Underwater excavations, carried out by the Caesarea Ancient Harbor Excavation Project (CAHEP) in Israel in the 1980s and by the Combined Caesarea Expeditions in the 1990s, revealed numerous concrete blocks (Area E blocks) at various points in the massive ruins of the now submerged harbour (harbour plan), along with some well-preserved wooden formwork (Area G forms). They were major structural elements of the two breakwaters King Herod constructed during the years 23 to 10/9 BC to define the harbour that served his principal Mediterranean port city. John P. Oleson and Robert L. Hohlfelder (University of Colorado at Boulder) were co-directors of this underwater excavation project, together with Prof. Avner Raban (Haifa University).

An analysis conducted by John P. Oleson and Graham Branton (University of Victoria) of samples of hydraulic concrete (mortar sample) recovered from one such building block (c.15 x 11.5 x 2m) from the North Breakwater produced striking and unexpected results. The tuff and pozzolana (tuff sample) contained in the sample had come from the Bay of Naples. These ingredients were the basis of a distinct type of Roman hydraulic concrete that could set while in contact with salt or fresh water. An enormous quantity of the raw material had been transported 1200 miles as bulk cargo on merchant vessels to the site of King Herod's port, an undertaking of extraordinary magnitude and complexity. Continued excavation of these blocks by Avner Raban and Chris Brandon (Pringle-Brandon Architects, London) has revealed evidence of the strikingly complex floating and submersible formwork into which this concrete was poured (barge-form being loaded). Was this block of concrete with a clear geological fingerprint pointing to the Bay of Naples an anomaly? Is it possible that all the raw material for the numerous concrete blocks and structures found at Caesarea were imported from Italy, or were appropriate local substitutes discovered and used? Did the basic mix of hydraulic concrete, first reported by Vitruvius c. 25 BC, change over time? How did the techniques of designing and deploying formwork and placing the concrete evolve over time? Can we see uniformity in composition of the concrete and design of formwork that might attest the activities of imperial architects following prescribed, standard procedures?

In order to answer some of these questions, in 2001 Oleson, Chris Brandon (architect, London) and Robert L. Hohlfelder (University of Colorado at Boulder) formed the ROMACONS project. We have been collecting and analyzing large core samples of hydraulic concrete taken from Roman submerged harbour sites and shoreline structures such as fish tanks around the Mediterranean basin. We plan to amass a large, geographically and chronologically diverse database that will serve as the beginning of the first comprehensive catalogue of hydraulic concrete used in Roman marine structures. Some specific goals of our investigations are:

1.  to analyse the concrete matrix of our samples to determine size, material, and proportions of micro and macro-aggregate.

2.  to identify the sources of pozzolana, tuff, and other aggregate used in the concrete structures studies.

3.  to compare the relative compressive strength and density of various concrete mixes.

4.  to determine the sequence and pattern of laying the concrete materials and aggregates and thus to reconstruct the delivery systems used to move and hold the concrete in position on the ocean floor while it cured.

5.  to assess the logistical systems employed for transport of massive quantities of raw material.

6.  to determine any compositional variations in the concrete samples collected from different geographical regions or chronological periods.

7.  where feasible, to compare cores from maritime structures with those from terrestrial structures at the same site to determine whether special formulas were used for the maritime construction.

8. finally, to investigate the practical challenges of building with hydraulic concrete through recreation of formwork and a pila in the sea with Roman type materials and procedures.

The team is uniquely qualified for this groundbreaking project. Oleson and Hohlfelder co-directed excavations at Caesarea from 1981-1985 and 1981-1990, respectively, and they both published extensively on the concrete and harbour design of King Herod's port. Oleson has published widely on ancient technology. Brandon has been one of the principal scholars studying hydraulic concrete found at Caesarea in the 1990s. He has also developed the methodology for drilling and recovering cores. The CTG Italcementi Group ( generously supplied the appropriate industrial concrete coring equipment for our use, and has agreed to carry out some analyses in their laboratories. The analyses have been carreid out by Dr. Emanuele Gotti, L. Bottalico, and R. Cucitore at the Italcementi laboratory in Bergamo.

