The mechanochemical synthesis of polycarboxylate superplasticizers(PCEs)was achieved using a planetary ball mill at ambient temperature.The effects of ball milling parameters,including speed,time,and stop method,on PC...The mechanochemical synthesis of polycarboxylate superplasticizers(PCEs)was achieved using a planetary ball mill at ambient temperature.The effects of ball milling parameters,including speed,time,and stop method,on PCE performance,molecular weight,and distribution were investigated to optimize conditions.The experimental results suggest that ball milling impacts PCE molecular weight and distribution,striking a balance between polymerization and mechanical degradation during synthesis.The optimal parameters were found to be 400 rpm,120 minutes total time,and 30 minutes milling plus 3 minutes rest cycles.Under these conditions,the PCE exhibits excellent dispersibility with a cement paste fluidity of 260 mm.The mechanochemical approach eliminates heating requirements,and also reduces the reaction time from 300 to 120 minutes compared to traditional aqueous synthesis.The optimized PCE demonstrates an increased density of long-side chains,leading to enhanced early strength,heightens adsorption,and diminished zeta potential in cement systems.These characteristics are comparable to traditionally synthesized PCEs.Moreover,at higher dosages,further augmentation of PCE adsorption and increased cement paste fluidity were noted here.展开更多
This article presents a preparation method for a tailing sand-specific polycarboxylate superplasticizer(AT9)containing multifunctional adsorption groups.By designing multifunctional adsorption groups(-COOH)as side cha...This article presents a preparation method for a tailing sand-specific polycarboxylate superplasticizer(AT9)containing multifunctional adsorption groups.By designing multifunctional adsorption groups(-COOH)as side chains grafted onto the main chain of conventional polycarboxylate ether,the antiadsorption effect is achieved.AT9 was characterized by gel permeation chromatography,and its performance was systematically evaluated in various tailings sand-cement mortar systems.A comparison was made between AT9 and traditional PCE in terms of their effects on the workability of concrete,and the interaction mechanism between AT9 and clay in cementitious systems was discussed.The results indicate that AT9 enhances the adsorption and dispersion effects of polycarboxylate superplasticizers on cement particles,and increases steric hindrance,thereby avoids intercalation adsorption of tailings sand,improves its water-reducing and slump-retaining performance,and also contributes to the strength enhancement of concrete in later stages.展开更多
To address the dual challenges of resource utilization of mining solid waste(e.g.,coal gangue)and performance enhancement of cemented rockfill,this study systematically investigates the mechanisms of ultrasonic disper...To address the dual challenges of resource utilization of mining solid waste(e.g.,coal gangue)and performance enhancement of cemented rockfill,this study systematically investigates the mechanisms of ultrasonic dispersion time and polycarboxylate superplasti-cizer(PCE)on the properties of cellulose nanofiber(CNF)-modified cemented rockfill.A series of comparative experiments were de-signed with varying ultrasonic dispersion times(0-60 min)and PCE dosages(0.1wt%-0.4wt%).Through mechanical testing,hydration product analysis,and microstructural characterization,the study revealed the advantages of PCE in promoting CNF dispersion to enhance the engineering applicability of cemented rockfill.The results demonstrate that:(1)Ultrasonic dispersion for 30 min increases the com-pressive strength by 37.7%compared to the untreated group;however,excessive ultrasonication(60 min)induces hydrolysis of CNF,re-leasing reducing sugars that retard hydration.(2)PCE facilitates CNF dispersion,achieving a 29.1%increase in compressive strength at a dosage of 0.4wt%,while simultaneously improving hydration products and microstructural development.(3)While ultrasonic dispersion yields slightly higher strength improvements,PCE demonstrates superior cost-effectiveness and operational convenience,rendering it more viable for industrial adoption.This study provides a theoretical foundation for the nano-enhanced modification of cemented rockfill,offering new insights into the recycling of solid waste and the development of high-performance materials.展开更多
Effects of polycarboxylate-type superplasticizer（PC） molecular structure on the hydration heat of tricalcium silicate（C3S） paste and polymerization degree of hydration products（C-S-H gel） were researched by usin...Effects of polycarboxylate-type superplasticizer（PC） molecular structure on the hydration heat of tricalcium silicate（C3S） paste and polymerization degree of hydration products（C-S-H gel） were researched by using TAM AIR isothermal microcalorimetry（TA） and 29Si nuclear magnetic resonance（NMR）.Methoxy polyethylene glycol-methacrylates-based polycarboxylate superplasticizers with different side chain lengths and main chain lengths were employed.PC molecules with shorter main chain or longer side chains caused stronger retardation of C3S early hydration and lesser increase of C3S 3 d hydration degree.NMR measurement indicated that the incorporation of PC increased the hydration degree of C3S paste and the polymerization degree of silicon-oxygen tetrahedron of C-S-H gel.The tendency for C3S 7 d hydration degree to improve was more pronounced while PC molecules with longer main chain or shorter side chain were added.Whereas,PC molecules with longer main chains or longer side chains increased the 7 d polymerization degree of C-S-H gel.展开更多
