高速铁路蒸养混凝土预制构件热伤损及其控制机理研究

Massive steam-cured concrete prefabricated components were applied for constructing large box girder and track structure in large scale high-speed railway in China. However, some defects like surface crack, internal pore coarsening and high brittleness in these steam-cured concrete prefabricated components are usually existed in practice, which greatly influence the service life and safety of high speed railway. Considering the structure characteristics of steam-cured concrete prefabricated components and steam curing technology, the present project focuses on researching the physical/chemical change of steam-cured concrete (prefabricated components) in the preparing process and further on exploring the mechanism of thermal damage by employing basic theory of cement chemistry, physical chemistry, mechanics and numerical simulation methods. The main factors influencing on the thermal damage of steam-cured concrete are also analyzed by macro/meso/microscopic experiments. Meanwhile, the project is also expected to investigate the thermal damage formations and evolutions as well as to develop some new methods for effectively restraining or alleviating thermal damage of steam-cured concrete prefabricated components. This study is aimed at achieving some breakthroughs in the understanding the mechanism of thermal damage formation and the corresponding controlling principles of steam-cured concrete prefabricated components, and therefore to provide some important theoretical and technical supports for the production of high quality steam-cured concrete prefabricated component and its safe service in practice.

我国高速铁路桥梁和轨道结构大量采用蒸养混凝土预制构件，这些构件在生产实践中常易出现表观裂缝、内部孔隙结构粗化、脆性较大等不良现象，影响其使用寿命和安全性。本项目拟结合高速铁路蒸养混凝土预制构件结构特点和蒸养工艺条件，运用水泥化学、物理化学、力学等相关基础理论和数值计算方法，通过试验研究和微观分析手段，研究蒸养混凝土及其构件在制备生产过程中的物理化学变化，探讨其热伤损机理；分析热伤损的主要影响因素；揭示热伤损的形成与演变规律；提出蒸养混凝土预制构件热伤损的控制原理和方法，从而有效抑制热伤损的发生或减轻热伤损的程度，为高质量蒸养混凝土预制构件生产制造及其长期安全服役提供理论和技术支撑。

为解决蒸养混凝土预制构件高品质制造核心问题，支撑我国大规模高速铁路基础结构高效、高质量建设，项目针对高速铁路蒸养混凝土预制构件生产实践中时常存在的表观裂缝、内部孔隙结构粗化、脆性较大等热伤损现象，结合高速铁路蒸养混凝土预制构件结构特点和蒸养工艺条件，运用理论分析、试验研究和数值计算等研究方法，开展了蒸养混凝土(预制构件)热伤损的多尺度特征及其试验表征方法、蒸养混凝土的水化反应动力学与物相变化、蒸养混凝土热伤损的形成与演变规律以及蒸养混凝土热伤损的抑制原理与方法等四方面内容的研究，取得如下创新研究成果：.（1）完善了混凝土宏-细-微观多尺度孔结构综合分析表征方法；建立了蒸养非稳态过程中混凝土肿胀变形和自收缩变形测试的非接触式试验方法；引入表面渗透系数指标提出了蒸养混凝土表层热伤损的测试表征方法，并由此评价蒸养混凝土质量等级。.（2）获得了蒸养过程中混凝土力学强度、变形性能及内部应力等的演变特征；阐明了蒸养条件下矿物掺合料对混凝土强度的影响效应；明确了蒸养温度对蒸养混凝土表层渗透性、断裂性能的影响规律；表明了相同水化程度下蒸养混凝土力学强度低于标养混凝土。.（3）基于等效龄期函数建立了蒸养非稳态过程中水泥体系水化放热模型，阐释了典型蒸养制度条件下水泥体系水化动力学行为。.（4）得到了蒸养水泥浆体物相的微纳观力学特性，掌握了蒸养过程中水泥石、界面区、混凝土的微结构演变规律，揭示了蒸养过程中混凝土物相变化、胶凝材料组份水化行为改变、内应力形成等蒸养混凝土热伤损的产生机制。.（5）提出了基于胶凝材料组成设计、蒸养制度与后续养护工艺优化及损伤愈合等原理的蒸养混凝土热伤损抑制方法。研发了蒸养适应性较好的胶凝材料组成，确立了有效降低热伤损的全过程养护工艺，提出了基于自溶性矿物自愈合和相变组份修复强化的蒸养混凝土热伤损抑制技术。.研究成果为蒸养混凝土热伤损理论确立和高品质蒸养混凝土预制构件制造提供重要理论和技术支撑。