The ancient roman architecture — the temple of god, the coven, the trough — is still standing for 2,000 years. In contrast, many modern concrete buildings have been damaged for decades. What makes ancient roman cement so long? Scientists have recently solved the mystery of this millennium and found that the building materials of the ancient romans contain intelligence that is not yet fully mastered by modern engineering。
The main component of modern concrete is portland cement, which is made up of limestone and clay scavengers, and hydrochemical reaction after water has been added to form a hardened body. However, this concrete is easily damaged by seawater erosion and usually has a useful life of 50 to 100 years. The ancient roman cement can be soaked in the sea water for 2,000 years and even hardened。
The secret is a special ingredient: ash. The ancient romans mixed lime with ash from the bozoli region, creating a material called “roman cement”. This ash is rich in aluminum silicate, with slow chemical reactions with lime and water, and produces a crystallized mineral called quartz。
In 2017, an international team of scientists from the united states, italy and china revealed microsecrets of ancient roman cement through advanced analytical techniques. They found that ancient roman cement contained a unique combination of minerals, including quail, calcium hydrosilicate and calcium hydroxide. Most crucially, these minerals continue to react over a long period of time, constantly “rehabilitating” small cracks。
When a crack emerges, the water penetrates into the unreactive components of the dissolved cement, re-clining in the crack to form a new quartz, thereby “healing” the crack. This self-rehabilitation capacity is lacking in modern concrete. When modern concrete cracks, moisture and salinity accelerate the erosion of internal steel bars, leading to structural damage。
Ancient roman cement is particularly good in the seawater environment. Chloride in seawater erodes steel bars in modern concrete, but has little effect on ancient roman cement, which is rarely used in ancient roman buildings. More importantly, sulphate in seawater reacts with aluminides in ancient roman cement, generating more quarries and further strengthening structures。
Ancient roman engineers have long recognized the superiority of this material. Old prinni has documented in natural history that the best cement uses pozoly ash, which, when mixed with lime, “not only hardens in air, but also becomes stronger in water”. Vitruway described cement formulations and construction techniques in detail in the ten building books。
Interestingly, the ancient roman cement formulas were lost in the middle ages. This may be partly due to disruptions in the supply of ash from the bozoli volcano or to changes in construction technology. Until the eighteenth century, engineer john smitton rediscovered similar principles, developed water hard lime for the construction of the edition lighthouse and initiated modern cement research。
Twenty-first century scientists are working on “reverse engineering” of ancient roman cement. The research team at the university of california at berkeley successfully replicated the ancient roman cement formula and tested its self-rehabilitation capability. They found that the durability of ancient roman cement stemmed not only from volcanic ash but also from carefully controlled mixing ratios and construction processes。
The ancient roman engineers used the stratification technique to moderate the thickness of each layer to ensure adequate response. They also add bones such as bricks and pottery to improve material performance. These practices reflect the deep understanding of materials science among the ancient romans, although they do not know the chemistry behind them。
The rediscovery of ancient roman cement is an important inspiration for modern architecture. First, it provides a more sustainable building material. The production of portland cement requires high temperatures, energy consumption and carbon dioxide emissions. The production temperature of ancient roman cement is lower and the carbon footprint is smaller。
Second, the self-rehabilitation capacity of ancient roman cement can significantly extend the building life and reduce maintenance costs. Researchers are trying to apply similar principles to modern concrete and to develop “smart concrete” materials。
Thirdly, ancient roman cement is of particular value in seawork buildings. As sea-level rise and coastal erosion increase, more durable marine engineering materials are needed. An ancient roman cement formulation may provide solutions to this。
However, the full implementation of ancient roman cement faces challenges. Its intensity is slower and its early intensity is lower than that of modern concrete. The ancient roman structures are mostly built on the weight of the stone itself. Modern buildings rely on steel and concrete, requiring rapid hardening of materials to support construction progress。
Scientists are looking for balanced solutions — the development of hybrid materials that integrate ancient roman wisdom and modern technology. For example, the addition of a modest amount of ash in portland cement increases durability and maintains sufficient early intensity. This “green concrete” has been applied in some projects。
The story of ancient roman cement reminds us that ancient technology may contain wisdom that has not yet been fully recognized. In pursuing innovation, we should not lose sight of historical experience. The knowledge accumulated by ancient roman engineers through repeated experiments, after 2,000 years of testing, remains worthy of an in-depth study of modern science。
The concrete dome of the great temple, 43 metres in diameter, has not been surpassed for 2,000 years. It shows not only the architectural achievements of ancient rome, but also the miracle of material science. Next time you stand in front of ancient roman monuments, think about these stones and cements, which contain the deep understanding of the natural materials of ancient engineers and their commitment to eternal buildings。
The durability of ancient roman cement ultimately stems from awe and exploitation of nature. Instead of trying to conquer materials, the ancient romans have learned to cooperate with them, understand their characteristics and adapt to their patterns. This philosophy is perhaps more worthy of learning than the specific formulation — while pursuing speed and efficiency, not forgetting the power of patience and respect for nature。
