Or, irregular shaped, fist-sized tufa blocks created a wall mosaic covering the concrete opus incertum B During the last century of the Republic and into the early empire, the favored method was to face concrete construction by regularized, diagonally arranged, square blocks of tufa opus reticulatum , as we see in these examples from Hadrian's Villa at Tivoli B50, B These small, square blocks were shaped like cones, their pointed ends firmly embedded in concrete.
By the early empire, the advantages of kiln-baked brick as facing had also been recognized although this system reached its greatest popularity in the 2nd-century B52, B In many instances, Romans, with their keen eclectic sensibilities, even mixed different materials for facing - opus incertum or opus reticulatum with brick, ashlar, and small stone-block construction.
This popular and practical method, not surprisingly, was referred to as opus mixtum, as this fine example from Pompeii illustrates B48, B All of these different facing materials were well bonded with the concrete core of the wall and they could be veneered over by still another, this time a more decorative material.
This surface veneer was often stucco or plaster, molded, patterned and painted sometimes to imitate blocks of marble. In exceptionally fine buildings, budgets allowing, marble incrustation was used as a luxury material par excellence, even incorporating a decorative use of the orders as applied on the wall in the form of pilasters or half-columns A Actually it has been argued that the concrete used by the Romans was of better quality than the concrete in use today.
Recent research from US and Italian scientists has shown that the concrete used to make Roman harbors in the Mediterranean was more resistant than modern concrete known as Portland cement. The production process was dramatically different. Portland cement is made by heating clays and limestone at high temperatures various additives are also added while the Romans used volcanic ash and a much smaller amount of lime heated at lower temperatures than modern methods.
For example, Roman harbors remain intact today after 2, years of waves breaking on the harbors' breakwaters whereas Portland concrete begins to erode in less than 50 years of sea battering. The concrete from ancient Rome also had bending properties that Portland concrete does not have due to its lime and volcanic ash, which explains why it does not crack after a few decades. Incredible facts about Roman concrete Reinforced concrete reinforced with steel rebar did not exist.
As a result, buildings lasted longer as they did not suffer from steel corrosion. Pozzolana derived from volcanic dust made the concrete more resistant to salt water than our modern-day concrete. But the Romans didn't refer to their concrete as " concretus. Ancient Romans made concrete in much the same way we do today. They made cement by mixing kilned limestone with water.
To thicken the mixture, they added the volcanic pozzolana, ground-up rocks, and sand. In a semi-liquefied state, the mixture was then poured into carved wooden molds to create smooth, sturdy pieces of concrete.
The Romans used concrete to build ramps, terraces, and roads. Pouring the mixture into molds allowed the Romans to build vaults, domes, and the arches of the empire's great aqueducts. By the second century BC, the Romans began making walls out of concrete and coating it with brick masonry, which they did for two reasons. First, the ancient Romans preferred the aesthetics of brick to the gray slab of unadorned concrete. Second, after the Great Fire of Rome in 64 AD that destroyed 10 of the city's 14 districts, concrete was revealed to be fire-resistant—though not fireproof.
The outer brick helped in that regard. What makes Roman concrete so impressive is its ability to endure substantial weathering, survive earthquakes, and withstand crashing waves in the sea. Consider one of the first great Roman projects. Concrete's rise to prominence within the Empire began with the daring engineering feat of Sebastos Harbor, in Caesarea, Israel.
The year was 23 BC, a time when concrete was still a largely unproven material. King Herod of Judea, whose land was a territory of the Roman Empire, wanted to improve his kingdom's economy. What better way than to build a port on the shores of the Mediterranean Sea? It was the perfect test of concrete's resilience. Construction of the harbor took eight years. The result was one of the largest harbors in the world, second only to that of Alexandria in Egypt.
The jetties and seawalls were made of pure concrete, likely lowered into the water with a crane. Divers—holding their breath—went into the Mediterranean to make adjustments to the structures' positioning. Once properly aligned, each heavy piece of concrete was tamped down. The city of Caesarea finished construction five years after the harbor was completed, and the thriving port earned King Herod the title "Herod the Great.
