(c) sufficiently recover its original properties and shape 

 after cyclical deformations; 



(d) remain in contact with the joint faces; (this means 

 that for all sealants, except those preformed sealants that exert 

 a force against the joint face, the sealant must Bond to the joint 

 face and not fail in adhesion nor peel at corners or other local 

 areas of stress concentration) ; 



C.e) not internally rupture (i.e., fail in cohesion); 



(f) resist flow due to gravity (or fluid pressure) or 

 unacceptable softening at higher service temperatures; 



(g) not harden or become unacceptably brittle at lower 

 service temperatures; and 



(h) not be adversely affected by aging, weathering or 

 other service factors for a reasonable service life under the 

 range of temperatures and other environmental conditions that 

 occur. 



(2) Performance Buried In Joints . Sealants buried in joints, such 

 as waterstops and gaskets, generally require similar properties. The 

 method of installation may, however, require the sealant to be in a different 

 form and, because replacement is usually impossible, exceptional durability 

 is required. In addition, depending on the specific service conditions, 



the sealant may be required to resist one or more of the following: intrusion 

 of foreign material, wear, indentation, pickup, and attack by chemicals. 

 Further requirements may be that the sealant be a specific color, resists 

 change of color, or is nonstaining. Finally, it must not deteriorate when 

 stored for a reasonable time before use. It must be relatively easy to 

 handle and install, and be free of substances harmful to the user and 

 concrete or other material that may abut. 



(3) Materials Available . No one material has the perfect proper- 

 ties necessary to fully meet each and every one of the requirements for 

 each and every application. Therefore, it is a matter of selecting from 

 among a large range of materials a particular one that has more of the 

 right properties at the right price to do the job. Table 20 lists commonly 

 used joint sealant materials. 



For many years oil-based mastics or bituminous compounds and metallic 

 materials were the only sealants available. In many applications these 

 traditional materials do not perform well and in recent years there has 

 been an active development of "elastomeric" sealants. The behavior of 

 these sealants is largely elastic rather than plastic, and the sealants are 

 flexible rather than rigid at normal service temperatures. Elastomeric 

 materials are available as field-molded and preformed sealants. Though 

 initially more expensive, they may be cheaper in the long run because they 

 usually have a longer service life. Furthermore, these materials can seal 

 joints where considerable movements occur that could not possibly be 

 sealed by the traditional materials. 



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