| | | | | market. |
| | | | | Most of below-ground control and construction joints |
| PVC waterstops are flexible profiles of various types | | | | are now waterproofed with bentonite waterstops. |
| and widths used for the waterproofing of | | | | Please check : |
| below-ground expansion and construction joints. | | | | “WATERPROOFING WITH BENTONITE |
| They are extruded from special types of | | | | WATERSTOPS: PROS AND CONS”. |
| thermoplastic PVC. | | | | SPLICING CONSIDERATIONS |
| PVC waterstops are used for the waterproofing both | | | | For PVC waterstops to perform efficiently, continuity is |
| of water-retaining: water tanks and towers, dams, | | | | of utmost importance. |
| culverts, water treatment plants etc. | | | | The majority of leaks come from improperly spliced |
| and water – excluding structures: basements, | | | | joints. |
| tunnels, foundations etc. | | | | Whenever possible use factory welded intersections |
| PVC waterstops have to be embedded into the | | | | which come in a big variety. |
| concrete usually in two different castings. Once in | | | | On-site splicing is possible if heat welding equipment is |
| place they form a reliable, waterproof diaphragm to | | | | available: a thermostatically controlled welding blade |
| prevent water passage even under considerable | | | | and an adjustable jig. |
| hydrostatic pressures. | | | | The two pieces should reach a temperature of about |
| There are so big differences among qualities of raw | | | | 200oC and then pressed firmly to achieve a perfectly |
| materials used that you have to make sure that you | | | | sealed welding. |
| compare apples with apples. | | | | APPLICATION OF PVC WATERSTOPS |
| Furthermore you can find formulae compatible with | | | | And here we come to the quintessence of PVC |
| asphalt or not. | | | | waterstops technology: waterproofing through an ideal |
| Although there are endless types of PVC waterstops, | | | | application procedure! |
| the most customary ones types are the ribbed types. | | | | 1. First of all: Deformed or damaged waterstops |
| These products are placed: | | | | should be discarded! Check if you can cure the |
| - either centrally (most regular use) | | | | situation by proper stretching or heat treatment. |
| - or externally (e.g. slabs-on-ground/ base-seal). | | | | 2. Waterstops should be installed symmetrically. |
| When used in practically non-working | | | | 3. Proper fastening should hinder displacement during |
| joints (e.g. construction or control joints) the ribbed | | | | concrete casting. Many waterstops have preinstalled |
| profiles are plain, without a center bulb. These types | | | | cyclical rings which help the easy and right fixing of |
| of PVC waterstops can accommodate only | | | | profile by fastening it to the reinforcement bars through |
| little transverse movements. | | | | simple wire. |
| When used in working (e.g. expansion joints), PVC | | | | Take care: Totally prevent misalignment! |
| waterstops have a center bulb to | | | | There are also techniques to form these rings in situ. |
| accommodate lateral, transverse and shear | | | | 4. In no case the center bulb should be encapsulated |
| movements. | | | | into the concrete mass when used in expansion |
| Obviously the larger the center bulb the large | | | | joints! The center bulb should stay in the void space |
| movement it can accommodate. | | | | and accommodate every kind of movement. |
| These types of PVC waterstops are the most | | | | 5. Try to secure right embedment of waterstop in the |
| versatile ones and can be used for every sort of joints | | | | concrete. |
| whether working or non – working. | | | | Gently vibrate the adjacent concrete mass so as to |
| Ribbed type PVC waterstops provide a better | | | | ensure total contact with the profile. Only then sealing |
| sealing effect than other, smooth types. The path the | | | | function could be taken for granted! Honeycombs, |
| water has to traverse to reach the opposite side is | | | | voids and segregation should be avoided at all costs |
| much longer and more difficult. | | | | and concrete should totally and safely embrace the |
| PVC WATERSTOPS CHOICE CRITERIA | | | | ribs. |
| PVC waterstops type, thickness and width are usually | | | | 6. Obvious things shouldn’t be neglected! |
| chosen according the following criteria. (Choice should | | | | * Thoroughly clean joint area with appropriate means |
| be made only by experienced civil engineers): | | | | before concrete casting! Remove any loose materials |
| * type of placement (internal or external) | | | | that could inhibit an excellent contact between |
| * head of hydrostatic pressure | | | | concrete and profile. |
| * reinforcement position | | | | * Never lap profiles! Use the right splicing technique. |
| * type of joint | | | | 7. To avoid cavities in horizontal placements, install |
| * thickness of building elements (walls, slabs etc.) | | | | profiles looking upwards with an angle of 10o - 15o. |
| * movement type and size to be accommodated | | | | 8. Heavier profiles should be used in certain |
| * compatibility with bitumen | | | | circumstances to prevent displacement. |
| * compatibility with potable water | | | | 9. Split type waterstops: For the first concrete |
| * granulometry of concrete | | | | casting do nail split legs to the bulkhead between end |
| * chemical resistance (for fluids other than water) etc. | | | | of profile and the last rib. |
| I never use widths less than 20cm and thickness less | | | | For the second casting (when forms are stripped) hold |
| than 3 – 3,5mm. | | | | legs together by use of rings every 25-30cm placed |
| THE TWO FACTORS THAT NEED OUR FULL | | | | again between profile edge and last rib. |
| ATTENTION | | | | 10. Take care to discard badly spliced profiles |
| PVC waterstops are difficult to install properly. This, for | | | | (misaligned, purely bonded, burnt etc.). |
| me, is beyond dispute. | | | | 11. Base seal waterstops should be fixed with |
| Also PVC waterstops in order to guarantee a reliable | | | | appropriate fixings either to well compacted sub grade |
| waterproofing they need to be spliced correctly. | | | | or to eventual formwork. Do align waterstop’s |
| Another thorny issue! | | | | centerlign with the joint. |
| These indisputable difficulties made inroads for self | | | | For vertical applications these profiles will be nailed in |
| – expanding (bentonite etc.) waterstops into the | | | | the margin area directly on the formwork. |