a method for cutting an arcuate groove in an uncured concrete coating on an arcuate surface . a jet stream of water is directed at the coating along a line extending tangentially of the surface in a downward direction . the object is rotated at a relatively low speed in relation to the stationary water jet . the invention also encompasses a method of applying a concrete coating to pipe wherein after the cement is forced onto the pipe a wrapping material is wound around the pipe in a spiral pattern to hold on the concrete . the wrapping material may be a water impervious plastic which will affect curing of the cement without the aid of chemical curing agents .