By the addition of superplasticizer and air entraining agent,manufactured sand selfcompacting concrete(MS SCC)with slump flow varying from 500 to 700 mm and air content varying from 2.0%to 9.0%were prepared and the pu...By the addition of superplasticizer and air entraining agent,manufactured sand selfcompacting concrete(MS SCC)with slump flow varying from 500 to 700 mm and air content varying from 2.0%to 9.0%were prepared and the pumpability of MS SCC was studied by a sliding pipe rheometer(Sliper).According to the Kaplan’s model,the initial pump pressure and the pump resistance of MS SCC were obtained.Meanwhile,rheological properties including the yield stress and the plastic viscosity of MS SCC were measured by a rheometer.The experimental results show that the increase of slump flow contributes to a higher pumpability and a proper air content,i e,6%is beneficial for the pumpability of MS SCC.Due to the existence of stone powder and stronger angularity of MS,the initial pump pressure of MS SCC is only about 60%-88%that of river sand(RS)SCC with the same slump flow and air content,indicating that MS SCC possesses a higher pumpability than RS SCC.展开更多
The rheological properties including the complex modulus G＊ and the phase angle δof matrix and warm mix asphalt （WMA）binders were measured by using the dynamic shear rheometer （DSR ） test at the medium temperatu...The rheological properties including the complex modulus G＊ and the phase angle δof matrix and warm mix asphalt （WMA）binders were measured by using the dynamic shear rheometer （DSR ） test at the medium temperature ranging from 16 to 40 ℃,and the relationships between the fatigue factor G＊ sinδand the matrix binder property,WMA additive and test temperature were established.It is found that G＊ decreases with the increasing temperature while δincreases inversely,and G＊ of the asphalt binder with high WMA additive dosage is large,and δis small.G＊sinδexponentially decreases with the increasing temperature and linearly increases with the increase in additive dosage,and the amplitudes of variation are large at low temperatures and high additive dosages.The effect of WMA additive on the rheological property is more remarkable for the matrix asphalt binder with low G＊.Besides,aging has a great effect on the property of matrix asphalt binder,and a slight effect on the interaction between asphalt and additive.The high additive dosage can increase the fatigue cracking potential of the asphalt binder.展开更多
To further clarify the dewatering performance and torque evolution during the tailings thickening process,a self-made rake was connected to a rheometer to monitor the shear stress and torque.The dewatering performance...To further clarify the dewatering performance and torque evolution during the tailings thickening process,a self-made rake was connected to a rheometer to monitor the shear stress and torque.The dewatering performance of the total tailings was greatly improved to a solid mass fraction of 75.33%in 240 min.The dewatering process could be divided into three stages:the rapid torque growth period,damping torque growth period,and constant torque thickening zone.The machine restart was found to have a significant effect on the rake torque;it could result in rake blockage.Furthermore,the simultaneous evolution of the torque and solid mass fraction of thickened tailings was analyzed.A relationship between the torque and the solid mass fraction was established,which followed a power function.Both the experimental and theoretical results provide a reference for the deep cone thickener design and operation to enhance the dewatering performance.展开更多
The objective of this paper was to find new modifier to improve the aging resistance and low temperature cracking resistance of asphalt. To investigate the aging resistance of modified asphalt binders, mesoporous nano...The objective of this paper was to find new modifier to improve the aging resistance and low temperature cracking resistance of asphalt. To investigate the aging resistance of modified asphalt binders, mesoporous nano-silica（doping Ti^（4＋）） was used as a asphalt modifier. Some physical properties including penetration, ductility, and softening point of asphalt were analyzed with RTFO（Rotating thin film oven） aging and ultraviolet aging. Moreover, the performances of high and low temperature of modified asphalt binders with pressure aging were tested by dynamic shear rheometer（DSR） test and bending beam rheometer（BBR） test. These results showed that the penetration decreased, low temperature ductility, and softening point increased when adding mesoporous nano-silica to base asphalt. After ultraviolet radiation aging, the penetration loss and ductility loss of modified asphalt decreased than that of original asphalt, the increase of softening point was also significantly reduced than that of base asphalt. Furthermore, The test results of DSR and BBR showed that the G＊sinδ and creep modulus‘s＇ of pressure aged asphalt decreased, but the creep rate ‘m＇ increased. It can be concluded that the aging resistance and cracking resistance of modified asphalt are improved by adding mesoporous nano-silica, especially the doping of Ti^（4＋） could improve the aging resistance obviously.展开更多
A rheometer for semi-solid high-melting point alloys was developed based on the principle of a double-bucket rheometer, with which the solidifying of semi-solid high-melting point alloy melt could be effectively contr...A rheometer for semi-solid high-melting point alloys was developed based on the principle of a double-bucket rheometer, with which the solidifying of semi-solid high-melting point alloy melt could be effectively controlled by the control of temperature and the outer force-field; and different microstructures have also been obtained. This rheometer can be used to investigate the rheological behavior under different conditions by changing the Theological parameters. By way of full-duplex communication between the computer and each sensor, automatic control of the test equipment and real- time measurement of rheological parameters were realized. Finally, the influencing factors on torque are also quantitatively analyzed .展开更多
