Date of Award

2020

Degree Type

Dissertation

Degree Name

Doctor of Philosophy in Civil and Environmental Engineering

Department

Civil and Environmental Engineering

First Advisor

Sumanta Das

Abstract

Infrastructure is the backbone of America’s 18.57 trillion-dollar economy. The current condition of America’s deteriorating infrastructure network, however, is the cause of serious safety, quality of life, and economic concerns. According to the recent American Society of Civil Engineers’ (ASCE) 2017 Report Card, America’s Infrastructure received a score of D+. According to ASCE’S annual report, the US economy is expected to lose $4 trillion in GDP by 2025 and $14 trillion in GDP by 2040 if current concerns are not addressed and infrastructure continues to deteriorate at current rates. Clearly, there is a need for bold and forward thinking solutions that adopt modern technologies, materials and design methodologies in these critical infrastructures. Improvement of the health of our infrastructure depends not only on closing the investment gap in the building and repair of these systems and networks, but also on development of innovative design-driven technologies to build the next-generation of durable infrastructure for our future. The central objective of this thesis stems from the afore-mentioned concerns and realities; to develop innovative durable infrastructure materials. Thus, this thesis explores development of innovative cementitious systems and polymer composites for durable infrastructure. Virtual design and numerical modelling of the innovative materials as applied to structures form a salient feature of this thesis that can enable designers and engineers alike with tools to facilitate optimized design. While concrete is notorious for its poor fracture performance, its exposure to freeze-thaw cycles and deicing salts in the temperate areas leading to loss of design life is a key concern. A part of this thesis addresses this by incorporating waste metallic particulates to improve fracture performance and phase change materials to improve freeze-thaw resistance. The phase change materials incorporated in cementitious systems are found to reduce the number of freeze-thaw cycles in a concrete structure thus significantly reducing the freeze-thaw induced cyclic damage and associated chloride ingress. Alternative binders such as alkali-activated blast furnace slag that can reduce cement consumption have been also been studied. Incorporation of metallic particulate reinforcement in such alternative binder enhances fracture performance of the composite by crack bridging and deflection. To enhance the life of existing infrastructure, the other part of this thesis aims to develop piezoresistive composites that can enable strain and damage sensing. Such smart composites are achieved by nanoengineered interfaces or waste iron powder in cementitious systems and the incorporation of CNTs in polymer composites. Multi-physical simulations that can capture the sensing capabilities of such heterogenous systems have been developed in an electro-mechanical framework. Owing to the heterogenous nature of such materials, accurate predictions entail capturing of detailed microstructural features which are facilitated by multiscale simulations. Damage sensing as enabled by electromechanical experiments leading to tomographic observations have also been carried out to validate the efficiency of inclusions in the smart composites. The application of nanoengineered films in aggregates in concrete and polymer weaves enables reversible strain sensing thus fostering a real-time health monitoring. The simulations involving the separation of inclusion-matrix interface and ensuing matrix damage when coupled with electromechanical responses of the constituents in a multiscale framework serve to elucidate the strain and damage sensing behavior of the composites. In a similar multiscale framework, the baseline conductivity serves as a-priori information in iron powder incorporated cementitious systems thereby enabling determination of spatial conductivity distribution inside the sample for spatial damage sensing by Electrical Resistance Tomography. The key findings of the studies involve the efficiency of iron powder volume fraction up to 40% demonstrating spatial damage sensing with suitable accuracy. For the self-sensing nanoengineered composites, the thin films brought about by percolating CNT networks similarly show reversible strain sensing ability thus elucidating the efficiency of such systems achieved by 0.01% volume fraction of CNTs in films as thin as 10 microns.

[Refer to PDF for graphic abstract portion]

Available for download on Saturday, August 13, 2022

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