To approach the rheological testing method based on L-box test for obtaining internal rheological parameters of fresh self-compacting concrete (SCC), an improved L-box without fiber bars and end wall is developed, and a flow investigation utilizing an image processing technique is operated. Specifically, the improved L-box test method is able to accurately reconstruct the process of free-surface evolution of fresh SCC when it is suddenly released in an open channel. The process involves the dam-break problem and open channel flow problem. In addition, by applying the image processing technique...