Composition, morphology, and structure of hydration products in hardened pastes of three kinds of blended cement（cement-silica fume, cement-quartz powder and cement-silica fume-quartz powder） hydrated under differen...Composition, morphology, and structure of hydration products in hardened pastes of three kinds of blended cement（cement-silica fume, cement-quartz powder and cement-silica fume-quartz powder） hydrated under different curing regimes（standard curing, 90 ℃ steam curing, 200 ℃ and 250 ℃ autoclave curing） were investigated by X-ray diffraction and field emission scanning electron microscope equipped with EDAX system. Results showed that the main hydration products in three kinds of hardened pastes under standard curing condition are all C-S-H gels, CH, and AFt. Under 90 ℃ steam curing condition, the main hydration products of cement-silica fume and cement-silica fume-quartz powder are C-S-H gels, whereas those of cement-quartz powder are C-S-H and CH. Under 200 or 250 ℃ autoclave curing condition, no obvious crystallized CH phase is found in hardened pastes of three kinds of blended cement, and C-S-H gels are transformed into one or more crystalline phases such as tobermorite, jennite, and xonotlite. The chemical composition and morphology of these crystalline phases depend on the composition of mixture and autoclave temperature.展开更多
The compressive strength of the cement-silica fume blends with 5mass%, 10mass%, 20mass% and 30mass% of silica fume and water to binder ratio of 0.28, 0.32 and 0.36 from three days to ninety days were investigated. The...The compressive strength of the cement-silica fume blends with 5mass%, 10mass%, 20mass% and 30mass% of silica fume and water to binder ratio of 0.28, 0.32 and 0.36 from three days to ninety days were investigated. The reaction degree of silica fume was calculated from the Q4 silica tetrahedron, which was used as a probe obtained from 29 Si solid state nuclear magnetic resonance analysis. The fl at of compressive strength after 28 days disappeared for blended cement with inereasing reaction degree of silica fume. The compressive strength of the blended cement pastes approached that of P.I. cement pastes after 56 days and exceeded that after 90 days. The addition of silica fume and the w/b ratio of blends are both critical to the reaction degree of silica fume. The appropriate addition of silica fume, high silica fume reaction degree and low w/b ratio are benefi cial to the compressive strength of the cement-silica fume blends.展开更多
为更好地研究硅灰对水泥胶砂耐硫酸侵蚀性能的影响,本文将硅灰按不同配合比进行试验,将水泥胶砂置于pH=1的硫酸侵蚀环境中。通过探究试样的外观、质量损失率、抗压强度损失率、硫酸侵蚀下的生成物、微观结构,并结合相关理论分析了硅灰...为更好地研究硅灰对水泥胶砂耐硫酸侵蚀性能的影响,本文将硅灰按不同配合比进行试验,将水泥胶砂置于pH=1的硫酸侵蚀环境中。通过探究试样的外观、质量损失率、抗压强度损失率、硫酸侵蚀下的生成物、微观结构,并结合相关理论分析了硅灰对水泥胶砂抗硫酸侵蚀作用的影响。实验研究表明:随着硅灰掺量的增加,水泥胶砂的抗硫酸侵蚀能力增强,XRD(x-ray diffraction)衍射表明,在硫酸侵蚀下表面生成物为二水石膏(CaSO_(4)·2H_(2)O),反应时会消耗Ca(OH)_(2),同时也会产生一定的体积膨胀;SEM(scanning electron microscope)检测表明,掺入硅灰可以提高试样的密实度,从而提高水泥胶砂的抗硫酸侵蚀性能。从宏观和微观角度综合来看,硅灰掺量为15%时的抗硫酸侵蚀性能最好。展开更多
This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical propertie...This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical properties enhancement mechanisms were analyzed and compared through the porosity structure test, XRD analysis, and scanning electron microscope observation. The results show that the introduction of nanosilica significantly improves the dispersion of carbon nanotubes in the cement matrix. At the same time, the addition of nanosilica not only effectively reduces the critical pore size and average pore size of the cement composite material, but also exhibits good synergistic effects with carbon nanotubes, which can significantly optimize the pore structure. Finally, a rationalization suggestion for the co-doping of nanosilica and carbon nanotubes was given to achieve a significant increase in the flexural strength, compressive strength and loss factor of cement-based materials.展开更多
