WATERSTOP INSTALLATION - WATERPROOFING.

PVC/Neoprene Rubber/Thermoplastic Rubber
Waterstops of this type are placed in the concrete formwork and tied or secured to firmly position the material during concrete placement. It is imperative that the waterstop is never allowed to fold over during concrete placement. Figure 2.23 shows some typical methods to secure the waterstop prior to the first concrete placement. Figure 2.24 details the method for installing waterstop using a keyed joint.

Securing of PVC waterstop for first concrete placement.
FIGURE 2.23 Securing of PVC waterstop for first concrete placement.



 Formwork with keyway joint sys- tem. Note the bulb is centered directly in midpoint of the joint to ensure proper functioning as an expansion joint.
FIGURE 2.24 Formwork with keyway joint sys-
tem. Note the bulb is centered directly in midpoint
of the joint to ensure proper functioning as an
expansion joint.

To secure the flange in place for both concrete placements, the waterstop is generally secured using wires tied to the reinforcing steel every 12 in. The wire should be tied through the first or second ribs of the waterstop flange, never going beyond the second flange as shown in Fig. 2.25.


Securing PVC waterstop for second con- crete placement.
FIGURE 2.25 Securing PVC waterstop for second con-
crete placement.
Note that in each of these details the center bulb is directly in the midpoint of the joint. This is to ensure that the waterstop acts properly as an expansion joint during anystructural movement.

The bulb must never be placed completely in one side of the placement or it will lose all its capability to act as an expansion material. Nails or any other construction debris should not be allowed to puncture the waterstop bulb or any part of the flange near the bulb.

When using waterstops at construction joints, material with bulb ends makes securing to reinforcing steel easier by using wire rings that pass through the bulb but not the flange. Figure 2.26 details the steps using this system for both halves of the concrete placement.

Placement procedures for end bulb waterstop.
FIGURE 2.26 Placement procedures for end bulb waterstop.

Placing PVC and rubber waterstops in the field usually requires some welding to joint ends of rolls or making necessary changes in plane. Waterstop should never be installed by merely lapping the ends together. The material must be heat-welded to fuse the ends together by using manufacturer-supplied splicing irons that melt the ends that are then held together until they cool, forming one continuous piece. Refer to Fig. 2.27 for a field weld application.

Field welding operation of PVC waterstop.
FIGURE 2.27 Field welding operation of PVC waterstop.
Testing of failed joints usually reveals that failures were either the cause of improperly positioned material, Fig. 2.28, (folded over during concrete placement) or where directional changes occurred in structure that the waterstop did not conform to. Whenever heat welding is used, the material is adversely affected at this point and its properties are not equal to the original material. Therefore it is recommended that whenever major directional changes are designed into a structure, the contractor should secure prefabricated fittings.

 Improperly positioned, placed, and secured waterstop.
FIGURE 2.28 Improperly positioned, placed, and secured waterstop.

Waterstop manufacturers will usually provide a variety of premolded splice pieces for directional changes,
as shown in Fig. 2.29. Also, most manufacturers will offer to custom-make the required splices to ensure the successful applications with their material.


Typical manufactured PVC waterstop splices and transition pieces.
FIGURE 2.29 Typical manufactured PVC waterstop splices and transition pieces.

At all penetrations in below-grade slabs or walls, waterstop should also be installed continuously around the penetration to protect against water penetration. Figure 2.30 details the use of waterstop installed continuously around a structural steel column that penetrates the concrete slab over the foundation.

Waterstop application around structural steel column foundation supports.
FIGURE 2.30 Waterstop application around structural steel column foundation supports.
Photographs in Figs. 2.31 and 2.32 show how complicated waterstop installations can become. Such detailing necessitates the use of premanufactured weld splices to ensure watertight applications. These photographs also emphasize how important proactive job-site quality-control procedures are, to verify that the PVC waterstop is installed and maintains proper positioning during concrete placement.

Placement of spliced PVC joint in form- work.
FIGURE 2.31 Placement of spliced PVC joint in form-
work.



 Field quality-control procedures ensure successful installation of waterstop.
FIGURE 2.32 Field quality-control procedures ensure successful
installation of waterstop.

1 comentarios:

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