Which material, composed of gravel and rubble set in lime and sand mortar, allowed Romans to span great distances?

Which material, composed of gravel and rubble set in lime and sand mortar, allowed Romans to span great distances?

• A. Concrete
• B. Marble
• C. Brick
• D. Lime plaster

Answer: (A)

Roman concrete is the material described, a lime-based mix with aggregate such as gravel and rubble that hardens into a strong, cohesive mass. The crucial aspect is that this concrete could be formed into arches, vaults, and domes, and, when blended with pozzolanic materials like volcanic ash, would gain a hydraulic set to harden in wet conditions. That combination let builders span long distances and create large, durable structures—long-lasting bridges, aqueducts, and monumental domes—because the material could be cast in place and distribute loads efficiently. Marble is decorative stone, brick consists of individual units, and lime plaster is a finishing coating, not the structural, spanning material Roman concrete provides.

Roman concrete is the material described, a lime-based mix with aggregate such as gravel and rubble that hardens into a strong, cohesive mass. The crucial aspect is that this concrete could be formed into arches, vaults, and domes, and, when blended with pozzolanic materials like volcanic ash, would gain a hydraulic set to harden in wet conditions. That combination let builders span long distances and create large, durable structures—long-lasting bridges, aqueducts, and monumental domes—because the material could be cast in place and distribute loads efficiently. Marble is decorative stone, brick consists of individual units, and lime plaster is a finishing coating, not the structural, spanning material Roman concrete provides.