大掺量粉煤灰-高内含氧化镁中热水泥混凝土耐久性评估与寿命预测

In order to reduce the internal temperature rise, compensate part of shrinkage and improve the resistance to cracking of concrete, concrete with large amount of fly ash and medium heat cement containing high MgO content was applied in large-scale water conservancy and hydropower projects, represented by the Three Gorges. Facing the long life expectancy of the Three Gorges Project for one hundred or even thousand years, it is urgent to establish durability evaluation system and service life prediction method of concrete with large amount of fly ash and medium heat cement containing high MgO content. Concrete with large amount of fly ash and medium heat cement containing high MgO content applied in the main dam of Three Gorges project is selected as the reseach subject in this project. The long-term time-varying law of macro performance, hydration products and micro-meso structure of concrete under different curing mechanisms were studied. Then, the multi-scale relationship between macro performance and micro-meso structure of concrete is revealed. In addition, the indoor accelerated aging test is established by simulating the service environment of the Three Gorges main dam. By means of the accelerated aging test, the degradation law of macro performance and the damage mechanism of micro-meso structure of concrete with large amount of fly ash and medium heat cement containing high MgO content were verified. Furthermore, the durability evaluation of concrete with large amount of fly ash and medium heat cement containing high MgO content is put forward and service life prediction model is built. To conclude, the research findings of this project are expected to provide scientific and methodological guidance for the assessment of the health status of the concrete of the Three Gorges Dam and the prediction of its service life, with important theoretical value and significant economic and social benefits.

为了减小混凝土内部温升、补偿部分收缩并提升抗裂性能，以三峡为代表的大型水利水电工程使用大掺量粉煤灰-高内含氧化镁中热水泥混凝土。面对三峡工程百年乃至千年的长寿命预期，亟需建立大掺量粉煤灰-高内含氧化镁中热水泥混凝土耐久性评估体系与服役寿命预测方法。本项目拟以三峡主坝大掺量粉煤灰-高内含氧化镁中热水泥混凝土为研究对象，开展不同养护条件下混凝土宏观性能、水化产物和微-细观结构长龄期时变规律的研究，揭示混凝土宏观性能与微-细观结构之间的多尺度关系；模拟三峡主坝服役环境建立室内加速老化试验机制，探明环境因素耦合作用下大掺量粉煤灰-高内含氧化镁中热水泥混凝土宏观性能劣化规律和微-细观结构的损伤机理，提出大掺量粉煤灰-高内含氧化镁中热水泥混凝土耐久性评价方法并建立寿命预测模型。项目研究成果有望为评估三峡大坝混凝土的健康状况并预测其服役年限提供科学和方法的指导，具有重要的理论价值和显著的经济、社会效益。

本项目聚焦于三峡主坝大掺量粉煤灰-中热水泥混凝土微-细观结构与宏观性能演变规律、机理和模型的研究。首先探明了光辐照作用引起的C-S-H凝胶脱水缩合效应，建立了多种大气环境因素协同作用下三峡主坝混凝土温度发展的时空模型，掌握了三峡大坝混凝土胶凝体系宏观性能的劣化行为与微-细观结构的劣化机理；探明了溶蚀作用下C-S-H凝胶化学结构和纳观形貌的演变规律，脱钙后C-S-H凝胶由层状结构转变为三维结构的无定型硅胶；揭示了三峡大坝混凝土胶凝体系溶蚀深度的时变规律，明晰了溶蚀作用下大坝混凝土胶凝体系孔隙结构和宏-细观力学性能的时空演变特性，基于钙离子溶解-扩散原理建立了三峡大坝混凝土溶蚀深度随时间变化的有限元模型。本项目研究成果证实了三峡主坝中热水泥-粉煤灰胶凝体系相较于普通硅酸盐水泥-粉煤灰胶凝体系更优的抗风化与抗溶蚀劣化性能，有望为真实服役环境下三峡大坝混凝土劣化机理、耐久性评价和寿命预测提供理论和数据支撑。在项目执行期间，发表了SCI收录论文7篇，申请国家发明专利2项。