NAME: Concetta (Tina) Rispoli
CURRENT TITLE: PhD Candidate (Thesis in progress!) at University Federico II of Naples (Italy)
PROJECT TITLE: Roman mortars: mix design, composition and secondary minerogenetic processes
LOCATION: University Federico II of Naples, Italy
TIMELINE: 3 years
AREA OF EXPERTISE: Applied mineralogy, archaeometry, and geoarchaeology. I have been studying Roman mortars, concrete and geomaterials since 2011. These materials are the main object of my research.
EDUCATION: Bachelor’s degree in geology, Master’s degree in geology and applied geology and innovative diagnostic methodologies for the safeguard, use and conservation of cultural heritage is my thesis in postgraduate school.
What’s the purpose of your project?
The aim of this research project was to improve the understanding of Roman construction techniques by means of detailed microstructural and compositional examination of the: a) cementitious binding matrix, and b) aggregates, to point out both mortars’ mix-design and provenance of raw materials both secondary minerogenetic processes and comparing the obtained results with the modern mortars. Several archaeological sites were chosen for mortar sampling, in particular those related both to ancient Roman structures built in subaerial environments, submerged later by seawater, and suitable structures in contact with “fresh” water (e.g. thermal baths and cisterns).
How are you setting up and testing your project?
The collected samples were used for an integrated analytical program using multiple methodologies such as: optical microscopy (OM) studies on thin sections, X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) analysis, energy-dispersion X-ray spectroscopy (EDS), X-ray fluorescence (XRF), thermal analyses (TGA-DTA) and mercury intrusion porosimetry (MIP).
Any results yet?
“Analysis of Roman mortars sheds light on existing modern concrete blends that have been used as more environmentally friendly partial substitutes for Portland cement, such as volcanic ash or fly ash from coal-burning power plants. The adopted materials and production techniques used by the ancient Romans could produce longer-lasting concrete that generates less carbon dioxide. It was estimated that pozzolan, which can be found in many parts of the world, could potentially replace ’40 percent of the world’s demand for Portland cement.’ If this is the case, ancient Roman builders may be responsible for making a truly revolutionary impact on modern architecture — one massive concrete structure at a time.” (Pruitt, 2013).
Recent studies using a variety of advanced microscopic and analytical techniques reveal that the cementitious hydrates of the ancient sea-water mortars show a fascinating range of compositions and microstructures which are astonishingly intricate, and beautiful in their own right . The principal poorly-crystalline cementitious component, calcium-aluminium-silicate-hydrate (C-A-S-H) ( Stanislao et al. 2011), is the focus of studies of environmentally-friendly concretes and mortars that incorporate diverse supplemental materials, including volcanic ash and industrial waste products, to replace kiln-fired Portland cement.
In some concrete and mortars, the principal crystalline cementitious component, Al-tobermorite, is a calcium-aluminium-silicate-hydrate mineral, with 11Å interlayer spacing, which occurs rarely in hydrothermal geologic environments such as Surtesy (Iceland). The crystals have a myriad of industrial applications but, at present, can only be produced in small quantities through laboratory syntheses at elevated temperatures (80 to 200°C) which is substantially higher than those that occur in conventional moist, air-cured concretes. For this, I had the good fortune to participate in the International Continental Drilling Program (ICDP) drilling project called SUSTAIN: System for thermophiles, Alteration Processes and ICDP. This project will include drilling through the 50-year-old Volcano edifice of Surtsey, the youngest of the Vestmannaeyjar Islands along the southern coast of Iceland to perform interdisciplinary time-lapse investigations of hydrothermal and microbial interactions with basaltic tephra.
Determination of rates of reaction and phase-stability relationships in the evolving Surtsey tuff as a function of time, temperature, and fluid interactions will provide an exceptionally well-constrained geological analog for innovative, pyroclastic rock concrete encapsulations of hazardous wastes that use ancient Roman concrete as a prototype. The formation of Al-tobermorite and phillipsite in massive Roman seawater concrete harbor structure and in some Roman mortars is in part controlled by elevated calcium-aluminum-silicate-hydrate (C-A-S-H) cementitious binder due to exothermic reactions, but these processes are poorly understood (Jackson et al., 2013).
What has been the most interesting/challenging?
The study of these geomaterials is very interesting, especially trying to understand the “secrets” of such enduring resistance. Actually the cisterns or Villae built by the Romans resisted the forces of waves and weathering of seawater for over two thousand years. They are a tangible example of a transformation product of geological materials (precisely, a geomaterial) that can last so long during the eras.
Even today the concept of “durability” is of great interest. The current concrete technologists try constantly to improve their formulations to achieve new special concrete to be able to resist to the aggressive agents such as seawater and sulphates.
The real challenge consists in receiving approval from the superintendent of interest to be able to perform the sampling and successive laboratory analysis, based on specific criteria such as: little invasivity, representativeness with limited sample size, and visual impact.
How will this project help society?
This project deals with the study of archaeological heritage. The archaeological heritage, as well as being a heritage of extraordinary beauty, belongs to our history and is essential to understand who we were and how we have become to be the people we are today.
This study represents an important contribution to any restoration work that allows the archaeological site to resist for so many years.
Defending this extraordinary heritage from aggression, selfishness, speculation and neglect means guarding our national identity, which is based on the beauty of a landscape inextricably linked to the work of human beings.
Stanislao, C., Rispoli, C., Vola, G., Cappelletti, P., Morra, V., and de’Gennaro, M. (2011) Contribution to the knowledge of ancient Roman seawater concretes: Phlegrean pozzolan adopted in the construction of the harbor at Soli-Pompeiopolis (Mersin, Turkey). Periodico di Mineralogia, 80, 471-488.
, M.D., , , , C., , R., , P., , A., , , S., , G., , H., Mineralogical Society of America, Volume 98, pages 1669–1687.
Brandon, C.J., Hohlfelder, R.L., Jackson, M.D., Oleson, J.P. (2013) Building for Eternity: The History and Technology of Roman Concrete Engineering in the Sea: Oxford Books.
M. D. Jackson, M. T. Gudmundsson , W. Bach, P. Cappelletti , N. J. Coleman , M. Ivarsson, K. Jónasson, S. L. Jørgensen , V. Marteinsson, J. McPhie, J. G. Moore, D. Nielson, J. M. Rhodes, C. Rispoli, P. Schiffman, A. Stefánsson, A. Türke, T. Vanorio, T. B. Weisenberger, J. D. L. White, R. Zierenberg, and B. Zimanowski (2015) – Time-lapse characterization of hydrothermal seawater and microbial interactions with basaltic tephra at Surtsey Volcano. Scientific Drilling, 20, pages 51–58.
For more information on Tina, see her A Day in the GeoLife Series guest blog about her typical day and advice for students.