Mercury intrusion porosimetry(MIP)is a simple and fast way to obtain the pore distribution of soil and can be used to estimate the soil-water characteristic curve(SWCC).In previous studies,soil was assumed to be a per...Mercury intrusion porosimetry(MIP)is a simple and fast way to obtain the pore distribution of soil and can be used to estimate the soil-water characteristic curve(SWCC).In previous studies,soil was assumed to be a perfect wettability material,and the contact angle(CA)of the soil-water interface was taken as zero in the SWCC prediction method.However,the CA has proved to be much greater than zero even for hydrophilic soils according to some soil wettability experiments,and it has a significant effect on predicting the SWCC.In this research,a method for predicting the SWCC by MIP,which takes the CA as a fitting coefficient,is proposed.The pore size distribution curves are measured by MIP,and the SWCCs of two loess soils are measured by pressure plate and filter paper tests.When the CA is taken as70°and 50°for the wetting and drying process,respectively,the SWCCs predicted by the pore size distribution curves agree well with the measured SWCCs.The predicted suction range of the proposed method is 0-105 k Pa.The consistency of the results suggests that utilizing the MIP test to predict the SWCC with a proper CA is effective for loess.展开更多
It is well-known that a close link exists between soil-water retention curve(SWRC)and pore size distribution(PSD).Theoretically,mercury intrusion porosimetry(MIP)test simulates a soil drying path and the test results ...It is well-known that a close link exists between soil-water retention curve(SWRC)and pore size distribution(PSD).Theoretically,mercury intrusion porosimetry(MIP)test simulates a soil drying path and the test results can be used to deduce the SWRC(termed SWRCMIP).However,SWRCMIP does not include the effect of volume change,compared with the conventional SWRC that is directly determined by suction measurement or suction control techniques.For deformable soils,there is a significant difference between conventional SWRC and SWRCMIP.In this study,drying test was carried out on a reconstituted silty soil,and the volume change,suction,and PSD were measured on samples with different water contents.The change in the deduced SWRCMIP and its relationship with the conventional SWRC were analyzed.The results showed that the volume change of soil is the main reason accounting for the difference between conventional SWRC and SWRCMIP.Based on the test results,a transformation model was then proposed for conventional SWRC and SWRCMIP,for which the soil state with no volume change is taken as a reference.Comparison between the experimental and predicted SWRCs showed that the proposed model can well consider the influence of soil volume change on its water retention property.展开更多
Many popular models have been proposed to study the fractal properties of the pores of porous materials based on mercury intrusion porosimetry(MIP).However,most of these models do not directly apply to the small-micro...Many popular models have been proposed to study the fractal properties of the pores of porous materials based on mercury intrusion porosimetry(MIP).However,most of these models do not directly apply to the small-micro pores of loess,which have a significant impact on the throat pores and tunnels for fluid flow.Therefore,in this study we used a combination of techniques,including routine physical examination,MIP analysis,and scanning electron microscope(SEM)image analysis,to study these small-micro pores and their saturated water permeability properties.The techniques were used to determine whether the fractal dimensions of six MIP fractal models could be used to evaluate the microstructure types and permeability properties of loess.The results showed that the Neimark model is suitable for analysis of small-micro pores.When applied to saturated water permeability,the results from this model satisfied the correlation significance test and were consistent with those from SEM analysis.A high clay content and density cause an increase in the number of small-micro pores,leading to more roughness and heterogeneity of the pore structure,and an increase in the fractal dimensions.This process further leads to a decrease in the content of macro-meso pores and saturated water permeability.Furthermore,we propose new parameters:the*Ellipse and its area ratios(*EAR).These parameters,coupled with 2D-SEM and 3D-MIP fractal dimensions,can effectively and quantitatively be used to evaluate the types of loess microstructures(from typeⅠto typeⅢ)and the saturated water permeability(magnitude from 1×10^(-4)cm/s to 1×10^(-5)cm/s).展开更多
Fallout volcanic deposits of SommaVesuvius(Campania,southern Italy),characterized by the presence of layers with contrasting textural and hydraulic properties,are frequently affected by shallow landslides during rainw...Fallout volcanic deposits of SommaVesuvius(Campania,southern Italy),characterized by the presence of layers with contrasting textural and hydraulic properties,are frequently affected by shallow landslides during rainwater infiltration.The soils of the stratigraphic sequence present intraparticle pores,originated by the gases escaped during magma decompression in the volcanic conduit,thus are characterized by double porosity(i.e.,intraparticle and interparticle pores),which is expected to affect their hydraulic behaviour,and to play a key role in rainwater infiltration through layered deposits.To understand the effect of double porosity on the hydraulic behaviour of the involved soils,controlled experiments have been carried out in an infiltration column.The experimental apparatus is provided with newly designed non-invasive Time Domain Reflectometry(TDR)probes,not buried in the investigated soil layers so as to minimize disturbance to the flow,allowing water content measurement during vertical flow processes.Specifically,transient flow experiments are carried out through reconstituted specimens of black scoriae and grey pumices,both loose pyroclastic granular soils from fallout deposits of Somma-Vesuvius,featuring double porosity with different pore size distributions,that were estimated by X-ray tomography and Mercury Intrusion Porosimetry.The experimental results highlight the effects of the double porosity and clearly indicate the different behaviour of the two soils during wetting and drying processes,mainly related to the different dimensions of intraparticle pores.展开更多
