C3S pastes containing 0%,5%,10%,and 15%nano-SiO2 mixed with de-ionized water and alkali solutions were prepared.When C3S was completely hydrated,the pastes were ground into powders with a particle size less than 80μm...C3S pastes containing 0%,5%,10%,and 15%nano-SiO2 mixed with de-ionized water and alkali solutions were prepared.When C3S was completely hydrated,the pastes were ground into powders with a particle size less than 80μm.Adsorption and desorption characteristics of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water immersed in alkali solutions and those in C3S-nano SiO2 pastes mixed with alkali solutions,were investigated.Meawhile,the adsorption mechanisms of alkali ions were discussed.Results showed that the contents of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water increased with increasing substitution levels of nano-SiO2 and/or the initial alkali concentrations.In C3S-nano SiO2 pastes mixed with de-ionized water,each paste was characterized by having a fixed alkali-adsorption capacity that was essentially independent of alkali concentration.No obvious difference between the adsorption capacity of a given paste for K~＋and Na~＋was observed.Adsorption of alkali ions in the pastes is considered to be caused by surface force which is related to the BET specific surface area of the paste,and charge compensation of C-S-H gel,mainly by electrostatic interactions.In C3S-nano SiO2 pastes mixed with alkali solutions,alkali ions may enter the structure of C-S-H gel to replace a part of Ca^2＋in the interlayer.This assumption is supported by the structural characterization of C-S-H gel using ^（29）Si MAS NMR.展开更多
以拌合液为KOH和NaOH混合溶液的C_3S-纳米SiO_2浆体为对象,研究了液固比对浆体在去离子水中释放K^+和Na^+的影响以及浆体对K^+和Na^+的滞留能力;并采用29Si MAS NMR分析讨论了K^+和Na^+在C_3S-纳米SiO_2浆体上的存在形式。结果表明:随...以拌合液为KOH和NaOH混合溶液的C_3S-纳米SiO_2浆体为对象,研究了液固比对浆体在去离子水中释放K^+和Na^+的影响以及浆体对K^+和Na^+的滞留能力;并采用29Si MAS NMR分析讨论了K^+和Na^+在C_3S-纳米SiO_2浆体上的存在形式。结果表明:随着液固比的增大,浆体释放的K^+和Na^+的百分数逐渐增大;经去离子水充分洗涤后仍有一部分K^+和Na^+存在于浆体中,且浆体对K^+和Na^+的滞留能力随着纳米SiO_2掺量的增加以及拌合液碱浓度的增大而增强。29Si MAS NMR分析证实了K^+和Na^+能够进入C-S-H凝胶层间形成不可逆的化学结合。K^+和Na^+通过取代C-S-H凝胶层间≡SiOCa+中的Ca2+,缩短了C-S-H凝胶中[SiO4]4-四面体链长,从而使凝胶中Q1和Q2峰向左移动。展开更多
The singlet and triplet potential energy surfaces of interstellar molecule C 3S are predicted at the UB3LYP/6-311(d) and UCCSD(T)/6-311+G(2df) (single-point) levels. The linear singlet isomer CCCS with 1∑ + ele...The singlet and triplet potential energy surfaces of interstellar molecule C 3S are predicted at the UB3LYP/6-311(d) and UCCSD(T)/6-311+G(2df) (single-point) levels. The linear singlet isomer CCCS with 1∑ + electronic state is found to be thermodynamically and kinetically the most stable species on the singlet surface followed by other four singlet isomers, which are unstable on the basis of calculated results. On the triplet surface, the lowest-lying species, which lies 248.79 kJ/mol above linear singlet species CCCS, is chain CCCS connectivity with 3A′ electronic state. Other four triplet isomers can be considered as unstable species by means of transition state and potential energy surface scan technologies. The structures, vibrational frequencies, dipole moments and rotational constants of all optimized species are also calculated.展开更多
基金Funded by the Program for Changjiang Scholars and Innovative Research Team in University(PCSIRT)(No.IRT1146)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘C3S pastes containing 0%,5%,10%,and 15%nano-SiO2 mixed with de-ionized water and alkali solutions were prepared.When C3S was completely hydrated,the pastes were ground into powders with a particle size less than 80μm.Adsorption and desorption characteristics of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water immersed in alkali solutions and those in C3S-nano SiO2 pastes mixed with alkali solutions,were investigated.Meawhile,the adsorption mechanisms of alkali ions were discussed.Results showed that the contents of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water increased with increasing substitution levels of nano-SiO2 and/or the initial alkali concentrations.In C3S-nano SiO2 pastes mixed with de-ionized water,each paste was characterized by having a fixed alkali-adsorption capacity that was essentially independent of alkali concentration.No obvious difference between the adsorption capacity of a given paste for K~＋and Na~＋was observed.Adsorption of alkali ions in the pastes is considered to be caused by surface force which is related to the BET specific surface area of the paste,and charge compensation of C-S-H gel,mainly by electrostatic interactions.In C3S-nano SiO2 pastes mixed with alkali solutions,alkali ions may enter the structure of C-S-H gel to replace a part of Ca^2＋in the interlayer.This assumption is supported by the structural characterization of C-S-H gel using ^（29）Si MAS NMR.
文摘以拌合液为KOH和NaOH混合溶液的C_3S-纳米SiO_2浆体为对象,研究了液固比对浆体在去离子水中释放K^+和Na^+的影响以及浆体对K^+和Na^+的滞留能力;并采用29Si MAS NMR分析讨论了K^+和Na^+在C_3S-纳米SiO_2浆体上的存在形式。结果表明:随着液固比的增大,浆体释放的K^+和Na^+的百分数逐渐增大;经去离子水充分洗涤后仍有一部分K^+和Na^+存在于浆体中,且浆体对K^+和Na^+的滞留能力随着纳米SiO_2掺量的增加以及拌合液碱浓度的增大而增强。29Si MAS NMR分析证实了K^+和Na^+能够进入C-S-H凝胶层间形成不可逆的化学结合。K^+和Na^+通过取代C-S-H凝胶层间≡SiOCa+中的Ca2+,缩短了C-S-H凝胶中[SiO4]4-四面体链长,从而使凝胶中Q1和Q2峰向左移动。
文摘The singlet and triplet potential energy surfaces of interstellar molecule C 3S are predicted at the UB3LYP/6-311(d) and UCCSD(T)/6-311+G(2df) (single-point) levels. The linear singlet isomer CCCS with 1∑ + electronic state is found to be thermodynamically and kinetically the most stable species on the singlet surface followed by other four singlet isomers, which are unstable on the basis of calculated results. On the triplet surface, the lowest-lying species, which lies 248.79 kJ/mol above linear singlet species CCCS, is chain CCCS connectivity with 3A′ electronic state. Other four triplet isomers can be considered as unstable species by means of transition state and potential energy surface scan technologies. The structures, vibrational frequencies, dipole moments and rotational constants of all optimized species are also calculated.