More than 2, years later, the concrete harbor is still intact. You just can't see it from the land. Sebastos Harbor was built directly atop a fault. Earthquakes struck every few centuries, causing the jetties and seawalls to slowly submerge under the Mediterranean. But Sebastos Harbor was only the beginning.
The Romans would go on to erect some of the most famous concrete structures in the world. The victor was general Flavius Vespasianus, better known as Vespasian. After becoming emperor, he set out to build the largest theater in the world.
He would call it the Flavian Ampitheater, and it would hold more than 50, spectators and provide a full view of the events from every seat. It was the world's first stadium. Today we call it the Colosseum. The Roman Colosseum is an elliptical structure measuring feet long and feet high, with a base area of about 6 acres.
It has 80 entrances, four of which were for VIPs, and one for the emperor. The Colosseum was completed 1, years ago, and it stands today as one of the enduring symbols of the Roman Empire—and more literally as a testament to the endurance of Roman concrete. The Colosseum is not made entirely of concrete, however. Disproportionate quantities of brick and concrete can be found throughout the arena. Estimates of the amount of concrete have ranged widely, from 6, metric tons to , metric tons, according to Concrete Planet.
However, about 80 percent of the concrete was used for the foundations, so it stands to reason that 6, metric tons is lowballing the estimate significantly.
But it's difficult to say for sure. After all the bumps and bruises and earthquakes and lightning strikes that the structure has endured over the course of two millennia, what we have left today is only about a third of the original construction.
The most pristine ancient concrete structure in Rome, however, was not built for the people, but for the gods. After years, the Pantheon is as sturdy as ever. The engineers who constructed the great temple of Rome were far ahead of their time—perhaps even ahead of our time. The Pantheon was Emperor Hadrian's brainchild. Hadrian was always intrigued by architecture, and when he became emperor in AD he wanted to build the Empire's grandest structure as a testament to the gods.
He would do so with the largest dome the world had ever seen. It was a risky enterprise. The Pantheon's dome would span feet.
It was twice as wide and high as any dome ever created. The concrete was poured into a curved wooden mold, a perfect half sphere, propped up on scaffolding. Once the scaffolding was removed, the walls alone had to endure the pressure of the gargantuan concrete roof, which was immense even with the famed oculus in the dome's center relieving some of the load.
Roman engineers built those concrete walls incredibly thick and covered them with brick on the interior and exterior. On the interior, the bricks were laid to construct relieving arches to take stress away from the walls.
Eight barrel vaults also relieve stress, creating inset galleries for the faithful to stand before statues of the gods. An extra layer of brick was placed on the ground along the exterior perimeter of the building. In other words, the walls were tremendously reinforced, and incredibly, the dome was not. Today's engineers wouldn't dare build an unreinforced dome of that size. Such a structure with today's concrete would be in constant danger of collapsing.
How, then, did Hadrian and his engineers pull it off? They tinkered with the concrete recipes. The dome contained a bit more volcanic ash than rock to make it slightly lighter, while the walls contained much more rock aggregate to make them heavy and strong.
The research team was led by Paulo Monteiro, a UC Berkeley professor of civil and environmental engineering and a faculty scientist at Berkeley Lab, and Jackson, a UC Berkeley research engineer in civil and environmental engineering. They characterized samples of Roman concrete taken from a breakwater in Pozzuoli Bay, near Naples, Italy.
It was used in monuments such as the Pantheon in Rome as well as in wharves, breakwaters and other harbor structures. The recipe for Roman concrete was described around 30 B. The not-so-secret ingredient is volcanic ash, which Romans combined with lime to form mortar. They packed this mortar and rock chunks into wooden molds immersed in seawater. Rather than battle the marine elements, Romans harnessed saltwater and made it an integral part of the concrete.
0コメント