开裂后高延性水泥基材料（ECC）的微裂纹控制方法及渗透特性研究

Engineered Cementitious Composites was developed recently in order to overcome the brittleness and strain-softening property of traditional concrete. The tensile ductility and crack control ability of the material result in its applicability to the tensile part of structural members in cracked state. As a mismatch exists between microcrack control ability and ductility of ECC reinforced with mono fiber, the key to further improve ECC durability lies in how to reduce crack width significantly while retaining sufficient ductility. The present project proposes hybrid fiber method to coordinate the ductility and microcrack control ability of ECC. The crack bridging law of different types of fiber should be revealed firstly. Then a fracture mechanic based model should be developed to simulate the macroscopic mechanical properties of hybrid fiber ductile cementitious composites with fiber bridging properties as model inputs. The optimized volume fraction of hybrid fibers in consideration of both ductility and microcrack control ability of ECC will be provided by the model calculation. After that, Digital Image Correlation technique will be used to quantitatively characterize the multi-cracking patterns of ECC under load. Based on the characterization of crack patterns, a theoretical model that can correlate material composition and cracking permeability will be developed. This project is of great theoretical significance and practical value for establishing the durability based design method of high ductile cementitious composites and improving the durability of engineering structures.

高延性水泥基材料（ECC）是为了克服传统混凝土的脆性、突破其应变软化属性而发展起来的新型土木工程材料，该材料的拉伸延性与裂纹控制功能决定其适用于构件拉应力区带裂纹服役。开裂ECC的裂纹宽度对于工程耐久性至关重要，如何在保留材料延性的同时更有效地降低裂纹宽度是进一步提升ECC耐久性的关键。针对单掺纤维ECC的延性与微裂纹控制能力不匹配问题，本项目提出混杂纤维方法协调ECC的延性与微裂纹宽度，从不同品种纤维的裂纹间桥接规律入手，建立以纤维桥接特性为输入的混杂纤维材料断裂力学模型，探求能够匹配延性与微裂纹控制能力的最佳纤维组合；采用数字图像相关技术定量表征荷载作用下的ECC多缝开裂形态，以裂纹形态为节点建立能够联系材料基本构成与开裂渗透性的理论模型，以ECC延性与开裂抗渗性的匹配引导材料组成设计。本项目对于构建基于耐久性的高延性水泥基材料设计方法、提升工程结构耐久性具有重要的理论意义与实用价值。

高延性水泥基材料（ECC）是为了克服传统混凝土的脆性、突破其应变软化属性而发展起来的新型土木工程材料，该材料的拉伸延性与裂纹控制功能决定其适用于在结构构件的拉应力区胜任带裂纹服役。裂后ECC的裂纹宽度对于工程耐久性至关重要，如何在保留材料延性的同时更有效地降低裂纹宽度是进一步提升ECC耐久性的关键。本项目针对单掺纤维ECC表现出的延性与微裂纹控制能力不匹配的问题，提出了混杂纤维方法来协调ECC的延性与微裂纹宽度，从不同品种纤维的裂纹间桥接规律入手，建立了以纤维桥接特性为输入的混杂纤维材料断裂力学模型，获得了能够匹配延性与微裂纹控制能力的最佳纤维组合；利用数字图像技术，形成了定量表征荷载作用下ECC多缝开裂形态的方法，以裂纹形态为节点建立了能够联系材料基本构成与裂后渗透性的理论模型，实现了基于延性与裂后抗渗性匹配的ECC材料设计。本项目取得的成果对于构建基于耐久性的高延性水泥基材料设计方法、提升工程结构耐久性具有重要的理论意义与实用价值，未来在桥梁伸缩缝、水库坝体防渗层、挡浪墙防护层、隧（巷）道加固层等对于材料延性与抗渗性均要求较高的工程结构中具有广阔的转化应用前景。