This study introduces a material-efficient ribbed modular floor slab system produced with an innovative multimodal technique that combines 3D concrete printing with traditional casting methods. Conventional solid slabs consume large amounts of concrete, significantly contributing to global environmental impacts. In contrast, the proposed system optimizes material usage while preserving structural integrity and adaptability. The adoption of advanced concrete 3D-printing technologies in combination with high performance reinforcement materials as CFRP enables the creation of novel load-adapted concrete structures, transforming conventional construction methods into digital and automated processes. Our modular approach features individually fabricated modules, which are detachably connected and assembled through post-tensioning. The production technique comprises the 3D printing of slender, bi-directional oriented ribs onto a thin cast concrete slab, with CFRP reinforcement strategically integrated along the ribs. This method facilitates the creation of free-form, material-efficient slab modules with enhanced geometric flexibility and structural performance. To validate the practical application of this floor system, a full-scale demonstrator consisting of assembled modules was constructed. Experimental testing, including a punching shear test, was conducted to determine the load-bearing capacity. The results confirm the feasibility and effectiveness of the multimodal manufacturing approach. This comprehensive process – from design and fabrication to structural testing – demonstrates the potential of ribbed floor systems, leading to significant material savings and reduced environmental impact.