A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special m...A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special modifications and binder blending charts by Asphalt Institute were utilized. Modifications involved the development of a new kind of sample mold and different testing parameters were made to BBR testing procedure to capture the theological properties of bitumen mortars produced by mixing fresh binder with fine RAP materials or RAP aggregate. The stiffness relationship between binder and bitumen mortar was established based on the BBR test results. The blended binder stiffness in bitumen RAP mortar was estimated from the RAP mortar stiffness based on the binder-mortar relationship. And finally, the RAP binder stiffness was estimated from the blended binder and fresh binder stiffness based on the blending charts by Asphalt Institute. The results indicate that the new procedure can capture the rheological properties of bitumen mortar and can be used to estimate the low temperature stiffness of RAP binder without binder extraction and/or any chemical treatments.展开更多
Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton P...Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton Paar Physica MCR301 rheometer, including the concentric cylinder system,the parallel-plate system, the vane geometry, and the ball measuring system. All systems were smoothwalled. Flow curves were plotted and yield stress was determined using the Herschel-Bulkley model,showing differences among the different systems.Flow curves from the concentric cylinder and parallelplate systems involved two distinct regions, the low shear and the high shear regions. Yield stresses determined by data fitting in the low shear region were significantly lower than the values from the inclined channel test which is a practical method for determining yield stress. Flow curves in the high shear region are close to those from the vane geometry and the ball measuring system. The fitted values of yield stress are comparable to the values from the inclined channel test. The differences are caused by wall-slip effects in the low shear region.Vane geometry can capture the stress overshoot phenomenon caused by the destruction of slurry structure, whereas end effects should be considered in the determination of yield stress. The ball measuring system can give reasonable results, and it is applicable for rheological testing of debris flow slurries.展开更多
Blends of polyphenylene sulfide (PPS) containing trace amounts of branching and/or cross-linking in chain and Polyamide-66 (PA-66) have been prepared by melt blending. The rheological behavior of PPS/PA-66 blends has ...Blends of polyphenylene sulfide (PPS) containing trace amounts of branching and/or cross-linking in chain and Polyamide-66 (PA-66) have been prepared by melt blending. The rheological behavior of PPS/PA-66 blends has been studied by means of capillary rheometer, and compared with PPS. The effects of shear rate, shear stress and temperature on the how of PPS/PA-66 blends and PPS are discussed. The non-Newtonian indexes and the activation energies of viscous how are obtained. The results show that the apparent viscosity of PPS/PA-66 blends is not sensitive to shear rate and stress, but decreases with the elevation of temperature. On the contrary, the apparent viscosity of the PPS decreases obviously with the increasing of shear rate and shear stress, but it is increased by the elevation of temperature.展开更多
The flowability of a root canal sealer is clinically important because it improves the penetration of the sealer into the complex root canal system. The purpose of this study was to compare the flowabilities of four r...The flowability of a root canal sealer is clinically important because it improves the penetration of the sealer into the complex root canal system. The purpose of this study was to compare the flowabilities of four root canal sealers, measured using the simple press method （ISO 6876）, and their viscosities, measured using a strain-controlled rheometer. A newly developed, calcium phosphate-based root canal sealer （Capseal） and three commercial root canal sealers （AH Plus, Sealapex and Pulp Canal Sealer EWT） were used in this study. The flowabilities of the four root canal sealers were measured using the simple press method （n= 5） and their viscosities were measured using a strain-controlled rheometer （n=5）. The correlation between these two values was statistically analysed using Spearman＇s correlation test. The flow diameters and the viscosities of the root canal sealers were strongly negatively correlated （p= -0.8618）. The viscosity of Pulp Canal Sealer EWT was the lowest and increased in the following order： AH Plus〈Sealapex〈Capseal （P〈0.05）. All of the tested root canal sealers showed characteristic time- and temperature-dependent changes in their rheological properties. The viscosities measured using the strain-controlled rheometer were more precise than the flowabilities measured using the simple press method, suggesting that the rheometer can accurately measure the rheological properties of root canal sealers.展开更多
