The Handy Rheometer: Capturing Complex Rheology with just a Camera and a Cylinder

The growing need for practical, on-site rheological tools in 3D concrete printing motivates this study, which introduces a low-cost, computer-vision based method for characterizing complex flow behavior. A simple experiment is performed by pulling a cylinder through a fresh cementitious suspension while recording the surface motion of a contrasted reference line on the suspension's surface simply using a camera. A computer vision algorithm tracks the displacement field, enabling precise velocity profile extraction over time. By applying a moment balance to the two flow regions – Couette and Poiseuille – the flow is modeled as a Herschel-Bulkley fluid. This approach enables estimation of key rheological parameters, including yield stress, consistency, and flow index, from a single, portable experiment. The method bridges the gap between rheometer-based experiments and on-site quality control, offering a practical solution for assessing non-linear, shear-dependent properties critical to digital construction workflows.