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Current Commentary: Roman concrete for durable, eco-friendly construction – applications for tidal power generation, and protection against sea level rise

Posted on 9. May, 2018.

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A recent study has provided further insight into the cause of the remarkable durability of Roman concrete. As is stressed in the paper, the Ancient Romans were well aware of the robustness of their concrete, which they named opus caementicium.

Pliny the Elder recorded in his Naturalis Historia, ‘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’; while the Roman engineer and architect, Vitruvius, wrote in the first century BCE of ‘a kind of powdery earth (pulvis) that by its nature produces wonderful results’, and that when ‘...pumiceous ash (pulvis), lime (calx), and tuff (tofus) ... are brought together in one mixture, and suddenly they are put into contact with [sea-] water, they cohere into a single mass, quickly solidifying, hardened by the moisture, and neither the effect of he waves nor the effect of water can dissolve them’. 

The fact that some of their marine structures, including seawalls and harbour piers, still remain standing, and in good condition after 2,000 years, attests to the remarkable robustness of Roman concrete, which might be used for the construction of modern seawalls, and for such tidal electricity generation facilities as the proposed Swansea Bay tidal lagoon power station, rather than the kinds of concrete that are now typically employed, which are eroded by the impact of the waves over far shorter periods of time. It is clear that the Romans exercised a considerable amount of effort and ingenuity in arriving at the correct formulation of their concrete, whose remarkable durability appears to be due to the presence of poorly crystalline, calcium-aluminum-silicate-hydrate (C-A-S-H binder) in the cementing matrix of the mortar, the sequestration of chloride and sulfate ions in discrete crystalline microstructures, and, as recently identified, the pervasive crystallisation of Al-tobermorite throughout the fabric of the material, frequently in association with the zeolite, phillipsite. Al-tobermorite is a rare, layered, calcium-silicate hydrate mineral composed of aluminosilicate chains bounded by an interlayer region and a calcium oxide sheet, and it is the widespread presence of tobermorite which prevents cracks from extending through the structure of the concrete, and maintains its integrity over time.

Read the full article in Science Progress, Volume 101, Number 1, March 2018, pp. 83-91(9).


Author: Christopher J. Rhodes
Fresh-lands Environmental Actions, 88 Star Road, Caversham, Berkshire RG4 5BE, UK

Keywords: Roman concrete, cement, tobermorite, phillipsite, seawall, tidal power, Swansea tidal lagoon, climate change, fly ash, sea level rise

Image: Complex sample of phillipsite along with herschelite from Mount Etna, Sicily, Italy. Credit: Didier Descouens,