Bridge polycarboxylate superplasticizers（PCs） with crosslink structure were synthesized by using polyethyleneglycol di-acrylate（PEGdA）, replacing partial polyethyleneglycol mono-acrylate （PEGmA） as crosslinking ...Bridge polycarboxylate superplasticizers（PCs） with crosslink structure were synthesized by using polyethyleneglycol di-acrylate（PEGdA）, replacing partial polyethyleneglycol mono-acrylate （PEGmA） as crosslinking agent. Structures of bridge PCs were analyzed by gel permeation chromatography, and dispersion ability was evaluated by cement paste dispersity variation on time and rheology test. The experimental results showed that, molecular weight（MW） of bridge PCs increased with increase of PEGdA proportion, and MW distribution curve changed from Gaussian to fiat like, which meant notable increase of highly crosslinked copolymer. Bridge PCs led to decreased initial cement paste dispersity and better dispersity retention due to slow releasing. Further research showed that, PEGdA proportion had slight effect on polymerization degree of backbone, MW distribution of backbone deviated from Gaussian distribution and shoulder peaks appeared on distribution curve when PEGdA increased.展开更多
Circulating fluidized bed combustion （CFBC） ash exhibits the desirable pozzolanic activity which makes it a potential supplementary cementitious material to replace cement for concrete production. However, the high ...Circulating fluidized bed combustion （CFBC） ash exhibits the desirable pozzolanic activity which makes it a potential supplementary cementitious material to replace cement for concrete production. However, the high unburnt carbon content and porous surface structure of CFBC ash may adsorb water reducer and thereby significantly reduce the efficiency of water-reducing agents. The adsorption mechanism of polycarboxylate superplasticizer in CFBC ash-Portland cement paste was investigated by ultraviolet-visible spectrophotometer, and the conception of ＂invalid adsorption site＂ of CFBC ash was presented. The results show that the adsorption behavior of polycarboxylate superplasticizer in coal ash-Portland cement paste can be described by Langmuir isothermal adsorption equation. The adsorption capacity of CFBC ash-Portland cement paste is higher than that of pulverized coal combustion （PCC） fly ash-Portland cement paste. Moreover, the adsorption amount of polycarboxylate superplasticizer increases with the ratio of ash-to-cement in the paste. At last, the fluidity of CFBC ash-Portland cement paste is lower than that of the PCC fly ash paste. This work suggests that when CFBC ash is used as concrete admixture, the poor flowability of the cementitious system due to the high adsorption of water and water-reducing agent should be taken into consideration.展开更多
Molecular structures of polycarboxylate（PCE） superplasticizer significantly affect the rheological properties of cement paste. Consequently, we employed self-synthesized PCE copolymers with different carboxylic dens...Molecular structures of polycarboxylate（PCE） superplasticizer significantly affect the rheological properties of cement paste. Consequently, we employed self-synthesized PCE copolymers with different carboxylic densities to investigate their influence on the rheological behavior of cement paste. Three typical rheological models were applied to analyze the rheological properties, including Power-law model, Bingham model as well as Herschel-Buikley model. In addition, the thixotropical performances of cement paste in the presence of PCE with different carboxylic densities were investigated. The results show that the carboxylic density of PCE greatly influences the dispersing performance of PCE superplasticizers. As carboxylic density increases, the dispersing capability of PCE improves, and P（PEG1-AA6） possesses the strongest dispersing capability, the initial fluidity and 1 h fluidity of cement paste are both the highest, and cement paste has the lowest viscosity and the smallest hysteresis loop.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
A low adsorption clay-resistant polycarboxylate superplasticizer(KN-PC)was synthesized using acrylic acid and isopentenol polyoxyethylene ether as the main reaction materials.The structural characterization and clay-r...A low adsorption clay-resistant polycarboxylate superplasticizer(KN-PC)was synthesized using acrylic acid and isopentenol polyoxyethylene ether as the main reaction materials.The structural characterization and clay-resistant mechanism of the KN-PC were explored using Fourier transform infrared spectroscopy and X-ray diffraction,and the effect of the KN-PC on the performance of composite paste with various montmorillonite(MMT)contents was analyzed.Compared with ordinary polycarboxylate superplasticizer(PC),the KN-PC has a low sensitivity to the MMT.By the action of the MMT,the adsorption dosage of the KN-PC on the MMT is much smaller than that of the PC.展开更多
The effects of various factors on the synthesis process and the performances of product, including batch feeding way and the dosage of the radical initiator, the system concentration, the reaction temperature and the ...The effects of various factors on the synthesis process and the performances of product, including batch feeding way and the dosage of the radical initiator, the system concentration, the reaction temperature and the reaction time were discussed. A kind of polycarboxylate superplasticizer with allyl alcohol polyethylene glycol, maleic anhydride and methacrylic acid sulfonic sodium as main raw materials has been synthesized. Their relative effectiveness as dispersants was evaluated in cement paste by measuring paste fluidity. The optimum parameters of technology and the appropriate proportion of raw materials were obtained. As a result,the new high performance superplasticizer suitable for high-performance concrete has been synthesized. The structure of copolymer was characterized and analyzed by FT-IR spectra. Results indicated that product copolymer structure was consistent with the ideal molecular structure designed.展开更多
