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Concrete Knowledge Part 2~
Concrete Knowledge Part 2~
Concrete History Through the Ages
Concrete History Through the Ages
So how did we arrive at the current state of concrete? Through a process of evolution, like so many other means of construction and development. First, ancient people made discoveries about naturally occurring materials they could use it to improve fundamental parts of their infrastructure — homes, fences, wells, etc. The generations who followed them built upon that knowledge, making improvements here and there until the industrial age descended and sped up building developments to their current level.
Origins and Precursors
Origins and Precursors
12 million years ago – Naturally occurring cement
On land that is now Israel, spontaneous combustion produced reactions between limestone and oil shale, resulting in natural deposits of “naturally occurring cement” that would make possible the future formation of concrete.
10,000 BC – Earliest limestone structure
Limestone — also often called “lime” — plays the earliest role in the story of concrete, as the base ingredient in cement, and it’s been used for millennia. Predating another massive stone temple, Stonehenge, by 6,000 years, the Göbekli Tepe in modern-day Turkey was the earliest known limestone structure. Limestone made up the T-shaped pillars of this temple, which were built and carved by prehistoric people who had not yet developed metal tools or even pottery.
The first concrete-like structures, secret underground cisterns for storing scarce water, were built by Nabataea or Bedouin traders who developed a small empire in the desert oases of southern Syria and northern Jordan. Some of these cisterns still exist in those areas today.
In the former country of Yugoslavia, in the area of Lepenski Vir along the Danube River, huts were found in the mid-1960s with a semblance of concrete floors. The lime cement that was used probably came from a deposit upriver and was mixed with sand, gravel, and water to resemble concrete mixtures of our time.
Monuments of Antiquity
Monuments of Antiquity
Limestone rocks or concrete blocks? Despite some hotly debated speculation about blocks in the Egyptian pyramids being formed with an early type of concrete more than 5,000 years ago, it’s more widely believed across the field of archaeology that the limestone blocks were hauled from quarries nearby. To make the mortar for holding the blocks together, the builders mixed straw with mud that contained crushed limestone, gypsum, and clay.
1400-1700 BC – Minoan structures on Crete
The Minoan society on the island of Crete, forerunners to the Greeks and credited as the first European civilization, used a building material that mixed clay and a type of volcanic ash called pozzolana for building for floors, foundations, and sewers.
*1300 BC – First “lime” coating
Middle Eastern builders burned limestone and mixed it with water, then used the mixture to coat the outsides of their pounded-clay walls. When the mixture reacted with the air, it formed a hard, protective surface — and laid the foundations, so to speak, for modern versions of cement.
The Mycenaeans used their early form of cement to build tombs. You can see some of them today in the Peloponnese in Greece.
770-476 BC – China’s Great Wall
The northern Chinese used a form of cement for building boats and their section of the Great Wall. Over the centuries of the wall’s construction, materials used for its entire span included reeds, willow branches, wood, compacted sand, mud, and 100 million tons of stone and brick. Where these weren’t cemented by limestone mortar, they were held together by a mortar made of glutinous, sticky rice.
* 700 BC – Kilns, mortar, and hydraulic lime
The same Bedouins who pioneered underground cisterns later built kilns to produce a rudimentary kind of hydraulic lime — cement that hardens underwater — for waterproof mortar that advanced the construction of houses, floors, and newly waterproof cisterns underground.
From Roman Empire to Renaissance
From Roman Empire to Renaissance
300-500 AD – Roman architecture
The Romans started with the same raw materials as the Minoans — volcanic ash found near Pompeii and Mount Vesuvius, which they used to thicken a mixture of kilned limestone, ground-up rocks, sand, and water — allowing them to build ramps, terraces, and the roads that eventually connected the whole empire. Pouring the mixture into molds soon allowed builders to create vaults and domes, as well as the arches of the empire’s iconic aqueducts and bathhouses. Roman concrete has endured earthquakes, lightning strikes, crashing sea waves, and thousands of years of weathering.
After Rome’s civil war, the emperor known as Vespasian set out to build the largest theater in the world, with more than 50,000 seats. Today we know the world’s first stadium, completed 1,937 years ago, as “The Colosseum.” About a third of the structure still stands nearly two millennia later, an iconic symbol of the Roman Empire.
117-125 AD – The Pantheon — and the loss of concrete
Rome’s Pantheon, soon to celebrate its 1,900th birthday, is as sturdy as ever. The temple’s unreinforced concrete dome was twice as wide and high as any dome ever created at the time, spanning 143 feet with its famed “oculus” in the center. Its mammoth weight is buttressed by incredibly thick concrete walls and eight barrel vaults, all reinforced with brick — but no internal support.
Today’s engineers wouldn’t dare build an unreinforced dome of that size, and they may never know the secret to the Pantheon’s enduring stability. We do know that Emperor Hadrian’s engineers adjusted the concrete recipes, using more volcanic ash than rock to make the dome lighter, and more rock aggregate in the walls for heavier reinforcement. But when the Roman Empire fell in 476 AD, the unprecedented Roman recipe for concrete was lost to the world.
1507 – The Renaissance – Pont Notre-Dame Bridge
Just after the Dark Ages, an Italian friar named Giovanni Giocondo built the Pont Notre-Dame Bridge in Paris using remnant information from the ancient Roman cement recipe. About 250 years afterward, the structure was demolished because houses built atop the bridge added too much weight. Giocondo would go down in history as the only person to attempt building with concrete during the Renaissance.
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