What type of concrete is required when pouring a structural concrete slab over a metal deck?

When pouring a structural concrete slab over a metal deck, lightweight concrete is the preferred choice due to its reduced density compared to normalweight concrete. This type of concrete offers the advantage of lowering the overall weight of the structure, which is particularly beneficial when dealing with metal deck systems that may have limitations on the load they can support.

Lightweight concrete is made with aggregates that are lighter than traditional aggregates, providing sufficient strength while minimizing the weight carried by the metal deck. This characteristic not only helps in reducing the dead load of the building but also enhances thermal insulation and fire resistance.

In contrast, normalweight and heavyweight concrete would add unnecessary weight to the metal deck, potentially leading to structural issues or requiring additional structural support. High-strength concrete, while providing increased load-bearing capacity, does not address the weight concerns that are critical when using metal decking. Therefore, lightweight concrete stands out as the ideal choice for this application.