Gaomiaozi(GMZ)bentonite is a potential buffer/backfill material for a deep geological disposal of highlevel radioactive waste.It has a wide pore size distribution(PSD)with sizes ranging from several nanometers to more...Gaomiaozi(GMZ)bentonite is a potential buffer/backfill material for a deep geological disposal of highlevel radioactive waste.It has a wide pore size distribution(PSD)with sizes ranging from several nanometers to more than one hundred microns.Thus,properly characterizing the pore structures of GMZ bentonite is a challenging issue.In this study,pressure-controlled porosimetry(PCP),ratecontrolled porosimetry(RCP),and scanning electron microscopy(SEM)were used to investigate the PSD of GMZ bentonite,The results indicate that each method has its limitation,and a combined use of PCP and RCP is suitable to obtain the full-scale PSD of GMZ bentonite.Moreover,we also compared the full-scale PSD with nuclear magnetic resonance(NMR)result.It is found that there is no significant difference in the range of PSD characterization between NMR and mercury intrusion method(PCP and RCP).However,in a ce rtain range,the detection accuracy of NMR is higher than that of mercury injection method.Finally,permeability prediction based on PCP and SEM data was conducted,and both of the two methods were found to be able to predict the permeability.The combined method is effective to obtain the full-scale PSD of GMZ bentonite,which is the key to estimation of the sealing ability of bentonite buffer.展开更多
The effects of mixing time and curing temperature on the uniaxial compressive strength(UCS) and microstructure of cemented hydraulic fill(CHF) and sodium silicate-fortified backfill(Gelfill) were investigated in the l...The effects of mixing time and curing temperature on the uniaxial compressive strength(UCS) and microstructure of cemented hydraulic fill(CHF) and sodium silicate-fortified backfill(Gelfill) were investigated in the laboratory.A series of CHF and Gelfill samples was mixed for time periods ranging from 5 min to 60 min and cured at temperatures ranging from 5 C to 50 C for 7 d.14 d or 28 d.Increasing the mixing time negatively influenced the UCS of Gelfill samples,but did not have a detectable effect on CHF samples.The curing temperature had a strong positive impact on the UCSs of both Gelfill and CHF.An elevated temperature caused rapid UCS development over the first 14 d of curing.Mercury intrusion porosimetry(MIP) indicated that the pore size distribution and total porosity of Gelfill were altered by curing temperature.展开更多
The influence of salts on concrete durability,pore structure of cement pastes with inorganic salts,including CaCl2,NaCl,Na2SO4,NaNO2,Ca(NO3)2 and Ca(NO2)2,was studied through mercury intrusion porosimetry (MIP),and hy...The influence of salts on concrete durability,pore structure of cement pastes with inorganic salts,including CaCl2,NaCl,Na2SO4,NaNO2,Ca(NO3)2 and Ca(NO2)2,was studied through mercury intrusion porosimetry (MIP),and hydration degree of each paste was also tested.The results show that porosity of the paste with inorganic salt cured for 3 d or 28 d was related with its hydration degree.For the pore size distribution,the pores smaller than 50 nm in paste with salts cured for 3 d increased;the amount of pores larger than 100 nm increased because of the addition of Ca (NO3)2 at 3 d,but these coarse pores turned into fine pores and reduced significantly at 28 d;coarse pores lager than 1000 nm in cement pastes containing NaCl and Na2SO4 increased.展开更多
The addition of cement for stabilization of expansive soils is one of the most commonly used methods.As with every calcium-based stabilizer,the time delay between the physical mixing of the stabilizer and compaction p...The addition of cement for stabilization of expansive soils is one of the most commonly used methods.As with every calcium-based stabilizer,the time delay between the physical mixing of the stabilizer and compaction plays an important role in achieving the desired results after stabilization.However,a clear insight on the determination of optimum time delay for achieving the maximum desired compaction properties of cement-stabilized soils is yet to be established.Furthermore,the recent studies highlighted the use of sulfate to mitigate the negative effect of compaction time delay.The only drawback with the use of sulfate along with calcium-based stabilizers is the formation of ettringite,which deteriorates the stabilized soil matrix.In view of this,the present study is aimed at using the sulfate resistant cement(SRC)as a stabilizer along with the controlled addition of sulfate solutions to mitigate the negative effect of compaction time delay in stabilizing the expansive soil.To bring out the above effects,three periods of time delays(0 h,6 h and 24 h)and three sulfate concentrations of 5000 parts per million(ppm),10,000 ppm and 20,000 ppm were adopted.The experimental results showed that the delay in compaction resulted in the formation of clogs and reduction of strength of SRC-stabilized expansive soil.Upon sulfate addition to SRC-stabilized expansive soil,the formation clogs was not curtailed and resulted in the formation of ettringite clusters.These formations were captured with the help of scanning electron microscope(SEM)images and validated with electron dispersive X-ray spectroscopy(EDAX)analysis.Further,an attempt is also made to explain the mechanism of density and strength reduction with the aid of physico-chemical properties and mercury intrusion porosimetry(MIP)studies.展开更多
The aim of this study is to show how fractal analysis can be effectively used to characterize the texture of porous solids. The materials under study were carbon papers, the backing material of the gas diffusion layer...The aim of this study is to show how fractal analysis can be effectively used to characterize the texture of porous solids. The materials under study were carbon papers, the backing material of the gas diffusion layer (GDL) in Proton Exchange Membrane Fuel Cell (PEMFC). The fractal dimensions were calculated by analyzing data from mercury porosimetry. The polytotrafluoroethylene (PTFE) treated carbon paper shows a significantly high fractal dimension value than pure sample, and the high fractal dimension signifies that the physical complexity of the pore surface is enhanced. The fractal dimension can be used as a valid parameter to monitor the textural evolution of the samples as the treatment progresses, as this behaves in a similar way to other textural parameters. The use of fractal analysis in conjunction with the results of classical characterization methods leads to a better understanding of textural modifications in the processing of materials.展开更多