The dispersion ability of polycarboxylate superplasticizer（PCE） in fresh concrete was much impeded by clay impurities. To improve the dispersion of PCE in the clay-contained concrete, a novel PCE with carboxyl as a ...The dispersion ability of polycarboxylate superplasticizer（PCE） in fresh concrete was much impeded by clay impurities. To improve the dispersion of PCE in the clay-contained concrete, a novel PCE with carboxyl as a specific branched chain terminal group was synthesized, using modified polyether as the raw material which was prepared through esterification between hexahydrophthalic anhydride（HHPA） and isobutenyl polyoxyethylene ether（IPEG） with hydroxy as the terminal group. The esterification product and PCE molecular structure were characterized by infrared spectroscopy and ~1HNMR resonance. The results confirmed that the product molecular structure was a comb-type copolymer with long-chain terminal carboxyl group and PEO attached directly to the backbone chain. The as-synthesized PCEs had favorable dispersibility in cement than conventional PCE in the presence of montmorillonite（Mmt） clay. This can be attributed to the introduction of electronegative carboxyl to PCE long-chain terminal group, which reduces the adsorption of PCE on Mmt, and thus improves the tolerance of PCE to the Mmt.展开更多
The infl uence law of clay on mortar fluidity mixed with polycarboxylate superplasticizer was studied. Several methods of inhibiting clay adsorption of polycarboxylate superplasticizer were discussed. The experimental...The infl uence law of clay on mortar fluidity mixed with polycarboxylate superplasticizer was studied. Several methods of inhibiting clay adsorption of polycarboxylate superplasticizer were discussed. The experimental results show that clay has signifi cant effect on the dispersion of polycarboxylate superplasticizer and montmorillonite clay has more signifi cant impact on mortar fluidity than other clays. The pH value and the salts of the solution can affect the adsorption of clay to polycarboxylate superplasticizer. The incorporation of a small amount of sodium hydroxide solution, sodium silicate or cationic surfactants can improve the effect of the clay on the dispersion of polycarboxylate superplasticizer.展开更多
A series of polycarboxylate-based superplasticizers(PCs) with different structures were synthesized and the effects of chemical structure on zeta potential and rheological property of cement paste were studied. Residu...A series of polycarboxylate-based superplasticizers(PCs) with different structures were synthesized and the effects of chemical structure on zeta potential and rheological property of cement paste were studied. Residual monomers in each sample of PCs were quantitatively determined. The property of the polymers in cement was tested by micro-electrophoresis apparatus and R/S rheometer. Results showed that the zeta potential and its rheological properties are related with the side-chain length and density of PCs. The PCs having shorter side chain and lower side chain density exhibit higher anionic charge density, thus resulting in higher zeta potential. The effect of side chain density on zeta potential is more notable compared with that of side-chain length, and thus affecting the initial shear yield stress and apparent viscosity of the cement paste. In addition, although increasing the side chain length will result in reduction of the anionic charge density, the steric hindrance effect is obvious, which can effectively improve the dispersion of the cement particles, and reduce the viscosity and shear yield stress of slurry.展开更多
A novel reactive polycarboxylic acid dye was synthesized by the reaction of polymaleic anhydride（PMA） with 3-methyl-1-（4- sulfonylphenyl）-4-（4-aminophenylazo）-2-pyrazoline-5-one.The structure of the novel dye wa...A novel reactive polycarboxylic acid dye was synthesized by the reaction of polymaleic anhydride（PMA） with 3-methyl-1-（4- sulfonylphenyl）-4-（4-aminophenylazo）-2-pyrazoline-5-one.The structure of the novel dye was characterized by FTIR,UV-vis and ^（13）C NMR spectra.The dyeing properties of dye on cotton were tested,and the novel dye possessed high fixation and good fastness.展开更多
A procedure was developed for the determination of residual monomers in polycarboxylate superplasticizer （PCs） by reversed-phase high performance liquid chromatography （RP-HPLC）.Four kinds of residual monomers wer...A procedure was developed for the determination of residual monomers in polycarboxylate superplasticizer （PCs） by reversed-phase high performance liquid chromatography （RP-HPLC）.Four kinds of residual monomers were well separated and determined on a SinoChrom ODS-BP （C18） column with mobile phases composed of acetonitrile and phosphate buffer solution.The monomers were detected by UV detector at 205 nm and quantitatively analyzed with an external standard method.For those residual monomers,the linear response ranged from 4.0×10-6 mol·L-1 to 2.0×10-3 mol·L-1.The determination limit of acrylic acid,sodium methylallyl sulfonate and 2-Acrylamido-2-methylpropane sulfonic acid was 0.02×10-5 mol·L-1,while that of methoxy-polyethylene glycol monoacrylate was 0.1×10-5 mol·L-1.The relative standard deviation （RSD） of high concentration samples was less than 1%,while that of the low concentration samples was between 1%-4%.The standard （additional） recovery ratio was 97.4% -104.2%.展开更多