At the start we identified numerous target sites in Greece, Turkey, France, Spain, Algeria, Tunisia, Libya, and Israel. The first phase of the project consisted of the investigation of the concrete at a number of Roman harbours in Italy. In March 2001, the ROMACONS team carried out reconnaissance at Cosa and numerous other sites where hydraulic concrete was extensively used (e.g. Portus, Antium, Puteoli, Astura, Terracina, Ponza, Egnazia, Baia, Misenum, etc.), to plan for future seasons of field work collecting samples. We also held discussions with Italian archaeologists whose research interests are relevant to our project (e.g., E. Felici and P. Gianfrotta), and we explored sources of tuff and pozzolana throughout Italy and collected samples of these materials. In August 2002 we began our field work by taking six cores from Claudian and Trajanic harbour structures at Portus, and the Neronian breakwater at Anzio (see preliminary reports of all our field season on this site). Subsequent campaigns were carried out at Cosa and Santa Liberata in 2003, Santa Liberata in 2004, Caesarea in Israel in 2005, Baia and Portus Iulius in 2006, Alexandria in Egypt and Chersonissos in Greece in 2007, at Egnazia in 2008, and at Pompeiopolis in 2009. In 2004 the team constructed a reproduction pila in the harbour of Brindisi with Vitruvian type concrete. During the three years since construction, we have taken cores from this pila at 6 month intervals.

The final publication of the project appeared in 2014 (see below).


For full information see the final publication:

Brandon, C., Hohlfelder, R.L., Jackson, M. and Oleson, J.P. Edited by J.P. Oleson. Building for Eternity: The History and Technology of Roman Concete Engineering in the Sea. Oxford: Oxbow Press, 2014. 325 pp. 320 figs.

Brandon, C., Hohlfelder, R.L., Oleson, J.P., and C. Stern, 2005. “The Roman Maritime Concrete Study (ROMACONS). The Roman harbour of Chersonisos in Crete and its Italian connection,” Mediterranée, 1.2: 25-9.

Brandon, C., Hohlfelder, R.L., and J. P. Oleson, 2008. “The Concrete Construction of the Roman Harbours of Baiae and Portus Iulius: The ROMACONS 2006 Field Season,” International Journal of Nautical Archaeology 37 (2008) 374-92.

Gotti, E., Oleson, J. P., Bottalico, L., Brandon, C., Cucitore, R, and R. L. Hohlfelder, 2008. “A Comparison of the Chemical and Engineering Characteristics of Ancient Roman Hydraulic Concrete with a Modern Reproduction of Vitruvian Hydraulic Concrete.” Archaeometry 50.4: 576-90.

Hohlfelder, R. L., Brandon, C., and J. P. Oleson, 2005. “Building a Roman pila in the sea – experimental archaeology at Brindisi, Italy, September 2004,” The International Journal of Nautical Archaeology 34.1: 123-27.

Hohlfelder, R. L., Brandon, C., and Oleson, J. P., 2007, “Constructing the Harbour of Caesarea Palaestina, Israel: New Evidence From the ROMACONS Field Campaign of October 2005,” The International Journal of Nautical Archaeology 36.2: 409-415.

Hohlfelder, R. L., Brandon, C., and Oleson, J. P., 2008. “The Roman Maritime Concrete Study:  Brief Summary of Fieldwork from 2002 to 2005,” pp. 297-304 in R. L. Hohlfelder, ed., The Maritime World of Ancient Rome. Memoirs of the American Academy in Rome, Suppl. 6. Ann Arbor: University of Michigan Press.

Oleson, J.P., Brandon, C., and R.L. Hohlfelder 2004. “The Roman Maritime Concrete Study (ROMACONS): Fieldwork at Portus, Anzio, Santa Liberata, Cosa, 2002-2003,” pp. 185-94 in F. Maniscalco (ed.), Mediterraneum. Tutela e valorizzazione dei beni culturali ed ambientali Vol. 4, Tutela del patrimonio culturale sommerso—Protection of Underwater Cultural Heritages, Naples.
Oleson, J. P., Brandon, C., Cramer, S. M., Cucitore, R., Gotti, E., and R. L. Hohlfelder, 2004. “The ROMACONS Project: A Contribution to the Historical and Engineering Analysis of the Hydraulic Concrete in Roman Maritime Structures,” The International Journal of Nautical Archaeology 33.2: 199-229.

