多场耦合多元调控作用下现代混凝土早期体积稳定性控制

There has been a serious contradiction between early-age shrinkage cracking and durability of modern concrete, which is a significant theoretical issue for concrete science and should be solved urgently. Shrinkage deformation is one of the most important reasons for early-age concrete cracking. However, the regulation methods of shrinkage deformation has not been well developed. Early-age shrinkage deformation of concrete is closely related to its microstructure as well as the temporal and spatial distribution of internal water, which depends fundamentally on the multi-filed coupling conditions of hydration, temperature, humidity and deformation. Some induction methods will be adopted in this project to reduce shrinkage deformation, including adding internal curing agent, hydration heat regulation materials, expansion agent, and shrinkage-reducing agent, and their multi-component coupling. By means of in-situ test technology, the process of hydration of concrete will be tracked, and the modern micro-testing technology (for example, environmental scanning electron microscopy method) will also be utilized to reveal the mechanism of multi-component synergistic action in microstructure formation. Based on that, models of hydration and microstructure will be established respectively. Then, the evolution and migration of water in concrete under hydration-thermo-hygro multi-field coupling will be studied by modern imaging technologies (i.e. low field nuclear magnetic resonance and computed tomographic scan), and a model of water distribution based on microstructure will be built. Finally, the experiment of volume deformation of concrete will be performed, and the mechanism of multi-component regulation of concrete will be explored by analyzing the quantitative relationship among macroscopic deformation, microstructure and water evolution. In addition, based on the principle of equivalent stress and homogenization method, a multi-scale model of early-age deformation of modern concrete considering multi-component regulation and multi-field coupling will be proposed. These research achievements could be used for fundamentally resolving the inherent contradiction between early-age shrinkage cracking and durability, and provide technical support to extend the service life of concrete.

现代混凝土早期开裂与其耐久性之间存在着严重矛盾，是砼科学急需解决的重大理论问题。砼收缩变形是早期开裂主要原因，但有关收缩变形调控至今未能很好解决。砼早期收缩变形与其微结构和水分时空分布密切相关，存在着水化-温度-湿度-变形多场耦合作用。本课题拟以内养护、水化热调控材料、膨胀剂、减缩剂及多元复合为调控手段，采用原位测试技术连续追踪砼水化过程，借助环境扫描电镜等现代微观测试技术，揭示微结构形成的多元调控机制，建立水化和微结构模型；基于低场核磁和X-CT成像技术，研究水化-温度-湿度多场耦合作用下砼内部水分演变与迁移规律，建立基于微结构的水分分布模型；开展砼体积变形试验研究，分析宏观体积变形与微结构、水分演变之间定量关系，揭示其多元调控机理；基于等效应力原理和均匀化方法，建立多场耦合多元调控作用下砼早期变形多尺度模型。课题研究成果可为调和砼早期开裂与耐久性矛盾、提升服役寿命提供理论支撑。

现代混凝土早期开裂与其耐久性之间存在着严重矛盾，是混凝土科学急需解决的重大理论问题。混凝土收缩变形是早期开裂主要原因，但有关收缩变形调控至今未能很好解决。本课题经过4年持续不断深入研究，取得如下成果：（1）开展了内养护、水化热调控材料、膨胀剂、减缩剂及复合对水泥基材料水化和微结构影响试验研究，开发了基于低场核磁信号的水泥基材料水化过程表征方法，揭示了水泥基材料水化动力学机理和微结构形成调控机制，建立了水化和微结构模型；（2）开展了水泥基材料早期内部水分演变与迁移规律试验研究，开发了基于低场核磁信号的内养护材料吸-释放水表征方法，构建了水化-温度-湿度多场耦合模型；（3）开展了调控组分对水泥基材料早期体积变形影响试验研究，揭示了宏观体积变形与微结构、水分演变之间定量关系，建立了多元调控下混凝土早期变形多尺度模型。.在基金资助下参加了在重庆大学召开的第十届无机材料结构、性能及测试表征技术研讨会，作报告“基于低场核磁共振技术的水泥基材料水分传输研究”；在郑州大学召开的第16届混凝土岩石断裂学术会议，作报告“高性能混凝土早期水化-温-湿-力多场耦合试验与模型研究”等；并于2019年12月~2020年12月赴美国俄勒冈州立大学进行访学，合作导师J. Weiss教授，开展内养护混凝土力学与体积变形方面的研究。.在基金资助下已发表SCI论文17篇（其中第1作者16篇，通讯作者1篇），中文EI论文1篇，授权发明专利6项，参编行业标准2部、江苏省地方标准1部、省级团体标准1部，出版专著2部（分别为第1、2作者），获省部级科技进步奖二等奖2项（排名分别为2、3）。以项目研究为依托，毕业硕士研究生29名，培养博士研究生2名。根据本课题研究成果凝练的“现代混凝土结构施工期裂缝防控基础理论与关键技术”，应用于安徽省牛岭大坝、浙江省双溪口重力拱坝、上海市新川沙泵闸等大型工程中，对土木、水利工程行业的科技进步具有推动作用。