This study proposes a model to determine the content of cement in mortars using the background of X-ray diffraction （XRD） spectra taking advantage of the fact that fluorescence radiation for the Cu anticathode is di...This study proposes a model to determine the content of cement in mortars using the background of X-ray diffraction （XRD） spectra taking advantage of the fact that fluorescence radiation for the Cu anticathode is different in cement paste and aggregates, and also that cement paste and aggregates have different crystallinity degrees. The method has been tested for limestone mortars with five different types of cement： I52,5N/SR, CEMII/A-L32,5N, IIIA42,5N/SR, IVA（V）32,5N/SR y CAC.展开更多
Considering the fact that free calcium oxide content is an important parameter to evaluate the quality of cement clinker, it is very significant to predict the change of free calcium oxide content through adjusting th...Considering the fact that free calcium oxide content is an important parameter to evaluate the quality of cement clinker, it is very significant to predict the change of free calcium oxide content through adjusting the parameters of processing technique. In fact, the making process of cement clinker is very complex. Therefore, it is very difficult to describe this relationship using the conventional mathematical methods. Using several models, i e, linear regression model, nonlinear regression model, Back Propagation neural network model, and Radial Basis Function （RBF） neural network model, we investigated the possibility to predict the free calcium oxide content according to selected parameters of the production process. The results indicate that RBF neural network model can predict the free lime content with the highest precision （1.3%） among all the models.展开更多
A new type of high water content material which is made up of two pastes is prepared, one is refute from lime and gypsum, and another is based on Ba-bearing sulphoaluminate cement. It has excellent properties such as ...A new type of high water content material which is made up of two pastes is prepared, one is refute from lime and gypsum, and another is based on Ba-bearing sulphoaluminate cement. It has excellent properties such as slow single paste solidifing ,fust double pustes solidifing ,fast coagulating and hardening, high early strength, good suspeasion property at high W/C ratio and low cost. Meanwhile, the properties and hydration mechanism of the material were analyzed by using XRD, DTA- TG and SEM. The hydrated products of new type of high water content material are Ba-bearing ettringite, BaSO4 , aluminum gel and C-S-H gel.展开更多
The effects of four sand contents on the compressive, flexural and splitting-tensile strength of cement mortars were evaluated. Moreover, we experimentally investigated the pore structure of cement mortar brought abou...The effects of four sand contents on the compressive, flexural and splitting-tensile strength of cement mortars were evaluated. Moreover, we experimentally investigated the pore structure of cement mortar brought about by changing the sand content and water/cement ratio. The changes in the pore structure were quantified by measuring the porosity and pore size distribution obtained by using mercury intrusion porosimetry（MIP） technique. The test results show that the strengths of cement mortar increase with increasing sand content. It is also suggested that the traditional water/cement ratio law can be applied to cement mortar with different sand contents, provided that a slight modification is introduced. Sand content is an important parameter influencing the pore structure of cement mortar. Moreover, there is a good relationship between the pore structure and strength of cement mortar.展开更多
The influence of water content on the conductivity and piezoresistivity of cement-based material with carbon fiber （CF） and carbon black （CB） was investigated. The piezoresistivity of cement-based material with bo...The influence of water content on the conductivity and piezoresistivity of cement-based material with carbon fiber （CF） and carbon black （CB） was investigated. The piezoresistivity of cement-based material with both CF and CB was compared with that of cement-based material with CF only, and the changes in electrical resistivity of cement-based material with both CF and CB under static and loading conditions in different drying and soaking time were studied. It is found that the piezoresistivity of cement-based material with both CF and CB has better repeatability and linearity than that of cement-based material with CF only. The conductivity and the sensitivity of piezoresistive cement-based material with both CF and CB are enhanced as the water content in piezoresistive cement-based material increases.展开更多
