Building blocks, wall structures made therefrom and methods of making the same

A masonry wall structure formed of superimposed courses of masonry building blocks, each block having a pair of spaced opposite generally parallel side walls, spaced top and bottom faces and a pair of end spaces, an intermediate generally centrally extending horizontal groove in the top face, a pair of narrower grooves, one on either side of said centrally extending groove on said top face, an intermediate generally centrally extending groove in the bottom face on the center line of the groove on the top face, a generally flat land on each side of said intermediate groove in the bottom face adapted to span and overlie the two narrower grooves in the top face of a next subjacent block, an intermediate vertical passage of generally double keyhole shape in said block having a central portion corresponding in width over substantially its length to the widest portion of the central groove on said top and bottom faces, and two opposed leg portions extending lengthwise of and narrower than said grooves, said vertical passage connecting said central grooves, a pair of generally elongate rectangular rounded end vertical passage on each side of said intermediate double keyhole vertical passage extending from the top narrower grooves to the bottom face and a vertical recess in at least one end intermediate the side walls connecting said central grooves and having a cross section substantially equal to one half of said intermediate vertical passage and said blocks being laid up in staggered adjacent superimposed courses with the vertical passages in vertical alignment throughout the height of the wall and the horizontal grooves forming continuous horizontal passages intersecting the vertical passages throughout the length of the wall, metal reinforcing bars in at least a major portion of the intermediate double keyhole vertical passages and the passages formed by the horizontal mating intermediate grooves in the top and bottom faces and a network of solidified hydraulic cement grout filling said intermediate passages both horizontal and vertical and around the reinforcing bars.