Roman concrete uses a volcanic ash-lime mortar that is virtually crack-resistant combined with chunks of volcanic stone and other materials, often brick. Today’s concrete is made with limestone-based Portland cement, which requires a temperature of 1,450C (2,642F) to create and releases upwards of 7% of the world’s carbon emissions annually. Roman concrete, by contrast, does not require such high heat and could lead to the development of greener concrete through the use of volcanic material as the Romans did over two millennia ago.
Pont du Gard: a Roman aqueduct in France, constructed about 19 BCE. This technical and artistic masterpiece was built to allow the aqueduct of Nîmes to cross the Gard river. It is about 50m high and has three levels, the longest of which measures 275m long.
Julius Caesar dedicated the Temple of Venus Genetrix in Rome on this day in 46 BCE. Caesar traced his ancestry to Aeneas, son of the Roman goddess of love and beauty. In dedicating the temple to Venus Genetrix, Caesar drew attention to her role as mother. Typical of Roman temples, the sanctuary was raised on a high podium and held a cult statue of Venus as well as portrait statues of Caesar himself. The original temple was destroyed by fire in 80 CE and was rebuilt by Emperor Domitian and restored by Trajan. Three columns survive from the second temple.
Temple of Venus Genetrix, rebuilt by Trajan 113 CE, Rome
Plan of Imperial Fora, Rome
Silver denarius of Julius Caesar, reverse: Aeneas carrying palladium and his father Anchises, 47-46 BCE. New York: The Metropolitan Museum of Art: Rogers Fund, 1908.170.80
Elaborate public baths constructed by the Emperor Caracalla around 216 CE, were a center of Roman social life and one of the great engineering triumphs of the 3rd Century. Sprawling over some 33 acres on Rome’s outskirts, the baths were a vast complex of business and entertainment establishments. At the center of everything were the baths themselves - a “frigidarium” (cold bath), several “tepidaria” (warm baths) and a “calidarium” (steam bath); most bathers passed through them in that order. Aqueducts fed thousands of gallons of mountain water into the system. Water for the tepidaria and calidarium was heated by the wood-burning furnaces connected to a network of steam pipes beneath the floors. The baths would remain in use until the 6th century when Goths destroyed aqueducts that supplied the baths with water.
It’s the most common human-made material on earth, the second most consumed substance after water, and the veritable foundation of contemporary society. Despite all that, and the fact that modern concrete is by many measures an advanced building material, it pales in comparison to Roman concrete. For proof, simply compare today’s version—which often shows degradation after 50 years—with concrete-based Roman monuments that still stand after two millenia. Even more impressive are underwater Roman structures that show little decay in the presence of harsh marine environments.
In his history of early Rome, Dionysius of Halicarnassus credits the success of the empire not the heroics of Aeneas, republican rectitude, or the virtues of the emperor, but to unglorious feats of civil engineering:
The extraordinary greatness of the Roman Empire manifests itself above all in three things: the aqueducts, the paved roads, and the construction of the drains.
Roman Antiquities, 3.67.5
The great cities of the Roman Empire viewed public amenities like baths, fountains, latrines and sewers as indices of civilization that distinguished them from barbarians. Those amenities were dependent on an abundant and regular supply of clean water, usually in excess of local supplies. Water from distant elevated regions were brought into the city via aquaeductus (aquae = waters; ductus = led, directed), or aqueduct. The aqueduct system consisted mainly of underground pipes and tunnels, but occasionally to maintain the correct elevation and grade, or to ovecome a topographical obstacle like a ravine or valley, the water had to be carried above ground over bridges.
The overland aqueduct spans are the product of two building technologies invented by the Romans—the arch and concrete. Unlike the Greek post and lintel system, the arch supported much greater weights and spanned longer distance. Whereas the Greeks essentially piled cut stone into stacks to make walls and columns, the Roman mixed rubble with quicklime and water into concrete, which could be moulded into whatever shaped the tensile strength of the aggregate would bear. The combination of the arch and concrete made the gigantic structures of the empire possible, including the aqueduct, which is a sequence of arches, or arcade, made of concrete covered with stone or brick revetment. The aqueduct system, in turn, quadrupled the water supply into Rome, enabling its rapid expansion and causing its population to rise due to the health benefits of fresh, running water.
Water traveled along a deep trench at the top of the arcades, which was often covered to prevent evaporation and contamination. Deep valleys and ravines could be spanned and rivers traversed by bridges composed of superimposed arcades, without fear of wind sheer or currents. Some of the more elaborate spans, such as the Pont-du Gard in Provence have roads and walkways added at different levels allowing them to serve as roadway bridges as well as aqueducts. In the city, the aqueducts were incorporated into the city walls, the arch openings serving as gateways. The attic storey of the Porta Maggiore in Rome carries water from two separate aqueducts, the Aqua Anio Vetus and the Aqua Claudia, both of which originated near Agosta,, some 67km away. The Aqua Claudia, begun by Caligula and finished by Claudius in A.D. 47 delivered 185,000 cubic meters of water everyday, 20% of the city’s supply.
When the water reached the city it emptied into a castellum, a large cistern on a hill; from there ceramic or lead pipes directed the water to the various access points. In ancient Rome, water was free and no one had to walk more than 150 feet to the nearest public fountain. Waste waters from latrines and baths and rain water emptied into the cloaca or underground sewer system which emptied into the Tiber at a point just south of they city.
Many of the Roman aqueducts are still working today.
Dover - the Roman lighthouse of the 2nd Century AD, showing a primary view and details of the exterior and interior. Much of the fabric of the adjacent Saxon period church comes from recycled Roman brick and flint building material. Originally there were 2 lighthouses several hundred meters apart on this promontory overlooking the Channel, as well as a Roman fort near today’s harbor. Dover Castle is just beyond. Photo Credit: Clio Ancient Art and Antiquities