Tamusu mudstone formation, located in the Alxa area in western Inner Mongolia, is considered a potential host formation for high-level radioactive waste(HLW) underground disposal in China. In this study, complementary...Tamusu mudstone formation, located in the Alxa area in western Inner Mongolia, is considered a potential host formation for high-level radioactive waste(HLW) underground disposal in China. In this study, complementary analyses with X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), mercury intrusion porosimetry(MIP), and N_(2) physisorption isotherm were conducted on the Tamusu mudstone to characterize its physical characteristics and microstructural features, such as mineral compositions and pore structure. Several minerals, including carbonates, feldspar, clays and analcime, were identified in Tamusu mudstone by XRD. Images from FE-SEM show that pores in the Tamusu mudstone were dominantly on nanometer scale and generally located within their mineral matrix or at the interface with non-porous minerals. The combination of the MIP and N_2 physisorption curves indicated that the Tamusu mudstone has diverse pore sizes, a porosity varying from 2.34% to 2.84%, and a total pore volume in the range of 0.0065—0.0222 cm^(3)/g with the average pore diameter ranging from 9.6 nm to 19.23 nm. The specific surface area measured by MIP(2.572—5.861 m^(2)/g) was generally higher than that by N_(2) physisorption(1.29—3.04 m^(2)/g), due to the pore network effect, pore shape(e.g. ink-bottle shape), or technique limits. The results related to pore information can be applied as an input in the future to model single-or multi-phase fluid flow and the transport of radionuclides in porous geomedium by migration and diffusion.展开更多
In this paper,mercury intrusion porosimetry(MIP)is used to test the pore structure of non-dispersible underwater concrete so as to study the influence of pouring and curing environment,age and slag powder on the pore ...In this paper,mercury intrusion porosimetry(MIP)is used to test the pore structure of non-dispersible underwater concrete so as to study the influence of pouring and curing environment,age and slag powder on the pore characteristics of concrete,analyze the pore characteristics,porosity and pore distribution of concrete in different hydration stages,and reveal the relationship between pore structure and permeability of concrete.The results show that the pore-size distribution of concrete in fresh water condition is better than that in sulfate environment and mixed salt environment,and therefore,sulfate as well as mixed salt are not conducive to the development of pore structure of non-dispersible underwater concrete;chlorine salt has little effect on the pore structure of nondispersible underwater concrete;under the three conditions of sulfate,chlorine and mixed salt,the porosity of concrete mixed with slag powder is lower than that of concrete without slag powder.The results indicate that the addition of slag powder can ameliorate the pore size distribution of non-dispersed underwater concrete,reduce the porosity,and make the concrete structure more compact,which is beneficial to improve the permeability resistance of concrete at the macro level.展开更多
The deterioration of concrete over time is the result of various mechanical, physical, chemical and biological processes, with the corrosion of reinforcement being the most serious problem of durability of reinforced ...The deterioration of concrete over time is the result of various mechanical, physical, chemical and biological processes, with the corrosion of reinforcement being the most serious problem of durability of reinforced concrete structures. Over the last 50 years, a tremendous effort has been spent by the international scientific community with laboratory research and experimental field studies in order to increase the resistance of concrete over corrosion. This paper presents an experimental study of the corrosion behavior of 5 different concrete mix designs. The compositions were developed as per the latest concrete regulations and International Standards which are as follows: conventional concrete C30/37, conventional concrete with corrosion inhibitor as an additive, conventional concrete with surface spray sealant, fine aggregate concrete and self-compacting concrete. Their behavior against corrosion was determined via the following tests: water absorption test, water permeability test, mercury intrusion porosimetry, rapid chloride penetration test (RCPT), and accelerated carbonation test. The experimental results showed that the corrosion systems examined in the study provide anti-corrosion protection on steel rebars against corrosion comparing with the reference group. Also, an inversely proportional relationship of the water/cement ratio of a composition with its corrosion behavior was observed. Smaller w/c values (0.4 instead of 0.5) lead to better anti-corrosion resistance. In addition, an analogous relationship between the cement content of a composition and its corrosion behavior was observed.展开更多
The aim of this study is to examine the performance of nano additives in two different sets of mortar specimens armed with reinforcing steel rebars. In particular, three sets of reinforced concrete cylinders with addi...The aim of this study is to examine the performance of nano additives in two different sets of mortar specimens armed with reinforcing steel rebars. In particular, three sets of reinforced concrete cylinders with additives of 0.1% wt of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been exposed to a solution of 3.5% NaCl, and further examined for the impact of nano-modification on corrosion performance. The anti-corrosive performance of these additives was investigated through linear polarization technique (LPR), mass loss and mercury porosimetry technique (MIP). From the investigation results, it is found that the addition of CNTs/CNFs causes lower steel corrosion, whereas the pore structure of concrete with CNTs/CNFs can significantly reduce the mass loss rate and the relative permeability.展开更多
