Collaborators: Prof Sebastian Skatulla (University of Cape Town), Prof Hans Beushausen (University of Cape Town) and Prof Pilate Moyo (University of Cape Town)
Summary
While it is known that reinforcing steel provides strength and ductility only through bond and anchorage to the concrete, the effectiveness of this connection can be reduced through deterioration of the steel, concrete or both. Therefore, the durability of con- crete structures depends on the resistance of the concrete against chemical and physical factors and its ability to protect the embedded reinforcement against corrosion. In view of the fact that a large number of existing structures are being deteriorated with time by reinforcement corrosion due to environmental exposure, corrosion is one of the main causes for the limited durability of reinforced concrete. The corrosion product, rust, resides at the interface between reinforcement and concrete, degrading the bond be- tween rebar and concrete and thus reducing the service life of the structure. The nonuniformity in bond stress distribution causes difficulties in assessment of the effects of corrosion on bond and thus on the structures.
In this context, so-called generalised continuum formulations have proven to provide a remedy. They allow for the incorporation of internal length scale parameters which reflect the micro-structural influence to the macroscopic material response. In this way, size-scale effects of very small structures as well as heterogeneous material behaviour can be addressed in a very elegant manner.
Reinforced concrete members can, from the mechanics perspective, be clearly viewed as multiphase continuum or porous medium. In terms of deterioration of concrete due to physical or chemical causes, the mobility of fluids or gases through the concrete are nearly always involved. The overall susceptibility, or penetrability of a concrete structure, especially when compounded by additional environmental or exposure challenges, is the key to its ultimate serviceability and durability. This research project studies the impact of permeability and rebar corrosion in concrete by means of computer modelling and estimate their effects with respect to its durability. For this purpose the multiphase material model of the in-house simulation software SESKA will be calibrated to reflect the properties of reinforced concrete material. It will also be necessary to identify and implement a suitable relation which describes the mass production linked to rebar rusting.