Archaeologists have unearthed a significant find within the remnants of Pompeii, shedding light on the methods that enabled the Romans to construct their grand empire.

The excavation revealed a construction area that remained untouched by the catastrophic eruption of Mount Vesuvius in 79 AD. This site uncovers the secrets behind the Romans’ durable, self-repairing architecture that played a pivotal role in their architectural advancements.

For years, experts have been intrigued by the techniques and materials employed by the Romans, which have ensured the longevity of iconic structures such as the Pantheon and the Colosseum for over two millennia.

The discovery at Pompeii highlighted the Romans’ use of a process known as ‘hot mixing.’ This involved combining quicklime—dry limestone previously exposed to high temperatures—with water, volcanic rock, and ash. The reaction generated heat naturally, resulting in a robust building material.

The ancient site included several rooms filled with construction materials and shards of everyday ceramics, preserved for reuse during the restoration of the surrounding walls.

The Romans industrialized concrete, beginning in the first century BC and AD.

Admir Masic, a MIT  professor of civil and leader of the study, said: ‘Modern concretes generally lack intrinsic self-healing capability, which is increasingly important as we seek longer-lasting, lower-maintenance infrastructure.

Archaeologists excavating Pompeii uncovered an untouched construction site, revealing how the Romans created concrete that has withstood the sands of time

‘So while the ancient process itself is not a direct replacement for modern standards, the principles revealed can inform the design of next-generation durable, low-carbon concretes.’ 

An indispensable building material, concrete helped the Romans erect structures including stadiums like the Colosseum, domed temples like the Pantheon, public baths and other big buildings, aqueducts and bridges unlike any fashioned to that point in history. 

Because the concrete could harden underwater, it was vital for constructing harbors and breakwaters. 

‘Studying it truly felt as if I had traveled back in time and was standing beside the workers as they mixed and placed their concrete,’ Masic said. 

Pompeii was covered in ash when Mount Vesuvius erupted in 79 AD, killing everyone in its path and burying the area.

The town was forgotten until its rediscovery in the 1700s when researchers found dozens of bodies that had been preserved from the soot and ash that covered the streets, buildings and people.

Excavations of Pompeii began in 1748, and although Vesuvius’s eruption completely destroyed the city, the pyroclastic deposits preserved the victims, buildings and art.

The victim’s soft tissue had decayed over the millennia, but their outlines remained intact and were recovered by filling the cavities with plaster, thus preserving their DNA.

Pompeii was covered in ash when Mount Vesuvius erupted in 79 AD, killing everyone in its path and burying the area.

The Pompeii discovery showed the Romans used a technique called ‘hot mixing’ in which a material called quicklime, dry limestone that was previously heated, is combined directly with water and a blend of volcanic rock and ash, producing a chemical reaction that naturally heats the mixture

At the site, materials were carefully organized and stored by type. 

The atrium probably held pre-mixed dry lime and pozzolanic sand for making mortar, while room 28 stored tiles and stone. 

Water for mixing the dry materials was likely added at the fountain pool in room 2.

This organized system allowed workers to access what they needed quickly and keep construction moving efficiently.

Analysis showed that some mortar samples share a similar composition, suggesting they came from the same pre-mixed materials. 

Other samples had higher calcium levels, probably because extra lime was added to improve workability or strength for repairs and finishing layers. 

Evidence of lime stored in amphorae at the site supports this.

The team uncovered several rooms at the site, containing concrete materials and tiles to mend broken walls 

The team determined that materials, pozzolan, lime and aggregates likely came from the nearby Somma-Vesuvius area and were prepared consistently. 

Hot mixing left behind lime clasts with cracks and porosity, and was used both for 

Quicklime was hot-mixed with pozzolanic materials, while slaked lime was added later for finishing mortars and frescoes. 

 The structure of the mortar is dense and uniform, showing careful and consistent mixing. 

Over time, the lime and volcanic glass continued to react, filling voids and strengthening the concrete. This process even allowed the material to “self-heal,” reducing cracks and improving durability.

The victim’s soft tissue had decayed over the millennia, but their outlines remained intact and were recovered by filling the cavities with plaster, thus preserving their DNA

The excavation of Domus 1 in Pompeii shows that Roman builders had a highly organized approach. 

Dry materials were prepared and stored, water was added in controlled steps, and broken amphorae were used to transport mortar. Workers applied it with trowels, checked alignment with plumb lines, and shaped aggregates with axes.

Scientific analyses confirmed that Romans used hot mixing of quicklime for strong, durable mortar, supplemented with slaked lime for repairs and finishing layers. 

The pre-mixed dry materials were central to this strategy, allowing construction and repair work to proceed efficiently.

Understanding these methods can help modern restorers replicate original techniques for historically accurate and durable repairs. 

The study showed that both original construction and post-earthquake repairs relied on these advanced Roman mortar techniques, highlighting their careful planning and material knowledge.