Analysis of carbon reinforced lightweight concrete structures and possible applications
Publicerad
Författare
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Steel-reinforced concrete has made intricate constructions feasible for more than
the past hundred years. There are many benefits of using this effective composite
although the service life is challenged by reinforcement corrosion. For applications
where a low dead weight is necessary, lightweight concrete (LWC) has become an
alternative to normalweight concrete (NWC). However, the drawbacks to LWC are
that it is vulnerable for reinforcement corrosion and have a low tensile strength
compared to NWC. Still, there is a potential way forward to create lightweight structures
that are simultaneously resistant to corrosion. To explore this alternative further,
new reinforcement materials must be investigated, e.g. carbon fibre reinforcement
(CFR). The material has advantages due to the corrosion resistance of the carbon
reinforcement, but carbon bundles and cords have problems with low bond strength
between the carbon reinforcement and the concrete, as well as interfilament slip in
the reinforcement. Currently, there is a large gap in research regarding the pros
and cons of CFR and understanding of how CFR can be optimized using different
methods. This study is an attempt to close that gap and provide some answers.
To gain knowledge of the behaviour of the reinforcement and the interaction with
the concrete, pull-out and four-point bending tests with carbon fibre reinforcement
in straight bundles and braided cords have been carried out prior to this thesis. The
data from the pull-out experiments were analysed and the data that were deemed
characteristic were used as input to a bond stress versus slip model applied in the
FE-program DIANA. This bond-slip model was used in FE-analyses of the
fourpoint bending tests, and the results were compared to the experimental results.
Finally, the bond-slip model was used in analyses of stocky columns, where the
carbon reinforcement was used to provide lateral confinement.
The analyses of the tests proved that the CFR had a low bond strength to the LWC
and that only a few percent of the strength and stiffness of the materials was utilised.
The analyses gave a good resemblance to the experimental results, thus they gave
a good estimation of the behaviour of the composite. The knowledge gained was
further used to discuss suitable applications, e.g. floating pontoons, sewage culverts
and edge beams used for bridges. This study attempted to fill the gaps in research
regarding CFR in LWC. In the future, more research within this field will be pivotal
to further broaden the scope of potential applications and evaluate both advantages
and disadvantages.
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Keywords: Carbon fibre reinforcement, CFR, Lightweight concrete, LWC, Bond slip, Interfilament slip, Pull-out test, Four-point bending test, FE-model