Path Optimization in 3D Concrete Printing to Minimize Weak Bonds Formation

Abstract

3D concrete printing has proven to be a highly favorable construction method in terms of time reduction, cost optimization, architectural flexibility, sustainability, energy use, and others. However, the quality of the final product certainly has a priority over all of these attractive features of the technology. Yet research has given little consideration to investigating the structural integrity of 3D printed concrete structures. Research states that printed structures exhibit sufficient strength as compared to traditionally built structures. Nevertheless, the fact that this strength is sensitive to numerous factors including the machine setup, the printing process, existing conditions (e. g. temperature) and others, should be studied. A major determinant of the reliability and quality of printed structures is the adhesion level between subsequent layers. Poorly adhered concrete surfaces result in weak bonds that in turn reduce rupture strength. The time elapsed between printing successive concrete layers should be bounded to ensure that concrete is flowable enough to adhere to previous layers. For a given concrete mixture design, this time is a function of travel distance and speed. Thus, this research aims at finding the optimum printing path that minimizes the formation of weak bonds without compromising buildability for a given structure and a defined speed. The research employs Discrete Event Simulation to model the printing process for numerous possible travel paths and assess their adequacy by comparing travel time to allowable time limits.

Numerical modelling of planned corner deposition in 3D concrete printing

“…Bos et al [17] mentioned that square nozzles should be tangent to the toolpath when moving the printhead to overcome the twisting of the filament. AlSakka et al [18] identified the optimal deposition path of the 3DCP, which reduces the weak bonds and preserves the buildability of the extruded material by using a discrete event model.…”