Final answer:
Roman imperial monuments built using concrete were characterized by their vaulted structures, large domes, and arch construction. These innovations permitted the Romans to build enduring and monumental spaces, with examples like the Pantheon's coffered dome and the Colosseum's vast arena. Vaulting and domes also facilitated the creation of impressive interior spaces without heavy reliance on interior supports.
Step-by-step explanation:
The characteristics of the Roman imperial monuments built using concrete include vaulted structures, large domes, and arch construction. The combination of concrete with the structural capacity of the arch allowed Roman architects to create durable and lofty structures, many of which stand to this day. Famous examples include the Colosseum and the Pantheon, the latter boasting a coffered concrete dome that at the time was unprecedented in terms of size and lacked interior supports.
Roman engineering innovations extended the practicality of arches into vaults and domes. Vaults enabled the construction of buildings that were tall and could cover large areas without the need for as many supporting columns. Domes, such as the Pantheon's, were able to encapsulate vast interiors that were awe-inspiring and functional.
These engineering feats were not just limited to grand temples or amphitheaters; they were also utilized in practical infrastructure like aqueducts, which delineated the prowess of Roman engineering across the Empire. Additionally, the use of concrete allowed for more flexibility in design and the construction of structures quickly and efficiently, as seen in the brick-faced concrete walls lightened with relieving arches and vaults.