Gas hydrates are solid inclusion compounds that are composed of a three-dimensional hydrogen-bonded network of water cages that can trap small gas molecules, such as methane and carbon dioxide. Understanding the rheol...Gas hydrates are solid inclusion compounds that are composed of a three-dimensional hydrogen-bonded network of water cages that can trap small gas molecules, such as methane and carbon dioxide. Understanding the rheological properties of gas hydrate crystals in solution can he critical in a number of energy applications, including the transportation of natural gas in suhsea and onshore operations, as well as technological applications for gas separation, desalination, or sequestration. A number of exper- imental and modeling studies have been done on hydrate slurry rheology; however, the link between theory and experiment is not well-defined. This article provides a review on the current state of the art of hydrate slurry viscosity measurements from high- and low-pressure rheometer studies and high-pressure flowloops over a range of different sub-cooling （ATsub = TequiI Texp） and fluid conditions, including for water and oil continuous systems. The theoretical models that have been developed to describe the gas hydrate slurry relative viscosity are also reviewed. Perspectives＇ linkage between the experiments and theory is also discussed.展开更多
A non-reacting system and a reacting system are run with an on-line slit rheometer devel-oped by the authors.It is found that the polyurethane-urea system behaves slightly elastic and theZaremba-Fromm-Dewitt model may...A non-reacting system and a reacting system are run with an on-line slit rheometer devel-oped by the authors.It is found that the polyurethane-urea system behaves slightly elastic and theZaremba-Fromm-Dewitt model may be employed to describe its rheological behaviors.After the geltime,the inside pressure of the testing materials varies dramatically.Reports in this respect have notbeen found in literature,as yet its mechanism warrants further studies.展开更多
A slit die apparatus is used to measure hole pressures for two polymer melts.Hole pressures up to 110kPa are determined and shear rates reach 200 s<sup>-1</sup>.Viscosity data obtained from the same appara...A slit die apparatus is used to measure hole pressures for two polymer melts.Hole pressures up to 110kPa are determined and shear rates reach 200 s<sup>-1</sup>.Viscosity data obtained from the same apparatus agreewell with the values obtained from a cone-and-plate rheometer or a capillary rheometer.The hole pressuresobtained by direct measurements are all positive and increase with increasing shear stress.The values of the firstnormal stress difference obtained from hole pressures according to the Higashitani-Pritchard（HP）theory are ofthe right order of magnitude,but appear to be on the low side when compared with values obtained from a cone-and-plate rheometer or with values obtained via exit pressures.It is believed that the hole pressure is a measureof fluid elasticity,but cannot yield accurate values of the first normal stress difference according to the HP theory.展开更多
The work principle of flat-plate structure under shearing mode is expounded based on a vertical type rheometer for MRF which combined data acquisition with treatment and result display.The formula to calculate shearin...The work principle of flat-plate structure under shearing mode is expounded based on a vertical type rheometer for MRF which combined data acquisition with treatment and result display.The formula to calculate shearing stress is deduced.Based on different recipe for MRF,experiments under different working gap length were done by altering the intensity of magnetic field.The rheological model for MRF was established and the relationships between shearing stress,viscosity and magnetic field intensity were deduced.Experiments indicate that MRF has the flowing characters:with an increase of the magnetic induction and the nominal shear rate,the shear stress of MRF increases.However,as the working gap decreases,the shear stress increases.MRF has shear thinning property under magnetic field.展开更多
The operating principle of measuring rheological properties of magnetorheological(MR) fluid was expounded by means of a new rheometer with double driving discs rotating at the same speed in the opposite directions.The...The operating principle of measuring rheological properties of magnetorheological(MR) fluid was expounded by means of a new rheometer with double driving discs rotating at the same speed in the opposite directions.The constitutive equation of MR fluid was established with theoretical analysis from experimental data.The conventional power spectrum approach was unable to detect the existence of quadratic phase coupling for dynamic rheological measurement.Bispectrum analysis is emerging as a new powerful technique in signal processing,which can describe nonlinear coupling,restrain Gaussian noise and reserve phase component.An autoregressive(AR) model of the third order cumulant,the bispectra and bispectral contours were utilized for analyzing the dynamic characteristics of the MR rheometer by merely using the sampled output torque signals when a zero mean non-Gaussian white noise interferes with the rotary disc system.The measurement and analysis process based on virtual instruments were automatically controlled by computer in this paper.The experimental and theoretical results show that rheological properties and dynamic characteristics of MR fluid can be measured with this double disc rheometer.展开更多
