U Box Apparatus

The U-Box Apparatus is specialized testing equipment used to evaluate the confined flowability and self-compacting capability of fresh Self-Compacting Concrete (SCC) within restricted geometries. By measuring the final equilibrium height the concrete achieves after flowing through a standardized rebar obstacle, the test provides a direct measure of passing ability, filling performance, and freedom from aggregate blocking.

Constructed from a rigid, heavy-gauge steel frame with smooth internal faces to minimize wall friction, the apparatus is divided into two vertical compartments separated by a sliding gate and a three-bar reinforcing steel grid. Once the sample is placed in the charging compartment and the gate is rapidly opened, the concrete flows through the rebar obstacle into the receiving chamber, allowing operators to measure the vertical rise quickly to determine mix compatibility and stability.