The effects of circulating fluid bed(CFB) ash on the adsorption performance of polycarboxylate superplasticiser and the mechanism of this influence on the dispersive property of the polycarboxylate superplasticiser we...The effects of circulating fluid bed(CFB) ash on the adsorption performance of polycarboxylate superplasticiser and the mechanism of this influence on the dispersive property of the polycarboxylate superplasticiser were investigated by determing the cement paste fluidity, total organic carbon adsorption, infrared spectroscopic analyses and ζ potential test. The experimental results show that the addition of an inorganic salt into the mixture to change the content of SO42-and Fe2O3can improve the adaptability between the CFB ash and polycarboxylate superplasticiser. Adsorption may occur between the polycarboxylate superplasiciser and Fe2O3, SO42-or other components in CFB ash, leading to a significant reduction in paste fluidity. As the content of Na2SO4in CFB ash reaches 3% or Fe2O3reaches 9%, the paste loses its liquidity. The organic carbon content in the liquor decreases with an increase in Na2SO4or Fe2O3content. Adding some Ba(NO3)2and Na2S to the liquor can recover the organic carbon content to a certain extent, and the absolute value of ζ potential will increase. The addition of Ba(-NO3)2or Na2S reduces the adsorption property of Na2SO4or Fe2O3in CFB ash on the polycarboxylate superplasticiser.展开更多
Influences of different superplasticizers （ STP. KSJSTO and LMS-P） on rheological behavior of low-cement castables and the mechanisms were analyzed. The shear stress and viscosity under different shear rates of matr...Influences of different superplasticizers （ STP. KSJSTO and LMS-P） on rheological behavior of low-cement castables and the mechanisms were analyzed. The shear stress and viscosity under different shear rates of matrix slurry were determined using a NXS-I IA rotary viscometer. Effects of different admixtures on the rheological properties of slurry was analyzed theoretically. Sodium tripolyphosphate and poly＇carboxylate superplasticizers KS-JSTO and LMS-P） can improve the fluidity and initial setting time. With STP. the slurry is plastic flow. With KS-JS70 or LMS-P increasing, the slurrv changes from plastic.flow, pseudoplastic flow to dilatant flow successively. Th, e optimum dosages of STP. KS-JSTO and LMS-P are 0. 15%. 0. 25% and 0. 40%, respectively. KS-JS70 and LMS-P can significantly reduce the slurry viscosity and shear stress to improve the workability of construction. Both shear stress and viscosity shall be taken into account for on-site construction.展开更多
A new kind of polycarboxylate superplasticizer with high slump loss resistance was obtained by designing scheduled molecular structure.The number average molecular mass of the polymer was characterized by the gel perm...A new kind of polycarboxylate superplasticizer with high slump loss resistance was obtained by designing scheduled molecular structure.The number average molecular mass of the polymer was characterized by the gel permeation chromatography measurements.And chemical structure of the polymer was observed by the Fourier transform infrared spectroscopy(FT-IR).The results show that the good workable maintaining of self-compacting concrete could be achieved through direct adjustment of number average molecular mass and different unsaturated monomer in synthetic process.The FT-IR analysis illustrated that the high slump loss resistance of polycarboxylate superplasticizers with ester and carboxyl group and expectations of molecular structure were designed.展开更多
Using ethylene glycol monovinyl polyoxyethylene ether,2-acrylamido-2-methylpropane sulfonic acid(AMPS)and acrylic acid as the main synthetic monomers,a high robustness polycarboxylate superplasticizer was prepared.The...Using ethylene glycol monovinyl polyoxyethylene ether,2-acrylamido-2-methylpropane sulfonic acid(AMPS)and acrylic acid as the main synthetic monomers,a high robustness polycarboxylate superplasticizer was prepared.The effects of initial temperature,ratio of acid to ether,amount of chain transfer agent,and synthesis process on the properties of the superplasticizer were studied.The molecular structure was characterized by GPC(Gel Permeation Chromatography)and IR(Infrared Spectrometer).As shown by the results,when the initial reaction temperature is 15℃,the ratio of acid to ether is 3.4:1 and the acrylic acid pre-neutralization is 15%,The AMPS substitution is 10%,the amount of chain transfer agent is 8%,and the performance of the synthesized superplasticizer is the best.Compared with commercially available ordinary polycarboxylate superplasticizer in C30 concrete prepared with manufactured sand and fly ash,the bleeding rate decreases by 52%,T50 decreases by 1.2 s,and the slump time decreases by 1.1 s.In C60 concrete prepared with fly ash and river sand,the bleeding rate decreases by 46%,T50 decreases by 0.8 s,and the slump time decreases by 3.2 s.展开更多
Graphene oxide(GO)as a new nano-enhancer in cement-based materials has gained wide attention.However,GO is easy to aggregate in alkaline cement mortar with poor dispersibility.This hinders its application in practical...Graphene oxide(GO)as a new nano-enhancer in cement-based materials has gained wide attention.However,GO is easy to aggregate in alkaline cement mortar with poor dispersibility.This hinders its application in practical infrastructure construction.In this work,GO-M18 polycarboxylate compound superplasticizer(GM)were obtained by compounding the M18 polycarboxylate superplasticizer with GO solution at different mass ratios.The dispersion of GM in alkaline solution was systematically studied.The phases and functional groups of GM were characterized by XRD and FTIR.The effects of GM on the cement mortar hydration and the formation of microstructure were investigated by measuring the heat of hydration,MIP,TG/DSC,and SEM.The results show that the long-chain structure of the M18 polycarboxylate superplasticizer can increase the interlayer spacing of GO and weaken the force between GO sheets.The modified GO can be uniformly dispersed in the cement slurry.GM can accelerate the early hydration process of cement,which can increase the content of Ca(OH)2 and decrease the grain size.It can optimize the pore size distribution of cement-based materials,increase the density of harmless and less harmful pores,thereby improving mechanical properties.Such methods can transform traditional cement-based materials into stronger,more durable composites,which prolong the life of cement-based materials and reduce the amount of cement used for later maintenance.This provides an idea for achieving sustainability goals in civil engineering.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.U1905216 and 52108208)the Henan Provincial Science and Technology Research Project(No.212102310559)。