Wall slip behavior of three commercial polymer melts polypropylene(iPP),low-density polyethylene(LDPE)(branched chains) and high-density polyethylene(HDPE)(linear chains) were studied by using a capillary rheometer wi...Wall slip behavior of three commercial polymer melts polypropylene(iPP),low-density polyethylene(LDPE)(branched chains) and high-density polyethylene(HDPE)(linear chains) were studied by using a capillary rheometer with twin bores at different temperatures.The results show that a sudden first-stick-then-slip transition was observed for HDPE and a first-slip-then-stick transition was observed for LDPE and iPP as the shear rate sweep was done in an increased order,which shows that the chain structure has an obvious effect on the wall slip behavior of polymers.The critical shear stress for the onset of stick-slip transition increases linearly with temperature for HDPE,which accords with the disentanglement mechanism proposed by Brochard and de Gennes.While the extrapolation length used to quantify the magnitude of the transition remains about 0.05-0.09 mm for HDPE at 150-230 ℃.Also the relationship between the critical shear stress for the onset of wall slip and the molecular mass for polymer samples agrees with the disentanglement model of Brochard and de Gennes.The onset of slip-stick transition for LDPE and iPP at a critical shear stress may be interpreted as the shear thinning of the polymer chains at high shear rates,preventing further development of wall slip behavior.展开更多
The low-temperature rheological properties of binders in the recycled asphalt pavement （RAP） material without the damaging effects of solvent extractions were analyzed. The developed procedure is based on testing of...The low-temperature rheological properties of binders in the recycled asphalt pavement （RAP） material without the damaging effects of solvent extractions were analyzed. The developed procedure is based on testing of bitumen-RAP mortars produced by mixing the fresh （virgin） binder with RAP material smaller than # 8 sieve. Different mortars were prepared, containing RAP material passing the #8 sieve and 15% by weight of fresh binder. Low temperature properties of these mortars were investigated by using the bending beam rheometer （BBR） test procedure that is specially modified for testing of the RAP mortars. The modification involved the development of a new kind of mold and different testing parameters. The RAP material used in the experimental study were both extracted from real reclaimed pavement and prepared in the laboratory, by aging binder through repeated PAV cycles. The results indicate the new procedure can capture the effect of aged properties of bitumen in the RAP and can be used to estimate the PG low temperature grade of the blended binder. Although data is limited in size, the modification of the BBR appears to be simple and provide repeatable data.展开更多
A new method was used to evaluate the fatigue properties of the bonding layer used in the bridge deck pavement. The shear fatigue test of three bonding layers was conducted on a dynamic shear rheometer（DSR）. The fat...A new method was used to evaluate the fatigue properties of the bonding layer used in the bridge deck pavement. The shear fatigue test of three bonding layers was conducted on a dynamic shear rheometer（DSR）. The fatigue formulas were gained for these layers. The experimental results indicate that, at the same torque level or at the same frequency, neoprene latex asphalt bonding layer exhibits excellent fatigue performance when compared to other two bonding layers.展开更多
Based on the rheology characteristic and the resistivity variation under alternating electric-field of Portland cement hydration by means of AR2000 advanced rheometer and non-contacting electrical resistivity device, ...Based on the rheology characteristic and the resistivity variation under alternating electric-field of Portland cement hydration by means of AR2000 advanced rheometer and non-contacting electrical resistivity device, the influence of cement kinds and the chemical admixtures on the initial rheology characteristic and structure forming and developing of cement hydration was studied. The relationship between the rheology characteristic, the initial hydration structure forming and the hydration process at very early ages was analyzed by macro properties and microstructure tests. The results showed that, the storage modulus, acted as S, could be described more subtle distinction accompanying with hydration of fresh paste model at very early period. Combining the resistivity alterations, a sudden change on structure forming emerged when the hydration of cement becoming inducing age. The rheology characteristic was interrelated to the hydration structure forming, development and the physical mechanics properties. The sudden change on storage modulus moved up due to the addition of retarder, but the structure forming and developing was retarded to a certain extent.展开更多
In order to study the chemical modification mechanism and rheological properties of polyphosphoric acid (PPA)-modified asphalt,asphalt modified with different PPA contents were characterized by four-component test,ato...In order to study the chemical modification mechanism and rheological properties of polyphosphoric acid (PPA)-modified asphalt,asphalt modified with different PPA contents were characterized by four-component test,atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR).In the test,changes in asphalt chemical composition and colloidal structure were analyzed for different PPA contents,and infrared spectra were fitted with a Gaussian function.The reaction mechanism of PPA and matrix asphalt was also discussed.Based on dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test,rheological index G~*/sinδ and S/m were used to evaluate the modification effect of PPA on asphalt.The results show that,with an increase in PPA content,both large and small honeycomb structures increased in the three-dimensional topography seen in the atomic force microscope (AFM).In a certain space range,some of the micelles in the asphalt are connected each other to form interlocking skeleton structures,and locally form dense spatial network structures.The added PPA does not chemically react with the functional groups in the functional-group area of the infrared