Interfacial bond properties for ECC overlay systems
Date
2007-03
Authors
Stander, Heinrich
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
Bonded overlays are increasingly used in concrete and reinforced concrete repair and rehabilitation applications,
despite the high probability of interfacial debonding. Reasons for such failures include inefficient
substrate surface preparations, inappropriate overlay materials, poor curing conditions and time dependent
influences.
The introduction of engineered cement-based composite (ECC) as an overlay or repair material, does
not only address durability aspects but also structural performance. The associated ductility of the material
induces a high performance aspect where applied. It is crucial to execute reliable design methods,
especially at interfacial level, in order to harness the ductility at hand. The fact of the matter is that
through identifying the required performance, one can engineer an optimal bond through implementation
of reliable substrate surface preparation techniques (SSPT’s).
ECC is a material which exhibits ductile mechanical behaviour. The material matrix is reinforced with
synthetic fibres, in the case of this study, poly vinyl alcohol (PVA) fibres were used. The introduction of
fibres induces strain-hardening behaviour when in tension. Strain-hardening occurs from the first crack
onwards and is accompanied by ductile behaviour, due to a multiple cracking phenomenon. Multiple
cracking continues until the increased tensile load incurs localising of an existing crack.
The literature study investigates bond properties and bond model parameter test methods. A review of
composite design, mainly concrete to concrete, in local and international codes discloses design specifications
towards calculating interfacial shear bonds. The interfacial transition zone (ITZ) between the
aggregate and cement matrix of concrete is used to define the interfacial bond characteristics and processes.
The next step is to investigate a variety of interfacial shear and tensile test methods, in order to
implement the most suitable tests.
Description
Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2007.
Keywords
Theses -- Civil engineering, Dissertations -- Civil engineering