Polycarboxylate water-reducing admixture possesses the capability which could meet with the comprehensive performance of high performance concrete used in passenger dedicated line engineering.The problems of polycarbo...Polycarboxylate water-reducing admixture possesses the capability which could meet with the comprehensive performance of high performance concrete used in passenger dedicated line engineering.The problems of polycarboxylates water-reducing admixtures existed in the engineering application of were analyzed.At present the key for polycarboxylates application was to settle the compatibility between the water-reducing admixture and the cement and to keep the quality retention of this admixture.展开更多
Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures,most previous reports on the cement-admixture compatibility did not provide suficient information on the stru...Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures,most previous reports on the cement-admixture compatibility did not provide suficient information on the structure of the admixture.Hence,the evaluation and generalization of the reports on the cement-admixture compatibility are challenging.In this study,three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content,anionic/nonionic molar ratio,and main chain length and different side chain lengths were produced.The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated.In addition,an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type,admixture/cement ratio,and elapsing time to the Marsh funnel flow time,mini-slump,slump flow,and compressive strength.The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems.However,the admixture having the shortest side chain was better with regard to flow retention.The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures.Regarding the behaviors of the admixtures in the cementitious systems,an optimal admixture side chain molecular weight is proposed.展开更多
N-2000 is an admixture for concrete,with a low slump loss,high range water-reducing ratio and long-time retarding.The N-2000 is made up of naphthalene-sulfonic-maldehyde polycondensation(NSMP)and ATMP.Its characterist...N-2000 is an admixture for concrete,with a low slump loss,high range water-reducing ratio and long-time retarding.The N-2000 is made up of naphthalene-sulfonic-maldehyde polycondensation(NSMP)and ATMP.Its characteristic results from the synergistic effects of NSMP and ATMP.The results show that when 0.7%-1.2%of N-2000 is added to concrete(by mass of cement),the water reducing ratio is up to 20%-30%,and the slump of fresh concrete can be retained for 2 hours without significant loss.N-2000 can not only improve the workability of fresh concrete but also increase the strength of the hardened concrete,especially early strength.It is also proved to have a good compatibility with various cements.展开更多
Four typical admixtures,polycarboxylate superplasticiser(PCE),tartaric acid(TA),sorbitol and polyacrylamide(PAM),were selected to systematically investigate their regulatory mechanisms on the formation of ettringite t...Four typical admixtures,polycarboxylate superplasticiser(PCE),tartaric acid(TA),sorbitol and polyacrylamide(PAM),were selected to systematically investigate their regulatory mechanisms on the formation of ettringite through Fourier transform infrared spectroscopy,X-ray diffraction,particle size analysis and nucleation kinetic model.The experimental results indicate that the admixtures alter the formation of ettringite through physical adsorption,complexation and solution viscosity modulation without changing its chemical structure.Low concentrations of PCE inhibit size growth by forming an adsorption layer on the surface of ettringite,whereas high concentrations of PCE alter the size change of ettringite by modulating the distribution of ionic concentrations.TA significantly reduces the size of ettringite by complexing Ca^(2+).Sorbitol and PAM promote the local growth of ettringite at low concentrations,leading to larger sizes.But at high concentrations,the size growth of ettringite is inhibited due to the increase in viscosity or the enhancement of complexation.Matlab nucleation kinetic modelling further shows that the addition of admixtures enhances the initial nucleation during ettringite synthesis,with values ranging from 14.45%to 114.25%.However,the subsequent nucleation rate of ettringite is significantly affected,decreasing by 12.79%to 71.74%.The results provide a theoretical basis for the design of ettringite materials and the optimisation of the application of admixtures.展开更多
This study investigated the factors contributing to intravenous admixture preparation errors(IAPEs)within Pharmacy Intravenous Admixture Services(PIVAS).A retrospective analysis was conducted on IAPEs documented in th...This study investigated the factors contributing to intravenous admixture preparation errors(IAPEs)within Pharmacy Intravenous Admixture Services(PIVAS).A retrospective analysis was conducted on IAPEs documented in the PIVAS unit of a large multi-specialty hospital in China,which houses over 2000 beds,covering the period from January 1,2015 to December 31,2022.Drug preparation records were examined using a generalized linear mixed model(GLMM)to identify both univariate and multivariate factors associated with IAPE occurrences.A total of 824 IAPE cases were recorded during the study period,yielding an overall error rate of 0.018%.Univariate analysis identified drug categories(general drugs,anti-infective drugs,and antineoplastic drugs),preparation time(workdays),and years of work experience as significant determinants(P<0.05).Multivariate analysis further confirmed that drug categories(general and antineoplastic drugs),preparation time(workdays),and work experience remained statistically significant predictors of IAPE incidence(P<0.05).IAPEs in PIVAS were influenced by multiple factors,predominantly those related to personnel and drug characteristics.Targeted interventions,informed by multivariate analysis,are essential to mitigating these errors and enhancing medication safety.展开更多
