PVC Waterstops for Concrete Joints

PVC, an acronym for?polyvinyl chloride, is a sturdy, brittle plastic in its natural state. Because concrete joints are subject to movement (lateral, transverse, and shear) and shrinkage due to water loss from concrete hydration, a tough, rigid polymer would not be a good waterstop material choice. To compensate for this shortcoming, manufacturers compound the raw PVC resin with?fillers?(such as calcium carbonate) and?plasticizers (phthalates)?to alter the mechanical properties of the polymer. In this case, modern PVC waterstop manufacturers add a class of heavy metal esters (most frequently?phthalates?[which are on the California Prop 65 list as known carcinogens]).?These plasticizers enable the waterstop to elongate and move like the thermoset rubber waterstops that they largely replaced.

PVC waterstop is specified in the United States at the federal level around a specification called CRD-C-572 (the last revision was in 1974). CRD-C-572 is just a measurement of plasticizer extraction when the exposed material to alkalies and a simulated accelerated aging test. Section 6.2 of the specification requires 1,000 psi tensile strength across a waterstop weld but is ambiguous regarding the testing procedure to follow. A Specifier of PVC waterstop should request an?independent?lab test report to the physical properties stated in their literature from the manufacturer before specifying their waterstop product.

PVC is the first thermoplastic used as a waterstop, and it largely replaced thermoset rubbers (neoprene, natural, styrene butadiene,?et al.). Thermoplastics have a distinct advantage of thermosets: Namely, they can be reshaped or reformed by the application of heat. In PVC waterstop’s case, indirect heat is applied (waterstop splicing iron), the waterstop material becomes molten in the weld area, and the two sides are pressed together and allowed to cool. The two joined waterstops will exhibit nearly the same physical and mechanical properties of the parent material once cooled. If a PVC waterstop lists 1,900 psi tensile strength, the Contractor will be able to achieve at least 80% of that value by field welding the product. Thermosets do not share this advantage. Once thermoset waterstops are cured, they can not easily be heat-welded into continuous lengths and changes of direction as required by the concrete joint layout. It is for this reason that PVC and other thermoplastics are a superior polymer choice for waterstop.

Suggested Proprietary Short Form Guide Specification

Flexible PVC Waterstop

Waterstop indicated in drawings and specifications for contraction (control), expansion and construction joints shall be Earth Shield? Polyvinyl Chloride (PVC) Waterstop Part No. #### [Designer insert appropriate part number here] as manufactured by J P Specialties, Inc.; Murrieta, CA 92562; Phone 951-763-7077

1. Flexible Polyvinyl Chloride (PVC) Waterstop shall be manufactured with prime virgin resin.
2. Flexible Polyvinyl Chloride (PVC) Waterstop shall be independently certified for use in potable water per NSF/ANSI Standard 61. Third-party certified documentation to be provided by the manufacturer.
3. Flexible Polyvinyl Chloride (PVC) Waterstop shall be California Prop 65 compliant and contain no hazardous phthalates.
4. No equals or substitutions are allowed.