Experimental assessment of fracture and autonomous healing of concrete and polymer systems

Scriptie/Masterproef: Doctoral Thesis

Samenvatting

The PhD thesis deals with newly developed smart concrete and polymer composites that carry encapsulated adhesive agent. The agent is autonomously activated as soon as cracking damage occurs. The released adhesive material fills the crack void and locally restores damaged zones. Most studies in the field have proposed simplified and empirical fracture tests and evaluated the healing potential by considering only the load bearing capacity of healed material. The findings were rather controversial and no general agreement regarding the mechanical characterization of healing phenomena could be obtained. This research investigates in detail the healing testing configurations proposed in
literature. The use of Tapered Double Cantilever Beam test set-up to quantify the
healing efficiency of polymer systems is critically reviewed. The shortcomings of
TDCB design are detected and alternative geometries are proposed. Additionally,
the plethora of test set-ups applied to evaluate healing on concrete systems are
considered. By using advanced optical and acoustic methods the study builds full-field experimental measuring systems that detects healing activation and clarifies the process and conditions under which damage and subsequent healing occurs. Digital Image Correlation and optical microscopy continuously monitor fracture and healing evolution, detect crack initiation and propagation and highlight the fracture process when both concrete and polymers are tested. Acoustic Emission and ultrasound pulse technique obtained by using embedded piezoelectric transducers locate in time and in space damage phenomena, qualitatively evaluate the fracture mode and the impact of healing process on material resistance. Concerning the analytical models describing the mechanical behavior of polymerand concrete systems, the main contribution of this work is the application of classical fracture theories on reverse damage phenomena: crack closure and restore. For the first time in literature, the contribution of encapsulated agent on the matrix toughness is quantified. The nature of healing agent and encapsulation design is clarified. The healing computation is redefined. The efficiency of autonomous healing mechanism is investigated on realistic cracking phenomena and on realscale concrete structures. Additionally, the performance of the newly developed advanced monitoring system is evaluated on large-scale concrete samples that are autonomously healed. The thesis dealing with the first generation of healing polymers and concrete systems aspires to provide a key tool to future healing real-life applications.
Datum prijs19 mrt 2015
Originele taalEnglish
Prijsuitreikende instantie
  • Vrije Universiteit Brussel
BegeleiderDanny Van Hemelrijck (Promotor) & Dimitrios Angelis (Co-promotor)

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