Behaviour of RCC columns confined with ferrocement

Abstract

Retrofitting of the existing structures has become a large part of the construction activity. Columns are the most authoritative structural element in any structure that transfers the entire loads to the foundation. Slenderness ratio is an important aspect that determines the load carrying capacity of the columns. In general, the load carrying capacity of the concrete columns decreases with increase in slenderness ratio. Therefore, the strengthening of deficient columns is necessary to increase the load carrying capacity, ductility and energy absorption capacity that can be achieved by external confinement of column. External confinement can be done by using different materials such as ferrocement, fibre reinforced polymers (FRP), steel jacketing. Ferrocement confinement is one of the oldest, efficient and cost effective techniques of re-strengthening of deteriorated and weak columns. Ferrocement is a form of thin wall reinforced concrete using wire mesh and high strength mortar. Small diameter of wires used as reinforcement, leads to a higher specific surface, providing homogeneity to the ferrocement. Closely spaced wires provide more ductility and energy absorption capacity. The structures confined with ferrocement undergo deformation above elastic point, unlike conventional concrete structures that undergo brittle failure. Considering all these points in view, the present study focused on the behaviour of RCC columns with different slenderness ratios on the unconfined columns and ferrocement confined columns. In the experimental part of this thesis, a total of 27 column specimens with three different slenderness ratios () were casted. Three slenderness ratios were considered (i) =3; (ii) =7; and (iii) =15. These specimens were further divided in to three categories. First category consisted of three unconfined control columns from each size group, second category consisted of three column confined with ferrocement using one layer of wire mesh and third category consisted of three columns confined with ferrocement using two layers of wire mesh. All the columns were tested under monotonic uniaxial compression loading. The results showed that ferrocement confinement increased the load carrying capacity and stability of the column by decreasing the lateral deflection. The increase in slenderness ratio resulted in decrease of strength of the ferrocement confinement. It was also observed that in the ferrocement the wire mesh is more effective up to one or two layers.