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”和虎门二桥重点工程，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，探明功能组分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。

本文对比研究了水和5%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体积稳定性能的影响规律，并通过XRD、水化微量热仪、²⁹Si和²⁷Al NMR、化学结合水法等测试技术，研究了采用MgSO₄溶液拌合水泥-粉煤灰胶凝浆体，MgSO₄溶液浓度和功能组分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. 粉煤灰掺量为0%、10%、20%的水泥浆体强度在各龄期相差不大，10%粉煤灰掺量的水泥浆体强度略高于纯水泥浆体；粉煤灰掺量为30%的试块早期强度低于纯水泥浆体，后期强度接近纯水泥浆体。粉煤灰掺量为40%、50%的浆体在各龄期强度明显低于纯水泥浆体。水化后期时，随着粉煤灰掺量的增加，其浆体的膨胀率开始逐渐降低，后逐渐增大，当粉煤灰掺量为20%时，浆体膨胀率最小，当粉煤灰掺量为30%时，浆体膨胀率接近纯水泥浆体，粉煤灰掺量超过30%时，浆体膨胀率超过纯水泥浆体。
2. 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，随着水化龄期增加，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0.34%（海水）时，SO₄^2-主要促进Alite、Belite水化，对粉煤灰几乎无激发作用，5%和10% MgSO₄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10% 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；5% 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；10% 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。
4. 侵蚀性离子传输抑制剂可提高水泥粉煤灰浆体的水化程度，并提高其平均分子链长及Al[4]/Si。且20kg/m³提升作用最为明显。水化温升抑制剂延缓水泥粉煤灰浆体的水化，但未改变其水化产物组成。

关键词：硫酸镁拌合；²⁹Si NMR；²⁷Al NMR；水化动力学；微结构；功能组分

Abstract

Our proposed new maritime strategy led to the upsurge in marine environment major infrastructure construction, and the South China Sea islands and reefs are relatively scarce freshwater resources in the region, the use of sea water mixing concrete, existing research is focused on its work and mechanical properties, but for the sea Research mixing concrete hydration mechanism and microstructure formation and evolution of the law has not yet been carried out. This paper relies on the national "973" key project "basis under the harsh environment of concrete materials and structures long life" Humen Bridge and key projects to study the complex seawater mixing concrete cementitious hydration - water erosion reaction of interaction hardening mechanism, and the formation of microstructure evolution, proven impact on the functional components of seawater mixing concrete complex cementitious hydration kinetics and microstructure of hydration products for the harsh marine environment, its long-life concrete water process control and optimization and micro structures provide a theoretical basis.

In this paper, a comparative study of water and 5% magnesium sulfate solution were mixing cement - fly ash pastes, ash content influence of the mechanical properties of cementitious slurry volume and stable performance, and by XRD, hydration trace calorimeter, 29Si and 27Al NMR, chemically bound water method testing techniques, research using MgSO4 solution mixing cement - fly ash cementitious slurry, MgSO4 concentration and functional components dynamics and hydration of cementitious slurry influence mechanism of micro-structure, the results showed that:

1. Fly ash content of 0%, 10%, 20% of the cement paste strength in every age or less, cement paste strength of 10% fly ash was slightly higher than pure cement paste; Fly content of 30% of the early strength of the test piece is less than pure cement paste, the late strength of body mud near the water. Fly ash content of 40%, 50% slurry in age strength significantly lower than that of pure cement paste. Hydration late, with the increase of fly ash, the slurry expansion began to decrease gradually increases, when fly ash is 20%, the smallest expansion slurry, when pulverized coal ash content of 30%, the slurry expansion close to the pure cement paste, when more than 30% fly ash, slurry expansion than pure cement paste.

2. MgSO₄ mixing cement-fly ash cementitious slurry formed Mg(OH)₂, attached to the surface of cement particles, reducing its rate of hydration, hydration with age increase, Mg₂ into the C-S-H gel is formed C-M-S-H,M-S-H gel, cement hydration rate of speed; mixing at a concentration of 0.34% (seawater) when, SO₄^2- mainly promote Alite, Belite hydration of fly ash excited almost no effect, 5% and 10% MgSO₄ mixing concentration of SO₄^2- hydration of cement and fly ash are promoted, in which 10% MgSO₄ SO₄^2- excitation effect of fly ash on the most obvious.

3. simulated seawater mixing, SO₄^2- promote Alite, Belite of Al into the C-S-H gel, Al[4]/Si increases, increased its average molecular chain length; when 5% MgSO₄ mixing, SO₄^2- and cement Inspiring effect of fly ash has increased, but the main SO₄^2- off Al in C-(A)-S-H gel to ettringite; when 10% MgSO₄ mixing in the early hydration of SO₄^2- powder ash stimulate significant role promoting the Al into the C-S-H gel, improving Al[4]/Si, but as age increases hydration, off Al SO₄^2- role of C-(A)-S-H gel enhancements, Al[4]/Si reduced, and Mg into the C-S-H gel, and the gel forming C-M-S-H,M-S-H gel, increasing its average molecular chain length.

4. Aggressive ion transport inhibitors can improve the degree of hydration of cement and fly ash slurry and increase its average molecular chain length and Al[4]/Si. And 20kg/m³ enhance the role of the most obvious. Inhibitors slow the hydration of cement fly ash slurry temperature of hydration, hydration products but did not change its composition.

Key words：magnesium sulfate mixing; ²⁹Si NMR; ²⁷Al NMR; hydration kinetics; microstructure；functional component

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