Evaluation of aggregates, fibers and voids distribution in 3D printed concrete

3D printed concrete technology has received a traffic attention in construction industry in recent years, due to the potential advantage: time and labor savings, cost reduction, low environmental impact. In this study, the influence of distribution of aggregate and steel fiber on the mechanical properties of 3 D printed concrete is experimentally investigated. The distribution characteristic of aggregate and steel fiber in 3 D printed concrete are evaluated by using X-ray computed tomography (X-CT) with 2 D image analysis method. The cast concrete is performed as reference. It is found that the aggregate and fiber in cast concrete are relatively evenly distributed and no alignment, while there is an orientation probability of more than 40% for aggregate, and 74% for fiber, respectively, along the printing direction in ± 20° in printed concrete. Meanwhile, using X-CT, the porosity, void sizes, shapes and distributions in printed and cast concrete are also investigated. Furthermore, it is observed that the printed and cast samples comprise of different voids, due to the different construction processes. Finally, the results prove that the performance difference for the printed concrete at different directions possibly depends on the orientation distribution of the aggregate/fiber, as well as the irregular voids, since the aggregates/fibers are orientated by the nozzle along the printing direction.