离子驱动内养生路面混凝土水分传输机制及多尺度损伤模型研究

The early micro cracks caused by dry shrinkage and autogenous shrinkage often happen in the application process of concrete pavement, which belongs to typical thin plate structure. Dry shrinkage and autogenous shrinkage would not only lead to the different types of concrete pavement diseases, but also result in significant decrease of durability, which is difficult to be solved by traditional curing method. However, as a new type of modified material, Super Absorbent Polymer (SAP), under the driving action of ion implantation, could supply the hydration water inside the pavement concrete to cure early micro cracks caused by moisture loss radically. This project will study the adsorption-desorption mechanism of SAP subjected to the ion driving action by using the water release ability test equipment of concrete pavement internal curing, which was developed independently by our research group. Then the water equivalent diffusion coefficient will be introduced to establish the nonlinear moisture transfer model of internal curing cement concrete, which is also based on the Flory thermodynamic and swelling kinetics theory; Based on Load-Temperature-Humidity coupling effect, the attenuation performance of SAP pavement concrete will be studied systematically and the mechanism of SAP on the early shrinkage and attenuation of pavement concrete will be revealed; The pavement concrete pore, fracture and interfacial transition zone of fine microstructure evolution of macro, inside the SAP concrete pavement will be explored through using modern testing and image analysis techniques. The macro and micro damage model will be studied from multi-scale to forecast service life of the SAP concrete pavement.The research results of this paper have important scientific significance for the design of SAP pavement cement concrete, revealing the mechanism of water absorption and release of SAP, and the establishment of shrinkage compensation mechanism.

水泥路面为薄板结构，其干缩及自收缩导致的早期微裂纹非常普遍，传统养生方式难以抵制裂纹的产生，进而引发各种病害，危及路面耐久性。超吸水性聚合物（SAP）可用于内养生，在路面混凝土内部离子驱动下适时补给水分，可根治因湿度损失引发的早期裂纹。本项目将利用课题组研发的SAP内养生路面混凝土释水能力测试装置，基于Flory热力学、溶胀动力学等理论，研究离子驱动下路面混凝土内SAP的吸液解吸机理；引入内养生水等效扩散系数，建立内养生路面混凝土非线性水分传输模型；通过荷载-温度-动水耦合作用下SAP路面混凝土的性能衰减研究，揭示SAP对路面混凝土早期收缩及性能衰减的遏制机理；运用现代图像分析技术研究SAP路面混凝土孔、裂隙及界面过渡区细微观结构演化规律，建立宏观及细微观多尺度损伤模型，预测使用寿命。本项目研究成果对SAP路面水泥混凝土设计、揭示SAP吸水-释水机理、建立收缩补偿机制具有重要的科学意义。

水泥混凝土路面为大面积薄板结构，施工成型后因水分蒸发和水化耗水而产生干缩、自收缩裂缝，为外界有害介质提供了侵入通道，增大了路面开裂风险，严重危及路面耐久性。传统外部养生方式难以使水分浸润内部，无法抑制混凝土内部早期裂缝。超吸水性树脂（SAP）能够在混凝土内部引入养生水分，抑制混凝土早期收缩开裂，增强服役期耐久性，但SAP对路面混凝土的内养生机理及耐久性影响规律尚不明晰。因此，本项目围绕SAP内养生路面混凝土水分传输特性、性能增强机理、多尺度损伤模型展开研究，主要研究内容及成果如下：.（1）研究了SAP物理特征及微环境对SAP吸水-储水-释水行为的影响规律，明确了SAP吸液动力学及释水机理，为SAP释水养护效果奠定了理论基础。.（2）基于SAP内养生混凝土内部各形式水分的依时含量分布测试分析，探明了SAP对混凝土内部不同层位相对湿度的影响规律，通过数值计算深入分析了内养生对混凝土内部水分扩散系数的影响。.（3）分析了SAP对胶凝材料浆体早期水化进程的影响，确定了SAP对胶凝材料体系水化程度的提升作用，明确了内养生浆体水化产物组成及水化增强效果。.（4）计算分析了SAP内养生作用下的路面板内收缩发展与湿度应力，探明了SAP对路面混凝土的收缩调控作用；评估了SAP内养生混凝土的阻裂效果，建立了其与力学强度的相关关系。.（5）研究了SAP粒径及掺量对混凝土抗渗性能、抗盐冻性能及疲劳性能的影响规律，结合细微观结构特征揭示了SAP对路面混凝土耐久性的增强机理，构建了抗氯离子渗透、盐冻融损伤以及疲劳预测模型。.（6）探索了耦合作用下SAP路面混凝土的性能衰减规律，并结合耦合作用下路面混凝土的孔结构演化规律，揭示了SAP对路面混凝土性能劣化的抑制机理，建立了耦合作用下SAP路面混凝土的多尺度损伤模型。.综上成果，本研究揭示了SAP内养生材料在混凝土内部的吸-释水行为及机理，阐明SAP的减缩阻裂机理和耐久性增强机制，为SAP内养生材料在水泥混凝土工程领域的合理使用提供理论指导和依据。