The book under review presents the history, procedures and results of the Roman Maritime Concrete Survey (ROMACONS) conducted by Christoph J. Brandon, Robert L. Hohlfelder and John P. Oleson from the years 2002 to 2009. Although the authors stress that they have not written a general introduction to Roman concrete engineering, their publication is far more than just a report of their project. It is also a collection and translation of Greek and Roman written sources describing maritime concrete, a catalogue of known Roman maritime concrete structures as well as a detailed typology of Roman form-work design for maritime construction. Thus, it is of interest to not only students dealing with Roman concrete engineering, but also those concerned with the distribution of raw materials within the Mediterranean, the spread of technological innovations, and coastal archaeology in Roman Republican and Imperial times.
The book is divided into nine chapters and four appendices. After a brief introduction into the character of Roman maritime concrete and recent research on Roman concrete, the research questions of the ROMACONS are outlined. On the one hand, the project is concerned with technical aspects such as the regional and chronological variations in the composition of mortar. On the other hand, the authors address historical questions such as the distribution and logistics of transport, the architects and work forces that built Roman harbors, and the knowledge transfer of the use of volcanic ash in maritime concrete. The research of ROMACONS is based on 36 cores taken from maritime infrastructure of 12 different sites mainly located on the Italian peninsula, but also from sites in Greece, Turkey, Israel and Egypt. The cores were analyzed in a standard fashion using macroscopic and microscopic techniques, chemical analysis and mechanical testing by scientists of Italcementi in Italy.
Before giving a detailed account on the history of the ROMACONS and on the development and usage of the coring equipment, 32 passages of 16 ancient authors as well as two inscriptions concerned with maritime concrete in one way or another are presented. Each of these written sources is briefly introduced followed by the original Greek or Latin text with a translation by John P. Oleson and a short discussion. These new translations are strongly influenced by the newly gained knowledge of Roman maritime concrete by the ROMACONS and often correct older translations. The texts reveal different aspects of the technology and perception of littoral constructions. As a result, this collection is not only of interest for students of Roman concrete engineering but also for people working on ancient harbors and coastal sites.
Chapter 4 is labeled as “Narrative of the ROMACONS Fieldwork,” giving the impression of being a mere transcript of a field or laboratory book. The field work with its obstacles are described, and also the results for the interpretation and dating of several of the sides. Only a few of the many outcomes are briefly summarized here. For example, the oldest preserved/datable site where maritime concrete was used was the entrance channel to Portus Iulius in the Gulf of Pozzuoli from 37 BC, whereas the maritime installations at Cosa — previously dated to the late second or early first century — are most likely from the age of Augustus. The coring in the east bay of Alexandria revealed modification (the use of volcanic ash) to the harbor basin next to the submerged island of Anthirodos in early Imperial period. The construction techniques show strong similarities to the contemporary harbor of Caesarea Maritima. The volcanic ash used in the maritime concrete from the bay of Naples was not only used in maritime installations in Italy but also in harbors in the eastern Mediterranean such as Caesarea Maritima, Alexandria, Pompeiopolis in southern Turkey and Chersonesos on Crete.
Besides coring Roman maritime concrete, the authors also constructed a concrete pila of eight cubic meters in the inner harbor of Brindisi to analyze technical aspects of the production process, the setting of the mortar and the development of its maximum strength. In Chapter 5 the construction methods and the conclusions from this experimental archaeological project are described in detail. Brandon, Hohlfelder and Oleson used a passage from Vitruvius (5, 12, 2) on the composition of maritime concrete as a guideline for the construction of the pila. After the construction it was cored within several time intervals: this led to the discovery of striking similarities in structure and material to ancient pilae, which leads to the conclusion that the Vitruvian formula for pozzolanic concrete was correct.
The following catalogue (Chapter 6) is a collection of harbor installations, fish ponds and other elements of Roman maritime concrete in the Mediterranean. It briefly documents the maritime places by listing plans, recent literature, and longitudinal and latitudinal coordinates. Two-thirds of those places can be found in Italy because of the number of fish ponds built there in late Republican times as well as because of the comparatively advanced state of the current research in Italy. Nevertheless, the catalogue underlines the widespread use of volcanic ash in maritime concrete in the Mediterranean.
