A waterstop is an element of a concrete structure, intended to prevent the passages of fluids (such as water) when embedded in and running continuously through concrete joints. Waterstops are frequently manufactured from extruded plastics such as flexible polyvinyl chloride PVC, polyethylene (PE) or thermoplastic vulcanizate rubber (TPV); formed metal such as stainless steel, copper, or carbon steel; or extruded thermosets such as natural rubber, styrene-butadiene rubber, or neoprene rubber.
Hydrophobic Polymer waterstops such as PVC, PE, TPV, or rubber are supplied to the construction site in coils (usually 50 lineal feet long), and are generally anywhere from 4 inches to 12 inches wide in a variety of profiles that are designed to simultaneously provide an interlock with the concrete they are installed in and to provide for a limited amount of movement within the joint. PVC, PE and TPV waterstops are made continuous for the length of the concrete joint by heat welding, using simple thermoplastic welding equipment.[1] Thermoset rubbers and metallic waterstops are more difficult to fabricate to continuous lengths and are specified far less frequently by architects and engineers.
PE and TPV waterstops are generally installed in joints of secondary containment structures to prevent the passage of hazardous fluids other than water such as fuel oils, acids, or process chemicals.[2]
Hydrophilic or "water-loving" waterstops are strips of rubber, modified with a hydrophilic agent (such as bentonite) so they swell in the presence of moisture to effectively seal concrete construction joints. Hydrophilic strip applied waterstops should not be used in contraction or construction joints per the instructions of most commercial manufacturers. Hydrophilic waterstops can only be effective if they are allowed to swell; therefore, a moisture source must be present to activate the hydrophilic agent. Initial leaking is possible until the waterstop expands to seal the joint.
