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How Limestone, Rocks, and Volcanic Ash Built the Modern World

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How Limestone, Rocks, and Volcanic Ash Built the Modern World 26/11/2017 The Rock Solid History of Concrete ALEXANDERVANLOON/WIKIMEDIA The Rock Solid History of Concrete By Jonathan Schifman Oct 12, 2017 1.5k HOW LIMESTONE, ROCKS, AND VOLCANIC ASH BUILT THE MODERN WORLD. The story of concrete is so ancient that we don't even know when and where it begins. It is a story of discovery, experimentation, and mystery. Emperors and kings became legends for erecting great concrete structures, some of which are still a mystery to engineers today. Many of history's most skilled architects found inspiration in slabs of the gray building material. Common bricklayers advanced the technology, and a con man played a crucial role in the development of concrete recipes. Today, the world is literally filled with concrete, from roads and sidewalks to bridges and dams. The word itself has become a synonym for something that is real and tangible. Press http://www.popularmechanics.com/technology/infrastructure/a28502/rock-solid-history-of-concrete/ 1/22 26/11/2017 The Rock Solid History of Concrete your handprints into the sidewalk and sign your name to history. This is the story of concrete. The First Cement—and Maybe Concrete? Let's get this out of the way right here: cement and concrete are not the same thing. Cement, a mixture of powdered limestone and clay, is an ingredient in concrete along with water, sand, and gravel. Concrete's invention was made possible by the development of cement, and to trace the history of cement, we must trace the use of its components. ADVERTISEMENT - CONTINUE READING BELOW The earliest known use of limestone in a structure has been dated back about 12,000 years. It was found in the Göbekli Tepe temple in modern-day Turkey. The historic temple suggests that perhaps humanity's transition from nomadism to civilization was sparked not by agriculture, but by a desire to gather and worship in a great construction. Limestone made up the carved, T-shaped pillars of the Göbekli Tepe. The ruins of Göbekli Tepe, the oldest known temple in the world. TEOMANCIMIT/WIKIMEDIA http://www.popularmechanics.com/technology/infrastructure/a28502/rock-solid-history-of-concrete/ 2/22 26/11/2017 The Rock Solid History of Concrete In the millennia that passed between that structure and the amazing concrete of Roman times, cultures around the world developed better building materials, some of which you might see as a kind of proto-concrete. Recently, for example, archaeologists have questioned whether an early form of concrete can be found in the Egyptian pyramids. The hypothesis holds that the Egyptians may not have hauled every building block to the pyramids, but that the blocks toward the top of the pyramids could have been cast in a mold just as we pour concrete into a mold today to give it its shape. However, most archaeologists believe there is no evidence that any blocks are made of an artificial material like concrete. Instead, it is widely believed that they are made of limestone, which may have naturally contained clay as well. There is also no evidence that the Greeks used concrete. However, the Minoans of Crete did use an artificial building material for floors, foundations, and sewers, according to Robert Courland's book Concrete Planet: The Strange and Fascinating Story of the World's Most Common Man-Made Material. This Minoan material may not have been the concrete we know today, but it was a mixture of a similar sort. Clay was a major component, and a volcanic ash, today called pozzolana, was also used. Pozzolana is derived from Pozzuoli, Italy, which is the site of Mount Vesuvius, whose eruption destroyed the Roman city of Pompeii in 79 AD. The same volcanic ash that covered that ancient city and froze its citizens in time also helped the Romans create the first known concrete in the world—and the strongest concrete humanity has ever seen. Rome The connection between Rome and concrete is so strong that we even take the name "concrete" from them. It's derived from the Latin term concretus, meaning "to grow together," just the way the components of concrete mix to form a solid building block. But the Romans didn't refer to their concrete as "concretus." In fact, they misleadingly called their concrete caementis, meaning "rocky stuff." Caementis is of course the word that gave us "cement." http://www.popularmechanics.com/technology/infrastructure/a28502/rock-solid-history-of-concrete/ 3/22 26/11/2017 The Rock Solid History of Concrete Mt. Vesuvius looms over the ruins of Pompeii. GETTY ADVERTISEMENT - CONTINUE READING BELOW 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 http://www.popularmechanics.com/technology/infrastructure/a28502/rock-solid-history-of-concrete/ 4/22 26/11/2017 The Rock Solid History of Concrete 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. MICHAEL STILLWELL 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 http://www.popularmechanics.com/technology/infrastructure/a28502/rock-solid-history-of-concrete/ 5/22 26/11/2017 The Rock Solid History of Concrete 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 2,000 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 Peak of Roman Concrete ADVERTISEMENT - CONTINUE READING BELOW Ad Dell Inspiron 13 5000 No cai5378w10he1 R$3,529.00 R$4,029.00 Notebook Friday e Intel® Core™ After the fire of 64 AD and the death of Emperor Nero four years later, civil war came to Rome. 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 50,000 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. http://www.popularmechanics.com/technology/infrastructure/a28502/rock-solid-history-of-concrete/ 6/22 26/11/2017 The Rock Solid History of Concrete Sunset over the Colosseum in summertime. GETTY The Roman Colosseum is an elliptical structure measuring 615 feet long and 157 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 1,937 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 6,000 metric tons to 653,000 metric tons, according to Concrete Planet. However, about 80 percent of the concrete was used for the foundations, so it stands to reason that 6,000 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 1800 years, the Pantheon is as sturdy as ever.
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