U-box

The U-box test is used to measure the filling ability and passing ability of self-compacting concrete (SCC) — a type of concrete that, without vibration, must be able to flow out, fill formwork and completely encapsulate reinforcement on its own. The test provides a direct and practical indication of how the concrete actually behaves under real casting conditions.

The U-box is manufactured in stainless steel with smooth interior walls and equipped with a flow obstacle consisting of four vertical reinforcement bars with Ø 10 mm and a clear spacing of 35 mm. A guillotine-shaped gate separates the vertical section from the horizontal section. The vertical section is filled with concrete, the gate is lifted and the concrete flows freely into the horizontal section. The height difference between the two sides is measured — the smaller the difference, the better the flow and passing ability.