Structure and Hydration Kinetics of Silica Particles in Rice Husk Ash Studied by 29Si High‐Resolution Nuclear Magnetic Resonance
Structure and Hydration Kinetics of Silica Particles in Rice Husk Ash Studied by 29Si High‐Resolution Nuclear Magnetic Resonance
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29Si高分辨率核磁共振研究稻壳灰中二氧化硅颗粒的结构和水化动力学
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发表时间：
2005
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通讯作者：
M. A. Cincotto
中科院分区：
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作者：
R. F. Abreu;J. Schneider;M. A. Cincotto
用29Si-核磁共振波谱和自旋晶格驰豫技术研究了稻壳灰中二氧化硅颗粒的结构、表面分维和全局水化动力学。二氧化硅颗粒的无定形含量高于93%，有少量的二氧化硅-有机成键和晶型结构域。Fe-杂质优先位于颗粒表面。从这些顺磁离子对Q3和Q4硅酸盐基团自旋晶格驰豫的影响来看，颗粒表面是有效的二维结构(D=1.9±0.1)。在与石灰和水反应的过程中，监测了颗粒的水化动力学，时间为8-706天。这一过程可用幂函数来描述，其特征指数高于其它水泥的特征指数。此外，Johnson-Mehl-Avrami表达式与C-S-H的生长习性和形态参数吻合得同样好，在C-S-H中发现了两种类型的Q2四面体，这可以归因于C-S-H的“Dreier-Kette”结构模型预测的桥联和非桥联硅酸盐基团。
The structure, surface fractal dimension, and global hydration kinetics of silica particles obtained from rice husk ashes (RHAs) were studied with 29Si-NMR spectroscopy and spin–lattice relaxation techniques. Silica particles presented an amorphous fraction higher than 93%, with traces of silica-organic bonding and crystal-like domains. Fe-impurities are located preferentially on the surface of the particles. From the effect of these paramagnetic ions on the spin–lattice relaxation of Q3 and Q4 silicate groups, the surface of the particles was characterized as being effectively two-dimensional (D=1.9±0.1). The hydration kinetics of the particles during the reaction with lime and water was monitored from 8 to 706 days. The process can be described by a power law, with the characteristic exponent higher than those measured for other cements. Also, Johnson–Mehl–Avrami expressions reproduce equally well the experimental data, with parameters compatible with growth habits and morphology known for C–S–H. Two types of Q2 tetrahedra were identified in C–S–H, which can be attributed to the bridging and nonbridging silicate groups predicted by the “dreier-kette” structural model of C–S–H.