Steps of Isolated Footing Strengthening
An isolated footing is strengthened by increasing the size of the footing and the reinforcement steel bars as follows:- Excavating around the footing
- Cleaning and roughening the concrete surface.
- Installing dowels at 25-30cm spacing in both directions using an appropriate epoxy material.
- Fastening the new steel bars with the dowels using steel wires. The diameter and number of steel bars should be according to the design.
- Coating the footing surface with a bonding agent in order to achieve the required bond between old and new concrete.
- Pouring the new concrete before the bonding agent dries. The new concrete should contain a non-shrinkage material.
Fig: Steps for strengthening foundations
Jacketing of Foundations for Strengthening
The following photos (1 - 4) illustrate the practical way of jacketing a footing by reinforced concrete.
Fig. 1 – 4: Strengthening of footing by Jacketing
If the bearing area of footing has to be increased without strengthening of the column, soil pressure on the extended foundation area has to be transferred to the existing footing. Transfer of soil pressure to existing footing is difficult as excavation is required below the existing footing. The building has to be properly supported and settlement of foundation has to be avoided. In this case also, there is a tendency of the new concrete to split from the old concrete. To avoid this, sufficient numbers of well anchored/welded hoops are required. Read More: Strengthening of Concrete Structures and When its Required? Types of Foundation for Buildings and their Uses What is Punching Shear? Punching Shear in Slabs and Foundations Materials for Concrete Repair, Replacement and Jacketing