L Box Test for Self Consolidating Concrete (SCC)

L Box for Self Compacting Concrete (SCC)

The L Box for Self Consolidating Concrete (SCC) is an alternative method to determine flow and passing ability of self-consolidating concrete (SCC) mixes. This is used in Europe and some DOT’s in the US have adopted the procedure or are looking into it.

The apparatus is 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 is expressed as a blocking ratio. Some versions of this procedure require timing the flow with a stopwatch. The 12x1.25in (305x32mm) Steel Straightedge is an optional accessory for striking-off the concrete surface.

Dimensions: 8x24x32.5in. (203x610x26mm), WxDxH.

Meets Test Methods: ASTM C 1611 ASTM C 1621

What is the L Box Test?

The L Box Test is a standardized method to evaluate the flowability and passing ability of self-compacting concrete (SCC) through tight spaces and around obstacles. This test simulates real world scenarios, such as pouring concrete around reinforcing steel, so it’s an essential tool to ensure the quality and performance of SCC in various construction applications. The L Box Test originated from a Japanese design for underwater concrete and is described in the European standard BS EN 12350-10. By seeing how well the concrete can flow through confined spaces the test helps determine if SCC mixes are suitable for complex consolidating needs.

The L Box Test Apparatus is an L shaped box with a vertical and horizontal section separated by a sliding gate. The vertical section has vertical steel bars representing reinforcing steel and the horizontal section is open. To perform the test freshly mixed SCC is poured into the vertical section until it reaches a certain level. The gate is then lifted and the concrete flows into the horizontal section. Measurements are taken of the distance the concrete flows in the horizontal section and the time it takes to reach certain points. The L Box Test Apparatus is made of durable stainless steel to withstand repeated testing.

The results of the L Box Test give you valuable information about the flowability and passing ability of the SCC. Flowability is determined by the distance the concrete flows in the horizontal section, the more distance the better. Unfilled areas behind the steel bars indicate blocking issues which can be quantified by calculating the blocking ratio. The blocking ratio is the ratio of the concrete height in the horizontal section to the height in the vertical section. A minimum acceptable value of 0.8 is used to determine if the SCC meets the requirements. This ratio helps you determine if the concrete mix can flow past obstacles without segregation.

Benefits and Applications

The L Box Test has many benefits and applications in the construction industry. It’s simple and quick to do so it’s an efficient tool for quality control. The results give you valuable information about the SCC’s flowability and passing ability so you can place the concrete in complex geometries and around reinforcing steel. This test is useful to determine the effectiveness of SCC mixes in various construction applications such as high rise buildings, bridges and other infrastructure projects. You can also use the L Box Test to test different SCC mixes and optimize their composition for specific applications to get the best possible results in terms of strength and durability.