文摘The mechanochemical synthesis of polycarboxylate superplasticizers(PCEs)was achieved using a planetary ball mill at ambient temperature.The effects of ball milling parameters,including speed,time,and stop method,on PCE performance,molecular weight,and distribution were investigated to optimize conditions.The experimental results suggest that ball milling impacts PCE molecular weight and distribution,striking a balance between polymerization and mechanical degradation during synthesis.The optimal parameters were found to be 400 rpm,120 minutes total time,and 30 minutes milling plus 3 minutes rest cycles.Under these conditions,the PCE exhibits excellent dispersibility with a cement paste fluidity of 260 mm.The mechanochemical approach eliminates heating requirements,and also reduces the reaction time from 300 to 120 minutes compared to traditional aqueous synthesis.The optimized PCE demonstrates an increased density of long-side chains,leading to enhanced early strength,heightens adsorption,and diminished zeta potential in cement systems.These characteristics are comparable to traditionally synthesized PCEs.Moreover,at higher dosages,further augmentation of PCE adsorption and increased cement paste fluidity were noted here.
文摘This article presents a preparation method for a tailing sand-specific polycarboxylate superplasticizer(AT9)containing multifunctional adsorption groups.By designing multifunctional adsorption groups(-COOH)as side chains grafted onto the main chain of conventional polycarboxylate ether,the antiadsorption effect is achieved.AT9 was characterized by gel permeation chromatography,and its performance was systematically evaluated in various tailings sand-cement mortar systems.A comparison was made between AT9 and traditional PCE in terms of their effects on the workability of concrete,and the interaction mechanism between AT9 and clay in cementitious systems was discussed.The results indicate that AT9 enhances the adsorption and dispersion effects of polycarboxylate superplasticizers on cement particles,and increases steric hindrance,thereby avoids intercalation adsorption of tailings sand,improves its water-reducing and slump-retaining performance,and also contributes to the strength enhancement of concrete in later stages.
基金support from the National Natural Science Foundation of China(Nos.42372328,U23B2091,52478253,and 52374147)Natural Science Foundation of Jiangsu Province,China(No.BK20240209).
文摘To address the dual challenges of resource utilization of mining solid waste(e.g.,coal gangue)and performance enhancement of cemented rockfill,this study systematically investigates the mechanisms of ultrasonic dispersion time and polycarboxylate superplasti-cizer(PCE)on the properties of cellulose nanofiber(CNF)-modified cemented rockfill.A series of comparative experiments were de-signed with varying ultrasonic dispersion times(0-60 min)and PCE dosages(0.1wt%-0.4wt%).Through mechanical testing,hydration product analysis,and microstructural characterization,the study revealed the advantages of PCE in promoting CNF dispersion to enhance the engineering applicability of cemented rockfill.The results demonstrate that:(1)Ultrasonic dispersion for 30 min increases the com-pressive strength by 37.7%compared to the untreated group;however,excessive ultrasonication(60 min)induces hydrolysis of CNF,re-leasing reducing sugars that retard hydration.(2)PCE facilitates CNF dispersion,achieving a 29.1%increase in compressive strength at a dosage of 0.4wt%,while simultaneously improving hydration products and microstructural development.(3)While ultrasonic dispersion yields slightly higher strength improvements,PCE demonstrates superior cost-effectiveness and operational convenience,rendering it more viable for industrial adoption.This study provides a theoretical foundation for the nano-enhanced modification of cemented rockfill,offering new insights into the recycling of solid waste and the development of high-performance materials.
基金Funded by the National Basic Research Program of China(973 Program)(No.2009CB623201)
文摘Effects of polycarboxylate-type superplasticizer（PC） molecular structure on the hydration heat of tricalcium silicate（C3S） paste and polymerization degree of hydration products（C-S-H gel） were researched by using TAM AIR isothermal microcalorimetry（TA） and 29Si nuclear magnetic resonance（NMR）.Methoxy polyethylene glycol-methacrylates-based polycarboxylate superplasticizers with different side chain lengths and main chain lengths were employed.PC molecules with shorter main chain or longer side chains caused stronger retardation of C3S early hydration and lesser increase of C3S 3 d hydration degree.NMR measurement indicated that the incorporation of PC increased the hydration degree of C3S paste and the polymerization degree of silicon-oxygen tetrahedron of C-S-H gel.The tendency for C3S 7 d hydration degree to improve was more pronounced while PC molecules with longer main chain or shorter side chain were added.Whereas,PC molecules with longer main chains or longer side chains increased the 7 d polymerization degree of C-S-H gel.