spectra (3 100-2 750 cm^(-1),1 800-1 330 cm^(-1)),and the structure is very stable.However,there is an obvious new absorption peak below 1 330 cm^(-1) in the fingerprint area,that is,the chemical reaction between PPA and the matrix asphalt generates a new compound,inorganic phosphate.Infrared spectra of PPA-modified asphalt with different contents were fitted by a Gaussian function,which makes up for the limitation that the absorption intensity information of each superimposed functional group cannot be obtained directly from the original infrared spectra.Results of this qualitative analysis were further verified by quantitative analysis.The addition of PPA can effectively improve the high and low-temperature performance of asphalt,and the lower the temperature is in the negative temperature zone,the more obvious the improvement is.When PPA content is more than 1%,the improvement of asphalt low-temperature performance is not obvious.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.U1934206 and 52108260)the Foundation of China Academy of Railway Science Corporation Limited(No.2020YJ049)。
文摘By the addition of superplasticizer and air entraining agent,manufactured sand selfcompacting concrete(MS SCC)with slump flow varying from 500 to 700 mm and air content varying from 2.0%to 9.0%were prepared and the pumpability of MS SCC was studied by a sliding pipe rheometer(Sliper).According to the Kaplan’s model,the initial pump pressure and the pump resistance of MS SCC were obtained.Meanwhile,rheological properties including the yield stress and the plastic viscosity of MS SCC were measured by a rheometer.The experimental results show that the increase of slump flow contributes to a higher pumpability and a proper air content,i e,6%is beneficial for the pumpability of MS SCC.Due to the existence of stone powder and stronger angularity of MS,the initial pump pressure of MS SCC is only about 60%-88%that of river sand(RS)SCC with the same slump flow and air content,indicating that MS SCC possesses a higher pumpability than RS SCC.
基金The National Natural Science Foundation of China(No.51408043)the Natural Science Foundation of Shaanxi Province(No.2014JQ7278)
文摘The rheological properties including the complex modulus G＊ and the phase angle δof matrix and warm mix asphalt （WMA）binders were measured by using the dynamic shear rheometer （DSR ） test at the medium temperature ranging from 16 to 40 ℃,and the relationships between the fatigue factor G＊ sinδand the matrix binder property,WMA additive and test temperature were established.It is found that G＊ decreases with the increasing temperature while δincreases inversely,and G＊ of the asphalt binder with high WMA additive dosage is large,and δis small.G＊sinδexponentially decreases with the increasing temperature and linearly increases with the increase in additive dosage,and the amplitudes of variation are large at low temperatures and high additive dosages.The effect of WMA additive on the rheological property is more remarkable for the matrix asphalt binder with low G＊.Besides,aging has a great effect on the property of matrix asphalt binder,and a slight effect on the interaction between asphalt and additive.The high additive dosage can increase the fatigue cracking potential of the asphalt binder.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51804015 and 51834001)the Fundamental Research Funds for the Central Universities(No.FRF-TP-17-024A1).
文摘To further clarify the dewatering performance and torque evolution during the tailings thickening process,a self-made rake was connected to a rheometer to monitor the shear stress and torque.The dewatering performance of the total tailings was greatly improved to a solid mass fraction of 75.33%in 240 min.The dewatering process could be divided into three stages:the rapid torque growth period,damping torque growth period,and constant torque thickening zone.The machine restart was found to have a significant effect on the rake torque;it could result in rake blockage.Furthermore,the simultaneous evolution of the torque and solid mass fraction of thickened tailings was analyzed.A relationship between the torque and the solid mass fraction was established,which followed a power function.Both the experimental and theoretical results provide a reference for the deep cone thickener design and operation to enhance the dewatering performance.
基金Funded by the China Scholarship Council(201506375019)
文摘The objective of this paper was to find new modifier to improve the aging resistance and low temperature cracking resistance of asphalt. To investigate the aging resistance of modified asphalt binders, mesoporous nano-silica（doping Ti^（4＋）） was used as a asphalt modifier. Some physical properties including penetration, ductility, and softening point of asphalt were analyzed with RTFO（Rotating thin film oven） aging and ultraviolet aging. Moreover, the performances of high and low temperature of modified asphalt binders with pressure aging were tested by dynamic shear rheometer（DSR） test and bending beam rheometer（BBR） test. These results showed that the penetration decreased, low temperature ductility, and softening point increased when adding mesoporous nano-silica to base asphalt. After ultraviolet radiation aging, the penetration loss and ductility loss of modified asphalt decreased than that of original asphalt, the increase of softening point was also significantly reduced than that of base asphalt. Furthermore, The test results of DSR and BBR showed that the G＊sinδ and creep modulus‘s＇ of pressure aged asphalt decreased, but the creep rate ‘m＇ increased. It can be concluded that the aging resistance and cracking resistance of modified asphalt are improved by adding mesoporous nano-silica, especially the doping of Ti^（4＋） could improve the aging resistance obviously.