Objectives: To improve the aqueous solubility and dissolution of fexofenadine HCl, an attempt was made to prepare its fast dissolving tablets by lyophilization technique. Methods: For the preparation of lyophilized ta...Objectives: To improve the aqueous solubility and dissolution of fexofenadine HCl, an attempt was made to prepare its fast dissolving tablets by lyophilization technique. Methods: For the preparation of lyophilized tablets (F1-F32), the drug was dispersed in a hydrated solution of water-soluble polymers (gelatin/maltodextrin/acacia) containing glycine and mannitol. The blend was pelted down into the patches of a blister pack, frozen down and then lyophilized. Different characterization parameters viz. differential scanning calorimetry, hardness, weight variation, X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury porosimetry, solubility, wetting time and water absorption ratio, lyophilization tablet index, drug content, in vitro dissolution and stability were evaluated. Key findings: Tablets (F32) containing acacia were found to have fast disintegration and relatively higher mechanical strength with improved drug solubility. X-ray diffractogram and scanning electron micrograph indicated decrease in crystallinity of drug and a good porous structure property for prepared tablet, respectively. Dissolution study showed complete drug released within 5 min. Moreover, tablets (F32) were found to be stable for one month at 25 ± 2 °C/60 ± 5% relative humidity.展开更多
A fractal characterization approach was proposed to research pore microstructure evolution in car- bon/carbon (C/C) composites during the chemical vapor infiltration process. The data obtained from mercury porosimetry...A fractal characterization approach was proposed to research pore microstructure evolution in car- bon/carbon (C/C) composites during the chemical vapor infiltration process. The data obtained from mercury porosimetry determinations were analyzed using the sponge fractal model and the thermo- dynamics relation fractal model, respectively. The fractal dimensions of C/C composites at different densification stages were evaluated. The pore microstructure evolution with densification time was studied by fractal dimension analysis. The results showed that C/C composites belong to porous frac- tal structure. The fractal dimensions increase on the whole with decreasing porosity as the densifica- tion proceeds. The fractal dimensions are influenced by the texture of pyrocarbon and decrease with increasing anisotropy from isotropic pyrocarbon to high textural one. Both the complicacy of pore structure and the textural morphology of pyrocarbon can be represented simultaneously by the fractal dimension. The pore evolution of C/C composites in the densification process can be monitored using fractal dimension.展开更多
During the past two years the shale gas exploration in Southern Sichuan basin received some exciting achievements.Data of a new appraisal well showed that the gas producrtions of vertical well and horizontal well are^...During the past two years the shale gas exploration in Southern Sichuan basin received some exciting achievements.Data of a new appraisal well showed that the gas producrtions of vertical well and horizontal well are^1.5×104 m3/day/well(with maximum^3.5×104 m3/day/well)and^12.5×104 m3/day/well(with maximum^40×104 m3/day/well),respectively,indicating a good gas potential in this area.Eight core samples from the reservoir were investigated by using a carbon sulfur analyzer,microphotometry,x-ray diffractometry,field-emission scanning electron microscopy(FE-SEM),mercury injection porosimetry(MIP),and low-pressure nitrogen adsorption to obtain a better understanding of the reservoir characteristics of the Upper OrdovicianeLower Silurian organic-rich shale.Results show that the total organic carbon(TOC)content ranges from 0.5%to 5.9%,whereas the equivalent vitrinite reflectance(VRr)is between 2.8%and 3.0%.Pores in the studied samples were observed in three modes of occurrence,namely,interparticle pores,intraparticle pores,and intraparticle organic pores.The total porosity(P)ranges from 1.6%to 5.3%,and MIP data sets suggest that pores with throats larger than 20 nm contribute little to the pore volume.Low-pressure N2 adsorption isotherms indicate that the total specific surface area(SBET)ranges from 9.6 m2/g to 18.9 m2/g,and the pore volume(V)ranges from 0.011 cm3/g to 0.020 cm3/g.The plot of dV/dW versus W shows that the fine mesopores(pore size(BJH)<4 nm)mainly contribute to the pore volume.The P,SBET,and V show a good positive correlation with TOC and a weak positive correlation with the total clay mineral content,thus indicating that the nanopores are mainly generated by the decomposition of organic matter.The reservoir characteristics of the Upper OrdovicianeLower Silurian organic-rich shale are comparable with commercial shale gas plays in North America.The sample gas contents with TOC>2%are more than 3.0 m3/ton.The observation can be a good reference for the future exploration and evaluation of reservoir in this area.展开更多
Rice husk ask (RHA) is not a ultra-fine material as silica fume (SF),but possesses a very high specific surface area because of its porous structure. With the similar chemical composition of RHA and SF,the activity of...Rice husk ask (RHA) is not a ultra-fine material as silica fume (SF),but possesses a very high specific surface area because of its porous structure. With the similar chemical composition of RHA and SF,the activity of RHA,therefore,is different from that of SF. The objective of this work is to study the hydration and the microstructure of Portland cement blended with RHA in comparison with SF. The test results show that SF refined the pore structure of cement paste better than RHA. However,the effect of RHA on cement hydration is more pronouned than that of SF for the mixture with low water to binder ratio.展开更多
Special deposition environment makes organic-rich shales in Ningwu Basin have typeⅢkerogen and high kaolinite content,which are also famous as the kaolinite ore.The specific composition of shale in Ningwu Basin can c...Special deposition environment makes organic-rich shales in Ningwu Basin have typeⅢkerogen and high kaolinite content,which are also famous as the kaolinite ore.The specific composition of shale in Ningwu Basin can change the pore structure and thus,influence the shale gas storage and transport.This study focuses on the pore structure and its evolution in shales with typeⅢkerogen and high kaolinite content.In this study,14 Upper Paleozoic shale samples,whose total organic matter contents(TOC)range from 0.39%to 5.91%and maturities(represented by vitrinite reflectance)range from 1.22%to 2.06%,were collected.Scanning electron microscopy(SEM),high-pressure mercury injection,and low-tempera-ture N2 adsorption experiments were used to analyze pore structure of these shale samples.Results show that when the TOC content is smaller than 1.4%,the kaolinite content decreases linearly and quartz content increases linearly with increasing the TOC content.In contrast,when TOC content is>1.4%,the clay content tends to increase with increasing TOC.Based on the SEM images,organic pores and clay pores were identified in shale samples with typeⅢkerogen and high kaolinite content.During the maturation process,the kaolinite content decreases and illite content increases with increasing the vitrinite reflectance.At the same time,the pore volume and pore surface area both increase with increasing the vitrinite reflectance,and it may be because more organic pores and clay pores in the illite were generated during the maturation process.This study can provide further understandings of shale gas accumulation in shale with typeⅢkerogen and high kaolinite content.展开更多