An evaluation method for self-healing capacity was designed,which includes the control of initial cracks and subsequent permeability testing.This method was employed to evaluate the self-healing behavior of mortars in...An evaluation method for self-healing capacity was designed,which includes the control of initial cracks and subsequent permeability testing.This method was employed to evaluate the self-healing behavior of mortars incorporating crystalline admixtures(CAs)under various conditions,including water immersion,limewater soaking,and wet-dry cycles,with varying CA dosages and crack widths.The experimental results indicate that cement possesses inherently self-healing capability.Limewater environments inhibits healing compared with water immersion;however,wet-dry cycles enhance the effectiveness of higher CA dosages.Increasing the CA content can not improve healing performance,and wide cracks(0.3 mm)substantially reduce the intrinsic self-healing potential of cement.展开更多
In this paper,the effects of four different mineral ginseng materials on the mechanical properties of mortar were studied,and the results showed that high territory,fly ash,and silica fume had an inhibitory effect on ...In this paper,the effects of four different mineral ginseng materials on the mechanical properties of mortar were studied,and the results showed that high territory,fly ash,and silica fume had an inhibitory effect on the drying shrinkage of mortar,and mineral powder increased the drying shrinkage of mortar.The high territory in the mineral admixture has the best effect on the inhibition of mortar drying shrinkage.The compressive strength and flexural strength of the mortar can be improved by adding a certain amount of mineral admixture,which increases the compressive strength by about 20%-40%and the flexural strength by about 20%-30%compared with the control group,and the improvement effect difference between different components is not large.展开更多
In the present study, we aimed to analyze the irrational medical orders and evaluate the effect of pharmacy intervention on pharmacy intravenous admixture services of outpatient and emergency departments in our hospit...In the present study, we aimed to analyze the irrational medical orders and evaluate the effect of pharmacy intervention on pharmacy intravenous admixture services of outpatient and emergency departments in our hospital. The irrational medical orders of PIVAS at the outpatient and emergency departments were retrospectively analyzed in Jun. 2015. We strengthened the pharmacy intervention on irrational medical orders since July 2015. All the cases were selected by systematic sampling method. Cased studied in Jun. 2015 served as the control group, whereas those studied in Jan. 2016 served as the intervention group. The irrational rate and the irrational number of daily average were compared between the control group and intervention group. The common type of irrational outpatient and emergency intravenous orders mainly included irrational use of solvents, irrational dosing interval and inappropriate compatibility of drugs. The irrational rate was reduced from 17.4% to 3.3% （P〈0.01）, and the irrational number of daily average was decreased from 5.23 to 1.00 （P〈0.01）. Pharmacy intervention can reduce the irrational rate of medical orders in our hospital, which is of great significance to promote rational drug use and improve medical quality.展开更多
The expansion and micro-cracks of the mortar with composite mineral admixtures （fly ash, zeolite and slag） due to the alkali-silica reaction （ASR） are studied. Results show that composite mineral admixtures cannot...The expansion and micro-cracks of the mortar with composite mineral admixtures （fly ash, zeolite and slag） due to the alkali-silica reaction （ASR） are studied. Results show that composite mineral admixtures cannot absolutely diminish the ASR of mortar bars with the low-alkali cement and a highly reactive aggregate. But the expansion rate and the deleterious expansion of the mortar bar are mostly reduced with increasing composite mineral admixture. The influence of mineral admixtures on the fluidity of the paste and the strength of the mortar is also studied.展开更多
The rice husk ash （ RHA） and silica （ Si02） nanoparticles are prepared from rice husk charcoal （RHC） by the methods of ventilated calcining and chemical precipitation, respectively, to remove the residual carbon...The rice husk ash （ RHA） and silica （ Si02） nanoparticles are prepared from rice husk charcoal （RHC） by the methods of ventilated calcining and chemical precipitation, respectively, to remove the residual carbon which is harmful to cement composites. The structures and morphologies of these products are investigated by the Fourier transform infrared spectroscopy, X-ray diffraction, scanning/ transmission electron microscopy and N2 adsorption- desorption analyzer. The results show that the as-produced RHA and Si02 nanoparticles exist in amorphous phase without residual carbon, and exhibit porous structures with specific surface areas of 170.19 and 248. 67 m2 /g , respectively. The micro particles of RHA are aggregated by numerous loosely packed Si02 gel particles with the diameter of 50 to 100 nm. The Si02 nanoparticles are well dispersed with the average size of about 30 nm. Both the RHA and Si02 nanoparticles can significantly reduce the conductivity of saturated Ca（OH）2 solution and increase the early strength of the cement composites. They also exhibit high pozzolanic activity, indicating that they can be used as ecological nano mineral admixtures.展开更多
