The HM-35 L-Box offers an alternate method of determining flow and passing ability of self-consolidating concrete (SCC) mixes. This method is in use in Europe and some DOT’s in the United States have adopted the procedure or are examining it. An ASTM procedure is pending at the time of this writing.
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. Fresh concrete 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. The HMA-135 11.8x1.6in (300x40mm) Stainless Steel Straightedge is a suggested accessory for striking-off the concrete surface. The HM-35 is constructed of durable stainless steel with welded joints.