Final answer:
False. Joists are typically used in wood or steel-framed structures, not concrete. Lightweight concrete, which contains materials like shale or clay, is used to reduce dead load and improve spans in concrete construction.
Step-by-step explanation:
The statement that joists are used in a concrete slab to lighten the dead load of the concrete and create more efficient spans is false. Joists are typically used in wood-framed or steel-framed structures to span open spaces and provide support for flooring or ceilings. In contrast, in concrete construction, lightweight concrete may be used to reduce the dead load and allow for more efficient spans. This lightweight concrete is created by mixing in lightweight coarse aggregates such as shale, clay, or slate, which have the advantages of reducing load and improving the thermal insulation of the structure.
The Romans employed the innovation of the true arch, employing wedge-shaped stones called voussoirs and a central keystone to support substantial loads over wider spans in their architecture. The combination of concrete with this arch design allowed for the construction of vaults and domes, hence creating impressive and spacious interior structures.