Multiple parameters optimization and construction procedure for 3D printed reinforced concrete frame elements.

Abstract

Concrete 3D printing is seen to revolutionize the construction industry as it promises a solution for problems that have plagued the construction industry in the last decades, such as productivity loss, material waste, process inefficiencies, limitations on geometric complexity due to the rigidity of tools used, and low innovation levels. However, this technology is still in its infancy and suffers from many shortcomings itself. One obvious limitation for the industrialization of concrete 3D printing around the globe is the lack of a practical and efficient procedure to reinforce 3D printed concrete elements. Although some research has been published on procedures to reinforce 3D printed concrete, each proposed method still has its flaws that would still favor using traditional methods for construction. Given the inherent deficiencies in the existing system, and the lack of a suitable method to reinforce 3D printed concrete, a new procedure is proposed in this study that makes use of a predetermined behavior of fresh material properties to optimized the nozzle speed (process parameter) as the machine prints, in order to manufacture concrete 3D printed samples that can be reinforced with traditional longitudinal and transversal steel bars. The hardened properties and structural performance of the 3D printed samples is tested, analyzed, and compared with traditionally cast samples to validate the viability of the proposed procedure. The method used in this study was mainly laboratory experimentation, testing, and measurement of the mechanical properties of 3D printed concrete. Results show that a properly executed 3D printed plain concrete element might yield compressive and flexural strengths similar or higher than that of regularly cast concrete depending on the direction of loading, whereas reinforced concrete 3D printed beams yielded a strength slightly lower than that of regularly cast beams. Cracking patterns are observed to initiate similarly in 3D printed and regular samples, yet and due to the layered n