INSTALLATION OF WATERSTOPS-Hebei Zaoqiang Dacheng Rubber Co.,Ltd

The performance of waterstop is to a great degree dependent upon the care and skill with which they are installed, and it is the purpose of this article to discuss some of the basic pro c e d u res which experience indicates will assure best results. In the discussion that follows it is necessarily assumed that the joints have been properly designed, located and formed, and the procedures which are discussed relate wholly to the handling and installation of waterstops. First off, analyze the joint across which the waterstop is to be installed. The type ( contraction, isolation, expansion, etc.) As well as the spacing of the joint will have a great bearing on the amount of movement to be expected and, there f o re, the waterstop to be used. Choose the shape and size of waterstop that is best suited to the job at hand.

There are so many varieties of waterstops on the market today that it would be impractical to try to present detailed installation instructions for each of the many variations. We will, however, give a few suggestions that apply to most waterstops. The various manufacturers are prepared to supply details based on wide experience with their own particular types.

A crucially important aspect of waterstop installation is the care with which splices are made. Most flexible waterstops are available in 50- to 125-foot rolls; this means that for many structures in which waterstops are used there will be a considerable number of splices. If these splices are made haphazardly, water leakage is sure to be objectionably great .There are a number of jointing
patterns commonly used in waterstop work, and some manufacturers provide a range of fittings to facilitate handling in the field. The waterstop must be cut neatly and to a true angle if an effective splice is to be made. Be sure the knife used for cutting is sharp. For polyvinylchloride materials, heat to 450 degrees F. a 1/4-inch steel plate on a plumber’s torch. Apply the two cut
edges of the waterstop to the plate until melting of the plastic commences. This will take from 15 to 50 seconds, depending on the thickness and composition of the material. Hold the two edges together until they have cooled completely and fused together. If a splice is to be made with one section of the waterstop already installed in a slab, the hot steel plate can be held against the waterstop. While the plastics are probably the easiest of the waterstop materials to splice, the tensile strength (resistance to stretching forces) at splices will usually be only 60 to 70 percent of that of the unspliced sections. Rubber waterstops can be cold lap spliced. In this technique, the ends of the waterstop are overlapped about three inches with falt surfaces pressed together. Coatings of rubber cement and uncured gum rubber are placed on the surfaces in contact at the splice and are held together by bolting between flat stainless steel plates. Cold lap splices are
relatively easy to make and do not require any electricity; but the tensile strength provided at the joint is low. A considerably stronger splice can be made by vulcanizing. For this type of splice, small portable vulcanize are used which commonly are electrically heated. The edges to be butted are beveled to 45 degrees or flatter. Rubber cement and uncured gum rubber are then applied to the ends and vulcanized, usually at around 290°F. Metal waterstops are spliced by
means of welding. Although this produces a very watertight splice, it necessitates special equipment, electricity, skilled workmen and much time—especially when part of the metal waterstop is embedded in concrete. In addition, metal waterstops require more splices because
they cannot be conveniently handled in long sections. Since the integrity of the joints will depend to such a high degree upon the workmanship in making waterstop splices, especially careful supervision must be exercised over this aspect of installation.

Other points
Before casting concrete, make sure that the waterstop material is clean. If it is cove red with dirt and grime or if foreign materials have become lodged between the ribs (especially likely when the material has been protruding for some time from a cast section) it will be impossible to achieve intimate contact with the concrete. Without such contact, pull-out is a much greater likelihood . Flexible waterstops should be braced against nearby rebars to render them better able to resist the disrupting effects of concrete placement. Thoroughly vibrate concrete near the waterstops to make sure that it is completely consolidated a round all the configurations of the waterstop. Be certain that the center bulb, V-bend or other provision in the waterstop shape for joint movement is positioned directly at the joint opening. Often a period of several days passes while concrete is curing and preparations are underway for the next placement. Du ring this time
the exposed half of the waterstop should be protected from damage by impact and thermal extremes. After both portions of the concrete have been cast there re mains still the application of the joint filler. There are a number of excellent preparations on the market today that provide both a high degree of water impermeability and great elasticity to accommodate joint movement. They protect the waterstop material from the adverse effects of the atmosphere (especially important when using rubber). sufficient time should elapse after casting before application of the joint filler to allow the greater part of shrinkage caused by drying of the concrete to occur. The filler material will then be called upon to accommodate only the movements
caused by loading and thermal variations. Waterstops have come to play an important role in modern concrete construction. Their part in achieving watertight structures should not be underestimated. Through the constant research carried on by manufacturers and others interested in promoting quality construction, the waterstop has become an easily installed, inexpensive and durable device to insure watertight joints in walls, floors and decks.