Abstract:
Serviceability of a concrete structure is determined by its deflection, cracking, extent
of corrosion of its embedded reinforcement and surface deterioration. A satisfactory
performance of reinforced concrete structures over their design life under a
combination of various types of loads requires a crack free structure so as to prevent
ingress of moisture by diffusion. This ultimately leads to corrosion of steel,
carbonation of concrete and leaching of soluble soft lime products. Thus, the life and
strength of the structure is reduced. Serviceability of the structure can be greatly
improved providing a low permeable cover such as ferrocement overlay to the
reinforced concrete elements. If this cover can be used as formwork for the structural
elements it may significantly reduce the cost of timber shuttering and forrriwork for
those elements.
An attempt has been made in this research to study the behavior of reinforced
concrete beams with ferrocement overlay. An analytical model has been developed
based on the basic assumptions of reinforced concrete and on the idealized stressstrain
diagrams of the constituent materials. A linear elastic finite element study was
also carried out to observe the serviceability of such beams. The performance of both
the analytical and the layered finite element model for the composite beam is
validated by comparing these results with some existing experimental results. The
proposed analytical model is found to perform quite well within the serviceability
limit and fair enough at the ultimate limit state.
The analytical method proposed is used to calculate the load-displacement response
for three sets of beams with varying ferrocement properties. The serviceability of the
beams is found to be significantly improved by increasing the number of mesh layers
for a constant ferrocement thickness. The confinement effect of the ferrocement
overlay on the concrete core is also investigated using the finite element model. The
. resulting flexural stresses in the concrete core were found to be significantly improved
compared to its unconfined state under identical loading condition. Obviously,
ferrocement overlay improves the ductility of the RC beams which is very important
for the structures in seismic regions. The inherent crack arresting capacity of
ferrocement is expected to enhance the life of concrete beams and hence the
durability.
