Adorned with magnificent edifices and palaces, including a large amphitheatre and aqueduct, Caesarea was the symbol of Roman rule and Greek culture in Judea. Remains of many of these impressive structures can still be seen today.

Caesarea was constructed by Herod the Great on the Mediterranean coast of Judea as a sea port and centre of government. It was named in honour of Emperor Caesar Augustus, Herod’s patron, and was the official residence of the Roman procurators as well as the Herods.

Caesarea was the home of Cornelius, the Roman centurion, who was accepted into the household of faith through the revelation to Peter “that God is no respecter of persons; but in every nation he that feareth him and worketh righteousness is accepted with him” (Acts 10:34-35). It was home, too, to Philip, who took the gospel to Samaria and assisted the Ethiopian to understand that Jesus was the Christ that should come (Acts 8:5; 34-35). It was also at Caesarea that Paul was held pending his voyage to Rome to stand before Caesar (Acts 24-26).

One of the outstanding features of the city is the harbour which is protected by a massive breakwater that was formed using enormous rocks and concrete. At the time of its completion, it was the largest artificial harbour ever built in the open sea.1 It is regarded as one of the most remarkable examples of Roman engineering of the Augustan Age. Parts of the underwater concrete construction, which are visible today, show little erosion or damage 2000 years later.2

Research by scientists studying Roman concrete used to construct underwater structures has revealed that its durability is due to a rare chemical reaction that appears to strengthen the concrete over time.3 It is thought that the pozzolanic reaction (the chemical reaction upon the addition of volcanic material to the mix) of volcanic ash with hydrated lime creates a fabric that contributes to its durability.4

First century Roman scholar and historian, Pliny the Elder, noted the processes involving volcanic ash and water-rock interaction, observing: “that as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass (fierem unum lapidem), impregnable to the waves and every day stronger”.5 It appears that this is the secret of the long-term chemical resilience of Roman maritime concrete.

Vitruvius, a Roman architect and engineer writ- ing about 30BC, described this process earlier. He described this pozzolanic reaction and the “latent”heat released when tu (volcanic rock), pumiceous ash, and lime from the Campi Flegrei and Vesuvius volcanic districts “come into one mixture and suddenly take up water and cohere together”.6

It is usual for modern cement mixtures to erode over time, particularly when they come into contact with seawater, but by combining volcanic ash, lime, seawater, and a mineral called aluminium tobermorite, the Romans created a mixture that resists these processes. Researchers found that seawater continually ramming into the structures for hundreds of years, created a reaction that allowed the concrete to develop resistance and prevent cracks from expanding. Unlike modern cement-based concrete, the Romans created a rock-like concrete that is strengthened by open chemical exchange with seawater.7

The Romans used a timber formwork into which layers of cement combined with large lumps of stone or tuff aggregate were poured. This mixture set into a solid mass that has endured the ravages of the sea for centuries. According to Vitruvius, the ideal pozzolanic material for building structures of concrete in the sea came from the Bay of Pozzuoli. Scholars have found that the Romans transported the material long distances so that they could use it to advantage in construction. For example, chemical analysis by researchers of the pozzolana used in the concrete at the harbour of Caesarea found that the material had been shipped from the Bay of Naples in Italy, a distance of some 2,000 kilometres.8

Edifices of the ancient world have outlived their creators by thousands of years. The pyramids of Egypt and the monuments of Greece and Rome still stand today, but the empires of these once mighty kingdoms have passed into history. Roman concrete may endure even when subject to seawater and the force of ocean waves, but “all flesh is grass”, and soon fades and dies, while the promises of our God will stand forever.

References:

  1. Robert L. Hohfelder, Christopher Brandon and John P. Oleson, Constructing the harbour of Caesarea on the Sea: new evidence from the ROMACONS field campaign of October 2005, [Online] https://web.uvic.ca/~jpoleson/ROMACONS/Caesarea2005.htm
  2. Jim H., “Roman Concrete: The Volcanic Material at Erected the Roman Empire” Historic Mysteries, [Online] https://www.historicmysteries.com/roman-concrete/          “Roman concrete”, Wikipedia, [Online] https://en.wikipedia.org/wiki/Roman_concrete
  3. Aric Jenkins, “Scientists Have Figured Out How Ancient Rome’s Concrete Has Survived 2,000 Years”, Time, 6 July 2017 [Online] http://time.com/4846153/ancient-rome-concrete-cement-seawater/
  4. Marie D. Jackson, Sean R. Mulcahy, Heng Chen, Yao Li, Qinfei Li, Piergiulio Cappelletti and Hans-Rudolf Wenk, “Phillipsite and Al-tobermorite mineral cements produced through low-temperature water-rock reactions in Roman marine concrete”, American Mineralogist, v. 102, no. 7 (July 2017) p. 1435–1450. [Online] http://ammin.geoscienceworld.org/content/102/7/1435#skip-link
  5. Pliny, the Elder, Naturalis Historia 35.166 quoted in Marie D. Jackson.
  6. Vitruvius Pollio, De Architectura 2.6.1–4 quoted in Marie D. Jackson.
  7. Marie D. Jackson.
  8. Christopher Brandon, Robert L. Hohlfelder, John Peter Oleson and Charles Stern, “The Roman Maritime Concrete Study (ROMACONS): the harbour of Chersonisos in Crete and its Italian connection”, Journal of Mediterranean Geography, 104 (2005) p. 25-29 [Online] https://mediterranee.revues.org/1952