The effect of two types of C-S-H on the elasticity of cement-based materials: Results from nanoindentation and micromechanical modeling
The effect of two types of C-S-H on the elasticity of cement-based materials: Results from nanoindentation and micromechanical modeling
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DOI：
10.1016/s0008-8846(03)00230-8
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发表时间：
2004-01-01
影响因子：
11.4
通讯作者：
Ulm, FJ
中科院分区：
文献类型：
--
作者：
Constantinides, G;Ulm, FJ
长期以来，水泥化学界一直认为水化硅酸钙(C-S-H)存在于水泥基材料中，但对这两种C-S-H对材料力学性能的影响却知之甚少。通过对未降解和钙淋滤水泥浆体的纳米压痕试验，证实了两种C-S-H的存在，并研究了这两种相对水泥基材料弹性性能的不同作用。结果表明：(1)高密度C-S-H受钙浸出的影响小于低密度C-S-H，(2)两相在C-S-H基质中所占的体积分数不受钙浸出的影响。纳米压痕结果也提供了定量的证据，表明C-S-H相的弹性性能是内在的材料性能，与水泥基材料的配合比无关。提出了一种新的两步均质化模型，该模型利用材料性质和体积分数来预测水泥浆体的宏观弹性性能，具有较高的精度。与先进的物理化学模型相结合，在给定的水/碳比下，该模型可以确定两种C-S-H的体积分数，该模型可以应用于任何水泥浆体，无论是否含有波特兰石、熟料等。特别是，通过对脱钙水泥浆体的应用表明，C-S-H相的脱钙是宏观弹性模量退化的主要来源，在水泥基材料体系中，宏观弹性模量退化主要受波特兰石溶解的影响。(C)2003爱思唯尔有限公司。保留所有权利。
It has long been recognized, in cement chemistry, that two types of calcium-silicate-hydrate (C-S-H) exist in cement-based materials, but less is known about how the two types of C-S-H affect the mechanical properties. By means of nanoindentation tests on nondegraded and calcium leached cement paste, the paper confirms the existence of two types of C-S-H, and investigates the distinct role played by the two phases on the elastic properties of cement-based materials. It is found that (1) high-density C-S-H are mechanically less affected by calcium leaching than low density C-S-H, and (2) the volume fractions occupied by the two phases in the C-S-H matrix are not affected by calcium leaching. The nanoindentation results also provide quantitative evidence, suggesting that the elastic properties of the C-S-H phase are intrinsic material properties that do not depend on mix proportions of cement-based materials. The material properties and volume fractions are used in a novel two-step homogenization model, that predicts the macroscopic elastic properties of cement pastes with high accuracy. Combined with advanced physical chemistry models that allow, for a given w/c ratio, determination of the volume fractions of the two types of C-S-H, the model can be applied to any cement paste, with or without Portlandite, Clinker, and so on. In particular, from an application of the model to decalcified cement pastes, it is shown that that the decalcification of the C-S-H phase is the primary source of the macroscopic elastic modulus degradation, that dominates over the effect of the dissolution of Portlandite in cement-based material systems. (C) 2003 Elsevier Ltd. All rights reserved.