Residence Time Distribution Evaluation Method for Inline Mixing Processes in Digital Concrete

The application of digital manufacturing technologies in the construction industry has shown rapid development in recent years. Digital concrete fabrication enables efficient design options with the increased shape of freedom by removing traditional formwork. Also, unlike the traditional concrete process, which is labor-intensive, digital fabrication technology primarily aims to enhance the productivity rate through digitalization. Most digital fabrication processes require pumping, placement, and then the subsequent buildup of strength after placement. This final requirement, often called buildability, often relies on controlling hydration to increase building rates through the addition of an activator or set accelerator. Adding an activator into ‘an inline mixing system’ introduces the additional requirement of controlling the mixing inside the inline mixer. In inline mixing, the distribution of the accelerator through mixing gains importance in monitoring building rates and selecting proper parameters such as accelerator dosage, flow rate of concrete, and inline mixing speed. To comprehend the mixing patterns within the inline mixer, it is essential to assess the residence time distributions of the accelerator. This research introduces a novel approach employing cost-effective and user-friendly image analysis. In contrast to techniques using μXRF and SEM-EDX, which require a higher degree of sample preparation and enable investigation of only small surface areas, the image analysis proposed allows for the examination of the entire sample area, giving a faster and more complete picture of mixing behavior.