文摘A rheometer for semi-solid high-melting point alloys was developed based on the principle of a double-bucket rheometer, with which the solidifying of semi-solid high-melting point alloy melt could be effectively controlled by the control of temperature and the outer force-field; and different microstructures have also been obtained. This rheometer can be used to investigate the rheological behavior under different conditions by changing the Theological parameters. By way of full-duplex communication between the computer and each sensor, automatic control of the test equipment and real- time measurement of rheological parameters were realized. Finally, the influencing factors on torque are also quantitatively analyzed .
基金Project(200831800044) supported by the Ministry of Communication of ChinaProject(50878054) supported by the National Natural Science Foundation of ChinaProject(06Y31) supported by the Department of Communication of Zhejiang Province,China
文摘A new testing procedure to estimate the low-temperature stiffness of the reclaimed asphalt pavement （RAP） binder was developed. In the testing procedure, the SuperpaveTM Bending Beam Rheometer （BBR） with special modifications and binder blending charts by Asphalt Institute were utilized. Modifications involved the development of a new kind of sample mold and different testing parameters were made to BBR testing procedure to capture the theological properties of bitumen mortars produced by mixing fresh binder with fine RAP materials or RAP aggregate. The stiffness relationship between binder and bitumen mortar was established based on the BBR test results. The blended binder stiffness in bitumen RAP mortar was estimated from the RAP mortar stiffness based on the binder-mortar relationship. And finally, the RAP binder stiffness was estimated from the blended binder and fresh binder stiffness based on the blending charts by Asphalt Institute. The results indicate that the new procedure can capture the rheological properties of bitumen mortar and can be used to estimate the low temperature stiffness of RAP binder without binder extraction and/or any chemical treatments.
基金financially supported by the Key Research Program of the Chinese Academy of Sciences (CAS) (Grant No. KZZD-EW-05-01)the Youth Talent Team Program of Institute of Mountain Hazards and Environment, CAS (Grant No. SDSQB-2013-01)the National Natural Science Foundation of China (Grant No. 41201011)
文摘Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton Paar Physica MCR301 rheometer, including the concentric cylinder system,the parallel-plate system, the vane geometry, and the ball measuring system. All systems were smoothwalled. Flow curves were plotted and yield stress was determined using the Herschel-Bulkley model,showing differences among the different systems.Flow curves from the concentric cylinder and parallelplate systems involved two distinct regions, the low shear and the high shear regions. Yield stresses determined by data fitting in the low shear region were significantly lower than the values from the inclined channel test which is a practical method for determining yield stress. Flow curves in the high shear region are close to those from the vane geometry and the ball measuring system. The fitted values of yield stress are comparable to the values from the inclined channel test. The differences are caused by wall-slip effects in the low shear region.Vane geometry can capture the stress overshoot phenomenon caused by the destruction of slurry structure, whereas end effects should be considered in the determination of yield stress. The ball measuring system can give reasonable results, and it is applicable for rheological testing of debris flow slurries.
基金This work was supported by the National High Technology Program Fund(863)of China.
文摘Blends of polyphenylene sulfide (PPS) containing trace amounts of branching and/or cross-linking in chain and Polyamide-66 (PA-66) have been prepared by melt blending. The rheological behavior of PPS/PA-66 blends has been studied by means of capillary rheometer, and compared with PPS. The effects of shear rate, shear stress and temperature on the how of PPS/PA-66 blends and PPS are discussed. The non-Newtonian indexes and the activation energies of viscous how are obtained. The results show that the apparent viscosity of PPS/PA-66 blends is not sensitive to shear rate and stress, but decreases with the elevation of temperature. On the contrary, the apparent viscosity of the PPS decreases obviously with the increasing of shear rate and shear stress, but it is increased by the elevation of temperature.
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2011-0014231)supported by the National Research Foundation of Korea funded by Ministry of Education, Science and Technology (2009-0086835)+1 种基金supported by a grant from the Kyung Hee University in 2013 (KHU-20131045)supported by Grant No. 04-2009-0032 from the SNUDH Research Fund
文摘The flowability of a root canal sealer is clinically important because it improves the penetration of the sealer into the complex root canal system. The purpose of this study was to compare the flowabilities of four root canal sealers, measured using the simple press method （ISO 6876）, and their viscosities, measured using a strain-controlled rheometer. A newly developed, calcium phosphate-based root canal sealer （Capseal） and three commercial root canal sealers （AH Plus, Sealapex and Pulp Canal Sealer EWT） were used in this study. The flowabilities of the four root canal sealers were measured using the simple press method （n= 5） and their viscosities were measured using a strain-controlled rheometer （n=5）. The correlation between these two values was statistically analysed using Spearman＇s correlation test. The flow diameters and the viscosities of the root canal sealers were strongly negatively correlated （p= -0.8618）. The viscosity of Pulp Canal Sealer EWT was the lowest and increased in the following order： AH Plus〈Sealapex〈Capseal （P〈0.05）. All of the tested root canal sealers showed characteristic time- and temperature-dependent changes in their rheological properties. The viscosities measured using the strain-controlled rheometer were more precise than the flowabilities measured using the simple press method, suggesting that the rheometer can accurately measure the rheological properties of root canal sealers.