The scope of the present paper is to understand the effects of crystalline admixture on the selfhealing capacity of the cementitious composites. Previous studies were examined and a conclusion was drawn to the effect ...The scope of the present paper is to understand the effects of crystalline admixture on the selfhealing capacity of the cementitious composites. Previous studies were examined and a conclusion was drawn to the effect that different additives to crystalline admixture tend to improve self-healing of concrete for larger cracks. It is recommended that initial treatment with chemical admixture can stimulate and heal further cracks and it has the better repeatability trend in mixing with the concretes and mechanical recovery is possible even under repetitive preloading. Effective self-healing with chemical admixtures even under open-air exposure, leads to study the importance of a service ability design parameter including the maximum allowable crack width by repeatability analysis as a function of the exposure with the concept of sealable crack width.展开更多
Owing to the high viscosity of sodium silicate solution, fly ash geopolymer has the problems of low workability and rapid setting time. Therefore, the effect of chemical admixtures on the properties of fly ash geopoly...Owing to the high viscosity of sodium silicate solution, fly ash geopolymer has the problems of low workability and rapid setting time. Therefore, the effect of chemical admixtures on the properties of fly ash geopolymer was studied to overcome the rapid set of the geo-polymer in this paper. High-calcium fly ash and alkaline solution were used as starting materials to synthesize the geopolymer. Calcium chloride, calcium sulfate, sodium sulfate, and sucrose at dosages of 1wt% and 2wt% of fly ash were selected as admixtures based on concrete knowledge to improve the properties of the geopolymer. The setting time, compressive strength, and degree of reaction were recorded, and the microstructure was examined. The results show that calcium chloride significantly shortens both the initial and final setting times of the geopolymer paste. In addition, sucrose also delays the final setting time significantly. The degrees of reaction of fly ash in the geopolymer paste with the admixtures are all higher than those of the control paste. This contributes to the obvious increases in compressive strength.展开更多
The influence of anti-freezing admixture on the alkali aggregate reaction in mortar was analyzed with accelerated methods. It is confirmed that the addition of sodium salt ingredients of anti-freezing admixture accele...The influence of anti-freezing admixture on the alkali aggregate reaction in mortar was analyzed with accelerated methods. It is confirmed that the addition of sodium salt ingredients of anti-freezing admixture accelerates the alkali silica reaction to some extent, whereas calcium salt ingredient of anti-freezing admixture reduces the expansion of alkali silica reaction caused by high alkali cement. It is found that the addition of the fly ash considerably suppresses the expansion of alkali silica reaction induced by the anti-freezing admixtures.展开更多
The improvements of the mechanical properties, including bulk density of fresh mixtures, elastic modulus, and compressive strengths of four high-performance concrete mixtures, made with the addition of fly ash, refine...The improvements of the mechanical properties, including bulk density of fresh mixtures, elastic modulus, and compressive strengths of four high-performance concrete mixtures, made with the addition of fly ash, refined ground blast - furnace microslag (microslag) and silica fume are studied. The concrete mixtures were determined based on the dispersion testing results. The study indicates that the elastic modulus at 28 and 91 days, and compressive strengths of the concretes are improved a lot when fly ash and microslag by 25 percent by weight of cement are added into the mixtures individually. The improvement is especially evident when silica fume by 5 percent and fly ash by 25 percent by weight of cement are added together into the mixture, while the fresh concrete mixture keeps a good workability. Through the analysis of chemically combined water ratios of the four mixtures at various hydration ages, it is found that the addition of all these mineral mixtures are beneficial to the hydration process, especially, at later stages, which might be one of the reasons for the improvement of mechanical properties. (Author abstract) 4 Refs.展开更多
Mortar prisms made with different cements or mineral admixtures plus 30% mass of limes tone filler were stored in 2% magnesium sulfate solution at 5±1 ℃ for 1 year and their visual appearance,strength developmen...Mortar prisms made with different cements or mineral admixtures plus 30% mass of limes tone filler were stored in 2% magnesium sulfate solution at 5±1 ℃ for 1 year and their visual appearance,strength development were measured at intervals.The formation of thaumasite was checked and confirmed by XRD and FTIR.The results show that the relative resistance to thaumasite form of sulfate attack of the cements is outlined below,from best to worst:sulphoaluminate cement,sulfate resisting Portland cement,OPC.The resistance to thaumasite form of sulfate attack of mortar is remarkably improved by the addition of silica fume or ground granulated blastfurnace slag (SL),and the better the resistance to thaumasite form of sulfate attack,the more the addition of SL is.The thaumasite form of sulfate attack is decreased to a certain degree by a lower replacement of cement with fly ash,but it is accelerated by the addition of a higher amount of fly ash due to its lower reactivity.展开更多
