Multifunctional cement-based sensors with integrated piezoresistivity and hydrophobicity toward smart infrastructure
- Publication Type:
- Thesis
- Issue Date:
- 2021
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Concrete is the most widely used construction material for buildings, pavements, harbours and bridges. The piezoresistive cement-based sensor consists of the traditional cementitious composite and conductive fillers, thus the electrical conductivity is greatly improved and easily captured. Therefore, the cement-based sensors can be applied in concrete infrastructures to self-sense and monitor the damages and cracks through the measurements of concrete electrical resistivity, due to their low cost, easy manufacturing, high sensitivity and good durability compared to traditional sensors. However, several factors ranging from types and contents of conductive fillers, additives and environmental factors can affect the piezoresistivity and restrict the practical application of cement-based sensors.
In this study, the conventional cementitious materials with different conductive fillers including conductive rubber products (rubber crumbs and fibres) and carbon nanomaterials (carbon black, carbon nanotube, graphene and graphite) were developed to produce cement-based sensors, whose sensitivity was dozens or hundreds of times higher than the commercially available strain gauge. Later, the effects of additives such as rubber fibres, polypropylene fibres and silica fume on the electrical, mechanical, microstructural and piezoresistive properties of carbon black filled cement-based sensors were investigated. It was observed the enhanced durability and sensitivity of cement-based sensors containing these additives. Given working environment can significantly affect the piezoresistive performance of cement-based sensors, the effects of temperature, humidity, freeze-thaw cycles, acid erosion and drop impact on the cement-based sensors containing nanomaterials were explored regarding to the electrical resistivity and piezoresistivity. To reduce the interference from working environment, multifunctional cement-based sensors were developed with combined self-sensing, self-healing, self-cleaning and superhydrophobicity. These functions can hinder the penetration of water and ions inside of cement-based sensors, thus reduce the influences of working environment on the piezoresistive performance of cement-based sensors. On the other hand, it provides the cement-based sensors with more functions to clean and heal themselves automatically.
In the end, this study carried out the piezoresistivity test on the small concrete beams and slabs with embedded cement-based sensors, to evaluate the sensing performance of cement-based sensors inside of concrete structures. Despite the inherent challenges, the multifunctional cement-based sensors have great potential for smart infrastructures. Overall, this study has comprehensively investigated the performance of cement-based sensors exposure to various conditions and taken a solid step forward for their practical application.
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