基金supported by the National Natural Science Foundation of China(Program No.41790442 and No.41772278)。
文摘Mercury intrusion porosimetry(MIP)is a simple and fast way to obtain the pore distribution of soil and can be used to estimate the soil-water characteristic curve(SWCC).In previous studies,soil was assumed to be a perfect wettability material,and the contact angle(CA)of the soil-water interface was taken as zero in the SWCC prediction method.However,the CA has proved to be much greater than zero even for hydrophilic soils according to some soil wettability experiments,and it has a significant effect on predicting the SWCC.In this research,a method for predicting the SWCC by MIP,which takes the CA as a fitting coefficient,is proposed.The pore size distribution curves are measured by MIP,and the SWCCs of two loess soils are measured by pressure plate and filter paper tests.When the CA is taken as70°and 50°for the wetting and drying process,respectively,the SWCCs predicted by the pore size distribution curves agree well with the measured SWCCs.The predicted suction range of the proposed method is 0-105 k Pa.The consistency of the results suggests that utilizing the MIP test to predict the SWCC with a proper CA is effective for loess.
基金Shanghai Key Innovative Team of Cultural Heritage Conservation and the financial support from the National Sciences Foundation of China(Grant Nos.41977214 and 41572284)the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.Z013008)。
文摘It is well-known that a close link exists between soil-water retention curve(SWRC)and pore size distribution(PSD).Theoretically,mercury intrusion porosimetry(MIP)test simulates a soil drying path and the test results can be used to deduce the SWRC(termed SWRCMIP).However,SWRCMIP does not include the effect of volume change,compared with the conventional SWRC that is directly determined by suction measurement or suction control techniques.For deformable soils,there is a significant difference between conventional SWRC and SWRCMIP.In this study,drying test was carried out on a reconstituted silty soil,and the volume change,suction,and PSD were measured on samples with different water contents.The change in the deduced SWRCMIP and its relationship with the conventional SWRC were analyzed.The results showed that the volume change of soil is the main reason accounting for the difference between conventional SWRC and SWRCMIP.Based on the test results,a transformation model was then proposed for conventional SWRC and SWRCMIP,for which the soil state with no volume change is taken as a reference.Comparison between the experimental and predicted SWRCs showed that the proposed model can well consider the influence of soil volume change on its water retention property.
基金supported by the China Geological Survey Project(No.DD20190642)the Shaanxi Provincial Key Research Program of China(No.2019ZDLSF07-07-02)。
文摘Many popular models have been proposed to study the fractal properties of the pores of porous materials based on mercury intrusion porosimetry(MIP).However,most of these models do not directly apply to the small-micro pores of loess,which have a significant impact on the throat pores and tunnels for fluid flow.Therefore,in this study we used a combination of techniques,including routine physical examination,MIP analysis,and scanning electron microscope(SEM)image analysis,to study these small-micro pores and their saturated water permeability properties.The techniques were used to determine whether the fractal dimensions of six MIP fractal models could be used to evaluate the microstructure types and permeability properties of loess.The results showed that the Neimark model is suitable for analysis of small-micro pores.When applied to saturated water permeability,the results from this model satisfied the correlation significance test and were consistent with those from SEM analysis.A high clay content and density cause an increase in the number of small-micro pores,leading to more roughness and heterogeneity of the pore structure,and an increase in the fractal dimensions.This process further leads to a decrease in the content of macro-meso pores and saturated water permeability.Furthermore,we propose new parameters:the*Ellipse and its area ratios(*EAR).These parameters,coupled with 2D-SEM and 3D-MIP fractal dimensions,can effectively and quantitatively be used to evaluate the types of loess microstructures(from typeⅠto typeⅢ)and the saturated water permeability(magnitude from 1×10^(-4)cm/s to 1×10^(-5)cm/s).
文摘Fallout volcanic deposits of SommaVesuvius(Campania,southern Italy),characterized by the presence of layers with contrasting textural and hydraulic properties,are frequently affected by shallow landslides during rainwater infiltration.The soils of the stratigraphic sequence present intraparticle pores,originated by the gases escaped during magma decompression in the volcanic conduit,thus are characterized by double porosity(i.e.,intraparticle and interparticle pores),which is expected to affect their hydraulic behaviour,and to play a key role in rainwater infiltration through layered deposits.To understand the effect of double porosity on the hydraulic behaviour of the involved soils,controlled experiments have been carried out in an infiltration column.The experimental apparatus is provided with newly designed non-invasive Time Domain Reflectometry(TDR)probes,not buried in the investigated soil layers so as to minimize disturbance to the flow,allowing water content measurement during vertical flow processes.Specifically,transient flow experiments are carried out through reconstituted specimens of black scoriae and grey pumices,both loose pyroclastic granular soils from fallout deposits of Somma-Vesuvius,featuring double porosity with different pore size distributions,that were estimated by X-ray tomography and Mercury Intrusion Porosimetry.The experimental results highlight the effects of the double porosity and clearly indicate the different behaviour of the two soils during wetting and drying processes,mainly related to the different dimensions of intraparticle pores.