The improvement of question soils with cement shows great technical, economic and environmental advantages. And interest in introducing electrical resistivity measurement to assess the quality of cement treated soils ...The improvement of question soils with cement shows great technical, economic and environmental advantages. And interest in introducing electrical resistivity measurement to assess the quality of cement treated soils has increased markedly recently due to its economical, non-destructive, and relatively non-invasive advantages. This work aims to quantify the effect of cement content （aw）, porosity （nt）, and curing time（T） on the electrical resistivity （p） and unconfined compression strength （UCS） of cement treated soil. A series of electrical resistivity tests and UCS tests of cement treated soil specimen after various curing periods were carried out. A modified Archie empirical law was proposed taking into account the effect of cement content and curing period on the electrical resistivity of cement treated soil. The results show that nt/（aw·T） and nt/（aw·T^1/2） ratio are appropriate parameters to assess electrical resistivity and UCS of cement treated soil, respectively. Finally, the relationship between UCS and electrical resistivity was also established.展开更多
Estimation of stressses within the tailings slurry during self-weight consolidation is a critical issue for cost-effective barricade design and efficient backfill planning in underground mine stopes.This process requi...Estimation of stressses within the tailings slurry during self-weight consolidation is a critical issue for cost-effective barricade design and efficient backfill planning in underground mine stopes.This process requires a good understanding of self-weight consolidation behaviors of the tailings slurry within practical stopes,where many factors can have significant effects on the consolidation,including drainage condition and cement addition.In this paper,the prepared tailings slurry with different cement contents(0,4.76wt%,and 6.25wt%)was poured into1.2 m-high columns,which allowed three drainage scenarios(undrained,partial lateral drainage near the bottom part,and full lateral drainage boundaries)to investigate the effects of drainage condition and cement addition on the consolidation behavior of the tailings slurry.The consolidation behavior was analyzed in terms of pore water pressure(PWP),settlement,volume of drainage water,and residual water content.The results indicate that increasing the length of the drainage boundary or cement content aids in PWP dissipation.In addition,constructing an efficient drainage boundary was more favorable to PWP dissipation than increasing cement addition.The final stable PWP on the column floor was not sensitive to cement addition.The final settlement of uncemented tailings slurry was independent of drainage conditions,and that of cemented tailings slurry decreased with the increase in cement addition.Notably,more pore water can drain out from the cemented tailings slurry than the uncemented tailings slurry during consolidation.展开更多
The influences of cement type, cement content, and curing time on the unconfined compression strength （UCS） of soil-cement were investigated. The influence of groundwater on UCS of soil- cement was also studied. The...The influences of cement type, cement content, and curing time on the unconfined compression strength （UCS） of soil-cement were investigated. The influence of groundwater on UCS of soil- cement was also studied. The experimental results indicate that the soil treated with high grade cement presents a higher UCS. Additionally, the UCS of soil-cement presents linearly increased with the cement content. A logarithm correlation between UCS and curing time presents to forecast the strength development. Compared with the UCS of samples immersed in distilled water, those immersed in groundwater oresent a hizher value.展开更多
Completely weathered phyllite(CWP)has the characteristics of difficult compaction,low shear strength after compaction and large settlement after construction.The traditional improvement method using a single agent of ...Completely weathered phyllite(CWP)has the characteristics of difficult compaction,low shear strength after compaction and large settlement after construction.The traditional improvement method using a single agent of red clay or cement for CWP satisfies the subgrade requirements for ordinary railway,but cannot meet the requirements of immediate strength and long-term post-construction settlement of high-speed railway at the same time.A series of experimental investigations were undertaken for the blended CWP soils,with three additives used.The first additive was red clay,the second was cement and the third was a combination of both red clay and cement at various portions.Results of consolidation test and shear strength test carried out for the treated CWP soils show that:1)The effect of cement on improving the compression modulus of CWP is much better than that of red clay;2)The settlement of an embankment of 10 m high formed by blended soil of CWP with 3%cement can be controlled within 15 mm,while the settlement will be 25.15 mm for the same embankment of blended soil of CWP with 40%red clay;3)The shear strength and ultimate bearing capacity of CWP improved by red clay are much better than those of 5%cement;4)The ultimate bearing capacity of CWP improved by 40%red clay is 3.42 times of that by 3%cement and 2.95 times by 5%cement.Furthermore,the bearing capacity of CWP when improved by red clay can meet railway subgrade requirements immediately after compaction,while cement improved CWP needs a curing time of 1 day or longer.This is an impediment to rapid construction process.The improvement mechanism of red clay is mainly filling effect and grading improvement effect,while the improvement mechanism of cement is mainly hardening reaction,which produces high strength material to cement.It is found that 40%red clay and 3%cement treated CWP,which is considered to be optimum,can meet the subgrade requirements of both immediate bearing capacity and long-term post-construction settlement for the high-speed railway.展开更多
