RCC Precast Manhole System
Precast manholes consist of three components: namely the base, the riser and the cone. The base, as the name suggests, is the bottom part of a precast manhole and is also where the sewage/water pipe is connected. The cone section is the topmost part of a precast manhole and is where access to the manhole is provided. The risers in a precast manhole are mainly there to help achieve the necessary depth from ground level. The wall thickness and grade/type of concrete used will vary based on the technical requirement of the client.
A manhole is the top opening to an underground utility vault used to house an access point for making connections, inspection, valve adjustments or performing maintenance on underground and buried public utility and other services.
The Viswak’s watertight Perfect Manhole System is a precast off-site solution which enables contractors to install a modular water tight manhole without the need for a concrete surround.
This quick assembly system comprises of a monolithic precast concrete base pre-benched to any inlet / outlet configuration, together with thick walled chamber rings with water tight joints incorporating an elastomeric gasket and a sealed cover slab. The system also incorporates push fit elastomeric seals for inlet and outlet pipes.
Precast Manhole System
- Base
- Transition Plates
- Risers
- Cone section
- Adjusting Rings
- Manhole cover Frames
- House connections
- Gully gratings
SUSTAINABLE BENEFITS OF PRECAST CONCRETE
Recycling: Precast plants reuse formwork, in itself a conservationist practice. Offsite casting significantly reduces construction waste that would otherwise be generated on the job site. In addition, cementitious materials used in concrete often contain manufacturing by products such as fly ash and blast furnace slag that would otherwise find their way to a landfill. Wastewater at the plant can be recycled for use in manufacturing. Steel used for concrete reinforcement is typically comprised of 95% post-consumer recycled content.
Reduced Site Impact: Since precast concrete manholes are manufactured off site and delivered on demand, there is a significant reduction in truck traffic, dust, noise and debris from formwork associated with poured-in-place products. Because precast concrete manhole components are modular and standardized, they are installed in a quicker fashion and also result in reduced construction times and energy usage, less noise and fewer emissions from on-site equipment.
Durability: Concrete is a very strong and durable material, which is a significant sustainable attribute. It will not rust, rot or burn and has a service life of in excess of 100 years.
Nasty Weather? No Problem: Precast concrete increases efficiency, because weather will not delay production of the manholes. In addition, weather conditions at the job site do not significantly affect the schedule, because less time is required to install precast compared with other construction materials, such as cast-in place concrete or brick.
Watertight – Darn Right Standard watertight sealants and gaskets are available that are specially designed for use with precast concrete, making multiple-seam precast concrete manholes very easy to construct. Vacuum testing is an easy means of verifying water tightness, either in the plant or in the field.
Rough, Tough and Long-Lasting: Precast concrete strengthens with time, while other materials can deteriorate, experience creep and stress relaxation.
Will Sit Tight Without Tie-Downs: With a specific gravity of 2.40 and superior frictional resistance, precast concrete manholes resist buoyant forces better than all other manhole materials. Fiberglass has a specific gravity of 1.86 and HDPE has a specific gravity of 0.97, requiring the use of tie downs and ultimately increasing project costs and installation headaches.