文摘Gas hydrates are solid inclusion compounds that are composed of a three-dimensional hydrogen-bonded network of water cages that can trap small gas molecules, such as methane and carbon dioxide. Understanding the rheological properties of gas hydrate crystals in solution can he critical in a number of energy applications, including the transportation of natural gas in suhsea and onshore operations, as well as technological applications for gas separation, desalination, or sequestration. A number of exper- imental and modeling studies have been done on hydrate slurry rheology; however, the link between theory and experiment is not well-defined. This article provides a review on the current state of the art of hydrate slurry viscosity measurements from high- and low-pressure rheometer studies and high-pressure flowloops over a range of different sub-cooling （ATsub = TequiI Texp） and fluid conditions, including for water and oil continuous systems. The theoretical models that have been developed to describe the gas hydrate slurry relative viscosity are also reviewed. Perspectives＇ linkage between the experiments and theory is also discussed.
基金Supported by the National Natural Science Foundation of China.
文摘A non-reacting system and a reacting system are run with an on-line slit rheometer devel-oped by the authors.It is found that the polyurethane-urea system behaves slightly elastic and theZaremba-Fromm-Dewitt model may be employed to describe its rheological behaviors.After the geltime,the inside pressure of the testing materials varies dramatically.Reports in this respect have notbeen found in literature,as yet its mechanism warrants further studies.
文摘A slit die apparatus is used to measure hole pressures for two polymer melts.Hole pressures up to 110kPa are determined and shear rates reach 200 s<sup>-1</sup>.Viscosity data obtained from the same apparatus agreewell with the values obtained from a cone-and-plate rheometer or a capillary rheometer.The hole pressuresobtained by direct measurements are all positive and increase with increasing shear stress.The values of the firstnormal stress difference obtained from hole pressures according to the Higashitani-Pritchard（HP）theory are ofthe right order of magnitude,but appear to be on the low side when compared with values obtained from a cone-and-plate rheometer or with values obtained via exit pressures.It is believed that the hole pressure is a measureof fluid elasticity,but cannot yield accurate values of the first normal stress difference according to the HP theory.
基金Projects(10472134,50490274) supported by the National Natural Science Foundation of China
文摘The work principle of flat-plate structure under shearing mode is expounded based on a vertical type rheometer for MRF which combined data acquisition with treatment and result display.The formula to calculate shearing stress is deduced.Based on different recipe for MRF,experiments under different working gap length were done by altering the intensity of magnetic field.The rheological model for MRF was established and the relationships between shearing stress,viscosity and magnetic field intensity were deduced.Experiments indicate that MRF has the flowing characters:with an increase of the magnetic induction and the nominal shear rate,the shear stress of MRF increases.However,as the working gap decreases,the shear stress increases.MRF has shear thinning property under magnetic field.
基金Project(2005H035) supported by the Programs of Science and Technology of Fujian Province of China
文摘The operating principle of measuring rheological properties of magnetorheological(MR) fluid was expounded by means of a new rheometer with double driving discs rotating at the same speed in the opposite directions.The constitutive equation of MR fluid was established with theoretical analysis from experimental data.The conventional power spectrum approach was unable to detect the existence of quadratic phase coupling for dynamic rheological measurement.Bispectrum analysis is emerging as a new powerful technique in signal processing,which can describe nonlinear coupling,restrain Gaussian noise and reserve phase component.An autoregressive(AR) model of the third order cumulant,the bispectra and bispectral contours were utilized for analyzing the dynamic characteristics of the MR rheometer by merely using the sampled output torque signals when a zero mean non-Gaussian white noise interferes with the rotary disc system.The measurement and analysis process based on virtual instruments were automatically controlled by computer in this paper.The experimental and theoretical results show that rheological properties and dynamic characteristics of MR fluid can be measured with this double disc rheometer.
基金Projects(ZMF07020038) supported by the Young Teacher's Scientific Research Fund of Jiangsu Polytechnic University,China
文摘Wall slip behavior of three commercial polymer melts polypropylene(iPP),low-density polyethylene(LDPE)(branched chains) and high-density polyethylene(HDPE)(linear chains) were studied by using a capillary rheometer with twin bores at different temperatures.The results show that a sudden first-stick-then-slip transition was observed for HDPE and a first-slip-then-stick transition was observed for LDPE and iPP as the shear rate sweep was done in an increased order,which shows that the chain structure has an obvious effect on the wall slip behavior of polymers.The critical shear stress for the onset of stick-slip transition increases linearly with temperature for HDPE,which accords with the disentanglement mechanism proposed by Brochard and de Gennes.While the extrapolation length used to quantify the magnitude of the transition remains about 0.05-0.09 mm for HDPE at 150-230 ℃.Also the relationship between the critical shear stress for the onset of wall slip and the molecular mass for polymer samples agrees with the disentanglement model of Brochard and de Gennes.The onset of slip-stick transition for LDPE and iPP at a critical shear stress may be interpreted as the shear thinning of the polymer chains at high shear rates,preventing further development of wall slip behavior.