基金Funded by the National Natural Science Foundation of China(Nos.51272193,51372183,51072150)Program for New Century Excellent Talents in University(No.NCET-10-0660)the National Key Research Projects(No.2016YFB0303501)
文摘Composition, morphology, and structure of hydration products in hardened pastes of three kinds of blended cement（cement-silica fume, cement-quartz powder and cement-silica fume-quartz powder） hydrated under different curing regimes（standard curing, 90 ℃ steam curing, 200 ℃ and 250 ℃ autoclave curing） were investigated by X-ray diffraction and field emission scanning electron microscope equipped with EDAX system. Results showed that the main hydration products in three kinds of hardened pastes under standard curing condition are all C-S-H gels, CH, and AFt. Under 90 ℃ steam curing condition, the main hydration products of cement-silica fume and cement-silica fume-quartz powder are C-S-H gels, whereas those of cement-quartz powder are C-S-H and CH. Under 200 or 250 ℃ autoclave curing condition, no obvious crystallized CH phase is found in hardened pastes of three kinds of blended cement, and C-S-H gels are transformed into one or more crystalline phases such as tobermorite, jennite, and xonotlite. The chemical composition and morphology of these crystalline phases depend on the composition of mixture and autoclave temperature.
基金Funded by the National Basic Research Program of China(No.2009CB623100)
文摘The compressive strength of the cement-silica fume blends with 5mass%, 10mass%, 20mass% and 30mass% of silica fume and water to binder ratio of 0.28, 0.32 and 0.36 from three days to ninety days were investigated. The reaction degree of silica fume was calculated from the Q4 silica tetrahedron, which was used as a probe obtained from 29 Si solid state nuclear magnetic resonance analysis. The fl at of compressive strength after 28 days disappeared for blended cement with inereasing reaction degree of silica fume. The compressive strength of the blended cement pastes approached that of P.I. cement pastes after 56 days and exceeded that after 90 days. The addition of silica fume and the w/b ratio of blends are both critical to the reaction degree of silica fume. The appropriate addition of silica fume, high silica fume reaction degree and low w/b ratio are benefi cial to the compressive strength of the cement-silica fume blends.
文摘为更好地研究硅灰对水泥胶砂耐硫酸侵蚀性能的影响,本文将硅灰按不同配合比进行试验,将水泥胶砂置于pH=1的硫酸侵蚀环境中。通过探究试样的外观、质量损失率、抗压强度损失率、硫酸侵蚀下的生成物、微观结构,并结合相关理论分析了硅灰对水泥胶砂抗硫酸侵蚀作用的影响。实验研究表明:随着硅灰掺量的增加,水泥胶砂的抗硫酸侵蚀能力增强,XRD(x-ray diffraction)衍射表明,在硫酸侵蚀下表面生成物为二水石膏(CaSO_(4)·2H_(2)O),反应时会消耗Ca(OH)_(2),同时也会产生一定的体积膨胀;SEM(scanning electron microscope)检测表明,掺入硅灰可以提高试样的密实度,从而提高水泥胶砂的抗硫酸侵蚀性能。从宏观和微观角度综合来看,硅灰掺量为15%时的抗硫酸侵蚀性能最好。
文摘This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical properties enhancement mechanisms were analyzed and compared through the porosity structure test, XRD analysis, and scanning electron microscope observation. The results show that the introduction of nanosilica significantly improves the dispersion of carbon nanotubes in the cement matrix. At the same time, the addition of nanosilica not only effectively reduces the critical pore size and average pore size of the cement composite material, but also exhibits good synergistic effects with carbon nanotubes, which can significantly optimize the pore structure. Finally, a rationalization suggestion for the co-doping of nanosilica and carbon nanotubes was given to achieve a significant increase in the flexural strength, compressive strength and loss factor of cement-based materials.
