'Crack-free' and smart `self-sealing' composites with improved microstructure, early-age properties, and durability

加拿大和世界各地的基础设施正在迅速老化。据估计，仅修复加拿大桥梁的赤字就超过80亿美元。导致结构寿命缩短的一个关键因素是建筑材料过早退化。我们老化的基础设施需要创新和耐用的材料来进行新的和修复项目。我们迫切需要使用先进的非接触无损评估(NDE)技术来监控基础设施的健康状况，以预测结构的安全剩余寿命。*提出的计划*近年来，人们研究了使用碳纳米管(CNT)来增强水泥基材料。虽然水泥基复合材料传统上是在宏观尺度上表征的，但为了充分了解碳纳米管的影响，也必须在纳米尺度上进行研究。该计划将重点研究纳米级的特性，以开发“纳米级混杂纤维增强水泥复合材料”(NHyFRCC)。碳纳米管和微碳纤维的混合组合将降低成本，同时解决混合和分散这种组合所面临的问题。UVIC将使用世界上最高倍率的电子全息显微镜来研究钢筋的分散和微观结构的改性。胶凝材料的早期行为对其长期耐久性影响很大，因此将研究早期收缩开裂的可能性。NHyFRCC的这种“自密封”和止裂能力将使用申请人发明的专利技术进行量化。*将研究NHyFRCC在压缩、拉伸和弯曲方面的本构性能。将建立一个数学模型，定义(由于碳强化的存在)减小的电阻抗与尺寸变化之间的关系，以量化传感能力。开发的材料将作为薄薄的覆盖层应用于UVic现有的仪表式试验台，以模拟桥面上的现场条件。这两种材料的现场性能(包括脱粘)将使用传感器、远程监控和无损检测技术(包括加拿大的一种便携式激光扫描振动仪(LSV))进行监测。*益处*这项研究计划将促进对纳米级增强胶凝材料行为的基本理解。NHyFRCC有望成为建筑业的下一个重大突破，具有广泛的适用性，作为一种无裂缝、自密封并具有传感能力的薄覆层。LSV的使用将改变我们评估老化基础设施状况的方式。包括研究生和本科生在内的高素质人员将获得与基础设施管理各方面相关的专业培训和宝贵经验。**

NECESSITY***Infrastructure in Canada and around the world is aging rapidly. According to estimates, the deficit to repair Canadian bridges alone has exceeded $8 billion. A key factor responsible for the reduced life of structures is premature deterioration of construction materials. Our aging infrastructure needs innovative and durable materials for new and rehabilitation projects. There is a dire need to monitor health of our infrastructure using advanced non-contact Non-destructive Evaluation (NDE) techniques to predict safe remaining life of structures.******PROPOSED PROGRAM***In recent years, use of Carbon Nanotubes (CNTs) to reinforce cement-based materials has been investigated. While cementitious composites are traditionally characterized at the macroscale, for full understanding of the influence of CNTs, studies must also be conducted at the nanoscale. The proposed program will focus on studying characteristics at the nanoscale to develop “Nano Scale Hybrid Fiber Reinforced Cement Composites” (NHyFRCC). Hybrid combinations of CNTs and micro carbon fibers will allow lowering the cost while addressing issues faced with mixing and dispersing this combination. One of world's highest magnification electron holography microscope at UVic will be utilized to study the reinforcement dispersion and microstructure modification.******Early-age behavior of cementitious materials greatly influences its long-term durability, hence early-age shrinkage cracking potential will be studied. This ‘self-sealing' and crack arresting ability of NHyFRCC will be quantified using a patented technique invented by the applicant.******Constitutive properties of NHyFRCC in compression, tension, and flexure will be investigated. A mathematical model defining the relationship between the reduced electrical impedance (due to presence of carbon reinforcement) and dimension change will be developed to quantify the sensing capabilities. The developed material will be applied as a thin overlay on an existing instrumented test bench at UVic to simulate field conditions on a bridge deck. Field performance of both materials (including debonding) from the substrate will be monitored using sensors, remote monitoring, and NDE techniques including one of its kind portable Laser Scanning Vibrometer (LSV) in Canada.******BENEFITS***This research program will advance the fundamental understanding about the behavior of cementitious materials reinforced at the nanoscale. NHyFRCC is expected to be the next major breakthrough in the construction industry with wide applicability as a thin overlay that is crack-free, self-sealing and has sensing capabilities. The use of LSV will change the way we assess condition of our aging infrastructure. Highly qualified personnel including graduate and undergraduate students will gain specialized training and valuable experience related to various aspects of infrastructure management.**