基金Funded by the Western Region Traffic Construction Technology Program of the Ministry of Transport of China(No.2007319811130)
文摘Bridge polycarboxylate superplasticizers（PCs） with crosslink structure were synthesized by using polyethyleneglycol di-acrylate（PEGdA）, replacing partial polyethyleneglycol mono-acrylate （PEGmA） as crosslinking agent. Structures of bridge PCs were analyzed by gel permeation chromatography, and dispersion ability was evaluated by cement paste dispersity variation on time and rheology test. The experimental results showed that, molecular weight（MW） of bridge PCs increased with increase of PEGdA proportion, and MW distribution curve changed from Gaussian to fiat like, which meant notable increase of highly crosslinked copolymer. Bridge PCs led to decreased initial cement paste dispersity and better dispersity retention due to slow releasing. Further research showed that, PEGdA proportion had slight effect on polymerization degree of backbone, MW distribution of backbone deviated from Gaussian distribution and shoulder peaks appeared on distribution curve when PEGdA increased.
基金Funded by the National Natural Science Foundation of China(Nos.51132010 and 51272222)the Programs for Science and Technology Development of Yantai City,Shandong Province,China(No.2012ZH249)
文摘Circulating fluidized bed combustion （CFBC） ash exhibits the desirable pozzolanic activity which makes it a potential supplementary cementitious material to replace cement for concrete production. However, the high unburnt carbon content and porous surface structure of CFBC ash may adsorb water reducer and thereby significantly reduce the efficiency of water-reducing agents. The adsorption mechanism of polycarboxylate superplasticizer in CFBC ash-Portland cement paste was investigated by ultraviolet-visible spectrophotometer, and the conception of ＂invalid adsorption site＂ of CFBC ash was presented. The results show that the adsorption behavior of polycarboxylate superplasticizer in coal ash-Portland cement paste can be described by Langmuir isothermal adsorption equation. The adsorption capacity of CFBC ash-Portland cement paste is higher than that of pulverized coal combustion （PCC） fly ash-Portland cement paste. Moreover, the adsorption amount of polycarboxylate superplasticizer increases with the ratio of ash-to-cement in the paste. At last, the fluidity of CFBC ash-Portland cement paste is lower than that of the PCC fly ash paste. This work suggests that when CFBC ash is used as concrete admixture, the poor flowability of the cementitious system due to the high adsorption of water and water-reducing agent should be taken into consideration.
基金the State Key Laboratory of Silicate Materials for Architectures(SYSJJ2018-09)the Shaanxi Provincial High Performance Concrete Engineering Laboratory(SHPC201701)
文摘Molecular structures of polycarboxylate（PCE） superplasticizer significantly affect the rheological properties of cement paste. Consequently, we employed self-synthesized PCE copolymers with different carboxylic densities to investigate their influence on the rheological behavior of cement paste. Three typical rheological models were applied to analyze the rheological properties, including Power-law model, Bingham model as well as Herschel-Buikley model. In addition, the thixotropical performances of cement paste in the presence of PCE with different carboxylic densities were investigated. The results show that the carboxylic density of PCE greatly influences the dispersing performance of PCE superplasticizers. As carboxylic density increases, the dispersing capability of PCE improves, and P（PEG1-AA6） possesses the strongest dispersing capability, the initial fluidity and 1 h fluidity of cement paste are both the highest, and cement paste has the lowest viscosity and the smallest hysteresis loop.
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.
基金Funded by National Natural Science Foundation of China(No.51778378)。
文摘A low adsorption clay-resistant polycarboxylate superplasticizer(KN-PC)was synthesized using acrylic acid and isopentenol polyoxyethylene ether as the main reaction materials.The structural characterization and clay-resistant mechanism of the KN-PC were explored using Fourier transform infrared spectroscopy and X-ray diffraction,and the effect of the KN-PC on the performance of composite paste with various montmorillonite(MMT)contents was analyzed.Compared with ordinary polycarboxylate superplasticizer(PC),the KN-PC has a low sensitivity to the MMT.By the action of the MMT,the adsorption dosage of the KN-PC on the MMT is much smaller than that of the PC.
基金Funded by the National Natural Science Foundation of China(No.50972170)
文摘The effects of various factors on the synthesis process and the performances of product, including batch feeding way and the dosage of the radical initiator, the system concentration, the reaction temperature and the reaction time were discussed. A kind of polycarboxylate superplasticizer with allyl alcohol polyethylene glycol, maleic anhydride and methacrylic acid sulfonic sodium as main raw materials has been synthesized. Their relative effectiveness as dispersants was evaluated in cement paste by measuring paste fluidity. The optimum parameters of technology and the appropriate proportion of raw materials were obtained. As a result,the new high performance superplasticizer suitable for high-performance concrete has been synthesized. The structure of copolymer was characterized and analyzed by FT-IR spectra. Results indicated that product copolymer structure was consistent with the ideal molecular structure designed.
