Interface Behavior and Interface Tensile Strength of a Hardened Concrete Mixture with a Coarse Aggregate for Additive Manufacturing

Abstract

3D concrete printing technology (3DCP) is a relatively new technology that was first established in the 1990s. The main weakness of the technology is the interface strength between the extruded layers, which are deposited at different time intervals. Consequently, the interface strength is assumed to vary in relation to the time of concrete casting. The proposed experimental study investigated the behavior of a hardened concrete mixture containing coarse aggregates that were up to 8 mm in size, which is rather unusual for 3DCP technology. The resulting direct tensile strength at the layer interface was investigated for various time intervals of deposition from the initial mixing of concrete components. To better understand the material behavior at the layer interface area, computed tomography (CT) scanning was conducted, where the volumetric and area analysis enabled validation of the pore size and count distribution in accordance with the layer deposition process. The analyzed CT data related the macroscopic anisotropy and the resulting crack pattern to the temporal and spatial variability that is inherent to the additive manufacturing process at construction scales while providing additional insights into the porosity formation during the extrusion of the cementitious composite. The observed results contribute to previous investigations in this field by demonstrating the causal relationships, namely, how the interface strength development is determined by time, deposition process, and pore size distribution. Moreover, in regard to the printability of the proposed coarse aggregate mixture, the specific time interval is presented and its interplay with interface roughness and porosity is discussed.

Study of the Interaction of Cement-Based Materials for 3D Printing with Fly Ash and Superabsorbent Polymers

“…Three-dimensional concrete printing (3DCP) [1], also known as 3D printed concrete (3DPC) [2,3] or 3D printable cementitious material (3DPCM) [4], was established in the late 1990s and early 2000s [4]. Since that time, additive manufacturing has been used worldwide.…”

Hygrothermal and Microstructural Investigation of PLA and PLA-Flax Printed Structures

“…AM covers various applications areas ranging from prototyping, architectural design, industrial, and engineering [14][15][16]. It can be stated that AM has reached a mature state in many applications including civil engineering [17][18][19]. For instance, it has been considered a key technology to design new generation of cementitious materials using crafting technology [20][21][22].…”