The reinforced concrete construction industry continually evolves to adapt to gains in knowledge, market pressures and new technologies. However, two new promising technologies, 3D printing and computational structural optimization, have not yet extensively penetrated the construction market; despite being important drivers of change in other fields. This study has the potential to overcome the major barriers to adoption of both technologies by using them in combination to obtain lighter, more efficient, and resilient reinforced concrete structures. While the structural performance of 3D printed buildings and components are being studied under different loading conditions, the large size of the printer itself is a significant disadvantage. Moreover, the materials used for 3D printing in construction have questionable long-term durability. Instead of printing structures, in this research 3D printing is used to fabricate formwork for use in construction of reinforced concrete structures. Topology optimization is done through finite element modeling coupled with strut-and-tie design methods which have the ability to change the existing structural form. This method allows for structural form to be optimized with openings. Use in practice is limited as the intricate shapes that often result from such optimizations are not affordably constructible using existing methods. Additionally, these methods are highly automated and lend themselves to modular construction. As a proof-of-concept, two specimens, approximately 1/10th – scale with an aspect ratio of 4, are tested under monotonic lateral loading to compare the strength and stiffness of slender reinforced concrete walls designed and constructed using (a) conventional methods, in accordance with ACI 318 and (b) optimized topology based on strut-and-tie models, using 3D printing technology to fabricate formwork, and high-strength concrete materials. The percentage volume reduction for optimized specimen is 43% as compared to the convention specimen. The optimized shear wall has a higher drift ratio of 5% at failure while the conventional shear wall has a drift ratio of 3.5%. Performance of the optimized shear wall under lateral load is observed to be more efficient compared to the conventional shear wall; in terms of strength, stiffness, damage under load, and material use.