Influence of microstructure on the transport properties of concrete

世界上大多数基础设施都是用混凝土建造的，每年为地球上的每个人生产超过1立方米的混凝土。然而，混凝土结构逐渐恶化，这是一个世界性的大问题。所有常见的变质过程都是由水和侵蚀剂通过微观结构中固有的孔隙和微裂纹渗透控制的。预测这种迁移的能力将使对剩余寿命的预测更加可靠，并将促进更耐用结构的发展。该项目旨在了解混凝土的微观结构如何控制水和侵蚀剂的渗透，然后开发预测运输特性的模型。混凝土微观结构将采用结合光学、场发射电子和三维激光扫描共聚焦显微镜的多尺度方法进行量化。这将允许以适当的长度尺度对所有相关相进行表征，从而提供全局信息（体积分数、比表面积）、形态（形状）、拓扑（弯曲度、连通性、收缩性）和空间可变性。将对一系列样品进行测试，以确定不同成分、比例、加工和暴露历史对微观结构的影响。对混凝土耐久性最重要的输运特性将在平行样品上进行测量，并与微观结构相关联，以确定不同类型和大小的孔隙、微裂缝和其他相的影响和相对贡献。使用显微镜数据重建微观结构的多尺度模型，并从经典输运理论、有效介质近似和使用网络模型的流动模拟中开发预测输运性质的模型。这将有助于今后发展更耐用的材料和更可靠的使用寿命预测模型，并将与放射性废物的储存有关。

Most of the world's infrastructure is built in concrete with more than 1m3 of concrete being produced every year for every person on the planet. However, concrete structures gradually deteriorate and this is a major problem around the world. All of the commonly occurring deterioration processes are controlled by the penetration of water and aggressive agents via pores and microcracks inherent in the microstructure. An ability to predict this transport would allow more reliable prediction of remaining life and would facilitate the development of more durable structures. This project aims to develop an understanding of how the microstructure of concrete controls penetration of water and aggressive agents and then to develop models for predicting transport properties. Concrete microstructure will be quantified using a multi-scale approach combining optical, field emission electron and 3D laser scanning confocal microscopy. This will allow all relevant phases to be characterised at the appropriate length scale giving global information (volume fraction, specific surface), morphology (shape), topology (tortuosity, connectivity, constrictivity) and spatial variability. A range of samples will be tested to establish the effect of different ingredients, proportions, processing and exposure history on the microstructure. The transport properties most important to concrete durability will be measured on parallel samples and correlated to the microstructure, to identify the influence and relative contribution of different types and sizes of pore, microcrack and other phases. A multi-scale model of the microstructure will be reconstructed using data from microscopy and models for predicting transport properties will be developed from classical transport theories, effective medium approximation and flow simulation using network models. This will facilitate future development of more durable materials and more reliable service life prediction models and will also be relevant to the storage of radioactive waste.