Water tightness is the main parameter in the construction of water retaining structures. The locations of construction joints are the critical feature that challenging the water tightness in practical construction procedure. These construction joints are facilitating path for water penetration. Minimizing the construction joints is an important consideration for water retaining structures like water sump, water tank and manholes.
So, sealing the construction joints with any appropriate material (water bar) should be carried out at sites to avoid the water penetration in all the below ground structures and water retaining structures.
Waterbars or waterstops are strip like elements which are usually made of galvanized steel, copper, rubber bituminous material or plastic material. These flexible, impervious strips are embedded in the concrete at the locations of construction joints. They are acting as joining strips along the construction joints thus preventing the water leakage through the construction joints.
Generally, these bars should be carefully placed along the centreline of the construction joints to prevent the leakage from either side of the waterbar efficiently.
The Functions of Waterbars
- Acting as a waterproofing seal at the joint locations
- Allowing the independent movement of each sections at the joints. So no harm to structural movements of the sections.
Waterbars can be classified as two categories, flexible and rigid. Rigid waterbars are formed with the copper or steel strips. The flexible waterbars can be classified as follows,
- Central bulb type
- Dumbbell type
- Flat or surface type
Among those, the central bulb types are used for the expansion and contraction joints, the dumbbell types are used for contraction and construction joints and the third type, flat or surface types are used in floor slabs.
Available of Waterstops
- PVC Waterstop
- HDPE Waterstop
- TVP Waterstop
- Rubber Waterstop
Mild steel (MS) strips are generally preferred at sites as at the construction joints for water tightness. The MS strips are welded to the reinforcements to ensure no collapse causing during the concrete placement.
The following figure shows the schematic diagram of water bar placement at the construction join in between base slab and wall.
The General Requirements of waterbars
- Very durable under operating conditions
- Non-toxic materials should be used to make the waterbars for water tanks and water sumps used to contain drinking water
- Rigid enough to place firmly in position and shape during the installation and concrete placements.
- Have the bond between concrete without letting a pervious concrete.
- Required degree of flexibility for the easy operations