摘 要

我国海洋战略的提出带动了海洋环境下重大基础建设的新高潮，而南海岛礁地区淡水资源相对匮乏，采用海水拌合混凝土，现有的研究主要集中于其工作性能和力学性能，但对于海水拌合混凝土的水化硬化机理及其微结构形成演变规律的研究尚未开展。本文依托国家“973”重点项目“严酷环境下混凝土材料与结构长寿命的基础研究”，旨在研究海水拌和混凝土中复杂胶凝体系在水化-侵蚀反应交互作用下水化硬化机理，及其微结构形成演变规律，探明侵蚀离子拌合对海水拌合混凝土复杂胶凝体系的水化动力学及其水化产物微结构的影响，为海洋严酷环境下长寿命混凝土其水化进程及微结构优化调控提供理论依据。

本文对比研究了90℃与210℃蒸压养护条件下不同浓度的硫酸镁溶液分别拌合水泥-粉煤灰浆体，粉煤灰的掺量对胶凝浆体的力学性能及侵蚀离子吸附固化的影响规律，并通过XRD、²⁹Si和²⁷Al NMR、化学结合水法等测试技术，研究了采用不同养护制度条件下MgSO₄溶液拌合水泥-粉煤灰胶凝浆体，MgSO₄溶液浓度对胶凝浆体水化动力学及其微结构的影响机理，研究结果表明：

1. 在90℃与210℃两种养护制度下，粉煤灰掺量为0%、20%、30%、40%的水泥—粉煤灰浆体强度逐步增加，同时在粉煤灰掺量相同时，210℃养护条件下的试样较90℃养护条件下的试样强度为高。在养护温度与粉煤灰掺量一定时，MgSO₄拌合量增加会导致浆体力学性能下降，当MgSO₄拌合溶液掺量为4.2g/L时，强度降低仅为4%-5%，可忽略不计。
2. 90℃蒸养条件下MgSO₄溶液拌合水泥-粉煤灰胶凝浆体中形成的Mg(OH)₂，附着于水泥颗粒表面，降低其水化速率，当养护温度提高到210℃时，渗透压增大,Mg² 进入C-S-H凝胶，形成C-M-S-H凝胶和M-S-H凝胶，水泥水化速率加快；拌合浓度为4.2g/L（海水浓度）时，SO₄^2-主要促进Alite、Belite水化，对粉煤灰几乎无激发作用，12.6/LMgSO₄拌合浓度中的SO₄^2-对水泥和粉煤灰的水化均有促进作用，其中21g/L MgSO₄中的SO₄^2-对粉煤灰的激发作用最为明显。
3. 模拟海水拌合时，SO₄^2-促进Alite、Belite中的Al进入C-S-H凝胶，Al[4]/Si增加，提高了其平均分子链长；4.2g/L MgSO₄拌合时，SO₄^2-对水泥及粉煤灰的激发作用有所增强，但SO₄^2-主要脱去C-(A)-S-H凝胶中的Al，转化为钙矾石；21/L MgSO₄拌合时，在水化早期SO₄^2-对粉煤灰激发作用显著，促进了Al进入C-S-H凝胶，提高Al[4]/Si，但随着水化龄期的增加，SO₄^2-对C-(A)-S-H凝胶的脱Al作用增强，Al[4]/Si降低，同时Mg进入C-S-H凝胶，形成C-M-S-H凝胶和M-S-H凝胶，提高了其平均分子链长。

关键词：硫酸镁拌合；²⁹Si NMR；²⁷Al NMR；水化动力学；离子吸附固化；微结构

Abstract

China's marine strategy has led to a new upsurge of major infrastructure in the marine environment, while the freshwater resources in the South China Sea reef area are relatively scarce, using seawater mixed concrete, the existing research focused on its work performance and mechanical properties, but for the sea The hydration hardening mechanism of mixed concrete and its microstructural formation and evolution are not yet studied. Based on the "973" key project "basic research on the long life of concrete materials and structures in harsh environment" and the key project of Humen Second Bridge, the aim of this study is to study the complex hydration system of seawater mixed concrete under hydration-erosion reaction interaction Hardening mechanism and its microstructural formation and evolution laws, and to explore the influence of erosion ion mixing on hydration kinetics and hydration product microstructure of seawater mixed concrete complex gelled system, which is a long-life concrete in harsh marine environment Hydration process and microstructure optimization control.

In this paper, the effects of water and 5% magnesium sulfate solution on the mechanical properties and volumetric stability of cement mortar and fly ash were studied. The effects of water content on the mechanical properties and volume stability of cement paste were studied by XRD, IPC-MS The effects of the concentration of MgSO4 on the hydration kinetics and microstructure of cement paste were studied by using MgSO4 solution in cement-fly ash cement paste. The effects of MgSO4 solution concentration on the hydration kinetics and microstructure of cement paste were studied by using 29Si, 27S NMR and chemical reaction. ,Research indicates:

1, at 90 ℃ and 210 ℃ under the two curing system, the fly ash content of 0%, 20%, 30%, 40% cement - fly ash slurry strength gradually increased, while the fly ash content phase At the same time, the sample under the condition of 210 ℃ under the condition of curing under 90 ℃ is high. When the dosage of MgSO4 is 4.2 g / L, the decrease of the concentration of MgSO4 is only 4% -5% when the dosage of MgSO4 is 4.2 g / L. can be ignored.

2, MgSO4 solution mixed with cement - fly ash cement paste formed in the Mg (OH) 2, attached to the surface of cement particles, reducing its hydration rate, with the hydration age increased, Mg2 into the CSH gel, The formation of CMSH gel and MSH gel, cement hydration rate accelerated; mixing concentration of 4.2% (seawater concentration), SO42- mainly promote Alite, Belite hydration, the fly ash almost no excitation, 12.6% MgSO4 SO42- in the concentration of cement and fly ash hydration have a role in promoting, of which 21% MgSO4 in the SO42- fly ash to stimulate the most obvious.

3, simulated sea water mixing, SO42- promoted Alite, Alite in Belite into CSH gel, Al [4] / Si increased, increased its average molecular chain length; 4.2g / L MgSO4 mixing, SO42- Cement and fly ash were enhanced, but SO42- was mainly removed from Al in the C-(A) -SH gel and converted into ettringite. When 21% MgSO4 was mixed, the SO42- (4) / Si, but with the increase of hydration age, the effect of SO42- on the desorption of C- (A) -SH gel was investigated by the addition of Al into the CSH gel Enhanced, Al [4] / Si decreased, while Mg into the CSH gel, the formation of CMSH gel and MSH gel, increased its average molecular chain length.

Key words: magnesium sulfate mixing; 29Si NMR; 27Al NMR; hydration kinetics; ion adsorption;

目录

摘 要 3

Abstract 5

第一章 绪论 8

1.1研究背景 8

1.2 国内外研究现状 8

1.3本文主要研究内容 8

第2章 实验原料、方法及测试手段 10

2.1实验原料 10

2.1.1粉料 10

2.1.2拌合水 10

2.2实验配合比 10

2.3 试样制备、成型与养护 12

2.3.1宏观测试试样制备 12

2.3.2微观测试试样制备 12

2.4 测试方法 12

2.4.1抗压强度测试 12

2.4.2 XRD测试 12

2.4.3 ICP-MS测试 12

2.4.4 ²⁹Si和²⁷Al NMR测试 12

第3章 不同养护制度下MgSO₄拌合水泥-粉煤灰胶凝浆体力学性能与侵蚀离子吸附固化的能力 14