基金support of the National Natural Science Foundation of China(Grant Nos.51809263)the Open Fund of Key Laboratory of Deep Earth Science and Engineering(Sichuan University)(Grant Nos.DESE201906 and DESE201907)。
文摘Gaomiaozi(GMZ)bentonite is a potential buffer/backfill material for a deep geological disposal of highlevel radioactive waste.It has a wide pore size distribution(PSD)with sizes ranging from several nanometers to more than one hundred microns.Thus,properly characterizing the pore structures of GMZ bentonite is a challenging issue.In this study,pressure-controlled porosimetry(PCP),ratecontrolled porosimetry(RCP),and scanning electron microscopy(SEM)were used to investigate the PSD of GMZ bentonite,The results indicate that each method has its limitation,and a combined use of PCP and RCP is suitable to obtain the full-scale PSD of GMZ bentonite.Moreover,we also compared the full-scale PSD with nuclear magnetic resonance(NMR)result.It is found that there is no significant difference in the range of PSD characterization between NMR and mercury intrusion method(PCP and RCP).However,in a ce rtain range,the detection accuracy of NMR is higher than that of mercury injection method.Finally,permeability prediction based on PCP and SEM data was conducted,and both of the two methods were found to be able to predict the permeability.The combined method is effective to obtain the full-scale PSD of GMZ bentonite,which is the key to estimation of the sealing ability of bentonite buffer.
基金the financial support given by Natural Sciences and Engineering Research Council of Canada(NSERC)and Valesupport of National Silicate Inc.
文摘The effects of mixing time and curing temperature on the uniaxial compressive strength(UCS) and microstructure of cemented hydraulic fill(CHF) and sodium silicate-fortified backfill(Gelfill) were investigated in the laboratory.A series of CHF and Gelfill samples was mixed for time periods ranging from 5 min to 60 min and cured at temperatures ranging from 5 C to 50 C for 7 d.14 d or 28 d.Increasing the mixing time negatively influenced the UCS of Gelfill samples,but did not have a detectable effect on CHF samples.The curing temperature had a strong positive impact on the UCSs of both Gelfill and CHF.An elevated temperature caused rapid UCS development over the first 14 d of curing.Mercury intrusion porosimetry(MIP) indicated that the pore size distribution and total porosity of Gelfill were altered by curing temperature.
文摘The influence of salts on concrete durability,pore structure of cement pastes with inorganic salts,including CaCl2,NaCl,Na2SO4,NaNO2,Ca(NO3)2 and Ca(NO2)2,was studied through mercury intrusion porosimetry (MIP),and hydration degree of each paste was also tested.The results show that porosity of the paste with inorganic salt cured for 3 d or 28 d was related with its hydration degree.For the pore size distribution,the pores smaller than 50 nm in paste with salts cured for 3 d increased;the amount of pores larger than 100 nm increased because of the addition of Ca (NO3)2 at 3 d,but these coarse pores turned into fine pores and reduced significantly at 28 d;coarse pores lager than 1000 nm in cement pastes containing NaCl and Na2SO4 increased.
文摘The addition of cement for stabilization of expansive soils is one of the most commonly used methods.As with every calcium-based stabilizer,the time delay between the physical mixing of the stabilizer and compaction plays an important role in achieving the desired results after stabilization.However,a clear insight on the determination of optimum time delay for achieving the maximum desired compaction properties of cement-stabilized soils is yet to be established.Furthermore,the recent studies highlighted the use of sulfate to mitigate the negative effect of compaction time delay.The only drawback with the use of sulfate along with calcium-based stabilizers is the formation of ettringite,which deteriorates the stabilized soil matrix.In view of this,the present study is aimed at using the sulfate resistant cement(SRC)as a stabilizer along with the controlled addition of sulfate solutions to mitigate the negative effect of compaction time delay in stabilizing the expansive soil.To bring out the above effects,three periods of time delays(0 h,6 h and 24 h)and three sulfate concentrations of 5000 parts per million(ppm),10,000 ppm and 20,000 ppm were adopted.The experimental results showed that the delay in compaction resulted in the formation of clogs and reduction of strength of SRC-stabilized expansive soil.Upon sulfate addition to SRC-stabilized expansive soil,the formation clogs was not curtailed and resulted in the formation of ettringite clusters.These formations were captured with the help of scanning electron microscope(SEM)images and validated with electron dispersive X-ray spectroscopy(EDAX)analysis.Further,an attempt is also made to explain the mechanism of density and strength reduction with the aid of physico-chemical properties and mercury intrusion porosimetry(MIP)studies.
基金Funded by the Natural Science Foundation of Hubei ( No.2003ABA088) and the Special Scientific Research Foundation forCollege Doctor Subjects from Ministry of Education of China (No.20030497012)
文摘The aim of this study is to show how fractal analysis can be effectively used to characterize the texture of porous solids. The materials under study were carbon papers, the backing material of the gas diffusion layer (GDL) in Proton Exchange Membrane Fuel Cell (PEMFC). The fractal dimensions were calculated by analyzing data from mercury porosimetry. The polytotrafluoroethylene (PTFE) treated carbon paper shows a significantly high fractal dimension value than pure sample, and the high fractal dimension signifies that the physical complexity of the pore surface is enhanced. The fractal dimension can be used as a valid parameter to monitor the textural evolution of the samples as the treatment progresses, as this behaves in a similar way to other textural parameters. The use of fractal analysis in conjunction with the results of classical characterization methods leads to a better understanding of textural modifications in the processing of materials.
