The U-Box Test is a standardized laboratory method used to evaluate the filling ability and passing ability (or flowability through obstructions) of fresh self-compacting concrete (SCC). SCC is a highly fluid concrete that consolidates under its own weight without vibration, making it ideal for areas with dense reinforcement. Traditional tests like the slump test are unsuitable for SCC due to its high fluidity, so specialized tests like the U-Box are employed instead.

This test simulates the concrete’s ability to flow horizontally through confined spaces, such as around reinforcing bars, providing a direct measure of its performance in real-world applications like congested formwork.