文摘The dispersion ability of polycarboxylate superplasticizer（PCE） in fresh concrete was much impeded by clay impurities. To improve the dispersion of PCE in the clay-contained concrete, a novel PCE with carboxyl as a specific branched chain terminal group was synthesized, using modified polyether as the raw material which was prepared through esterification between hexahydrophthalic anhydride（HHPA） and isobutenyl polyoxyethylene ether（IPEG） with hydroxy as the terminal group. The esterification product and PCE molecular structure were characterized by infrared spectroscopy and ~1HNMR resonance. The results confirmed that the product molecular structure was a comb-type copolymer with long-chain terminal carboxyl group and PEO attached directly to the backbone chain. The as-synthesized PCEs had favorable dispersibility in cement than conventional PCE in the presence of montmorillonite（Mmt） clay. This can be attributed to the introduction of electronegative carboxyl to PCE long-chain terminal group, which reduces the adsorption of PCE on Mmt, and thus improves the tolerance of PCE to the Mmt.
基金Funded by the National Natural Science Foundation of China(50872151)the Beijing Municipal Education Commission Program Projects and Beijing University of Civil Engineering and Architecture,Dr.Fund
文摘The infl uence law of clay on mortar fluidity mixed with polycarboxylate superplasticizer was studied. Several methods of inhibiting clay adsorption of polycarboxylate superplasticizer were discussed. The experimental results show that clay has signifi cant effect on the dispersion of polycarboxylate superplasticizer and montmorillonite clay has more signifi cant impact on mortar fluidity than other clays. The pH value and the salts of the solution can affect the adsorption of clay to polycarboxylate superplasticizer. The incorporation of a small amount of sodium hydroxide solution, sodium silicate or cationic surfactants can improve the effect of the clay on the dispersion of polycarboxylate superplasticizer.
基金Funded by the Western Region Traffic Construction Technology Program of the Ministry of Communications of China(No.2007319811130)
文摘A series of polycarboxylate-based superplasticizers(PCs) with different structures were synthesized and the effects of chemical structure on zeta potential and rheological property of cement paste were studied. Residual monomers in each sample of PCs were quantitatively determined. The property of the polymers in cement was tested by micro-electrophoresis apparatus and R/S rheometer. Results showed that the zeta potential and its rheological properties are related with the side-chain length and density of PCs. The PCs having shorter side chain and lower side chain density exhibit higher anionic charge density, thus resulting in higher zeta potential. The effect of side chain density on zeta potential is more notable compared with that of side-chain length, and thus affecting the initial shear yield stress and apparent viscosity of the cement paste. In addition, although increasing the side chain length will result in reduction of the anionic charge density, the steric hindrance effect is obvious, which can effectively improve the dispersion of the cement particles, and reduce the viscosity and shear yield stress of slurry.
基金supported by the State Key Program of National Natural Science Foundation of China(No. 20836001)the Program for Changjiang Scholars and Innovative Research Team in the University(No.IRT0711)
文摘A novel reactive polycarboxylic acid dye was synthesized by the reaction of polymaleic anhydride（PMA） with 3-methyl-1-（4- sulfonylphenyl）-4-（4-aminophenylazo）-2-pyrazoline-5-one.The structure of the novel dye was characterized by FTIR,UV-vis and ^（13）C NMR spectra.The dyeing properties of dye on cotton were tested,and the novel dye possessed high fixation and good fastness.
基金Funded by the Western Region Traffic Construction Technology Program of the Ministry of Communications of China(No.2007319811130)
文摘A procedure was developed for the determination of residual monomers in polycarboxylate superplasticizer （PCs） by reversed-phase high performance liquid chromatography （RP-HPLC）.Four kinds of residual monomers were well separated and determined on a SinoChrom ODS-BP （C18） column with mobile phases composed of acetonitrile and phosphate buffer solution.The monomers were detected by UV detector at 205 nm and quantitatively analyzed with an external standard method.For those residual monomers,the linear response ranged from 4.0×10-6 mol·L-1 to 2.0×10-3 mol·L-1.The determination limit of acrylic acid,sodium methylallyl sulfonate and 2-Acrylamido-2-methylpropane sulfonic acid was 0.02×10-5 mol·L-1,while that of methoxy-polyethylene glycol monoacrylate was 0.1×10-5 mol·L-1.The relative standard deviation （RSD） of high concentration samples was less than 1%,while that of the low concentration samples was between 1%-4%.The standard （additional） recovery ratio was 97.4% -104.2%.
