Waterproofing of joints with pvc waterstops
PVC waterstops are flexible profiles of various types and widths used for the waterproofing of below-ground expansion and construction joints. About the Author: Civil engineer with postgraduate studies in MBA and Marketing.
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They are extruded from special types of thermoplastic PVC.
PVC waterstops are used for the waterproofing both of water-retaining: water tanks and towers, dams, culverts, water treatment plants etc. and water ' excluding structures: basements, tunnels, foundations etc.
PVC waterstops have to be embedded into the concrete usually in two different castings. Once in place they form a reliable, waterproof diaphragm to prevent water passage even under considerable hydrostatic pressures.
There are so big differences among qualities of raw materials used that you have to make sure that you compare apples with apples.
Furthermore you can find formulae compatible with asphalt or not.
Although there are endless types of PVC waterstops, the most customary ones types are the ribbed types.
These products are placed:
- either centrally (most regular use)
- or externally (e.g. slabs-on-ground/ base-seal).
When used in practically non-working joints (e.g. construction or control joints) the ribbed profiles are plain, without a center bulb. These types of PVC waterstops can accommodate only little transverse movements.
When used in working (e.g. expansion joints), PVC waterstops have a center bulb to accommodate lateral, transverse and shear movements.
Obviously the larger the center bulb the large movement it can accommodate.
These types of PVC waterstops are the most versatile ones and can be used for every sort of joints whether working or non ' working.
Ribbed type PVC waterstops provide a better sealing effect than other, smooth types. The path the water has to traverse to reach the opposite side is much longer and more difficult.
PVC WATERSTOPS CHOICE CRITERIA
PVC waterstops type, thickness and width are usually chosen according the following criteria. (Choice should be made only by experienced civil engineers):
* type of placement (internal or external)
* head of hydrostatic pressure
* reinforcement position
* type of joint
* thickness of building elements (walls, slabs etc.)
* movement type and size to be accommodated
* compatibility with bitumen
* compatibility with potable water
* granulometry of concrete
* chemical resistance (for fluids other than water) etc.
I never use widths less than 20cm and thickness less than 3 ' 3,5mm.
THE TWO FACTORS THAT NEED OUR FULL ATTENTION
PVC waterstops are difficult to install properly. This, for me, is beyond dispute.
Also PVC waterstops in order to guarantee a reliable waterproofing they need to be spliced correctly.
Another thorny issue!
These indisputable difficulties made inroads for self ' expanding (bentonite etc.) waterstops into the market.
Most of below-ground control and construction joints are now waterproofed with bentonite waterstops.
Please check :
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