Hydraulic characteristic is a good indication of binder hydration, which determines the strength development of cemented paste backfill（CPB）. Therefore, the hydraulic characteristic should be communicated with the m...Hydraulic characteristic is a good indication of binder hydration, which determines the strength development of cemented paste backfill（CPB）. Therefore, the hydraulic characteristic should be communicated with the mechanical property to provide an advanced knowledge that can help mine workers make a rational strategy and reduce the mining cycle. An experimental program was performed to obtain the hydraulic（monitored by suction and volumetric water content） and mechanical properties（unconfined compressive strength（UCS） test） of CPB at the 28 days curing age. According to the monitoring and testing results, the relationships between the hydration reaction rate and volumetric water content（VWC）, suction and VWC, suction and UCS were established. The hydration degree showed a liner rise as the VWC decreased. Curves of the VWC and UCS were featured with a nonlinear reduction and nonlinear growth（both are exponential functions） as the suction rising, respectively. These established relationships validated the strong correlative mechanism of hydraulic and mechanics behavior for CPB. Also, the results of the present research indicated that the hydraulic characteristics and mechanical property were strongly coupled. These correlations and couplings will be of great importance to understand the hardening process of CPB and bring to a safe CPB field operation.展开更多
Steel-cemented WC was prepared by ball milling, cold compacting and microwave sintering with Fe powder as the matrix, WC as the hard phase and the addition of rare earth Y2O3. The results show that the interface of th...Steel-cemented WC was prepared by ball milling, cold compacting and microwave sintering with Fe powder as the matrix, WC as the hard phase and the addition of rare earth Y2O3. The results show that the interface of the WC particles and Fe matrix exhibits excellent wettability and liquidity when the microwave sintering temperature reaches 1,280℃. The density and mechanical properties of the steel bonded WC carbides could be greatly improved, the hard phases become finer and more uniform dispersed owing to the addition of Y2O3. With the increase of the Y2O3 contents, the grain becomes uniform and fine first, and then gathers and grows up. The relative density, microhardness and bending strength all rise first, reaching the maximum values of 97.29 %, HV1024 and 1,267.60 MPa at 0.5 % Y2O3, respectively, and then decrease. Moreover, the relative density and mechanical properties of the steel-cemented WC with nano-Y2O3 are higher than that with micron-Y2O3, which indicates that the effect of nano-Y2O3 is better than that of the micron-Y2O3.展开更多
The capillary absorption of water by unsaturated cement-based material is the main reason of degradation of the structures subjected to an aggressive environment since water often acts as the transporting medium for d...The capillary absorption of water by unsaturated cement-based material is the main reason of degradation of the structures subjected to an aggressive environment since water often acts as the transporting medium for damaging contaminants. It is well known that the capillarity coefficient and sorptivity are two important parameters to characterize the water absorption of porous materials. Generally, the former is used to describe the penetration depth or height of water transport, which must be measured by special and advanced equipment. In contrast, the sorptivity represents the relationship between cumulative volume of water uptake and the squareroot of the elapsed time, which can be easily measured by the gravimetric method in a normal laboratory condition. In the present study, an analytical method is developed to build up a bridge between these two parameters, with the purpose that the sorptivity or the gravimetric method can be used to predict the penetration depth of water absorption. Additionally, a new model to explain the dependence of sorptivity on initial water content of the material is developed in order to fit the in situ condition. The comparison of predicted results by the analytical method with experimental data or numerical calculation results, as well as some previous models, validates the feasibility of the methods presented in this paper.展开更多
文摘This study proposes a model to determine the content of cement in mortars using the background of X-ray diffraction （XRD） spectra taking advantage of the fact that fluorescence radiation for the Cu anticathode is different in cement paste and aggregates, and also that cement paste and aggregates have different crystallinity degrees. The method has been tested for limestone mortars with five different types of cement： I52,5N/SR, CEMII/A-L32,5N, IIIA42,5N/SR, IVA（V）32,5N/SR y CAC.
