Elastic Moduli of Hardened Portland Cement and Tricalcium Silicate Pastes: Effect of Porosity
Elastic Moduli of Hardened Portland Cement and Tricalcium Silicate Pastes: Effect of Porosity
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硬化波特兰水泥和硅酸三钙浆体的弹性模量：孔隙率的影响
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发表时间：
2017
期刊：
影响因子：
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通讯作者：
R. Helmuth
中科院分区：
文献类型：
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作者：
R. Helmuth
要了解混凝土的弹性、徐变和干燥收缩等重要性能，就需要了解硬化波特兰盐水泥浆体粘结剂的弹性模量。硬化波特兰水泥浆体的弹性模量取决于孔隙率和组成固相的弹性模量。固相包括一些结晶相，但主要成分是水泥凝胶，一种具有高比表面积的不良结晶材料。对波特兰水泥浆体和纯硅酸钙水合物的研究表明，这种凝胶是由小颗粒的多孔聚集体组成的（1，2）。由于颗粒尺寸小，不能直接测量颗粒的模量。本工作的目的是确定硬化膏体的弹性模量在其正常范围内的孔隙率，并开发的膏体的弹性模量和它们的孔隙率之间的关系。然后，当孔隙率接近零时，固体的平均模量可以从糊状物的模量值获得。已经发现，从硬化膏体的薄板（1-2 mm厚）的共振频率计算的弹性模量与经验方程（参见Eq.（8）由权力（3）提出。在已经发表的各种经验和理论方程中，只有这个方程和汉森（4）给出的方程与我们的数据相吻合。汉森方程是Hashin（5）导出的理论方程的修正。通过引入减小计算模量的因子来获得这种修改。该因素的影响如此之大，以至于修改后的方程很难被视为基于相同的理论。此外，虽然修正后的方程形式略有不同，但在可获得的孔隙度范围内，它给出的结果与Powers方程基本相同。因此，我们选择将我们的数据与Powers方程进行比较，因为它的形式更简单。-
SAN UNDERSTANDING of such important properties of concrete as elasticity, creep and drying shrinkage requires knowledge of the elastic moduli of the hardened portland cement paste binder. The elastic moduli of hardened portland cement pastes depend on both the porosity and the elastic moduli of the constituent solid phases. The solid phases include some crystalline phases, but the major constituent is the cement gel, a poorly crystallized material with a high specific surface area. Studies of portland cement pastes and pure calcium silicate hydrates indicate that this gel is composed of porous aggregations of small particles (1, 2). Direct measurement of the moduli of the particles cannot be made because of their small sizes. The objectives of the present work are to determine the elastic moduli of hardened pastes over their normal range of porosities, and to develop relationships between the elastic moduli of the pastes and their porosities. The average moduli of the solids can then be obtained from the values of the moduli of the pastes as the porosity approaches zero. Elastic moduli calculated from resonance frequencies of thin slabs (1-2 mm thickness) of hardened pastes have been found to agree well with an empirical equation (see Eq. 8 below) introduced by Powers (3). Of the various empirical and theoretical equations which have been published only this equation and one given by Hansen (4) were found to fit our data. Hansen's equation is a modification of a theoretical equation derived by Hashin (5). This modification is obtained by introducing a factor that reduces the calculated moduli. The effect of this factor is so great that the modified equation can hardly be regarded as being based on the same theory. Furthermore, although the modified equation is of slightly different form it gives essentially the same results as Powers' equation in the porosity range that can be obtained. We have therefore chosen to compare our data with Powers' equation because of its simpler form. -