In order to expand the advantages of strong durability and high compressive strength of calcium silicate hydrates(C-S-H),at the same time to make up for the poor early mechanical strength of magnesium silicate hydrate...In order to expand the advantages of strong durability and high compressive strength of calcium silicate hydrates(C-S-H),at the same time to make up for the poor early mechanical strength of magnesium silicate hydrates (M-S-H),we present the features and advantages of C-S-H and M-S-H and a comprehensive review of the progress on CaO-MgO-SiO_(2)-H_(2)O.Moreover,we systematically describe natural calcium and magnesium silicate minerals and thermodynamic properties of CaO-MgO-SiO_(2)-H_(2)O.The effect of magnesium on C-S-H and calcium on M-S-H is summarized deeply;the formation and structural feature of CaO-MgO-SiO_(2)-H_(2)O is also explained in detail.Finally,the development of calcium and magnesium silicate hydrates in the future is pointed out,and the further research is discussed and estimated.展开更多
The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectrometer (FTIR) and inductively coupled plasma atomic emission spectroscopy (...The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectrometer (FTIR) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) using in-vitro tests. The results show that the soaked fiber is surrounded by an outer calcium-magnesium silicate hydrated layer, and there exists a balancing function between the formation and abscission of the hydrated layer during the dissolution process. The concentrations of leached ions increase constantly, and the mass loss of the fibers and pH changes of the solution are found to rise rapidly during the initial dissolution process, then their increasing rates are controlled by the balancing function of the hydrated layer at the subsequent dissolution stages. The dissolution rate constant and time for complete dissolution are estimated to be 274 ng/(cm2·h) and 15.2 d, respectively, presenting preferable biosolubilities.展开更多
Crystallization characteristic of periclase in clinker and effect of Mg^2+ on hydrate of cement pastes were investigated. Morphologies and relative content of periclase were characterized with scanning electron micros...Crystallization characteristic of periclase in clinker and effect of Mg^2+ on hydrate of cement pastes were investigated. Morphologies and relative content of periclase were characterized with scanning electron microscopy and X-ray diffraction. Derivative thermogravimetry analysis and backscattered electron imaging were used to characterize the effect of Mg^2+ on hydrate of cement pastes. The experimental results show that in ample space, periclase forms octahedron structure, and subhedral or anhedral crystal is formed in limited space. Due to the accelerated burning temperature and prolonged holding time, coarse pericalase crystals are formed. Mg(OH)2 particle thickness increases due to faster crystal growth rate along c axis at later age. Mg^2+can substitute Ca^2+ in C-S-H or C-A-H to form magnesium silicate hydrate(M-S-H) or magnesium aluminate hydrate(M-A-H), and the substitution extent for C-A-H is higher than that for C-S-H. Cured in 80 ℃ water, the decalcification rate of C-A-H in pastes is higher than that cured in 50 ℃ water. M-A-H with an atomic Mg/Al ratio of 2 is formed through substitution of Ca by Mg in C-A-H.展开更多
The paste was prepared by mixing MgO, microsilica and H2O in the presence of water reducer at different reaction ratios and temperatures, and characterized by XRD, DTA, TGA, IR, and solid-state 29Si NMR. The experimen...The paste was prepared by mixing MgO, microsilica and H2O in the presence of water reducer at different reaction ratios and temperatures, and characterized by XRD, DTA, TGA, IR, and solid-state 29Si NMR. The experimental results showed that, besides Mg（OH）2, magnesium silicate hydrate （M-S-H） was formed at a low temperature such as 25 and 50 ℃. At a high temperature of 100 ℃, Mg（OH）2 can be further transformed into M-S-H completely, for instance, within ca. 1 month in an excess of microsilica. The average composition and structure of M-S-H was mainly related to the reaction mixture and curing temperature and was discussed in detail.展开更多
It was proved that MgO and MicroSilica can react at room temperature, giving a hardened product primarily comprised of Mg （ OH ）2 and Magnesium Silicate Hydrate （ M- S- H ）. The reaction ratio and process and the ...It was proved that MgO and MicroSilica can react at room temperature, giving a hardened product primarily comprised of Mg （ OH ）2 and Magnesium Silicate Hydrate （ M- S- H ）. The reaction ratio and process and the chemical composion of M- S- H were studied and analyzed by QXRD and DTA- TG. The experimental results indicate that much Mg（ OH）2 and less M-S-H were formed at early period. After 7 days there is no change in the quantity of Mg（ OH）2, while M-S-H was increased slowly. The chemical composion of M-S-H would vary with the mix proportion in the hydrution process , but M1.32 SH2.37 is finally the approximute form.展开更多
采用X射线衍射(XRD)和固体魔角核磁共振硅谱(^(29)Si MAS NMR)技术,研究了不同养护温度下MgO/SiO_2体系水化产物的结构特征.结果表明:死烧MgO比轻烧MgO衍射峰强度更大;水化硅酸镁(M-S-H)凝胶呈结晶性较差、短程有序的层状硅酸盐结构;M-...采用X射线衍射(XRD)和固体魔角核磁共振硅谱(^(29)Si MAS NMR)技术,研究了不同养护温度下MgO/SiO_2体系水化产物的结构特征.结果表明:死烧MgO比轻烧MgO衍射峰强度更大;水化硅酸镁(M-S-H)凝胶呈结晶性较差、短程有序的层状硅酸盐结构;M-S-H含量随着养护温度的升高而增多,相同养护温度下M-S-H的含量随着龄期的延长而增多,50℃下养护28d的试样M-S-H含量最多;养护温度过高会抑制M-S-H的生成;高温养护有利于Q^1向Q^2、Q^2向Q^3转化,使得M-S-H硅氧四面体聚合度提高.展开更多
基金Funded by Natural Science Basic Research Plan in Shaanxi Province of China (Nos.2021JQ-500, 2021GY-203, 2023-JCYB-096)Shaanxi Provincial Education Department of Key Scientific Research Plan (No.20JS079)Shaanxi Provincial Education Department of Normal Scientific Research Plan (No.20JK0727)。
文摘In order to expand the advantages of strong durability and high compressive strength of calcium silicate hydrates(C-S-H),at the same time to make up for the poor early mechanical strength of magnesium silicate hydrates (M-S-H),we present the features and advantages of C-S-H and M-S-H and a comprehensive review of the progress on CaO-MgO-SiO_(2)-H_(2)O.Moreover,we systematically describe natural calcium and magnesium silicate minerals and thermodynamic properties of CaO-MgO-SiO_(2)-H_(2)O.The effect of magnesium on C-S-H and calcium on M-S-H is summarized deeply;the formation and structural feature of CaO-MgO-SiO_(2)-H_(2)O is also explained in detail.Finally,the development of calcium and magnesium silicate hydrates in the future is pointed out,and the further research is discussed and estimated.
