Reinforced Particle-Bed Printing by Combination of the Selective Paste Intrusion Method with Wire and Arc Additive Manufacturing – A First Feasibility Study

The selective paste intrusion (SPI) is a particle-bed based Additive Manufacturing technology, which spreads particles in small layers and bonds them locally with cement paste. One advantage of this technology compared to other AM processes is that no support structures for cantilevers are required. Furthermore, SPI-made components achieve almost isotropic compressive strength (>70 MPa), high durability, and shape accuracy. However, to qualify the SPI process for the production of structural concrete elements, the inclusion of reinforcement is necessary. This paper presents an approach to print the reinforcement during SPI simultaneously by using Wire and Arc Additive Manufacturing (WAAM). WAAM enables the fabrication of geometrically complex steel reinforcement structures with high build-up rates, whereby properties similar to those of construction steel can be achieved. This allows producing reinforced concrete structures according to the principle “form follows force”, which leads to ecological and economical components. The major challenge that arises from the combination of WAAM and SPI is the occurrence of high temperatures (approx. 1600 °C) during WAAM. Thus, a detrimental effect on the penetration behaviour and loss of strength of the concrete matrix is expected. This paper focusses on the heat propagation during WAAM and its potential effect on the paste rheology. The results of the rheological measurements show that an application of both tested cement paste mixtures is possible for welding distances of approx. 62–68 mm and 82–84 mm to the particle-bed which reduce the temperature to 70 °C and 50 °C without additional cooling.