High-performance concrete （HPC） has specific performance advantages over conventional concrete in strength and durability. HPC mixtures are usually produced with water/binder mass ratios （mW/mB） in the range of 0....High-performance concrete （HPC） has specific performance advantages over conventional concrete in strength and durability. HPC mixtures are usually produced with water/binder mass ratios （mW/mB） in the range of 0.2-0.4, so volume changes of concrete as a result of drying, chemical reactions, and temperature change cannot be avoided. For these reasons, shrinkage and cracking are frequent phenomena. It is necessary to add some types of admixture for reduction of shrinkage and cracking of HPC. This study used a shrinkage-reducing admixture （SRA） for that purpose. Concrete was prepared with two different mW/mB （0.22 and 0.40） and four different mass fractions of SRA to binder （w（SRA） = 0%, 1%, 2%, and 4%）. The mineral admixtures used for concrete mixes were： 25% fly ash （FA） and 25% slag by mass of binder for the mixture with mW/mB = 0.40, and 15% silica fume （SF） and 25% FA for the mixture with mW/mB = 0.22. Tests were conducted on 24 prismatic specimens, and shrinkage strains were measured through 120 days of drying. Compressive strength, splitting strength, and static modulus of elasticity were also determined. The results show that the SRA effectively reduces some mechanical properties of HPC. The reductions in compressive strength, splitting tensile strength, and elastic modulus of the concrete were 7%-24%, 9%-19%, and 5%-12%, respectively, after 90 days, compared to concrete mixtures without SRA. SRA can also help reduce drying shrinkage of concrete. The shrinkage strains of HPC with SRA were only as high as 41% of the average free shrinkage of concrete without SRA after 120 days of drying.展开更多
A new kind of nano-rod shaped polycarboxylic acid slump-retaining agent was synthesized.Transmission electron microscope(TEM) experiment showed that the nano-rod was bound together as macromolecular aggregates in solu...A new kind of nano-rod shaped polycarboxylic acid slump-retaining agent was synthesized.Transmission electron microscope(TEM) experiment showed that the nano-rod was bound together as macromolecular aggregates in solution.Application performance studying suggested that this kind nano-sized polymer material had excellently plasticity-retaining performance in cement-based materials and could improve endurance performance of hardened cement-based materials distinctly.The concrete with an initial slump of 2-9 cm could achieve 3 h plasticity-retaining performance with the help of this kind nano-rod.The product had extremely wide application value in the market.展开更多
The effect of the admixtures of Al and Si metals and B4 C and MgAlON compounds on the oxidation of MgO/ Si3N4 composite refractory has been studied, which is a promising carbon free refractory for steel-making applica...The effect of the admixtures of Al and Si metals and B4 C and MgAlON compounds on the oxidation of MgO/ Si3N4 composite refractory has been studied, which is a promising carbon free refractory for steel-making application . The four kinds of admixtures can be used as anti-oxi-dants for Si3N4, but the mixture of Al and Si achieved the best result. The mixture can not only play the role as anti-oxidant, but also assist the sintering process and help form dense sintering layer, improving the property of the composite.展开更多
Concrete specimens made with ordinary portland cement or ordinary portland cement incorporating fly ash with the replacement of 10% or 20%, ground blast furnace slag with the replacement of 15% or 30%, or 15% fly ash ...Concrete specimens made with ordinary portland cement or ordinary portland cement incorporating fly ash with the replacement of 10% or 20%, ground blast furnace slag with the replacement of 15% or 30%, or 15% fly ash and 15% ground blast furnace slag were made and exposed to a cyclic sulfate environment. Concrete properties including relative dynamic elastic modulus, chloride ion diffusion coefficient, compressive strength and flexural strength were measured. Effect of mineral admixtures on the cyclic sulfate resistance of concrete was assessed based on the grey clustering theory. The experimental results indicate that the cyclic sulfate resistance of concrete incorporating ground blast furnace slag belongs to the higher grey grade, which exhibits that it possesses excellent cyclic sulfate resistance. With increasing addition of fly ash, the cyclic sulfate resistance of concrete changes from the medium grey grade to the lower grey grade, which shows that incorporation of fly ash is disadvantageous for the cyclic sulfate resistance of concrete.展开更多
Chemical admixtures are of paramount importance to the performance of modern cement based composites. In this paper, we performed a series of tests to investigate the effects of chemical admixtures on the cement aspha...Chemical admixtures are of paramount importance to the performance of modern cement based composites. In this paper, we performed a series of tests to investigate the effects of chemical admixtures on the cement asphalt mortar(CA mortar), i e, compressive strength, frost resistance, permeability, fatigue resistance, pore structure and microstructure. In particular, two types of chemical admixtures were tested, i e, defoamer(tributyl phosphate(TBP)) and polycarboxylate superplasticizer(PS). The results indicate that the addition of TBP and PS eliminates big bubbles and promotes small non-connected pores forming in matrix. Besides, an optimum dosage of TBP and PS may be determined with respect to the frost resistance, permeability and fatigue resistance of CA mortar. Further elaborative discussions are presented as well as experimental evidences from mercury intrusion porosimetry, scanning electron microscopy and energy dispersive spectroscopy.展开更多
文摘Polycarboxylate water-reducing admixture possesses the capability which could meet with the comprehensive performance of high performance concrete used in passenger dedicated line engineering.The problems of polycarboxylates water-reducing admixtures existed in the engineering application of were analyzed.At present the key for polycarboxylates application was to settle the compatibility between the water-reducing admixture and the cement and to keep the quality retention of this admixture.
