Installing the waterstop in such a way that it produces a continuous waterproof diaphragm is a must. The installation of a waterstop system is important to its efficiency and effectiveness; most failures occur because adequate steps are not performed.
Dumbbell and ribbed center-bulb waterstops should be positioned so that the waterstop’s longitudinal centerline aligns with the joint’s center. To provide the installer with a convenient means of fastening the waterstop to neighboring steel rebars, hog rings or grommets are added to the furthest edges of the waterstop profile (typically at 305-mm [12-in.] intervals) prior to the initial concrete pour. To attach the waterstop and maintain proper alignment, tie wire is passed through the hog rings.
Several manufacturers recommend positioning the waterstop such that it covers at least half of the concrete’s width. To avoid poor concrete consolidation caused by aggregate bridging, a minimum of two times the greatest aggregate size should be allowed between the waterstop and reinforcing steel.
In addition, for varied head pressures, one must follow the manufacturer’s requirements for concrete embedment depth.
As a general rule, the waterstop is installed with more concrete coverage for higher hydrostatic pressures.
Splicing is required at intersections, changes of direction, or to produce larger lengths of waterstops. Ends should be squared off before welding neighboring rolls together to make a continuous diaphragm. Welds should only be performed by qualified individuals using approved equipment and techniques.
For the convenience of handling and manufacturing, uncoil water stop coils and lay flat for 24 hours before installation.
To avoid sticking the waterstop material, heat is provided using a thermostatically controlled electric splicing iron with a Teflon-film cover. The waterstop ends are pressed against the hot iron until the material becomes somewhat molten after the iron has been preheated to the temperature indicated for the type of thermoplastic material.
The splicing iron is removed, and the molten ends are pushed together and kept in this position until cold (less than one minute). Waterstops constructed of thermoplastic materials should only be used with this heat-splicing procedure. Waterstops made of traditional rubber are often cold-spliced using specific adhesives.
Split-forming is utilized to keep the waterstop in place at vertical joints. Special split-leg profiles, on the other hand, can be nailed to regular concrete forms. The center of the profile must be aligned with the center of the joint in all installations.
The majority of waterstop failures are caused by weak welds or a lack of welding, according to investigations. Splices should be checked to ensure that they are welded through the entire profile thickness, not just on one side’s surface (i.e. edge welding).
Look for scorched, burned, or otherwise tainted welds as well. Furthermore, the central bulbs and ribs must be kept in the same place throughout the weld. Any product’s integrity is substantially jeopardized by edge welding waterstop.
Because the thin-edge weld lacks sufficient tensile strength and elongation compared to the parent material, even minor movement of concrete can rupture edge welded splices.
Field-welded mitered fittings have proven challenging to splice accurately in the past. As a result, directional change fittings (such as Ls, Ts, and crosses) should be prefabricated by the manufacturer, leaving only simple butt-splicing to be done in the field.
A conventional flat cross fitting, for example, includes 12 cuts and seven welds. All cuts and three welds are omitted from fieldwork when prefabricated fittings are used.
The directional change fittings are the most leak-prone location. Because the waterstop manufacturer has specialized equipment and templates unavailable to the contractor in the field, prefabricated fittings can eliminate or considerably decrease this problem. Both vertical and flat Ls, Ts, and crosses are offered.
During installation, debris, oil, or release agents must not be allowed to contaminate the waterstop surface. Surface contamination might obstruct concrete’s direct contact with the waterstop, reducing its effectiveness.
Concrete must be put with care so that the waterstop remains in place. During the first half of the concrete placement, the waterstop must be properly held in place, with one-half of the width immersed in the concrete. To guarantee the waterstop remains in place during both phases of the concrete installation and consolidation, this must be closely checked for quality control.
The PVC waterstop is frequently displaced, folded over, or misaligned with the joint, preventing it from functioning properly.
Additionally, any concrete that has extruded out into the flange must be removed in horizontal-run installations. Finally, employees installing the reinforcing bars frequently burn, puncture, or cut the waterstop, so it must be inspected for any damage.
Construction, contraction, and expansion joints can all benefit from base-seal profiles. Interior wall transitions should not be made using base-seal since the embedment ribs are only on one side and hence cannot operate properly.
Waterstops for the base is installed before the concrete is poured, and they can be set on compacted grade, mud slabs, or vertical formwork. Only the ribbed side of the waterstop engages the concrete when used as a base-seal waterstop.
Because the base-seal waterstop is not embedded in the concrete, it requires a firm substrate for initial support and proper in-service performance. When exposed to significant hydrostatic pressure, a lack of support might cause the waterstop’s edge to curl.
To avoid movement or displacement of the waterstop, care should be used when placing concrete. Base-seal types with a center-bulb tear-web can support the joint movement. Manufacturers recommend ribbed center-bulb inserted in concrete instead of base-seal products for high hydrostatic head pressures.
Finally, in tight areas, one must always wear protective equipment such as temperature-resistant gloves, safety eyewear, protective shoes, and a respirator. Welding should be done in an environment that is well ventilated.
Key Takeaway-Installing Waterstops
Installation of a waterstop system is important to its efficiency and effectiveness. Most failures occur because adequate steps are not performed.
Waterstops made of traditional rubber are often cold-spliced using specific adhesives. Thermoplastic materials should only be used with the heat-splicing procedures. Waterstop failures are caused by weak welds or a lack of welding, according to investigations.
Splices should be checked to ensure that they are welded through the entire profile thickness. Prefabricated waterstop fittings can eliminate or considerably decrease leaky fittings.
Waterstops for the base is installed before the concrete is poured, and they can be set on compacted grade, mud slabs, or vertical formwork. Because the base-seal waterstop is not embedded in the concrete, it requires a firm substrate for initial support.