A concrete post

Since the invention - or should we say the reinvention - of 'Portland Cement' in the 1830s, we bastions of the industrial and computer ages have made monumental buildings a matter of poured concrete. Most structures we drive on or live and work in would not be possible without the wonders of 'modern concrete'. It can be pumped hundreds of metres into the air and set hundreds of metres under the sea. It has made the twentieth and twenty-first centuries possible. No small thing for a mortar invented for canal construction.

But in essence, all we've done is reinvigorate a construction material discovered even before the Romans conquered most of the 'known' world. The Carthaginians were building multi-storey concrete buildings prior to 146 BC, and the Romans almost certainly adopted this Punic technology to build eight-storey tower blocks in Rome and other major cities...and some of these are still standing. Meanwhile the Pantheon, the world's largest uninterrupted enclosed space for 1900-years, offers a salute to the engineering we have only just rekindled. However Roman cities were just the beginning. Concrete built the roads and the aqueducts that fed an empire, and hundreds of thousands of tonnes of Roman concrete was poured into the sea. The sea you ask? Yes, perhaps the greatest achievement of all. Vast artificial harbours designed in a time before modern diving equipment, let alone cement mixing machines. King Herod built the artificial Caesarea Harbour in 20 BC, constructing it entirely from concrete bulwarks sunk in place...and still in place. North of Naples, Pliny the Elder's naval base used a similar technique, although in this case, parts of the harbour wall sink over one hundred feet below the sea's surface. How this was achieved and the how the sea floor was prepared raises a lot of questions, many of which we will have to look at in the future - such as - could any of this have been done without the use of stored or piped air for divers? The fact the Romans used concrete so freely must mean they used other accompanying technologies we remain oblivious to. Perhaps there's no concrete answer - but for more on Roman diving technology - check out 'A Body of Doubt' - live on Amazon now.