Chapter 7 is devoted to the material characteristics of maritime concrete cored by the ROMACONS and analyzed by Italcementi. The chief aim of this combined analysis of ancient texts and modern cement chemistry was to detect the sources for the coarse aggregates and the volcanic ash. While the former mainly derives from local sources, the origin of the latter is harder to determine. The samples removed from maritime installations of Italy are closest in mineral assemblages and trace elements of the volcanic ash coming from the Campi Flegrei. The removed material used for maritime concrete in harbors of the eastern Mediterranean most probably also originates from the Bay of Naples. This is especially surprising for the harbor of Chersonesos on Crete as deposits of volcanic ash would have been located far more conveniently on Aegean Islands such as Santorini. The analysis revealed a kind of standardized formula for maritime concrete that seems to have been based on practical experience in the mid to late first century BC.
This standardization in Roman maritime concrete construction is also underlined in Chapter 8 on the typology of formwork. Christopher J. Brandon classifies three different types of formwork that show several similarities in design and execution to ancient ship construction.1 The layout and construction process of the different types is illustrated with several drawings, thus, making it easy to follow the line of thoughts. Type 1 was a form constructed in situ in wood. It was the type used most widely, mainly in shallow or sheltered waters with a sandy sea bottom. Some local variations in Pompeiopolis, Kyme and San Cataldo were composed with ashlars as a permanent facing. Type 2 was also constructed in situ as a watertight cofferdam that could be drained of water and used for both hydraulic and non-hydraulic concrete. It is described by Vitruvius; however, its ancient usage has not been detected in the archaeological record so far. Furthermore, it is unknown how practical problems such as pumping out of the water were solved. Type 3 was a prefabricated form that was floated to the designated maritime construction side. This type was not mentioned by Vitruvius. Alhough their use must have been more widespread, only a few examples of prefabricated forms survived. Brandon not only adds prefabricated forms to Type 3 but also redundant ship hulls such as the huge vessel filled with concrete and sunk in the entrance of the Claudian basin of Portus.
The last chapter puts the research conducted by the ROMACONS in a wider Mediterranean context. The first part is devoted to the trade in volcanic ash and aggregates, and its transportation to the building sites. The analysis by the ROMACONS leads to the conclusion of a widespread long distance trade in volcanic ash from the Bay of Naples to several sides in the Mediterranean. For the transport to the harbor of Caesarea Maritima, Robert L. Hohlfelder thinks of the volcanic ash being used as ballast/primary cargo of the large grain freighters sailing from Puteoli first to Caesarea Maritima and from there further to Alexandria. The volcanic ash might not only have been spread by direct trade, but also by indirect trade. Merchants/ship owners could have loaded the volcanic ash as secondary cargo or ballast on their vessels, thus, being one factor for the wide spread usage of this material in maritime concrete. Concerning the indirect distribution of the material, however, Hohlfelder does not discuss the issue of the ownership of the sites where the volcanic ash was extracted. While the beach from which sand for the ballast of ships in Portus was taken was reserved for the saburrarii,2 the stretches of land with the best spots for exploiting volcanic ash along the Bay of Naples are likely to have been in private or imperial ownership.
The second part of the chapter deals with the spread and transfer of innovation in maritime concrete. The technological similarities between late Republican fish ponds and early Imperial harbor constructions indicate that the combination of maritime concrete with formworks was first developed along the shores of Campania and Latium in the second and first century BC. The further spread of this technology was fundamental for the development of extensive harbor works in the age of Augustan and the following decades for the economic and military expansion of the empire. As John P. Oleson underlines, the innovation was spread not only by merchants/ship-owners together with the raw material, but also through technical literature in Latin (now lost) intended for practical everyday use. A knowledge transfer must have taken place between the contemporary harbors of Caesarea Maritima and Alexandria during their construction phase. This transfer was most likely based on military engineers trained while building the imperial harbors in the Bay of Naples.
The book is well produced with several photographs, maps and plans. A glossary of technical terms is helpful for readers unfamiliar with Roman concrete structures. Three further appendices give detailed descriptions and photographs of the cores taken by the ROMACONS as well as of the compositional analyses of various components. This monograph is a major contribution to our understanding of the techniques and usages of Roman maritime concrete in the Mediterranean due to its wide scope, the state-of-the-art methods applied, the regionally and chronologically wide range of sites, as well as its attendant detailed analyses of these issues.
1. This classification was published in an earlier version as Christopher Brandon, Cements, Concrete, and Settling Barges at Sebastos: Comparisons with Other Roman Harbor Examples an the Description of Vitruvius, in: A. Raban – K. G. Holum (edd.), Caesarea Maritima. A Retrospective After Two Millennia, Leiden, 1996, 25-40.
2. Boudewijn Sirks, Food for Rome, Amsterdam, 1991, 265; Dorothea Rohde, Zwischen Individuum und Stadtgemeinde. Die Integration von collegia in Hafenstädten, Mainz, 2012, 183.