A slip form or mule for continuously laying concrete along the contoured side wall and top edge of a drainage ditch. The slip form is affixed to or pivotally mounted from the side of a construction machine that travels along the top side of the ditch. An integral open-bottomed sloping hopper feeds concrete to the slip form which has an adjustable top wall extension and an extendable end wall and sides that simultaneously adjust and are guided on the top slanted wall of the slip form to form a concrete slab of different widths. The frame also supports a trailing screed that is pivoted from and supported by one or more biased bell cranks and canted toward the slope of the ditch side. The hopper has a series of adjustable weirs and vibrating means to spread and consolidate the concrete before the front opening of the slip form. The top inside wall of the slip form and back bottom wall of the hopper may also be pivoted about a longitudinal axis to maintain the inside wall of the slab vertical as the height of the slip form is varied.
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