Apparatus for mixing construction materials

An apparatus for mixing construction materials and for placing the resulting mixture on a surface, comprising mixing trough means having an inlet for the construction material and a discharge end for the mixture, supply means arranged for supplying said construction materials into the inlet of said mixing trough means, first and second mixing tools supported for rotation about first and second side-by-side parallel longitudinal rotational axes in said mixing trough means for mixing and simultaneously transporting the materials from said inlet to said discharge ends, each mixing tool comprising a shaft mounted along one of said longitudinal, rotational axes and a plurality of mixing blades operatively secured to each shaft in helical succession with a 90.degree. circumferential staggering from blade to blade on the same shaft, whereby the blades form four in line rows of blades on each shaft, each blade having an axis extending radially relative to the respective longitudinal, rotational shaft axis, said blades being mounted with a uniform axial spacing between adjacent blades along both shafts, all the blades on both shafts further having the same configuration, said shafts being aligned with the uniform axial spacing between adjacent blades coinciding whereby the blade radial axes lie in equally spaced radial planes along the longitudinal rotational shaft axes perpendicular to said longitudinal axis, each blade being mounted on its shaft at a blade angle of attack relative to the respective radial plane, said two shafts being adjusted in their rotational angular position relative to each other so that any two blades on different shafts enclose a right angle between their respective radial axes at each quarter turn of the shafts when these radial axes are located in a common radial plane and so that said first and second shafts comprise a plurality of meshing blade pairs, each meshing pair comprising one blade from each shaft axially spaced from each other in next adjacent radial planes along said longitudinal rotational axes, said shafts being constructed and arranged for rotation in opposite directions with the blades moving upward from the center line between said axes and with the blades of each meshing pair overlapping the major portion of the area of said blades in the space between the shafts, the blades of each meshing pair being substantially parallel when the radial axes of said meshing blades are pointing toward and away from each other, thereby imparting a mixing shearing action to construction material in said trough means and moving said material upwardly along the zone between the mixing tool shafts and then laterally toward the walls of the trough.