SENSOR-INFRA: Smart Engineered Cementitious Composites for Intelligent Infrastructure

Current global infrastructure is plagued by ageing and deterioration and the scale of investment needed for maintaining its functionality is immense. With many nations having entered an era of austerity and financial restraint, the demand for infrastructure life-extension is currently more prevalent than ever. In these countries, however, asset owners have difficulties managing their infrastructure due to the absence of reliable data about the true 'state of health' of their assets.

The proposed research centres on the development of engineered cementitious composites with a built-in self-monitoring system termed smart-ECCs (s-ECCs). This self-monitoring feature can provide future civil engineering infrastructure with a 'brain and nervous' system, enabling structures to sense and respond to the internal changes and external environment without the need of additional sensors. Furthermore, introducing 'smartness' to ECCs could also give the material a number of non-structural applications thereby making the material multi-functional.

The research proposed will provide a comprehensive study of the rheological, mechanical and a.c. electrical properties of s-ECCs. It will be the first to undertake a detailed study into the electrical properties of ECCs from initial gauging, throughout setting and long-term hardening and into its piezo-resistive response under mechanical and environmental loading. A fuller understanding of these technical aspects will allow development standarised test protocols that can be further implemented in real-world applications.

The novelty of the proposed research lies in the use of recycled, milled carbon (MC) fibres as conductive filler in ECC systems. As the length of MC fibres is equivalent to the characteristic crack width of ECCs, it is anticipated that the fibres will not bridge the micro-cracks in ECC, allowing the material sensitivity to cracks formation to be maintained thereby fulfilling its function as a damage sensor. At the same time, the high aspect ratio of MC fibres would allow the formation electrical continuity within the ECC matrix at practically low dosage rates. This is 'percolated' fibre network is essential to ensure that the influence of hydration and moisture changes in the material will not have appreciable influence on the bulk conductivity thereby minimising false sensing.

High performance fibre reinforced cement composites represent a new generation of tough, durable construction materials for the 21st century. The engineered cementitious composite developed in this project not only addresses this overarching goal, but also adds 'smartness' to its inherent properties. The development of a smart structural material (s-ECC) that has the ability to monitor the condition and integrity of public infrastructure and to minimise the costs of repair, maintenance and the associated downtime, will have significant economical and societal implications on the global construction market. Project outcomes will lead to a new knowledge-base and improved understanding of the self-monitoring feature of this novel construction material. A fuller understanding of the mechanical, rheological, and electrical properties of s-ECCs could realise the potential of this material as a multi-functional material with self-monitoring capabilities which could, ultimately, be exploited in the market-place. The research will therefore have the potential of being transformative in the use of concrete as a construction material. Project outcomes will extend current UK technology and expertise in advanced cement-based systems and in structural health monitoring. The research will also have the potential to attract further investments in emerging industries such as fibre manufacturing.

Regular meetings with the industry partners will ensure that the proposed work will be suitable for practical implementation. Project outcomes will be shared with other academics, researchers and practicing engineers through dissemination via academic publications, presentations at conferences and a one-day workshop. In this respect, the project will help stimulate discussion between academics and practicing engineers working in UK construction industry, including precast plants, companies undertaking repair and retrofitting works as well as public and private sectors that are involved in the construction of public infrastructure. This project has the potential to impact on (worldwide) efforts to develop smart structural materials, which is a growing area of research.

The multidisciplinary aspects of the proposed project will be an excellent learning exercise for all involved, including the PI and project partners. More specifically, the project will result in the training of one PDRA and two PhD students on various aspects of the proposed work; they will also benefit from a considerable amount of publishable data and networking opportunities with academics and professionals.