Behaviour of Loaded RC Columns Encased With Polymer Modified Ferrocement Under Concentric Loading

Abstract

Concrete structures are the pivot of civil engineering due to its extensive use; they provide excellent performance in terms of structural behavior and durability. The zones which are exposed to severe mechanical and environmental loading require rehabilitation. Rehabilitation is provided to the structures which are deteriorated and to those elements whose load carrying capacity is decreased due to cracks. Rehabilitation of deteriorated concrete structures leads to significant user costs and is also a heavy burden from the scocio- economic viewpoint. As a consequence, Rehabilitation of structures must be developed.

The rehabilitation and strengthening of pre-existing reinforced concrete columns using wire mesh jacketing is done based on a well-established fact that due to application of jacketing lateral confinement of concrete is decreased and its axial compressive strength can sustainably increase. In recent years, various methods of external confinement of concrete are being used such as jacketing using Steel Angle, FRP, Bracing Infill walls, Ferrocement has emerged as a popular method of column retrofit. Retrofitting of element reduces the damage of an existing structure during a future earthquake. The basic aim is to strengthen a structure in accordance to the requirements of the current codes for seismic design. Therefore, rehabilitation of deficient columns is required to increase load carrying capacity and decrease the lateral deflection of column due to buckling. External confinement of the damaged column can be done by different materials such as Ferrocement and Polymer. Ferrocement confinement for re- strengthening of deteriorated columns is one of the oldest, efficient and cost effective techniques. Polymer induced Ferrocement is a form of thin wall reinforced concrete using wire mesh and high strength mortar mixed with polymer. The wires used as reinforcement in wire mesh provide a higher specific surface hence providing strength to the ferrocement.

Considering all these points, the present study focused on the behavior of RCC columns with different slenderness ratios on the Polymer induced Ferrocement confined. In the experimental part of this thesis, column specimens with three different slenderness ratios (λ) were casted. Three slenderness ratios were considered λ =3, λ =6, λ =12.

These specimens were further divided in to three categories. The first category was of control samples consisted of no Loading and no Ferrocement columns from each size group, second category consisted of normal samples and pre-loaded samples confined with Polymer (SBR) Ferrocement using one layer of wire mesh and third category consisted of normal samples and pre-loaded samples confined with Polymer (SBR) Ferrocement using two layers of wire mesh. In second and third category the 80% loading was done with respect to the peak load of control samples and the polymer used was SBR. All the columns were tested under monotonic uni-axial compression loading. As the slenderness ratio increased from λ =3, λ =6 to λ =12 the load carrying capacity decreased from 180kN , 154kN to 132kN, there was different trend while increasing the number of mesh as the load carrying capacity increased 53.1% to 70 % in λ =3 and the similar trend was seen in λ =12, increased from 39.8% to 51.2%.