Abstract: One concrete slab is laid adjacent to a previously laid slab with a slip forming machine while the concrete mix of the previously laid slab is still plastic. The slip forming machine includes a tractor of the type used with conventional slip-form mules, and in addition a slip-form mule that has the capability of laying a slab of plastic concrete mix against a previously laid slab of mix that is still plastic. The mule has a frame that is attached to the tractor, and the frame carries a hopper and slip form which are united into a single unit, with the hopper opening into the front end of the slip form. The unitized hopper and slip form pivot on the frame about a vertical axis that extends through the front of the frame. The rear end of the slip form moves on a transverse slideway and a hydraulic cylinder is connected between the frame and slip form to urge the side of the slip form snugly against the edge of the previously laid slab as concrete mix extrudes from the slip form to provide the adjacent slab.