基金financial support of the National Natural Science Foundation of China (Grant Nos.51979266,51879258 and 51991392)。
文摘Tamusu mudstone formation, located in the Alxa area in western Inner Mongolia, is considered a potential host formation for high-level radioactive waste(HLW) underground disposal in China. In this study, complementary analyses with X-ray diffraction(XRD), field emission scanning electron microscopy(FE-SEM), mercury intrusion porosimetry(MIP), and N_(2) physisorption isotherm were conducted on the Tamusu mudstone to characterize its physical characteristics and microstructural features, such as mineral compositions and pore structure. Several minerals, including carbonates, feldspar, clays and analcime, were identified in Tamusu mudstone by XRD. Images from FE-SEM show that pores in the Tamusu mudstone were dominantly on nanometer scale and generally located within their mineral matrix or at the interface with non-porous minerals. The combination of the MIP and N_2 physisorption curves indicated that the Tamusu mudstone has diverse pore sizes, a porosity varying from 2.34% to 2.84%, and a total pore volume in the range of 0.0065—0.0222 cm^(3)/g with the average pore diameter ranging from 9.6 nm to 19.23 nm. The specific surface area measured by MIP(2.572—5.861 m^(2)/g) was generally higher than that by N_(2) physisorption(1.29—3.04 m^(2)/g), due to the pore network effect, pore shape(e.g. ink-bottle shape), or technique limits. The results related to pore information can be applied as an input in the future to model single-or multi-phase fluid flow and the transport of radionuclides in porous geomedium by migration and diffusion.
基金This work is supported by the National Natural Science Foundation of China(51878116 and 51902270)Liaoning Province Key Project of Research and Development Plan(2020JH2/10100016)+1 种基金Dalian Science and Technology Innovation Fund Project(2020JJ26SN060)the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basins(China Institute of Water Resources and Hydropower Research),Grant No.IWHR-SKL-201910.
文摘In this paper,mercury intrusion porosimetry(MIP)is used to test the pore structure of non-dispersible underwater concrete so as to study the influence of pouring and curing environment,age and slag powder on the pore characteristics of concrete,analyze the pore characteristics,porosity and pore distribution of concrete in different hydration stages,and reveal the relationship between pore structure and permeability of concrete.The results show that the pore-size distribution of concrete in fresh water condition is better than that in sulfate environment and mixed salt environment,and therefore,sulfate as well as mixed salt are not conducive to the development of pore structure of non-dispersible underwater concrete;chlorine salt has little effect on the pore structure of nondispersible underwater concrete;under the three conditions of sulfate,chlorine and mixed salt,the porosity of concrete mixed with slag powder is lower than that of concrete without slag powder.The results indicate that the addition of slag powder can ameliorate the pore size distribution of non-dispersed underwater concrete,reduce the porosity,and make the concrete structure more compact,which is beneficial to improve the permeability resistance of concrete at the macro level.
文摘The deterioration of concrete over time is the result of various mechanical, physical, chemical and biological processes, with the corrosion of reinforcement being the most serious problem of durability of reinforced concrete structures. Over the last 50 years, a tremendous effort has been spent by the international scientific community with laboratory research and experimental field studies in order to increase the resistance of concrete over corrosion. This paper presents an experimental study of the corrosion behavior of 5 different concrete mix designs. The compositions were developed as per the latest concrete regulations and International Standards which are as follows: conventional concrete C30/37, conventional concrete with corrosion inhibitor as an additive, conventional concrete with surface spray sealant, fine aggregate concrete and self-compacting concrete. Their behavior against corrosion was determined via the following tests: water absorption test, water permeability test, mercury intrusion porosimetry, rapid chloride penetration test (RCPT), and accelerated carbonation test. The experimental results showed that the corrosion systems examined in the study provide anti-corrosion protection on steel rebars against corrosion comparing with the reference group. Also, an inversely proportional relationship of the water/cement ratio of a composition with its corrosion behavior was observed. Smaller w/c values (0.4 instead of 0.5) lead to better anti-corrosion resistance. In addition, an analogous relationship between the cement content of a composition and its corrosion behavior was observed.
文摘The aim of this study is to examine the performance of nano additives in two different sets of mortar specimens armed with reinforcing steel rebars. In particular, three sets of reinforced concrete cylinders with additives of 0.1% wt of carbon nanotubes (CNTs) and carbon nanofibers (CNFs) have been exposed to a solution of 3.5% NaCl, and further examined for the impact of nano-modification on corrosion performance. The anti-corrosive performance of these additives was investigated through linear polarization technique (LPR), mass loss and mercury porosimetry technique (MIP). From the investigation results, it is found that the addition of CNTs/CNFs causes lower steel corrosion, whereas the pore structure of concrete with CNTs/CNFs can significantly reduce the mass loss rate and the relative permeability.
文摘Objectives: To improve the aqueous solubility and dissolution of fexofenadine HCl, an attempt was made to prepare its fast dissolving tablets by lyophilization technique. Methods: For the preparation of lyophilized tablets (F1-F32), the drug was dispersed in a hydrated solution of water-soluble polymers (gelatin/maltodextrin/acacia) containing glycine and mannitol. The blend was pelted down into the patches of a blister pack, frozen down and then lyophilized. Different characterization parameters viz. differential scanning calorimetry, hardness, weight variation, X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury porosimetry, solubility, wetting time and water absorption ratio, lyophilization tablet index, drug content, in vitro dissolution and stability were evaluated. Key findings: Tablets (F32) containing acacia were found to have fast disintegration and relatively higher mechanical strength with improved drug solubility. X-ray diffractogram and scanning electron micrograph indicated decrease in crystallinity of drug and a good porous structure property for prepared tablet, respectively. Dissolution study showed complete drug released within 5 min. Moreover, tablets (F32) were found to be stable for one month at 25 ± 2 °C/60 ± 5% relative humidity.
