Shotcrete 3D printed reinforced concrete beam: design, testing, and comparison against conventional cast reinforced concrete solution

Abstract

Digital fabrication offers the opportunity to reintroduce force-flow-aligned reinforcement as a material-efficient solution in concrete construction. Nevertheless, it raises new questions regarding the structural design and performance of such elements. The current paper discusses design and structural performance of full-scale reinforced concrete beams of two types, with the same external dimensions but different reinforcement layout reflecting fabrication methods. One type was traditionally cast, and features modern orthogonal reinforcement composed of longitudinal bars and stirrups. The other type was digitally fabricated with Shotcrete 3D Printing (SC3DP) additive manufacturing method, and with force-flow aligned reinforcement in form of bent-up steel reinforcement bars. Both types were tested under three- and four-point bending, to investigate their response under shear force and bending moment respectively. The structural testing results prove that the two types of beams can be considered as equivalent under the bending moment at Ultimate and Serviceability Limit States, while the SC3DP beam contains only around half of steel reinforcement mass compared to the cast one. Furthermore, the challenges in calculation and verification of reinforced concrete beams with non-orthogonal reinforcement are discussed. Additionally, it is demonstrated that the same cementitious material exhibits higher mechanical performance when processed with SC3DP compared to casting in formwork, with similar or lower scatter. Finally, it is concluded that the reinforced SC3DP elements follow the same structural principles as the cast concrete ones, and as such can be designed using existing methods while respecting the reinforcement detailing as required per complex layouts.