基金The authors express their sincere gratitude to the Scientific and Technological Research Council of Turkey(Grant No.219M425)Bursa Uludag University Science and Technology Center(Grant Nos.AYP(MH)-2016/16,DDP(MH)-2018/9,and DDP(MH)-2019/15).The first author thanks TUBITAK for the scholarship provided by Grant No.217M408 during his PhD study.The authors would like to acknowledge Polisan Construction Chemicals Company and Bursa Ready Mixed Concrete for the provision of the materials and information on their properties.
文摘Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures,most previous reports on the cement-admixture compatibility did not provide suficient information on the structure of the admixture.Hence,the evaluation and generalization of the reports on the cement-admixture compatibility are challenging.In this study,three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content,anionic/nonionic molar ratio,and main chain length and different side chain lengths were produced.The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated.In addition,an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type,admixture/cement ratio,and elapsing time to the Marsh funnel flow time,mini-slump,slump flow,and compressive strength.The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems.However,the admixture having the shortest side chain was better with regard to flow retention.The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures.Regarding the behaviors of the admixtures in the cementitious systems,an optimal admixture side chain molecular weight is proposed.
基金Key Science and Technology Development Fund Project of Hubei Province.China(No.941PO106).
文摘N-2000 is an admixture for concrete,with a low slump loss,high range water-reducing ratio and long-time retarding.The N-2000 is made up of naphthalene-sulfonic-maldehyde polycondensation(NSMP)and ATMP.Its characteristic results from the synergistic effects of NSMP and ATMP.The results show that when 0.7%-1.2%of N-2000 is added to concrete(by mass of cement),the water reducing ratio is up to 20%-30%,and the slump of fresh concrete can be retained for 2 hours without significant loss.N-2000 can not only improve the workability of fresh concrete but also increase the strength of the hardened concrete,especially early strength.It is also proved to have a good compatibility with various cements.
基金Funded by the National Natural Science Foundation of China(Nos.51578412,51878479,52078372,and 52478272)the International Science and Technology Cooperation Project of the Key R&D Program of Science and Technology Innovation Yongjiang 2035(No.2024H023)。
文摘Four typical admixtures,polycarboxylate superplasticiser(PCE),tartaric acid(TA),sorbitol and polyacrylamide(PAM),were selected to systematically investigate their regulatory mechanisms on the formation of ettringite through Fourier transform infrared spectroscopy,X-ray diffraction,particle size analysis and nucleation kinetic model.The experimental results indicate that the admixtures alter the formation of ettringite through physical adsorption,complexation and solution viscosity modulation without changing its chemical structure.Low concentrations of PCE inhibit size growth by forming an adsorption layer on the surface of ettringite,whereas high concentrations of PCE alter the size change of ettringite by modulating the distribution of ionic concentrations.TA significantly reduces the size of ettringite by complexing Ca^(2+).Sorbitol and PAM promote the local growth of ettringite at low concentrations,leading to larger sizes.But at high concentrations,the size growth of ettringite is inhibited due to the increase in viscosity or the enhancement of complexation.Matlab nucleation kinetic modelling further shows that the addition of admixtures enhances the initial nucleation during ettringite synthesis,with values ranging from 14.45%to 114.25%.However,the subsequent nucleation rate of ettringite is significantly affected,decreasing by 12.79%to 71.74%.The results provide a theoretical basis for the design of ettringite materials and the optimisation of the application of admixtures.
