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Roman Concrete Healed Its Own Cracks. A Startup Is Bringing It Back.
DMAT cement (named for the tech company DMAT) was developed in an effort to replicate ancient Roman concrete, which has long been known to be particularly robust over time.
Research into this material suggests that Roman builders would sometimes add highly reactive pieces of lime into concrete using a process called hot mixing. Afterward, if water entered the concrete, those lime inclusions would seal small cracks. From this principle, DMAT was born.
The Pantheon’s dome, still the largest unreinforced concrete dome in the world nearly 1,900 years after it was poured. Photo: Livioandronico2013, CC BY-SA 4.0. Via Wikimedia Commons.
The Romans themselves referred to this special material as opus caementicium. Made of pieces of stone or broken building material embedded into mortar, it usually looked more like rubble held together by mortar than the smooth, consistent concrete that is common today.
Combined with lime, water, and volcanic materials that could react with the lime, it became highly resistant to damage. Pozzolana, the volcanic material most commonly found near the Bay of Naples (and named because the region was called Pozzuoli), is one of the distinguishing features that makes opus caementicium stand out.
The Role of Concrete in Roman Construction
The Baths of Caracalla in Rome. The brick facing is a surface treatment; the mass behind it is concrete. Photo: Paolo Villa, CC BY-SA 4.0. Via Wikimedia Commons.
Before concrete, the sprawling monuments and structures associated with ancient archaeological sites usually depended on cut stone that could carry its own weight. The advent of concrete allowed builders to circumvent this need, creating curves, vaults, domes, and other shapes that would formerly have collapsed. This is why Roman architecture has such an iconic look, especially vis-à-vis what came immediately before it.
However, Roman construction still took on a variety of forms. Wall-facing techniques, which changed what the external surface of a building looked like, could significantly alter aesthetics without changing the underlying structure. And increasingly, that underlying structure relied on Roman concrete.
The Pantheon, for instance, is the world’s largest unreinforced concrete dome. Roman builders achieved this by manipulating the aggregate; in other words, they used the heaviest concrete additions (e.g., pieces of broken building) at the bottom and waited until the top to include the lightweight volcanic materials. Thus, there’s no single recipe for “Roman concrete.” Builders adjusted for each project.
The composition of cement becomes even more nuanced when considering concrete made specifically for maritime uses. Harbor installations, breakwaters, piers, and poles would all harden when exposed to water due to the pozzolanic material, which made it especially robust. This also stimulated the local economy, which required large quantities of this valuable volcanic material to be quarried and shipped long distances to skilled laborers.
Why Has Concrete from Rome Lasted So Long?
The exposed concrete core of a tomb on the Via Appia Antica, stripped of its facing. This rubble-in-mortar texture is what opus caementicium actually looked like. Photo: MM, public domain. Via Wikimedia Commons.
While it is true that many Roman structures have collapsed despite the concrete used in them, it is also true that a surprising number have survived.
Historians attribute this longevity to numerous causes. First, of course, is the pozzolanic chemistry of the concrete. Volcanic materials reacting with lime and water create mineral binders that remain durable over time.
However, studies have also found that these chemical reactions can continue over extremely long periods. That means that even years after being constructed, some of these buildings were undergoing additional mineral formation, shoring up damage.
Roman Concrete in Modern Times
Pompeii, with Vesuvius behind it. Excavations here have yielded evidence of how Roman builders prepared their dry materials. Photo: ElfQrin, CC BY-SA 4.0. Via Wikimedia Commons.
A large portion of DMAT’s research in the modern day is focused on lime clasts. These white pieces present in Roman concrete have long been thought to be symptoms of poor mixing, but the DMAT team suggests that Roman builders might have used them on purpose through a technique called hot mixing.
This requires using quicklime (calcium oxide) instead of slaked lime (quicklime that has already been mixed with water). Because water hadn’t already been used in the mixture, concrete made using hot mixing would react with water later.
Researchers’ hypotheses were further confirmed in Pompeii, when they discovered direct evidence in 2025 that Pompeian builders had prepared piles of dry ingredients ahead of a project, and those materials already included intact quicklime fragments. This all but confirmed that hot mixing was the method of choice at the time.
Modern ready-mix concrete. Portland cement and steel reinforcement bought speed and predictability — but not the ability to reseal a crack. Photo: Fauzan, CC BY-SA 3.0. Via Wikimedia Commons.
When researchers examined Roman concrete containing lime clasts, they discovered that if they cracked it, damage up to around 0.5 millimeters could heal itself. But by the time that masonry had evolved into new forms in the 19th century, techniques had changed.
In 1824, English bricklayer Joseph Aspdin patented a binder called Portland cement. This binder became one of the most common inclusions in modern cement, as did steel reinforcement, to make masonry what we know it today.
These changes may not have the self-healing power of Roman cement, but they offer other benefits. They provide much more consistency and predictable strength, and buildings can be constructed in record time. But for Masic and Sabatini, the cofounders of DMAT, these modern solutions could be improved by learning from what the Romans did.
Based on their research, MIT has reported that DMAT’s technology could extend a structure’s lifespan by as much as 50% while reducing carbon emissions by 60% compared to conventional concrete.
DMAT’s endeavors to learn more about how Roman concrete functions on a molecular level demonstrate one of the most powerful elements of history: that it can continue to influence the present. For DMAT, the Roman approach to masonry carries significant untapped potential.
It is impossible to say what other historic inventions could be holding similarly revolutionary ideas, but it only takes people like Masic and Sabatini to discover potentially invaluable insight our ancestors once held, now forgotten or misunderstood.
Already, DMAT has made their concrete available for complex infrastructure across Europe, including for use in pavement, road barriers, and water tanks. The team plans to expand into the United States, and they hope to make their material the industry standard, maintaining the reliability and consistency of modern concrete while significantly improving durability and reducing emissions.The post Roman Concrete Healed Its Own Cracks. A Startup Is Bringing It Back. first appeared on History Defined.
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