Hydration of Binary Portland Cement Blends Containing Silica Fume: A Decoupling Method to Estimate Degrees of Hydration and Pozzolanic Reaction
Hydration of Binary Portland Cement Blends Containing Silica Fume: A Decoupling Method to Estimate Degrees of Hydration and Pozzolanic Reaction
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DOI：
10.3389/fmats.2019.00078
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发表时间：
2019-04-24
影响因子：
3.2
通讯作者：
Ma, Hongyan
中科院分区：
文献类型：
--
作者：
Liao, Wenyu;Sun, Xiao;Ma, Hongyan
确定混合水泥体系（即水泥和 SCM：补充水泥材料）组分的水合/反应程度对于评估系统的性能至关重要。尽管 RILEM TC238 推荐了确定不同 SCM 反应程度的最佳方法，但它们要么依赖昂贵的设备（例如核磁共振），要么依赖耗时的样品制备和数据处理（例如背散射电子图像分析）。此外，这些方法不能同时表征水泥的水化程度和SCM的反应程度。本研究提出了一种新的解耦方法，可以同时估计二元胶凝材料中水泥的水化程度和硅灰的反应程度。基于实验确定和理论验证的水泥水化和火山灰反应的化学计量参数，浆体中氢氧化钙和水合水的含量表示为水泥水化度和硅灰反应度的函数。通过热重分析确定这两个含量，可以用数学方法求解这两个度数。研究发现，在二元粘结剂中，硅粉的掺入会影响水泥的水化动力学，导致最终水化程度降低、休眠阶段缩短、加速阶段水化加快。因此，混合浆体中水泥的水化程度在早期（例如3天）比普通水泥浆体中的水化程度较高，但在后期（例如120天）较低。在给定的混合浆体中，硅粉的反应程度可以与水泥的水化程度相关。解耦方法有望快速估计混合系统中胶凝材料的水合/反应程度，因为它不需要昂贵的表征工具或复杂的数据处理方法。
Determination of degrees of hydration/reaction of components of blended cementitious systems (i. e., cement and SCMs: supplementary cementitious materials) is essential to estimate the systems' properties. Although the best methods for determining degrees of reaction of different SCMs have been recommended by RILEM TC238, they rely on either expensive equipment (e.g., nuclear magnetic resonance) or time-consuming sample preparation and data processing (e.g., backscattered electron image analysis). Furthermore, these methods cannot simultaneously characterize degree of hydration of cement and degree of reaction of SCMs. A novel decoupling method, which can simultaneously estimate the degree of hydration of cement and the degree of reaction of silica fume in binary cementitious materials, is proposed in this study. Based on experimentally determined and theoretically validated stoichiometric parameters of cement hydration and pozzolanic reaction, the contents of calcium hydroxide and hydrate water in pastes are expressed as functions of degree of hydration of cement and degree of reaction of silica fume. With the two contents determined by thermogravimetric analysis, the two degrees can be solved mathematically. It is found that in binary binders the incorporation of silica fume affects hydration kinetics of cement, leading to lower ultimate degree of hydration, shorter dormant stage, and faster hydration in the acceleration stage. As a result, the degree of hydration of cement in blended paste is higher at early ages (e.g., 3 days) but lower at later ages (e.g., 120 days) than that in plain cement paste. In a given blended paste, the degree of reaction of silica fume can be tied to the degree of hydration of cement. The decoupling method is promising for rapid estimations of degrees of hydration/reaction of cementitious materials in a blended system, since it does not require expensive characterization tools or complex data processing methods.