基金Projects(50872098, 51004080) supported by the National Natural Science Foundation of ChinaProject(B0903) supported by the Opening Fund of Research Center of Green Manufacturing and Energy-saving & Emission Reduction Technology of Wuhan University of Science and Technology, China
文摘The dissolution behavior of CaO-MgO-SiO2 glass fiber was investigated by scanning electron microscopy (SEM), Fourier-transform infrared spectrometer (FTIR) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) using in-vitro tests. The results show that the soaked fiber is surrounded by an outer calcium-magnesium silicate hydrated layer, and there exists a balancing function between the formation and abscission of the hydrated layer during the dissolution process. The concentrations of leached ions increase constantly, and the mass loss of the fibers and pH changes of the solution are found to rise rapidly during the initial dissolution process, then their increasing rates are controlled by the balancing function of the hydrated layer at the subsequent dissolution stages. The dissolution rate constant and time for complete dissolution are estimated to be 274 ng/(cm2·h) and 15.2 d, respectively, presenting preferable biosolubilities.
基金Funded by the National Key R&D Program of China(2016YFB0303400,2017YFB0309903-03)the Natural Science Foundation of Shaaxi Province of China(2017JM5097)
文摘Crystallization characteristic of periclase in clinker and effect of Mg^2+ on hydrate of cement pastes were investigated. Morphologies and relative content of periclase were characterized with scanning electron microscopy and X-ray diffraction. Derivative thermogravimetry analysis and backscattered electron imaging were used to characterize the effect of Mg^2+ on hydrate of cement pastes. The experimental results show that in ample space, periclase forms octahedron structure, and subhedral or anhedral crystal is formed in limited space. Due to the accelerated burning temperature and prolonged holding time, coarse pericalase crystals are formed. Mg(OH)2 particle thickness increases due to faster crystal growth rate along c axis at later age. Mg^2+can substitute Ca^2+ in C-S-H or C-A-H to form magnesium silicate hydrate(M-S-H) or magnesium aluminate hydrate(M-A-H), and the substitution extent for C-A-H is higher than that for C-S-H. Cured in 80 ℃ water, the decalcification rate of C-A-H in pastes is higher than that cured in 50 ℃ water. M-A-H with an atomic Mg/Al ratio of 2 is formed through substitution of Ca by Mg in C-A-H.
基金Funded by the National "973 Project"(2009CB623104)the Fundamental Research Funds for the Central Universities(2009ZZ0044)the Funds of Key Laboratory of Advance Civil Engineering Materials of the Ministry of Education
文摘The paste was prepared by mixing MgO, microsilica and H2O in the presence of water reducer at different reaction ratios and temperatures, and characterized by XRD, DTA, TGA, IR, and solid-state 29Si NMR. The experimental results showed that, besides Mg（OH）2, magnesium silicate hydrate （M-S-H） was formed at a low temperature such as 25 and 50 ℃. At a high temperature of 100 ℃, Mg（OH）2 can be further transformed into M-S-H completely, for instance, within ca. 1 month in an excess of microsilica. The average composition and structure of M-S-H was mainly related to the reaction mixture and curing temperature and was discussed in detail.
文摘It was proved that MgO and MicroSilica can react at room temperature, giving a hardened product primarily comprised of Mg （ OH ）2 and Magnesium Silicate Hydrate （ M- S- H ）. The reaction ratio and process and the chemical composion of M- S- H were studied and analyzed by QXRD and DTA- TG. The experimental results indicate that much Mg（ OH）2 and less M-S-H were formed at early period. After 7 days there is no change in the quantity of Mg（ OH）2, while M-S-H was increased slowly. The chemical composion of M-S-H would vary with the mix proportion in the hydrution process , but M1.32 SH2.37 is finally the approximute form.
文摘采用X射线衍射(XRD)和固体魔角核磁共振硅谱(^(29)Si MAS NMR)技术,研究了不同养护温度下MgO/SiO_2体系水化产物的结构特征.结果表明:死烧MgO比轻烧MgO衍射峰强度更大;水化硅酸镁(M-S-H)凝胶呈结晶性较差、短程有序的层状硅酸盐结构;M-S-H含量随着养护温度的升高而增多,相同养护温度下M-S-H的含量随着龄期的延长而增多,50℃下养护28d的试样M-S-H含量最多;养护温度过高会抑制M-S-H的生成;高温养护有利于Q^1向Q^2、Q^2向Q^3转化,使得M-S-H硅氧四面体聚合度提高.
