L-Box offers an alternate method of determining flow and passing ability of self-consolidating concrete (SCC) mixes. An ASTM procedure is pending. The apparatus consists of a vertical hopper with a sliding gate at the bottom. There are three bars representing reinforcing steel and a horizontal trough in front of the gate. A concrete specimen is placed in the vertical hopper without consolidating. Lifting the slide gate allows the concrete to flow past the bars into the horizontal trough. Final depth of the concrete at the gate and at the end of the trough is measured and the proportional difference expressed as a blocking ratio. Some versions of this procedure require timing the flow with a stopwatch.