基金The National Natural Science Foundation of China(Grant No.72474013)the Beijing Health Technology Promotion Project(Grant No.BHTPP2024007)。
文摘This study investigated the factors contributing to intravenous admixture preparation errors(IAPEs)within Pharmacy Intravenous Admixture Services(PIVAS).A retrospective analysis was conducted on IAPEs documented in the PIVAS unit of a large multi-specialty hospital in China,which houses over 2000 beds,covering the period from January 1,2015 to December 31,2022.Drug preparation records were examined using a generalized linear mixed model(GLMM)to identify both univariate and multivariate factors associated with IAPE occurrences.A total of 824 IAPE cases were recorded during the study period,yielding an overall error rate of 0.018%.Univariate analysis identified drug categories(general drugs,anti-infective drugs,and antineoplastic drugs),preparation time(workdays),and years of work experience as significant determinants(P<0.05).Multivariate analysis further confirmed that drug categories(general and antineoplastic drugs),preparation time(workdays),and work experience remained statistically significant predictors of IAPE incidence(P<0.05).IAPEs in PIVAS were influenced by multiple factors,predominantly those related to personnel and drug characteristics.Targeted interventions,informed by multivariate analysis,are essential to mitigating these errors and enhancing medication safety.
基金Funded by the International Science and Technology Cooperation Project of the Key R&D Program of Science and Technology Innovation Yongjiang 2035。
文摘An evaluation method for self-healing capacity was designed,which includes the control of initial cracks and subsequent permeability testing.This method was employed to evaluate the self-healing behavior of mortars incorporating crystalline admixtures(CAs)under various conditions,including water immersion,limewater soaking,and wet-dry cycles,with varying CA dosages and crack widths.The experimental results indicate that cement possesses inherently self-healing capability.Limewater environments inhibits healing compared with water immersion;however,wet-dry cycles enhance the effectiveness of higher CA dosages.Increasing the CA content can not improve healing performance,and wide cracks(0.3 mm)substantially reduce the intrinsic self-healing potential of cement.
基金Hunan Provincial Department of Water Resources:Research on Formula Optimization and Performance Evaluation System of Ecological Concrete for River Water Quality Purification Based on the Dual Carbon Goal(Project No.:XSKJ2024064-44)。
文摘In this paper,the effects of four different mineral ginseng materials on the mechanical properties of mortar were studied,and the results showed that high territory,fly ash,and silica fume had an inhibitory effect on the drying shrinkage of mortar,and mineral powder increased the drying shrinkage of mortar.The high territory in the mineral admixture has the best effect on the inhibition of mortar drying shrinkage.The compressive strength and flexural strength of the mortar can be improved by adding a certain amount of mineral admixture,which increases the compressive strength by about 20%-40%and the flexural strength by about 20%-30%compared with the control group,and the improvement effect difference between different components is not large.
文摘In the present study, we aimed to analyze the irrational medical orders and evaluate the effect of pharmacy intervention on pharmacy intravenous admixture services of outpatient and emergency departments in our hospital. The irrational medical orders of PIVAS at the outpatient and emergency departments were retrospectively analyzed in Jun. 2015. We strengthened the pharmacy intervention on irrational medical orders since July 2015. All the cases were selected by systematic sampling method. Cased studied in Jun. 2015 served as the control group, whereas those studied in Jan. 2016 served as the intervention group. The irrational rate and the irrational number of daily average were compared between the control group and intervention group. The common type of irrational outpatient and emergency intravenous orders mainly included irrational use of solvents, irrational dosing interval and inappropriate compatibility of drugs. The irrational rate was reduced from 17.4% to 3.3% （P〈0.01）, and the irrational number of daily average was decreased from 5.23 to 1.00 （P〈0.01）. Pharmacy intervention can reduce the irrational rate of medical orders in our hospital, which is of great significance to promote rational drug use and improve medical quality.
文摘The expansion and micro-cracks of the mortar with composite mineral admixtures （fly ash, zeolite and slag） due to the alkali-silica reaction （ASR） are studied. Results show that composite mineral admixtures cannot absolutely diminish the ASR of mortar bars with the low-alkali cement and a highly reactive aggregate. But the expansion rate and the deleterious expansion of the mortar bar are mostly reduced with increasing composite mineral admixture. The influence of mineral admixtures on the fluidity of the paste and the strength of the mortar is also studied.
