Joint cutter

Abstract

This invention relates to methods and apparatus for inducing planes of weakness in hydraulically bound materials, for example roller compacted concrete. A crack inducer vehicle for fabricating pre-cracked hydraulically bound materials, the vehicle comprises: a groove former to form a groove in fresh hydraulically bound material prior to curing, said groove former having a first, lowered position for forming a groove in said fresh hydraulically bound material, and a second, raised position; and a system to apply a de-bonding agent into said groove such that when said hydraulically bound material has cured it preferentially cracks along a said groove.

1 . A crack inducer vehicle for fabricating pre-cracked hydraulically bound materials, the vehicle comprising:
 a groove former to form a groove in fresh hydraulically bound material prior to curing, said groove former having a first, lowered position for forming a groove in said fresh hydraulically bound material, and a second, raised position; and   a system to apply a de-bonding agent into said groove such that when said hydraulically bound material has cured it preferentially cracks along a said groove.   
   
   
       2 . A crack inducer vehicle as claimed in  claim 1  wherein said vehicle comprises a road-roller to roller compact said hydraulically bound material such that after passage of said vehicle said hydraulically bound material is compacted to form a visibly continuous material. 
   
   
       3 . A crack inducer vehicle as claimed in  claim 1  wherein said groove former comprises a freely rotating wheel. 
   
   
       4 . A crack inducer vehicle as claimed in  claim 1  wherein said system to apply a de-bonding agent into said groove comprises a nozzle and a tap and pump to control application of said de-bonding agent into said groove. 
   
   
       5 . A crack inducer vehicle as claimed in  claim 4  wherein said de-bonding agent comprises bitumen. 
   
   
       6 . A crack inducer vehicle as claimed in  claim 1  wherein said hydraulically bound material comprises Roller Compacted Concrete. 
   
   
       7 . A method of inducing a plane of weakness in a hydraulically bound material-, the method comprising:
 using a vehicle as claimed in  claim 2  having a hanging groove to form a groove in said fresh hydraulically bound material prior to curing of said hydraulically bound material;   applying a de-bonding agent into said groove using said vehicle; and   roller-compacting said hydraulically bound material using said vehicle to form a visibly continuous material including a plane of weakness, wherein said cured hydraulically bound material will preferentially crack in a controlled manner along a said induced plane of weakness during shrinkage.