Roman Concrete

One of my Favorite scene in the movie "Gladiator" is when, Djimon Hounsou a former slave/gladiator arrived in Rome. He saw for the first time the coliseum and his first Words was " Have you ever seen anything like that before? I did not know that men could built such things" he was captured by the gigantic size of the coliseum. ( fast forward 1:15:43)

well, how does Romain come across concrete?

According to an article called "The ancient Roman secret to more ductile concrete"

Geophysicists at the Stanford University School of Earth, Energy, and environmental Sciences (Stanford, Calif.) have discovered concrete-like rock deep within a dormant Italian volcano they say could explain how ancient Romans invented the compound used to build structures like the still-standing Pantheon and Colosseum.

In a recent Stanford University video, Tiziana Vanorio, assistant professor of geophysics, explains that the concrete rock—uncovered at the Campi Flegrei volcano near Naples, Italy—is located in the middle of a large caldera (a cauldron- like volcanic feature formed by collapse of land following a volcanic eruption). The video can be found at .https://www.youtube.com/watch?v=MkUNxFwBfhY.

Vanorio explains in the video that in the Campi Flegrei caldera there is a cap-rock a harder rock that lies over- top a weaker rock layer that is rich in pozzolana, or volcanic ash specific to the region.

And upon studying the composition of the caprock, Vanorio and her col- leagues also noticed that the caprock contained tobermorite and fibrous minerals that also are found in manmade concrete, including ancient Roman concrete. Roman engineering is well known for its legacy aqueducts and amphitheaters. Less recognized but of comparable achievement are the enormous concrete structures created during the Imperial era. 

What does the the discovery of  concrete means for Roman architecture?

Indeed, the perceptive use of concrete to create monumental public buildings of daring scale and vaulted entirely in unreinforced concrete is unquestionably one of the Roman engineer’s most significant  accomplishments It means bigger, higher and faster constructions. Similarly dimensioned structures, with spans exceeding 25 m. However, an impressive number of these concrete tours de force remain extant today, some excellently preserved after nearly 2,000 years, including long periods without maintenance. Scholarly appraisals have tended to emphasize the architectural significance of the monuments, rather than exploring the structural considerations, which motivate the present investigation.

In examining the implications of Roman engineering captured in its concrete monuments, the most significant considerations refer to the structural scale; thus, the study proceeds on this level. While the endurance of many Imperial concrete constructions offers a rich collection of structures with diverse vaulting systems, little attention has been paid to how such buildings behave mechanically.

 Work cited:

Philip Brune1 and Renato Perucchio, M.ASCE2"Roman Concrete Vaulting in the Great Hall of Trajan’s Markets: Structural Evaluation"