基金NSFC (No. 60808024)the Fundamental Research Funds for the Central Universities (Wuhan University of Technology)
文摘Considering the fact that free calcium oxide content is an important parameter to evaluate the quality of cement clinker, it is very significant to predict the change of free calcium oxide content through adjusting the parameters of processing technique. In fact, the making process of cement clinker is very complex. Therefore, it is very difficult to describe this relationship using the conventional mathematical methods. Using several models, i e, linear regression model, nonlinear regression model, Back Propagation neural network model, and Radial Basis Function （RBF） neural network model, we investigated the possibility to predict the free calcium oxide content according to selected parameters of the production process. The results indicate that RBF neural network model can predict the free lime content with the highest precision （1.3%） among all the models.
文摘A new type of high water content material which is made up of two pastes is prepared, one is refute from lime and gypsum, and another is based on Ba-bearing sulphoaluminate cement. It has excellent properties such as slow single paste solidifing ,fust double pustes solidifing ,fast coagulating and hardening, high early strength, good suspeasion property at high W/C ratio and low cost. Meanwhile, the properties and hydration mechanism of the material were analyzed by using XRD, DTA- TG and SEM. The hydrated products of new type of high water content material are Ba-bearing ettringite, BaSO4 , aluminum gel and C-S-H gel.
基金Founded by the National Natural Science Foundation of China(Nos.51279054 and 51279052)
文摘The effects of four sand contents on the compressive, flexural and splitting-tensile strength of cement mortars were evaluated. Moreover, we experimentally investigated the pore structure of cement mortar brought about by changing the sand content and water/cement ratio. The changes in the pore structure were quantified by measuring the porosity and pore size distribution obtained by using mercury intrusion porosimetry（MIP） technique. The test results show that the strengths of cement mortar increase with increasing sand content. It is also suggested that the traditional water/cement ratio law can be applied to cement mortar with different sand contents, provided that a slight modification is introduced. Sand content is an important parameter influencing the pore structure of cement mortar. Moreover, there is a good relationship between the pore structure and strength of cement mortar.
基金Funded by the National Natural Science Foundation of China (No.50238040, 50538020)the Postdoctoral Science Foundation of China (No.20060390803)the High-Tech Research and Development Program of China (No. 2002AA335010)
文摘The influence of water content on the conductivity and piezoresistivity of cement-based material with carbon fiber （CF） and carbon black （CB） was investigated. The piezoresistivity of cement-based material with both CF and CB was compared with that of cement-based material with CF only, and the changes in electrical resistivity of cement-based material with both CF and CB under static and loading conditions in different drying and soaking time were studied. It is found that the piezoresistivity of cement-based material with both CF and CB has better repeatability and linearity than that of cement-based material with CF only. The conductivity and the sensitivity of piezoresistive cement-based material with both CF and CB are enhanced as the water content in piezoresistive cement-based material increases.
基金Project(BK2011618) supported by the Natural Science Foundation of Jiangsu Province, ChinaProject(51108288) supported by the National Natural Science Foundation of China
文摘The improvement of question soils with cement shows great technical, economic and environmental advantages. And interest in introducing electrical resistivity measurement to assess the quality of cement treated soils has increased markedly recently due to its economical, non-destructive, and relatively non-invasive advantages. This work aims to quantify the effect of cement content （aw）, porosity （nt）, and curing time（T） on the electrical resistivity （p） and unconfined compression strength （UCS） of cement treated soil. A series of electrical resistivity tests and UCS tests of cement treated soil specimen after various curing periods were carried out. A modified Archie empirical law was proposed taking into account the effect of cement content and curing period on the electrical resistivity of cement treated soil. The results show that nt/（aw·T） and nt/（aw·T^1/2） ratio are appropriate parameters to assess electrical resistivity and UCS of cement treated soil, respectively. Finally, the relationship between UCS and electrical resistivity was also established.