基金Funded by the National Key Research and Development Program of China(2017YFC0602903)the National Natural Science Foundation of China(51834001)
文摘The effects of circulating fluid bed(CFB) ash on the adsorption performance of polycarboxylate superplasticiser and the mechanism of this influence on the dispersive property of the polycarboxylate superplasticiser were investigated by determing the cement paste fluidity, total organic carbon adsorption, infrared spectroscopic analyses and ζ potential test. The experimental results show that the addition of an inorganic salt into the mixture to change the content of SO42-and Fe2O3can improve the adaptability between the CFB ash and polycarboxylate superplasticiser. Adsorption may occur between the polycarboxylate superplasiciser and Fe2O3, SO42-or other components in CFB ash, leading to a significant reduction in paste fluidity. As the content of Na2SO4in CFB ash reaches 3% or Fe2O3reaches 9%, the paste loses its liquidity. The organic carbon content in the liquor decreases with an increase in Na2SO4or Fe2O3content. Adding some Ba(NO3)2and Na2S to the liquor can recover the organic carbon content to a certain extent, and the absolute value of ζ potential will increase. The addition of Ba(-NO3)2or Na2S reduces the adsorption property of Na2SO4or Fe2O3in CFB ash on the polycarboxylate superplasticiser.
文摘Influences of different superplasticizers （ STP. KSJSTO and LMS-P） on rheological behavior of low-cement castables and the mechanisms were analyzed. The shear stress and viscosity under different shear rates of matrix slurry were determined using a NXS-I IA rotary viscometer. Effects of different admixtures on the rheological properties of slurry was analyzed theoretically. Sodium tripolyphosphate and poly＇carboxylate superplasticizers KS-JSTO and LMS-P） can improve the fluidity and initial setting time. With STP. the slurry is plastic flow. With KS-JS70 or LMS-P increasing, the slurrv changes from plastic.flow, pseudoplastic flow to dilatant flow successively. Th, e optimum dosages of STP. KS-JSTO and LMS-P are 0. 15%. 0. 25% and 0. 40%, respectively. KS-JS70 and LMS-P can significantly reduce the slurry viscosity and shear stress to improve the workability of construction. Both shear stress and viscosity shall be taken into account for on-site construction.
文摘A new kind of polycarboxylate superplasticizer with high slump loss resistance was obtained by designing scheduled molecular structure.The number average molecular mass of the polymer was characterized by the gel permeation chromatography measurements.And chemical structure of the polymer was observed by the Fourier transform infrared spectroscopy(FT-IR).The results show that the good workable maintaining of self-compacting concrete could be achieved through direct adjustment of number average molecular mass and different unsaturated monomer in synthetic process.The FT-IR analysis illustrated that the high slump loss resistance of polycarboxylate superplasticizers with ester and carboxyl group and expectations of molecular structure were designed.
基金the Scientific Research Foundation of Hubei University of Technology(GCRC2020012).
文摘Using ethylene glycol monovinyl polyoxyethylene ether,2-acrylamido-2-methylpropane sulfonic acid(AMPS)and acrylic acid as the main synthetic monomers,a high robustness polycarboxylate superplasticizer was prepared.The effects of initial temperature,ratio of acid to ether,amount of chain transfer agent,and synthesis process on the properties of the superplasticizer were studied.The molecular structure was characterized by GPC(Gel Permeation Chromatography)and IR(Infrared Spectrometer).As shown by the results,when the initial reaction temperature is 15℃,the ratio of acid to ether is 3.4:1 and the acrylic acid pre-neutralization is 15%,The AMPS substitution is 10%,the amount of chain transfer agent is 8%,and the performance of the synthesized superplasticizer is the best.Compared with commercially available ordinary polycarboxylate superplasticizer in C30 concrete prepared with manufactured sand and fly ash,the bleeding rate decreases by 52%,T50 decreases by 1.2 s,and the slump time decreases by 1.1 s.In C60 concrete prepared with fly ash and river sand,the bleeding rate decreases by 46%,T50 decreases by 0.8 s,and the slump time decreases by 3.2 s.
基金funded by the National Natural Science Foundation of China(No.51872137)and Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Graphene oxide(GO)as a new nano-enhancer in cement-based materials has gained wide attention.However,GO is easy to aggregate in alkaline cement mortar with poor dispersibility.This hinders its application in practical infrastructure construction.In this work,GO-M18 polycarboxylate compound superplasticizer(GM)were obtained by compounding the M18 polycarboxylate superplasticizer with GO solution at different mass ratios.The dispersion of GM in alkaline solution was systematically studied.The phases and functional groups of GM were characterized by XRD and FTIR.The effects of GM on the cement mortar hydration and the formation of microstructure were investigated by measuring the heat of hydration,MIP,TG/DSC,and SEM.The results show that the long-chain structure of the M18 polycarboxylate superplasticizer can increase the interlayer spacing of GO and weaken the force between GO sheets.The modified GO can be uniformly dispersed in the cement slurry.GM can accelerate the early hydration process of cement,which can increase the content of Ca(OH)2 and decrease the grain size.It can optimize the pore size distribution of cement-based materials,increase the density of harmless and less harmful pores,thereby improving mechanical properties.Such methods can transform traditional cement-based materials into stronger,more durable composites,which prolong the life of cement-based materials and reduce the amount of cement used for later maintenance.This provides an idea for achieving sustainability goals in civil engineering.
