Contents:
Types of Prestressed Concrete Pipes
Prestressed concrete pipes are classified into two different types as follows:- Prestressed Concrete Lined Cylinder Pipes
- Prestressed Concrete Non-cylinder Pipes
1. Prestressed Concrete Lined Cylinder Pipes
In this type of Prestressed Concrete Pipes, concrete core pipe is lined by steel cylinder which wrapped with a helix of highly prestressed wire and this wire arrangement is protected by a coat of cement mortar or dense concrete. Steel cylinder contains steel joint rings at its ends which are used to connect two pipes during installation.
Fig 1: Prestressed Concrete Lined Cylinder Pipe
2. Prestressed Concrete Non-cylinder Pipes
Prestressed Concrete Non-cylinder Pipes does not contain steel cylinder between prestressed wiring and the concrete core pipe and this is the only difference between cylinder and non-cylinder type pipes. In this type circular prestressing is directly provided on the concrete core pipe.
Fig 2: Prestressed Concrete Non-cylinder Pipe
Manufacturing Methods of Prestressed Concrete Pipes
Prestressed concrete pipes can manufactured in two different ways which are- Monolyte Construction
- Two Stage Construction
1. Monolyte Construction
- Monolyte method of prestressed concrete pipes making consists, a vertical steel mold which has an inner shell and outer shell.
- Outer shell of mold consists of longitudinal section which are hold together by spring arrangements. Inner shell of mold consist an expandable rubber membrane.
- In this method, concrete is poured from the top of the mold under high frequency vibration.
- Once the concrete is poured, the longitudinal sections of outer shell are permits the mold to expand and rubber membrane in the inner shell also starts expanding.
- This introduces prestress in concrete and curing is done by steaming in monolyte method.
- In monolyte construction, the whole production process is done in a single stage or cycle.
Fig 3: Prestressed Concrete Pipe Mold
2. Two Stage Construction
- Two stage construction of prestressed concrete pipes, contains two stages of making and this method can be used to make both cylinder and non-cylinder type pipes.
- To manufacture Non-cylinder type P.S.C pipe, concrete is cast over a tensioned longitudinal reinforcement in the first stage.
- After curing of concrete, in second stage, prestressed wires are wound around the circumference of concrete pipe under tension and cement mortar layer is coated on it.
- Longitudinal stresses induced in first stage are helpful in second stage to resist cracking due to circumferential winding and cracking during installation of pipes.
- In case of cylinder type pipes, steel cylinder is lined with concrete on the inside and this cylinder is wrapped using highly stressed wire.
- After wrapping the wire, a rich cement mortar is coated as a protection layer.
- The wires and the splices are fixed at ends by using tubular fasteners.
- For very high pressures, larger diameter pipes are used which may require double winding of wires and double mortar coating.
Fig 4: Typical PSC Pipe Showing Prestressed Wire Wound Around Steel Cylinder
Uses of Prestressed Concrete Pipes
Prestressed concrete pipes are used for many purposes as follows:- To supply water for domestic needs, where water needs high pressure to supply uniformly to distributed mains.
- For Industrial purposes such as re-circulating pipes, cooling water pipe lines etc.
- Used as Pipe lines which carry sewage using gravity.
- Run-off or rainwater collecting pipe lines.
- To construct culverts under roadway, railroad or through any obstruction etc.
- To construct inverted siphons.
Fig 5: Laying Prestressed Concrete Pipes