钢筋地聚物混凝土的抗氯离子侵蚀机理及初锈时间预测方法

Since carbon emission from the production of Portland cement has severe impact on the environment, low-carbon concrete is of significant importance for sustainable development of civil engineering. Geopolymer concrete has the advantage of low carbon emission and can be synthesized by industrial wastes such as fly ash, which makes it a potential material of promoting sustainable civil engineering. However very few investigations were conducted on the durability of geopolymer concrete. This project aims to study the resistance mechanism of geopolymer concrete to chloride ingress and the prediction method of corrosion initiation time of steel bars in geopolymer concrete. To achieve this goal, the pore structure of geopolymer binder and its factors will be investigated, and the relationship between the pore characteristics of binder and the diffusion coefficient of chloride will be determined. Moreover, the binding ability of different resultants in geopolymer binder to chloride is to be quantified. Thus, the model of diffusion coefficient for the chloride in geopolymer paste can be obtained. Furthermore, the morphology and properties of the interfacial zone between the geopolymer paste and fine and coarse aggregates will be observed and analyzed, and the forming mechanism of the interfacial zone will be revealed. Then, the model of diffusion coefficient of chloride in interfacial zone between the binder and aggregates will be proposed. The initial pH value of pore solution of the geopolymer concrete and the factors influencing the solution alkalinity will be studied. Subsequently, the threshold concentration of the chloride ions corresponding to the corrosion of steel bars will be determined. Finally the prediction approach of corrosion initiation time of steel bars in geopolymer concrete will be proposed. The application of this project will provide experimental and theoretical evidence for durability design and assessment of steel reinforced geopolymer concrete structures when considering ingress of chloride, and is essential for promoting applications of geopolymer concrete and development of sustainable civil engineering.

硅酸盐水泥混凝土造成的碳排放对环境产生严重影响，发展低碳混凝土对土木工程可持续发展至关重要。地聚物混凝土碳排放少、可利用工业废弃物制备，具有促进可持续土木工程的潜力，但关于其耐久性的研究较为匮乏。本项目研究地聚物混凝土的抗氯离子侵蚀机理及内部钢筋初锈时间预测方法。首先考察地聚物净浆微观孔结构及其影响因素，明确浆体孔结构与氯离子扩散的相关性，确定不同反应产物的氯离子固化能力，建立基于孔结构及氯离子固化的地聚物净浆氯离子扩散系数模型；进而研究净浆与粗细骨料的界面形态，明确浆体-骨料界面区形成机制，提出界面区氯离子扩散系数模型；分析浆体孔溶液的初始pH值及影响因素，确定钢筋锈蚀的氯离子临界浓度值，最终提出地聚物混凝土内钢筋初锈时间的预测方法。本项目将为氯盐侵蚀下钢筋地聚物混凝土结构的耐久性设计与评估提供试验与理论依据，并对推动地聚物混凝土应用及土木工程可持续发展具有重要意义。

硅酸盐水泥混凝土造成的碳排放对环境产生严重影响，发展低碳混凝土对土木工程可持续发展至关重要。地聚物混凝土碳排放少、可利用工业废弃物制备，具有促进可持续土木工程的潜力，但关于其耐久性的研究较为匮乏。本项目针对上述问题，研究了地聚物混凝土的抗氯离子侵蚀机理及内部钢筋初锈时间预测方法。首先基于选择性酸溶试验开发了可确定偏高岭土碱激发反应水平的分析方法，实现了复合胶凝材料中不同凝胶含量的定量分析；通过压汞试验考察了偏高岭土地聚物的孔结构形态及分布，阐明了地质聚合反应水平与孔结构特性间的相关性；然后研究了氯离子在地聚物浆体中的传输行为及浆体对氯离子的固化能力，在此基础上确定了地聚物浆体中的氯离子扩散系数；进而考察了岩石骨料与地聚物浆体的界面区形态及潜在反应行为，研究了氯离子在浆体-骨料界面区的传输性能，明确了氯离子在地聚物混凝土中的传输行为并得出了传输系数；研究了地聚物孔溶液的初始碱度和pH值，考察了原料配比及碱当量对地聚物浆体孔溶液初始pH值的影响，以及地聚物的泛碱行为；通过加速碳化试验考察了二氧化碳在地聚物混凝土中的扩散行为及浆体碳化速率，进而得到了不同碳化龄期下地聚物混凝土内沿深度的pH值分布模型，在此基础上根据引起钢筋锈蚀的临界氯离子浓度，提出了地聚物混凝土中钢筋除锈时间预测方法。本项目可为氯盐侵蚀下钢筋地聚物混凝土结构的耐久性设计与评估提供试验与理论依据，填补了钢筋地聚物混凝土结构耐久性能的知识空白，为地聚物混凝土的后续研究及应用奠定了基础。