基金The Key Program of the National Natural Science Foundation of China(No.51438003)the National Basic Research Program of China(973 Program)(No.2015CB655105)
文摘The rice husk ash （ RHA） and silica （ Si02） nanoparticles are prepared from rice husk charcoal （RHC） by the methods of ventilated calcining and chemical precipitation, respectively, to remove the residual carbon which is harmful to cement composites. The structures and morphologies of these products are investigated by the Fourier transform infrared spectroscopy, X-ray diffraction, scanning/ transmission electron microscopy and N2 adsorption- desorption analyzer. The results show that the as-produced RHA and Si02 nanoparticles exist in amorphous phase without residual carbon, and exhibit porous structures with specific surface areas of 170.19 and 248. 67 m2 /g , respectively. The micro particles of RHA are aggregated by numerous loosely packed Si02 gel particles with the diameter of 50 to 100 nm. The Si02 nanoparticles are well dispersed with the average size of about 30 nm. Both the RHA and Si02 nanoparticles can significantly reduce the conductivity of saturated Ca（OH）2 solution and increase the early strength of the cement composites. They also exhibit high pozzolanic activity, indicating that they can be used as ecological nano mineral admixtures.
文摘The scope of the present paper is to understand the effects of crystalline admixture on the selfhealing capacity of the cementitious composites. Previous studies were examined and a conclusion was drawn to the effect that different additives to crystalline admixture tend to improve self-healing of concrete for larger cracks. It is recommended that initial treatment with chemical admixture can stimulate and heal further cracks and it has the better repeatability trend in mixing with the concretes and mechanical recovery is possible even under repetitive preloading. Effective self-healing with chemical admixtures even under open-air exposure, leads to study the importance of a service ability design parameter including the maximum allowable crack width by repeatability analysis as a function of the exposure with the concept of sealable crack width.
文摘Owing to the high viscosity of sodium silicate solution, fly ash geopolymer has the problems of low workability and rapid setting time. Therefore, the effect of chemical admixtures on the properties of fly ash geopolymer was studied to overcome the rapid set of the geo-polymer in this paper. High-calcium fly ash and alkaline solution were used as starting materials to synthesize the geopolymer. Calcium chloride, calcium sulfate, sodium sulfate, and sucrose at dosages of 1wt% and 2wt% of fly ash were selected as admixtures based on concrete knowledge to improve the properties of the geopolymer. The setting time, compressive strength, and degree of reaction were recorded, and the microstructure was examined. The results show that calcium chloride significantly shortens both the initial and final setting times of the geopolymer paste. In addition, sucrose also delays the final setting time significantly. The degrees of reaction of fly ash in the geopolymer paste with the admixtures are all higher than those of the control paste. This contributes to the obvious increases in compressive strength.
文摘The influence of anti-freezing admixture on the alkali aggregate reaction in mortar was analyzed with accelerated methods. It is confirmed that the addition of sodium salt ingredients of anti-freezing admixture accelerates the alkali silica reaction to some extent, whereas calcium salt ingredient of anti-freezing admixture reduces the expansion of alkali silica reaction caused by high alkali cement. It is found that the addition of the fly ash considerably suppresses the expansion of alkali silica reaction induced by the anti-freezing admixtures.
基金Funded by the Reasearch Grant Council to Hongkong University of Science and Technology (Grant No. R1G94195. EG07).
文摘The improvements of the mechanical properties, including bulk density of fresh mixtures, elastic modulus, and compressive strengths of four high-performance concrete mixtures, made with the addition of fly ash, refined ground blast - furnace microslag (microslag) and silica fume are studied. The concrete mixtures were determined based on the dispersion testing results. The study indicates that the elastic modulus at 28 and 91 days, and compressive strengths of the concretes are improved a lot when fly ash and microslag by 25 percent by weight of cement are added into the mixtures individually. The improvement is especially evident when silica fume by 5 percent and fly ash by 25 percent by weight of cement are added together into the mixture, while the fresh concrete mixture keeps a good workability. Through the analysis of chemically combined water ratios of the four mixtures at various hydration ages, it is found that the addition of all these mineral mixtures are beneficial to the hydration process, especially, at later stages, which might be one of the reasons for the improvement of mechanical properties. (Author abstract) 4 Refs.
文摘Mortar prisms made with different cements or mineral admixtures plus 30% mass of limes tone filler were stored in 2% magnesium sulfate solution at 5±1 ℃ for 1 year and their visual appearance,strength development were measured at intervals.The formation of thaumasite was checked and confirmed by XRD and FTIR.The results show that the relative resistance to thaumasite form of sulfate attack of the cements is outlined below,from best to worst:sulphoaluminate cement,sulfate resisting Portland cement,OPC.The resistance to thaumasite form of sulfate attack of mortar is remarkably improved by the addition of silica fume or ground granulated blastfurnace slag (SL),and the better the resistance to thaumasite form of sulfate attack,the more the addition of SL is.The thaumasite form of sulfate attack is decreased to a certain degree by a lower replacement of cement with fly ash,but it is accelerated by the addition of a higher amount of fly ash due to its lower reactivity.
