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|Title: ||Detection of reinforcement corrosion by an acoustic technique|
|Authors: ||Ing, Matthew|
|Issue Date: ||2003|
|Publisher: ||© M.J. Ing|
|Abstract: ||Corrosion of reinforcing steel is a major serviceability issue with reinforced
concrete structures, often resulting in significant section and bond loss.
However, current non-destructive diagnostic techniques do not allow
corrosion to be reliably detected at the very early stages of the process,
before damage to the concrete occurs. This research describes the
development of an Acoustic Emission (AE) technique as a practical tool for
the early detection of corrosion of reinforcing steel embedded in concrete.
The study falls into three main areas: (i) determining the influential
material parameters of reinforced concrete that affect the magnitude of
the acoustic emissions; (ii) investigating the influence of diurnal and
seasonal temperature variations on corrosion rate and thus the rate of
acoustic emissions; and (iii) developing a testing and evaluation
procedure that combines the findings of the first two stages with existing
knowledge about corrosion and deterioration of concrete structures.
In the first phase of the research material parameters such as cover
thickness, compressive strength and rebar diameter were investigated to
ascertain the influence of varying these factors on the magnitude of AE
Energy obtained per gram of steel loss. The experimental results
confirmed that early age corrosion, verified by internal visual inspection
and mass loss measurements, can be detected by AE before any external
signs of cracking. Furthermore results show that compressive strength
was the primary influential parameter, indicating an exponential, empirical
relationship between compressive strength and AE Energy.
An increase in temperature usually induces an increase in corrosion
activity, which should be measurable using the AE technique.
Consequently the influences of seasonal and diurnal temperature
variations were investigated to determine their impact on undertaking AE
measurements. This phase of the research demonstrated that seasonal
variations in temperature impart a negligible influence on measured AE
Energy. However measurement of AE Energy per hour followed trends in
the diurnal temperature and corrosion rate evolution, these being in a
state of constant flux. Therefore AE measurements of corrosion in
reinforced concrete are more responsive to a change in temperature, and
so corrosion rate, as opposed to a specific and constant corrosion rate.
In the final phase practical experience with AE from site trials and
laboratory work were coupled with leading research and existing
knowledge of corrosion in concrete and structural deterioration, to develop
a testing and evaluation procedure for on-site application. This rigorous
procedure enables reliable corrosion measurements to be undertaken on
reinforced concrete structures using AE technology and enabling an
assessment of the rate of corrosion induced damage to be made. As far as
the author is aware this is the first site testing procedure for detecting
corrosion in reinforced concrete using AE. Future research in this area
might involve more site testing with a view to improving accuracy and
analysis of on-site data, underpinning the developed procedure.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Civil and Building Engineering)|
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