基金financially supported by the Young Scientist Project of the National Key Research and Development Program of China (No.2021YFC2900600)the Beijing Nova Program (No.20220484057)financial support from China Scholarship Council under Grant CSC No.202110300001。
文摘Estimation of stressses within the tailings slurry during self-weight consolidation is a critical issue for cost-effective barricade design and efficient backfill planning in underground mine stopes.This process requires a good understanding of self-weight consolidation behaviors of the tailings slurry within practical stopes,where many factors can have significant effects on the consolidation,including drainage condition and cement addition.In this paper,the prepared tailings slurry with different cement contents(0,4.76wt%,and 6.25wt%)was poured into1.2 m-high columns,which allowed three drainage scenarios(undrained,partial lateral drainage near the bottom part,and full lateral drainage boundaries)to investigate the effects of drainage condition and cement addition on the consolidation behavior of the tailings slurry.The consolidation behavior was analyzed in terms of pore water pressure(PWP),settlement,volume of drainage water,and residual water content.The results indicate that increasing the length of the drainage boundary or cement content aids in PWP dissipation.In addition,constructing an efficient drainage boundary was more favorable to PWP dissipation than increasing cement addition.The final stable PWP on the column floor was not sensitive to cement addition.The final settlement of uncemented tailings slurry was independent of drainage conditions,and that of cemented tailings slurry decreased with the increase in cement addition.Notably,more pore water can drain out from the cemented tailings slurry than the uncemented tailings slurry during consolidation.
基金Funded by the National Natural Science Foundation of China(Nos.51009061,51137002)the Chinese Ministry of Water Resources Funds for Science and Technology Promotion(No.TG1137)
文摘The influences of cement type, cement content, and curing time on the unconfined compression strength （UCS） of soil-cement were investigated. The influence of groundwater on UCS of soil- cement was also studied. The experimental results indicate that the soil treated with high grade cement presents a higher UCS. Additionally, the UCS of soil-cement presents linearly increased with the cement content. A logarithm correlation between UCS and curing time presents to forecast the strength development. Compared with the UCS of samples immersed in distilled water, those immersed in groundwater oresent a hizher value.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.52068027,51668018,51768021).
文摘Completely weathered phyllite(CWP)has the characteristics of difficult compaction,low shear strength after compaction and large settlement after construction.The traditional improvement method using a single agent of red clay or cement for CWP satisfies the subgrade requirements for ordinary railway,but cannot meet the requirements of immediate strength and long-term post-construction settlement of high-speed railway at the same time.A series of experimental investigations were undertaken for the blended CWP soils,with three additives used.The first additive was red clay,the second was cement and the third was a combination of both red clay and cement at various portions.Results of consolidation test and shear strength test carried out for the treated CWP soils show that:1)The effect of cement on improving the compression modulus of CWP is much better than that of red clay;2)The settlement of an embankment of 10 m high formed by blended soil of CWP with 3%cement can be controlled within 15 mm,while the settlement will be 25.15 mm for the same embankment of blended soil of CWP with 40%red clay;3)The shear strength and ultimate bearing capacity of CWP improved by red clay are much better than those of 5%cement;4)The ultimate bearing capacity of CWP improved by 40%red clay is 3.42 times of that by 3%cement and 2.95 times by 5%cement.Furthermore,the bearing capacity of CWP when improved by red clay can meet railway subgrade requirements immediately after compaction,while cement improved CWP needs a curing time of 1 day or longer.This is an impediment to rapid construction process.The improvement mechanism of red clay is mainly filling effect and grading improvement effect,while the improvement mechanism of cement is mainly hardening reaction,which produces high strength material to cement.It is found that 40%red clay and 3%cement treated CWP,which is considered to be optimum,can meet the subgrade requirements of both immediate bearing capacity and long-term post-construction settlement for the high-speed railway.