文摘High-performance concrete （HPC） has specific performance advantages over conventional concrete in strength and durability. HPC mixtures are usually produced with water/binder mass ratios （mW/mB） in the range of 0.2-0.4, so volume changes of concrete as a result of drying, chemical reactions, and temperature change cannot be avoided. For these reasons, shrinkage and cracking are frequent phenomena. It is necessary to add some types of admixture for reduction of shrinkage and cracking of HPC. This study used a shrinkage-reducing admixture （SRA） for that purpose. Concrete was prepared with two different mW/mB （0.22 and 0.40） and four different mass fractions of SRA to binder （w（SRA） = 0%, 1%, 2%, and 4%）. The mineral admixtures used for concrete mixes were： 25% fly ash （FA） and 25% slag by mass of binder for the mixture with mW/mB = 0.40, and 15% silica fume （SF） and 25% FA for the mixture with mW/mB = 0.22. Tests were conducted on 24 prismatic specimens, and shrinkage strains were measured through 120 days of drying. Compressive strength, splitting strength, and static modulus of elasticity were also determined. The results show that the SRA effectively reduces some mechanical properties of HPC. The reductions in compressive strength, splitting tensile strength, and elastic modulus of the concrete were 7%-24%, 9%-19%, and 5%-12%, respectively, after 90 days, compared to concrete mixtures without SRA. SRA can also help reduce drying shrinkage of concrete. The shrinkage strains of HPC with SRA were only as high as 41% of the average free shrinkage of concrete without SRA after 120 days of drying.
基金the Jiangsu Province Natural Science Foundation(No.BK2008520)the Jiangsu Postdoctoral Research Funds(No.0901008C)the China Postdoctoral Science Foundation(No.20090461120)
文摘A new kind of nano-rod shaped polycarboxylic acid slump-retaining agent was synthesized.Transmission electron microscope(TEM) experiment showed that the nano-rod was bound together as macromolecular aggregates in solution.Application performance studying suggested that this kind nano-sized polymer material had excellently plasticity-retaining performance in cement-based materials and could improve endurance performance of hardened cement-based materials distinctly.The concrete with an initial slump of 2-9 cm could achieve 3 h plasticity-retaining performance with the help of this kind nano-rod.The product had extremely wide application value in the market.
文摘The effect of the admixtures of Al and Si metals and B4 C and MgAlON compounds on the oxidation of MgO/ Si3N4 composite refractory has been studied, which is a promising carbon free refractory for steel-making application . The four kinds of admixtures can be used as anti-oxi-dants for Si3N4, but the mixture of Al and Si achieved the best result. The mixture can not only play the role as anti-oxidant, but also assist the sintering process and help form dense sintering layer, improving the property of the composite.
基金Funded by the Western Communication Construction Science and Technology Item (SN: 200631822302-08)
文摘Concrete specimens made with ordinary portland cement or ordinary portland cement incorporating fly ash with the replacement of 10% or 20%, ground blast furnace slag with the replacement of 15% or 30%, or 15% fly ash and 15% ground blast furnace slag were made and exposed to a cyclic sulfate environment. Concrete properties including relative dynamic elastic modulus, chloride ion diffusion coefficient, compressive strength and flexural strength were measured. Effect of mineral admixtures on the cyclic sulfate resistance of concrete was assessed based on the grey clustering theory. The experimental results indicate that the cyclic sulfate resistance of concrete incorporating ground blast furnace slag belongs to the higher grey grade, which exhibits that it possesses excellent cyclic sulfate resistance. With increasing addition of fly ash, the cyclic sulfate resistance of concrete changes from the medium grey grade to the lower grey grade, which shows that incorporation of fly ash is disadvantageous for the cyclic sulfate resistance of concrete.
基金Funded by the National Natural Science Foundation of China(Nos.U1134206,51178230)the Technological Development Projects of China Railway Engineering Corporation(No.Z2013-038-3)
文摘Chemical admixtures are of paramount importance to the performance of modern cement based composites. In this paper, we performed a series of tests to investigate the effects of chemical admixtures on the cement asphalt mortar(CA mortar), i e, compressive strength, frost resistance, permeability, fatigue resistance, pore structure and microstructure. In particular, two types of chemical admixtures were tested, i e, defoamer(tributyl phosphate(TBP)) and polycarboxylate superplasticizer(PS). The results indicate that the addition of TBP and PS eliminates big bubbles and promotes small non-connected pores forming in matrix. Besides, an optimum dosage of TBP and PS may be determined with respect to the frost resistance, permeability and fatigue resistance of CA mortar. Further elaborative discussions are presented as well as experimental evidences from mercury intrusion porosimetry, scanning electron microscopy and energy dispersive spectroscopy.
