Abstract: The precast I-beam concrete panels include an elongate I-beam embedded in an elongate concrete beam that has a platform or panel parallel to the upper flange of the I-beam. The I-beam is longer than the concrete beam so that opposite end portions of the I-beam project past the corresponding ends of the concrete beam. During installation, the projecting end portions of the I-beam may be seated into corresponding notches or recesses in spaced support beams. The sides of the concrete beam may be flat for abutting engagement with adjacent panels, or may be provided with opposing, stepped lip flanges for forming lap joints along longitudinal edges of adjacent panels. The sides of the precast I-beam concrete panels may be semi-parabolic, so that adjacent panels define an arch below interlocking panels. A plurality of the panels laid side-by-side and supported by the notched beams define a concrete floor or concrete foundation.