基金Funded by the National Natural Science Foundation of China (No. 50878054)
文摘The low-temperature rheological properties of binders in the recycled asphalt pavement （RAP） material without the damaging effects of solvent extractions were analyzed. The developed procedure is based on testing of bitumen-RAP mortars produced by mixing the fresh （virgin） binder with RAP material smaller than # 8 sieve. Different mortars were prepared, containing RAP material passing the #8 sieve and 15% by weight of fresh binder. Low temperature properties of these mortars were investigated by using the bending beam rheometer （BBR） test procedure that is specially modified for testing of the RAP mortars. The modification involved the development of a new kind of mold and different testing parameters. The RAP material used in the experimental study were both extracted from real reclaimed pavement and prepared in the laboratory, by aging binder through repeated PAV cycles. The results indicate the new procedure can capture the effect of aged properties of bitumen in the RAP and can be used to estimate the PG low temperature grade of the blended binder. Although data is limited in size, the modification of the BBR appears to be simple and provide repeatable data.
基金Funded by the National Natural Science Foundation of China (No. 50878171)
文摘A new method was used to evaluate the fatigue properties of the bonding layer used in the bridge deck pavement. The shear fatigue test of three bonding layers was conducted on a dynamic shear rheometer（DSR）. The fatigue formulas were gained for these layers. The experimental results indicate that, at the same torque level or at the same frequency, neoprene latex asphalt bonding layer exhibits excellent fatigue performance when compared to other two bonding layers.
文摘Based on the rheology characteristic and the resistivity variation under alternating electric-field of Portland cement hydration by means of AR2000 advanced rheometer and non-contacting electrical resistivity device, the influence of cement kinds and the chemical admixtures on the initial rheology characteristic and structure forming and developing of cement hydration was studied. The relationship between the rheology characteristic, the initial hydration structure forming and the hydration process at very early ages was analyzed by macro properties and microstructure tests. The results showed that, the storage modulus, acted as S, could be described more subtle distinction accompanying with hydration of fresh paste model at very early period. Combining the resistivity alterations, a sudden change on structure forming emerged when the hydration of cement becoming inducing age. The rheology characteristic was interrelated to the hydration structure forming, development and the physical mechanics properties. The sudden change on storage modulus moved up due to the addition of retarder, but the structure forming and developing was retarded to a certain extent.
基金Funded by National Natural Science Foundation of China (No. 11962024)Inner Mongolia Transportation Technology Project (No. NJ-2014-9)Research Fund for the Doctoral Program of Higher Education of China (RFDP)(No. BS2020042)。
文摘In order to study the chemical modification mechanism and rheological properties of polyphosphoric acid (PPA)-modified asphalt,asphalt modified with different PPA contents were characterized by four-component test,atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR).In the test,changes in asphalt chemical composition and colloidal structure were analyzed for different PPA contents,and infrared spectra were fitted with a Gaussian function.The reaction mechanism of PPA and matrix asphalt was also discussed.Based on dynamic shear rheometer (DSR) test and bending beam rheometer (BBR) test,rheological index G~*/sinδ and S/m were used to evaluate the modification effect of PPA on asphalt.The results show that,with an increase in PPA content,both large and small honeycomb structures increased in the three-dimensional topography seen in the atomic force microscope (AFM).In a certain space range,some of the micelles in the asphalt are connected each other to form interlocking skeleton structures,and locally form dense spatial network structures.The added PPA does not chemically react with the functional groups in the functional-group area of the infrared spectra (3 100-2 750 cm^(-1),1 800-1 330 cm^(-1)),and the structure is very stable.However,there is an obvious new absorption peak below 1 330 cm^(-1) in the fingerprint area,that is,the chemical reaction between PPA and the matrix asphalt generates a new compound,inorganic phosphate.Infrared spectra of PPA-modified asphalt with different contents were fitted by a Gaussian function,which makes up for the limitation that the absorption intensity information of each superimposed functional group cannot be obtained directly from the original infrared spectra.Results of this qualitative analysis were further verified by quantitative analysis.The addition of PPA can effectively improve the high and low-temperature performance of asphalt,and the lower the temperature is in the negative temperature zone,the more obvious the improvement is.When PPA content is more than 1%,the improvement of asphalt low-temperature performance is not obvious.