基金Funded by the National Natural Science Foundation of China(Nos.51574013,51374034,51674012)the Open Projects of State Key Laboratory of Coal Resources and Safe Mining,CUMT(No.12KF03)+1 种基金the State Key Research Development Program of China(Nos.2016YFC0600704,2016YFC0600709)Beijing Municipal Science and Technology Commission(No.Z161100001216002)
文摘Hydraulic characteristic is a good indication of binder hydration, which determines the strength development of cemented paste backfill（CPB）. Therefore, the hydraulic characteristic should be communicated with the mechanical property to provide an advanced knowledge that can help mine workers make a rational strategy and reduce the mining cycle. An experimental program was performed to obtain the hydraulic（monitored by suction and volumetric water content） and mechanical properties（unconfined compressive strength（UCS） test） of CPB at the 28 days curing age. According to the monitoring and testing results, the relationships between the hydration reaction rate and volumetric water content（VWC）, suction and VWC, suction and UCS were established. The hydration degree showed a liner rise as the VWC decreased. Curves of the VWC and UCS were featured with a nonlinear reduction and nonlinear growth（both are exponential functions） as the suction rising, respectively. These established relationships validated the strong correlative mechanism of hydraulic and mechanics behavior for CPB. Also, the results of the present research indicated that the hydraulic characteristics and mechanical property were strongly coupled. These correlations and couplings will be of great importance to understand the hardening process of CPB and bring to a safe CPB field operation.
基金supported by the Science and Technology Plan Projects of Jiangxi Province (No. 2011BBE50010)the Project from the Jiangxi Province Key Laboratory of Copper Tungsten New Materials (No. 2011-TW-08)
文摘Steel-cemented WC was prepared by ball milling, cold compacting and microwave sintering with Fe powder as the matrix, WC as the hard phase and the addition of rare earth Y2O3. The results show that the interface of the WC particles and Fe matrix exhibits excellent wettability and liquidity when the microwave sintering temperature reaches 1,280℃. The density and mechanical properties of the steel bonded WC carbides could be greatly improved, the hard phases become finer and more uniform dispersed owing to the addition of Y2O3. With the increase of the Y2O3 contents, the grain becomes uniform and fine first, and then gathers and grows up. The relative density, microhardness and bending strength all rise first, reaching the maximum values of 97.29 %, HV1024 and 1,267.60 MPa at 0.5 % Y2O3, respectively, and then decrease. Moreover, the relative density and mechanical properties of the steel-cemented WC with nano-Y2O3 are higher than that with micron-Y2O3, which indicates that the effect of nano-Y2O3 is better than that of the micron-Y2O3.
基金supported by the Key Programs of Ministry of Education of China(Grant No.109046)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Eduation Ministrythe Program of Innovative Research Team of Education of China(Grant No.IRT0518)
文摘The capillary absorption of water by unsaturated cement-based material is the main reason of degradation of the structures subjected to an aggressive environment since water often acts as the transporting medium for damaging contaminants. It is well known that the capillarity coefficient and sorptivity are two important parameters to characterize the water absorption of porous materials. Generally, the former is used to describe the penetration depth or height of water transport, which must be measured by special and advanced equipment. In contrast, the sorptivity represents the relationship between cumulative volume of water uptake and the squareroot of the elapsed time, which can be easily measured by the gravimetric method in a normal laboratory condition. In the present study, an analytical method is developed to build up a bridge between these two parameters, with the purpose that the sorptivity or the gravimetric method can be used to predict the penetration depth of water absorption. Additionally, a new model to explain the dependence of sorptivity on initial water content of the material is developed in order to fit the in situ condition. The comparison of predicted results by the analytical method with experimental data or numerical calculation results, as well as some previous models, validates the feasibility of the methods presented in this paper.
