Previously we wrote of the first use of what many believe to be the precursor for concrete technology. Its earliest believed use in the middle east by Nabataean traders, which may have led to its spread to other civilisation that made use of the materials special properties to build grand structures and marvellous wonders of the ancient world.
This article will continue that discussion, highlighting another ancient civilization.
Perhaps around the same time China was inventing new building methods. It is likely considering the difference in the method and the lack of evidence regarding contact with the Middle East at this stage, that it was developed completely separate to those other ancient civilisations at the time. It has been suggested that their technique was developed as early as that of the Egyptians, although it is much debated among historians and archaeologists.
The difference in the Chinese method of laying concrete was the addition of a simple ingredient, – rice soup. The Chinese used the glutinous soup mix from sticky rice (the actual name of a type of rice that was propagated by early the Chinese) and mixed it with a more familiar formula, including a lime based ingredient. This gave it a particular hardening and superior structural strength that was unmatched at the time. While the material was not always used as the basis of building complete buildings, it was used a highly adhesive bonding material and as such was used as mortar between bricks and mason building blocks. Its wet slurry form before setting was also highly malleable and easily worked creating better contact between surfaces, which not only contributed to its strength but often created an impermeable barrier, allowing the end product to be water proof. It was this product ability that led it also to be used in boat building.
One of the more important and famous uses was in the building of The Great Wall, allowing the Chinese to create a vast protective barrier to their empires that, because of its high strength, other ancient civilisations were unable to pull down.
ANCIENT GREEKS AND THE CLASSICAL WORLD
The use of concrete by these early ancient civilisations became the foundation for its use throughout the then known world. Evidence show that by 1000 BC various forms of concrete existed, although still more commonly being used as a mortar or adhesive material rather than providing large blocks for building or foundational support. This was most likely due to the fact that the material used to make the concrete, a natural occurring lime composition, had to be mined by hand. While quarries were found with significant resources, the process was slow.
By this time, evidence of the spread of concrete was now found around the Mediterranean, including on islands like Crete and Cyprus, but also as a more consistently used material in Greek architecture. This was still a very low grade concrete however and regardless of what the images may inspire of temples and stone columns, a lot of Classical Greek architecture was most clay bricks and straw. The use of the concrete was simply as a mortar and of comparatively lone strength. It wasn’t until the Romans bought with them a new formula (and the archway) that a more modern approach to building would take off.
While Rome borrowed a lot of their culture and behaviour form the Ancient Greeks, they were unique in inventing and discovering quite a number of their own methods, theories, devices and technologies. Initially, the Romans used the basic concrete formula at the time however were the first to use it more commonly, whether this was because they were the first to realise its full potential or simply had the ability to mine the required ingredients in a more efficient manner that led to the change, historians are unsure. What is known is that the more consistent use aligned with the way the material was utilised. Instead of becoming a simple mortar, or an outer layer of a building, they did something completely weird and unusual for the time. By aligning four planks of wood into a box shape, this material could be formed as a malleable slurry that would take the shape of the box below, worked to a smooth surface and then allowed to set. Once hard, the outer pieces of wood could be removed and what they had was a basic slab that could be created to any shape and depth required. This was further extended to include walls in what would be a common Roman method of architecture in that by creating arrays of vertically hollow bricks, the gap in the middle was then hand filled with concrete mortar before setting. At first, regardless of its increased use, this concrete was still quite weak and lacked the strength to create more important and longer lasting buildings and structures. This however would all change.
Whether by chance or severe testing, no one alive knows, but the Romans continued to develop their concrete formula and eventually created a substance that would stand the test of time. They added Pozzolana, a volcanic ash (that contains a high siliceous content and also reacts in the presence of water to form cement like properties) or pumice, a volcanic rock with similar properties. They also used seawater rather than fresh in their mixtures.
These additions created a concrete that was on par with todays in regards to strength allowing the Roman architecture and building methods to lift to a new level. Whole buildings now could be created out of the material and specific blocks could be created in particular shapes and forms from pre-made moulds.
One of the most famous Roman structures, the Colosseum in Rome, still stands today and was created form this new formula, proving it’s immense strength and longevity. Another is the Pantheon, the largest single form dome ever created. However, maybe due to the lack of resources of the new ingredients, this concrete was saved mostly for special purposes and the majority of buildings still used the old weaker methods.
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