessed by means of an appropriately defined P\'eclet number., Comment: The influence of the mushy-zone constant in simulations of melting and solidification (phase-change materials) using the enthalpy-porosity method

Given the insufficient knowledge on the influence of CFRP strength and water penetration, many building structures are highly vulnerable to recurrent deterioration after repair works. This study was planned to examine the hardened properties and water penetration of concrete wrapped with CFRP, particularly water permeability and water permeability coefficient. A total of 42 cubes with different concrete grades were prepared, casted, cured, wrapped with several CFRP layers, and tested. The concrete compressive strength was improved with upsurge the use of amount of CFRP layers. However, the increment percentage was not remarkable from layer to layer. The concrete with low water permeability reduced the deterioration effects that relate with water permeability, such as corrosion. A comparison exhibited that the permeability coefficient of the water of the wrapped concrete was several times larger than the equivalent permeability coefficient of the water of the control of identical concrete compressive strength. The penetration of wrapped concrete was substantially reduced with the increment within the numbers of CFRP layers. These findings prove that CFRP layers and epoxy play a substantial role as moisture barriers, potentially decreasing steel corrosion and concrete worsening. Therefore, the retrofitting works can ensure the increased sustainability, cost efficiency, and prolonged lifespan of building structures. Keywords: Carbon fiber-reinforced polymer (CFRP), CFRP wrap, Hardened properties, Water penetration

Nuclear magnetic resonance (NMR) technology has been widely used for predicting permeability coefficients of porous medium, such as shales, sandstones, and coals. However, there have been limited studies on the prediction model of clay-quartz mixtures based on NMR technology. In this study, evaporation tests at 40 &deg, C and NMR tests were simultaneously performed on eight clay-quartz mixtures with different mineral compositions. The results show that during the evaporation process, the decay rate of T2 total signal amplitudes was constant at first, and then decreased to 0 after a period of time. Based on the decay rate, the evaporation process was divided into two stages: the constant rate stage and the falling rate stage. Based on the two stages, the T2 cut-offs of eight mixtures were determined. The water in the mixture was divided into two parts by the T2 cut-off: the free water and the bound water. The prediction model of permeability coefficients of clay-quartz mixtures was established based on the Timur-Coates model. In order to simplify the process of predicting the permeability coefficient, fractal analysis was used to develop the relationship between the T2 cut-off and fractal dimension of the T2 spectrum of saturated mixture. A simplified method for predicting permeability coefficients of clay-quartz mixtures based on NMR technology without centrifugal and evaporation experiments was also proposed.

Pervious concrete is considered to be porous concrete because of its pore structure and excellent permeability. In general, larger porosity will increase the permeability coefficient, but will significantly decrease the compressive strength. The effects of water-cement ratio, fiber types, and fiber content on the permeability coefficient, porosity, compressive strength, and flexural strength were investigated. The pore tortuosity of the pervious concrete was determined by volumetric analysis and two-dimensional cross-sectional image analysis. The concept and calculation method of porosity tortuosity were further proposed. Results show that the permeability coefficient of the pervious concrete is the most suitable with a water-cement ratio of 0.30, the water permeability of the pervious concrete is influenced by fiber diameter. The permeability coefficient of pervious concrete with polypropylene thick fiber (PPTF) is greater than that with copper coated steel fiber (CCF) and the polypropylene fiber (PPF). The permeability coefficient is related to tortuosity and porosity, but when porosity is the same, the permeability coefficient may be different. Finally, general relations between the permeability coefficient and porosity tortuosity are constructed.

Soil-bentonite cutoff walls are usually used to contain the contaminants of landfills. The pumpability, permeability, and adsorption capability of the slurry are all crucial to the performance of the cutoff wall. In this study, the effect of polyvinyl alcohol (PVA) was used to improve the performance of bentonite slurry. A series of lab tests were conducted to evaluate the pumpability, permeability, and adsorption capacity with different concentrations of PVA treatment. Results show that the addition of PVA can increase the fluidity and pumpable period of slurry, which facilitates the casting and grouting during construction. The addition of PVA also helps to reduce the permeability coefficient of slurry and improve the adsorption capability which enhances the cutoff performance of the walls.

As the 2 m thick compacted clay liner with permeability coefficient of 1 × 10−7 cm/s is required in the Chinese technical specifications about landfill, the performance of this compacted clay liner was analyzed considering three different adsorption isotherms (convex, straight, and concave). The effects of source concentration, adsorption mode, and waterhead on the breakthrough curve and breakthrough time of Pb2+ were discussed. The results indicate that reducing the concentration of pollution sources is beneficial to prolonging the breakthrough time. With the waterhead of 10 m, the absolute breakthrough time, respectively, increased from 2.77 to 3.7 years (concave type isotherm), from 17.63 to 26.58 years (straight type isotherm), and from 35.43 to 59.6 years (convex type isotherm), as the source concentration decreased from 1000 mg/L to 10 mg/L. The effect of adsorption isotherm type on the performance of the barrier is very obvious: with the waterhead of 10 m, the absolute breakthrough time corresponding to the convex isotherm is more than twice that of the straight adsorption isotherm, and more than 12.8 times that of the concave isotherm. The absolute breakthrough time corresponding to 0.3 m waterhead is more than 4 times that of 10 m, and reducing the waterhead can effectively increase the breakthrough time.

