occur on warming) . If during the manufacturing process the neqprene is not 

 fully cured, the interior webs may adhere during service (often perma- 

 nently) when the seal is compressed. 



To facilitate installation of compression seals, liquid neoprene-based 

 lubricants are used. For machine installation, additives to make the 

 lubricant thixotropic have been found necessary. Special lubricant adhe- 

 sives, which both prime and bond, have been formulated for use where 

 improved seal to joint face contact is required. 



Neoprene compression seals are effective joint sealants over a wide 

 range of temperatures in most applications. Seals may be used individually, 

 or as components for modular systems. 



(b) Modular Systems . In modular systems designed to accommo- 

 date larger movements, standard compartmentalized compression seals or 

 rubber tubes are placed between vertical steel I-sections to form modules, 

 each of which can accommodate about 38.1-millimeter (1.5 inch) movement. 

 The complete unit of modules in a series to take the total anticipated 

 movement is supplied prefabricated, ready for installation at the appro- 

 priate precompression to suit conditions. A certain amount of out-of- 

 plane movement arising from skew or other causes can be accommodated, and 

 field modifications to allow for unanticipated irreversible opening or 

 closing of the joint can be made by adding or removing seals and separation 

 plates, as required. 



Individual seals must remain in at least 15 percent compression at the 

 widest opening. The allowable movement is approximately 40 percent of the 

 uncompressed seal width. 



(5) Tension-Compression Seals . One device of this type currently 

 in use consists of neoprene expansive elements combined with encased steel 

 bearing plates and anchorage angles to form a single unit that can be 

 extended or compressed without buckling. Such a unit can support traffic 

 or other loads on its upper surface. Individual units are available in 

 varying lengths up to 1.83 meter (6 feet) and may be butted side by side 

 along the length of the joint opening. The device is bolted directly to 

 the concrete surface at each side of the joint, and this mechanical anchor- 

 ing permits it to function in tension or compression in response to the 

 movement of the joint. 



To date, these devices have been used exclusively on bridge decks, and 

 special sections have been developed to fit curb contours. They may also 

 have application on dam faces or other locations where sealing against 

 considerable pressure and movement is required. 



The long-term performance of tension-compression seals remains to be 

 evaluated. Observations of performance indicate that careful installation 

 is important. 



9. Repair of Concrete. 



a. Evaluation of Damage and Selection of Repair Method . To objec- 

 tively evaluate the damage to a structure, it is necessary to determine 



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