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Characterisation of a vascular self-healing cementitious material system

Selvarajoo, Tharmesh 2020. Characterisation of a vascular self-healing cementitious material system. PhD Thesis, Cardiff University.
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Abstract

Over the last few decades, researchers have shown conclusively that is it possible to incorporate self-healing systems into concrete structures. Some of these are enhanced natural autogenic mechanisms, while others are based on autonomic (or engineered healing) techniques. One promising approach involves embedding channel networks in cementitious matrices as a delivery system for healing agents. These vascular healing systems have the advantage that they can be pressurised and provide a continuous supply of healing agent, which enables multiple cycles of damage to be healed. Although much experimental work had been undertaken on vascular systems for cementitious structural elements, the author found that there was not a complete characterisation study on any one system that was adequate for developing a comprehensive design or numerical model of the system. This provided the motivation for the work reported in the thesis, which involved an extensive experimental programme of work aimed at characterising the transport and mechanical behaviour of a cementitious vascular material system with cyanoacrylate as a healing agent. The tests series undertaken included (i) three-point flexural bending tests on unreinforced notched prisms, in which the effects of varying the healing period, healing agent pressure and loading rate were explored; (ii) flexural tests on notched beams with an offset arrangement of discontinuous reinforcement that were undertaken to study healing behaviour when complex crack patterns occur; (iii) direct tension tests on notched cubes with different crack openings for a range of healing periods; (iv) dynamic healing-agent flow tests that investigated the variation of the capillary meniscus contact angle with velocity; (v) the sorption of healing agent into a concrete specimen through a natural crack surface; and (vi) tests in which healing-agent curing adjacent to a cementitious substrate was studied. A particular focus of the present work is simultaneous damage-healing behaviour and the various properties that influence the associated response. This requirement governed the range of loading rates (crack opening rates), healing agent pressures and fixed healing periods considered in the test series. The test series successfully characterised the mechanical behaviour of the healing system for situations in which damage and healing are separated in time as well as for cases in which these processes overlap. In addition, the experimental programme provided data on the curing response of the healing agent and on its dynamic flow characteristics in flow channels, discrete cracks and within the cementitious continuum. This work guided the development of a series of constitutive models for both mechanical and transport behaviour. These formed the basis of a numerical model, which was developed by others, but used in a material tailoring exercise in the current study. This work is part of the EPSRC funded Resilient Materials for Life, (RM4L) project, undertaken by researchers at Cardiff, Cambridge, Bath and Bradford universities (EP/P02081X/1 and http://rm4l.com/).

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: Self-healing; Self-healing cementitious materials; Automatic healing; Characterisation of the vascular healing systems; Mechanical damage and healing; Damage-healing response; Flow and curing properties.
Date of First Compliant Deposit: 12 March 2020
Last Modified: 12 Mar 2020 10:14
URI: http://orca.cf.ac.uk/id/eprint/130332

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