In this paper, the transient pulse test is used to study the permeability and hydromechanical coupling effect of the fractured limestone. The permeability parameters (permeability, β factor of non-Darcy flow, and acceleration coefficient) of non-Darcy flow in fractured limestone are obtained by experimental data. The experimental results show that, in the process of transient seepage test of fractured Maokou limestone, the relationship between hydraulic pressure gradient and seepage velocity does not conform to Darcy’s law but meets Forchimer relationship. The relationship between hydraulic pressure difference and time can be fitted by quartic polynomial. The larger the confining pressure is, the more obvious the non-Darcy seepage effect of fractured rock seepage is. The seepage of rock fracture under high confining pressure is a highly nonlinear time-varying seepage. The permeability coefficient of rock decreases with the increase of volume stress. Under the action of low volume stress, the relationship between permeability coefficient and stress is more sensitive, while under the action of high volume stress, the relationship between permeability coefficient and volume stress is not significant. In the process of volume stress increasing, the β factor of non-Darcy flow appears negative. Under the action of low volume stress, the acceleration coefficient and β factor of non-Darcy flow increase, while under the action of high volume stress, the acceleration coefficient and β factor of non-Darcy flow decrease.

Moisture content is an important factor affecting the geotechnical properties of solidified municipal sludge (MMS). Typical municipal sludge in China was chosen to investigate the effects of initial moisture content (defined as w0) on geotechnical properties of MMS solidified by self-developed CERSM solidifying agent. In addition, the microstructure changes of solidified sludge samples in this study were explored with scanning electron microscopy and mercury intrusion porosimetry. Mechanical experiment results showed that the unconfined compressive strength, cohesion, and internal friction angle of the MMS increased with the decrease in initial moisture content, but the permeability coefficient changed oppositely. The permeability coefficient of solidified sludge samples was between 10−8 and 10−10 cm/s. But after the drying-saturated process, the permeability coefficient of MMS can be increased up to 4 times, mainly due to the formation of a considerable number of microconnected pores and microcracks in the process of drying. The research results are of great significance to the safe disposal and utilization of municipal sewage sludge in China.

In all pavement structures, one or more support layers separate the pavement from the subgrade. In addition to offering structural support, these layers have several important functions, which include: providing a stable and uniform construction platform, facilitating drainage, mitigating pumping of the subgrade fines, and protecting the pavement from the effects of frost heave. Their performance is critical in achieving the desired pavement smoothness, and in extending the service life of the structure. A range of designs, making use of unbound or stabilized aggregates and in some cases geosynthetics, are employed by different agencies to fulfill these functions. This project was motivated by constructability and long term performance concerns with the existing base/subbase design employed by INDOT for concrete pavements, as well as the desire to identify state of the art design solutions that could be applicable to both concrete and asphalt pavements. The primary objectives of the study were to: critically reexamine INDOT’s existing design; perform a preliminary evaluation (based on aggregate compaction, hydraulic conductivity, strength and compatibility properties) of select unbound design options identified in collaboration with the Study Advisory Committee (SAC); explore the potential use of geotextiles as separator; and develop recommendations for base/subbase aggregate laboratory testing and evaluation.

Permeability is one of the most important engineering properties of clayey soil. However, the traditional method for determining the permeability coefficient is time-consuming. To establish a simple and accurate predictive method to obtain the permeability coefficient of artificial clayey soil based on the double cut-off transverse relaxation times (T2 cut-offs) using low-field nuclear magnetic resonance (NMR) technology, eight kinds of artificial clayey soil with different mineralogical compositions were prepared in the laboratory. Evaporation tests at 40°C were carried out on the saturated artificial clayey soil samples in an oven. During the evaporation process, NMR tests were also performed on the artificial clayey soil every hour. The results showed that the evaporation process could be divided into three stages according to different evaporation rates: the constant rate stage (CRS), the falling rate stage (FRS), and the residual stage (RS). The water evaporated in the CRS and FRS was defined as the absolute movable water and the partially movable water, respectively. The water that could not evaporate in the RS was defined as the immovable water. Based on the cumulative signal amplitudes in the T2 spectrum corresponding to different kinds of water, the double T2 cut-offs were defined. On the basis of the double T2 cut-offs and T2 spectrum of the saturated sample, an improved Timur–Coates (TC) model was established. The prediction capability of the improved model was evaluated by finding the determination coefficient (R2), mean absolute error (MAE), and root-mean-square error (RMSE). Compared with the typical TC model, the prediction accuracy of the improved model was much higher. In addition, the relationships between the double T2 cut-offs and fractal dimension (D) of the T2 spectrum of saturated artificial clayey soil were also identified.