This article is from
Creation 41(1):19, January 2019

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Ancient Roman concrete

… just like natural rock

by Jonathan O’Brien

The ancient Romans used a type of concrete that is far more durable in seaside applications than our modern concrete. Modern cement in constant contact with the sea eventually weakens, and the steel reinforcing inside then rusts as salty water travels into cracks in the structure. It takes only a few decades for the concrete to begin crumbling away.¹

However, Roman marine concrete actually cured into a very tough material identical to hard rock. Two millennia old Roman piers and breakwaters are still standing rock-solid today.

Natural processes

Scientists recently reported studying the ancient concrete to learn why it cured into such an enduring state. The Roman recipe of lime,² volcanic ash, and rock aggregate, mixed together with seawater, produced a concrete that under the microscope looks like natural rock.³ The scientists found that the mineral microstructure had grown stronger because of a naturally occurring chemical reaction between the lime and the ash in the presence of seawater, forming strong bonds between crystals.

Their results reveal one of the ways in which natural sedimentary formations can lithify (harden) very rapidly into rock. Pliny the Elder, writing in ancient times, recognized the correlation between natural rock, and man-made concrete.⁴ He described the rock-like cement produced by volcanic ash:

“Who, indeed, cannot but be surprised at finding the most inferior constituent parts of it, known as “dust” only, on the hills about Puteoli, forming a barrier against the waves of the sea, becoming changed into stone the moment of its immersion, and increasing in hardness from day to day—more particularly when mixed with the cement of Cumæ? There is an earth too, of a similar nature found in the districts about Cyzicus; but there, it is not a dust, but a solid earth, which is cut away in blocks of all sizes, and which, after being immersed in the sea, is taken out transformed into stone. The same thing may be seen also, it is said, in the vicinity of Cassandrea; and at Cnidos, there is a spring of fresh water which has the property of causing earth to petrify within the space of eight months. Between Oropus and Aulis, every portion of the land upon which the sea encroaches becomes transformed into solid rock.”⁵

Volcanic ash is not a requirement, however, for producing sedimentary rock. For instance, many natural sandstone formations are composed only of sand grains cemented by lime minerals. Abundant volcanic ash was available only in some areas of the world during the formation of the local geology, but wherever present, the ash often resulted in a tougher rock.

Rapid sedimentation and hardening

During the global Flood of Noah’s day, God caused the sea to rise and cover the land of the whole earth. The Flood lasted a year and involved widespread tectonic movement, break-up of the earth’s crust, and erosion and sedimentation on a massive scale. Volcanism was intense in places, and abundant evidence for this can be seen in many geological formations throughout the world. Both water-borne sediments and volcanic ash falls accumulated in sedimentary basins across the earth.

There is also geological evidence that vast quantities of lime minerals were present during the Flood, likely dissolved in subterranean waters that rose to the surface of the earth. These rock-making ingredients combined with seawater to create a perfect recipe for rapid sedimentary rock formation. Roman marine concrete provides an insight into how the world’s Flood deposits quickly hardened into the enduring sedimentary landforms we see around us today.