The 1820s are the decade that saw the United States of America come of age as a 50-year-old nation. A young government's growing pains shape…
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Thank you for this article, it is very interesting. You might want to check the date in the section about cement. 65,000 BC seems rather early.
AllisonGollosCornwell, I think the author may have gotten this information from:
Early Use of Concrete - From the International Association of Certified Home Inspectors:
The first concrete-like structures were built by the Nabataea traders or Bedouins who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan in around 6500 BC. They later discovered the advantages of hydraulic lime -- that is, cement that hardens underwater -- and by 700 BC, they were building kilns to supply mortar for the construction of rubble-wall houses, concrete floors, and underground waterproof cisterns. The cisterns were kept secret and were one of the reasons the Nabataea were able to thrive in the desert.
In making concrete, the Nabataea understood the need to keep the mix as dry or low-slump as possible, as excess water introduces voids and weaknesses into the concrete. Their building practices included tamping the freshly placed concrete with special tools. The tamping process produced more gel, which is the bonding material produced by the chemical reactions that take place during hydration which bond the particulates and aggregate together.