A slurry feed apparatus for depositing a slurry upon a moving forming web having a direction of travel, including: a headbox mounted transverse to the direction of travel of the moving web, having a back wall, sidewalls, a concave transverse front wall, an open top, and an open bottom for directing slurry onto the forming web; a moveable dam releasably attached to the back wall, a seal attached to a bottom wall of the dam; and a headbox support system extending from opposed the sidewalls. Also disclosed is a continuous process for depositing a uniform layer of a cementitious slurry containing reinforcing fibers from the headbox onto a traveling web.