An article of manufacture for building concrete structures from precast blocks and the process for making the structural system. The block comprises one or more annular tire wall stack units embedded in reinforced concrete. Prestressing and/or post-tensioning structural reinforcing techniques are used with assembled building blocks. The blocks are made by placing used tire stacks in a form that centralizes the stacks so that reinforced concrete can be placed around them while maintaining a hollow core through the stacks. Horizontal interlocking between blocks uses reinforcing bars and/or a tongue and groove configuration, and/or post-tension wire strand placed in a recess or post-tension tubes formed in the blocks and mortared in-place during construction. Vertical interlocking between blocks uses a tongue-and-groove interlock, shiplap splicing, and reinforcing bars. Post-tension wire strand, pipe, or H-piles are placed in and through the stacks and mortared in-place during construction.