基金Supported by the National Natural Science Foundation of China (Grant No. 50742008)
文摘A fractal characterization approach was proposed to research pore microstructure evolution in car- bon/carbon (C/C) composites during the chemical vapor infiltration process. The data obtained from mercury porosimetry determinations were analyzed using the sponge fractal model and the thermo- dynamics relation fractal model, respectively. The fractal dimensions of C/C composites at different densification stages were evaluated. The pore microstructure evolution with densification time was studied by fractal dimension analysis. The results showed that C/C composites belong to porous frac- tal structure. The fractal dimensions increase on the whole with decreasing porosity as the densifica- tion proceeds. The fractal dimensions are influenced by the texture of pyrocarbon and decrease with increasing anisotropy from isotropic pyrocarbon to high textural one. Both the complicacy of pore structure and the textural morphology of pyrocarbon can be represented simultaneously by the fractal dimension. The pore evolution of C/C composites in the densification process can be monitored using fractal dimension.
基金The authors are grateful to Lei Xie,Xiaowei Yang,Bing Shu and Yanni Ma,for their help in sampling and field work.This study was supported by the National Natural Science Foundation of China(Grant No.41302123)the Doctoral Program of Higher Education(Specialized Research Fund)of China(Grant No.20125121130001)the Science Foundation of Education Department of Sichuan Province(Grant No.13ZB0190).
文摘During the past two years the shale gas exploration in Southern Sichuan basin received some exciting achievements.Data of a new appraisal well showed that the gas producrtions of vertical well and horizontal well are^1.5×104 m3/day/well(with maximum^3.5×104 m3/day/well)and^12.5×104 m3/day/well(with maximum^40×104 m3/day/well),respectively,indicating a good gas potential in this area.Eight core samples from the reservoir were investigated by using a carbon sulfur analyzer,microphotometry,x-ray diffractometry,field-emission scanning electron microscopy(FE-SEM),mercury injection porosimetry(MIP),and low-pressure nitrogen adsorption to obtain a better understanding of the reservoir characteristics of the Upper OrdovicianeLower Silurian organic-rich shale.Results show that the total organic carbon(TOC)content ranges from 0.5%to 5.9%,whereas the equivalent vitrinite reflectance(VRr)is between 2.8%and 3.0%.Pores in the studied samples were observed in three modes of occurrence,namely,interparticle pores,intraparticle pores,and intraparticle organic pores.The total porosity(P)ranges from 1.6%to 5.3%,and MIP data sets suggest that pores with throats larger than 20 nm contribute little to the pore volume.Low-pressure N2 adsorption isotherms indicate that the total specific surface area(SBET)ranges from 9.6 m2/g to 18.9 m2/g,and the pore volume(V)ranges from 0.011 cm3/g to 0.020 cm3/g.The plot of dV/dW versus W shows that the fine mesopores(pore size(BJH)<4 nm)mainly contribute to the pore volume.The P,SBET,and V show a good positive correlation with TOC and a weak positive correlation with the total clay mineral content,thus indicating that the nanopores are mainly generated by the decomposition of organic matter.The reservoir characteristics of the Upper OrdovicianeLower Silurian organic-rich shale are comparable with commercial shale gas plays in North America.The sample gas contents with TOC>2%are more than 3.0 m3/ton.The observation can be a good reference for the future exploration and evaluation of reservoir in this area.
文摘Rice husk ask (RHA) is not a ultra-fine material as silica fume (SF),but possesses a very high specific surface area because of its porous structure. With the similar chemical composition of RHA and SF,the activity of RHA,therefore,is different from that of SF. The objective of this work is to study the hydration and the microstructure of Portland cement blended with RHA in comparison with SF. The test results show that SF refined the pore structure of cement paste better than RHA. However,the effect of RHA on cement hydration is more pronouned than that of SF for the mixture with low water to binder ratio.
基金supported by National Natural Science Foundation of China(Grant No.41872179).
文摘Special deposition environment makes organic-rich shales in Ningwu Basin have typeⅢkerogen and high kaolinite content,which are also famous as the kaolinite ore.The specific composition of shale in Ningwu Basin can change the pore structure and thus,influence the shale gas storage and transport.This study focuses on the pore structure and its evolution in shales with typeⅢkerogen and high kaolinite content.In this study,14 Upper Paleozoic shale samples,whose total organic matter contents(TOC)range from 0.39%to 5.91%and maturities(represented by vitrinite reflectance)range from 1.22%to 2.06%,were collected.Scanning electron microscopy(SEM),high-pressure mercury injection,and low-tempera-ture N2 adsorption experiments were used to analyze pore structure of these shale samples.Results show that when the TOC content is smaller than 1.4%,the kaolinite content decreases linearly and quartz content increases linearly with increasing the TOC content.In contrast,when TOC content is>1.4%,the clay content tends to increase with increasing TOC.Based on the SEM images,organic pores and clay pores were identified in shale samples with typeⅢkerogen and high kaolinite content.During the maturation process,the kaolinite content decreases and illite content increases with increasing the vitrinite reflectance.At the same time,the pore volume and pore surface area both increase with increasing the vitrinite reflectance,and it may be because more organic pores and clay pores in the illite were generated during the maturation process.This study can provide further understandings of shale gas accumulation in shale with typeⅢkerogen and high kaolinite content.
