Slipform paving is a method that converts the form into a geometric shape & surface finish with the help of plastic concrete mass. This is a popular option for larger jobs that require larger production rates. It makes use of a low-slump PCC that is essential so that PCC can hold its shape after slipform paver has passed over. This is made with a lesser amount of water and has higher compression and flexural strength compared to high slump mixes.
Paving process includes several processes like screeding, consolidation and initial finishing. At times pavers equip themselves with reinforced steel, dowel bars and tie rods as well. This process includes the following steps:
- Initial process:
The first process occurs underneath a paver where an auger spreads PCC in front of a strike off the plate. This is followed by the process of a strike off plate removing any excess auger placed PCC.
Once final elevation is achieved a PCC is consolidated by a group of vibrators. The most effective vibrator position is after the strike-off mechanism and at a final slab elevation. The vibrator setting usually ranges between 7000 – 9000 vibrations per minute; although this does depend on the mix design and slab depth.
A vibrator is usually positioned next to each other with an aim to influence zones overlap at normal paver speed. Pavers are fully adjustable vibrators spacing to account for different conditions and mix types and at the same time provide adequate influence zone overlap.
In case of the presence of a tamper, it pushes large aggregate particles below a slab surface. This final task is to level off the slab at a correct level of elevation and perform initial finishing.
- Initial finishing:
Initial finishing can be accomplished by extruding PCC mass through a moving form made up of a base course (this is the bottom), side forms (vertical edges of a paver) and profile pan (flat paver pieces mounted behind a vibrator).
There is an extruding PCC which provides a final slab dimension and also help larger aggregate particles below the surface. This ensures a smooth finish. At times pavers are also equipped with a hydraulic tamper bar usually found behind vibrators.
Benefits of Slipform paving
There are many advantages of using a slip form paving technology as per this list here:
- Slip form paving technology is an advanced form of technology for the purpose of paving construction work.
- They are high precision machines, thus provide good quality results.
- The conventional form of topping is error-prone and tends to have defects like undulations. Thus, this process reduces and almost eliminates all errors.
- This technology ensures a faster process as well, unlike the conventional method which takes very long.
- There is a reduction of labor cost as well since the entire operation is mechanized. A single machine is able to carry out this job and thus eliminates any chaos caused due to a need of a large number of labor workers.
Factors affecting a smoothness result:
The way this works is a slipform paver is pulled over all cement concrete by slipping over the material. This is very similar to the extrusion process. However, for the slip form paver the machine itself is moving while in the extrusion process it is the material that is moving. Hence, factors like mixing design and weather conditions play a big role in quality of the pavement. Weather conditions affecting this process are low humidity, high winds, high heat, etc. It is also essential to ensure the mix does not dry out since this will affect the final quality.