Selective Paste Intrusion: Integration of Reinforcement by WAAM — Concept and Overview of the Current Research

Abstract

Selective Paste Intrusion (SPI) is an additive manufacturing (AM) process in which thin layers of aggregates are selectively bonded by cement paste only where the structure is to be produced. In this way, concrete elements with complex geometries and structures can be created. Reinforcement is required to increase the flexural strength of the concrete elements and, thus, enable their applicability in practice. Integrating the reinforcement is a difficult task, particularly in the case of SPI due to the layer-wise printing method. Especially with respect to possible complex structures, the production of the reinforcement needs to be adapted to SPI, thereby offering a high degree of freedom. One concept for a reinforcement integration is combining the two additive manufacturing processes SPI and Wire and Arc Additive Manufacturing (WAAM). However, since the two processes serve different fields of application, their compatibility is not necessarily given. Ongoing investigations show that the temperatures caused by WAAM adversely affect both, the cement paste rheology required for sufficient paste penetration into the particle bed and the overall concrete strength. This paper provides an overview of ongoing research focusing on different cooling strategies and their effects on the compressive strength of SPI-printed concrete parts.

Integrating Wire Arc Additive Manufacturing into Selective Paste Intrusion for Reinforced Concrete Elements: Effect of Temperature on the Mechanical Performance

“…However, since WAAM may introduce higher temperatures than 70°C into the SPI concrete, it is essential to additionally focus on cooling strategies, as presented in previous research [14]. Further research should consider the longterm effects of temperature on the mechanical properties of concrete, as well as the potential need for and extent of additional cooling strategies in the combined SPI and WAAM processes.…”

“…Another study that deals with additional cooling strategies for the combined SPI and WAAM process demonstrates the temperatures present in the steel at various distances from the welding point [14]. Based on these findings, conclusions can be drawn in the following investigation as to whether further cooling measures are required.…”

“…But also increasing the protruding distance between the welding point and the particle bed surface [12]. Increasing this distance leads to lower temperature of the WAAM steel bar in the contact zone with the concrete matrix [9,14]. However, [12] demonstrate that this distance should not exceed 50 mm, as it would otherwise result in a decreased print quality (shape accuracy and mechanical performance).…”