Oleson, J. P., Bottalico, L., Brandon, C., Cucitore, R., Gotti, E., and R. L. Hohlfelder, 2006. “Reproducing a Roman Maritime Structure with Vitruvian pozzolanic concrete,” Journal of Roman Archaeology 19: 31-52.

Oleson, J.P., Brandon, C., and R.L. Hohlfelder 2008. “The Roman Maritime Concrete Study (ROMACONS): Activities to 2007,” pp. 325-29 in J. P. Delgado, ed., “Nautical and Maritime Archaeology, 2006-2007 Seasons,” American Journal of Archaeology 112: 307-35.



Brandon, Chris. “The Concrete-Filled Barges of King Herod's Harbor of Sebastos.” Pp. 45-58 in S. Swiney, R. Hohlfelder, H. Swiny, eds., Res Maritimae: Cyprus and the Eastern Mediterranean from Prehistory to Late Antiquity. Atlanta: Scholars Press, 1997.

Brandon, Chris. “Pozzolana, lime, and single-mission barges (Area K).” Pp. 169-78 in K. Holum, A. Raban, J. Patrich, eds., Caesarea Papers, 2. JRA Supp. 35. Portsmouth: JRA, 1999.

Gazda, Elaine K. “Cosa’s Contribution to the Study of Roman Hydraulic Concrete: An Historiographic Commentary.” Pp. 145-77 in N.W. Goldman, ed., Classical Studies in Honor of Cleo Rickman Fitch. New York: 2001.

Hohlfelder, Robert. “The Ports of Roman Baetica: A Preliminary Reconnaissance.” Journal of Field Archaeology 3 (1976) 465-68.

Hohfelder, R.L. “Procopius, De Aedificiis, 1.11.18-20: Caesarea Maritima and the Building of Harbours in Late Antiquity.” Mediterranean Historical Review 3 (1988).

Hohlfelder, R.L. “Building Harbours in the Early Byzantine Era: The Persistence of Roman Technology.” Byzantinische Forschungen 24 (1997) 367-80.

Hohlfelder, Robert L. “Building Sebastos: the Cyprus Connection.” International Journal of Nautical Archaeology 28 (1999) 154-63.

Hohlfelder, R.L., and R.L. Vann. “Cabotage at Aperlae in Ancient Lycia.” International Journal of Nautical Archaeology 29 (2000) 126-35.

Jackson, M, Marra, F., Deocampe, D., Vella, A. Kosso, C., and Hay, R., Geological observations of excavated sand (harenae fossiciae) used as fine aggregate in roman pozzolanic mortars, Journal of Roman Archaeology 20 (2007) 25-53.

Oleson, John Peter. “A Possible Physiological Basis for the Term Urinator, "Diver'.” American Journal of Philology 97 (1976) 22-9.

Oleson, John Peter. “Underwater Survey and Excavation in the Port of Pyrgi (Santa Severa), 1974.” Journal of Field Archaeology 4 (1977) 297-308.

Oleson, John Peter, R.L. Hohlfelder, A. Raban, L. Vann. “The Caesarea Ancient Harbor Excavation Project (C.A.H.E.P.): Preliminary Field Report on the 1979-83 Seasons,” Journal of Field Archaeology 11 (1984): 281-305.

Oleson, John Peter. “Herod and Vitruvius: Preliminary Thoughts on Harbour Engineering at Sebastos, the Harbour of Caesarea Maritima.” Pp. 165-72 in A. Raban, ed. Harbour Archaeology. Proceedings of the First International Workshop on Ancient Mediterranean Harbours, Caesarea Maritima, 24-28.6.83. British Archaeological Reports, Intl. Series, 257. Oxford: British Archaeological Reports, 1985.

Oleson, John Peter. “The Technology of Roman Harbours,” International Journal of Nautical Archaeology 17 (1988) 117-29

Oleson, John Peter, and Graham Branton. “The Technology of King Herod's Harbour.” Pp. 49-67 in R.L. Vann, ed., Caesarea Papers. Straton's Tower, Herod's Harbour, and Roman and Byzantine Caesarea. Journal of Roman Archaeology, Suppl. 5. Ann Arbor, 1992.

Oleson, John Peter, and Graham Branton. “The Harbour of Caesarea Palaestinae: A Case Study of Technology Transfer in the Roman Empire.” Mitteilungen, Leichtweiß-Institut für Wasserbau 117 (1992) 387-421.