Ancient construction experts around the world are renowned for creating structures that last for thousands of years. Whereas the lifespan of today’s buildings is usually only 50 to 100 years.
Therefore, more and more scientists are studying ancient materials, in the hope of learning something about how they have survived over the millennia.
irregular lime blocks
Roman architecture is an inspiration for many scientists. Many buildings have been built since 200 BC.
In a recent study, Admir Messick, a civil engineer at the Massachusetts Institute of Technology, and his team found that the strength of Roman concrete came from lime blocks scattered throughout the concrete panels, rather than being mixed evenly like modern techniques. Reason.
Admir Messick believes that some of the theories criticizing these “irregular” lime blocks suggest that the Romans did not mix the materials thoroughly. However, after conducting several analyzes of concrete samples from the ancient city of Privernum outside Rome (Italy), scientists found that this practice turned out to promote the “self-healing” ability of the material.
Messick explains that if cracks form on the structure, water can seep into the concrete. At this time, the water will “activate” the remaining lime blocks, causing chemical reactions to form a new mixture that can repair the damage.
Meanwhile, geologist Mary Jackson of the University of Utah (USA) discovered that the key may be hidden in the volcanic materials used by the Romans.
In particular, construction teams at the time often collected volcanic rocks left over from eruptions to mix into concrete. This material can react with certain natural elements to seal cracks that appear over time.
Mix building materials with juice
At Copán, an ancient Maya site in what is now Honduras, limestone structures and temples remain intact after more than 1,000 years in a hot and humid environment.
A study conducted in 2023 by a group of scientists from the University of Granada (Spain) revealed that the secret comes from plants.
Rodriguez-Navarro of the University of Granada visited local builders in Honduras to gain perspective by looking at samples of materials thousands of years old.
The team found extracts of local chukum and joyot trees in the Mayan lime mixture. While testing the recipe, the team added lime to water and added “juice” from the bark of chukum and geot trees. The team found that the resulting plaster was exceptionally durable, able to resist physical and chemical damage.
When they zoomed in on the material, the scientists discovered that some of the organic matter from this “juice” had become incorporated into the molecular structure of the building’s plaster. Thanks to this, Maya plaster can simulate strong natural structures such as sea shells and sea urchin spines.
Many other studies have found all kinds of natural ingredients like fruit extracts, milk, cheese curds, beer, even feces and urine mixed into ancient works.
The mortar used to assemble some of China’s most famous structures, including the Great Wall and the Forbidden City, contains traces of starch from glutinous rice.
Were ancient builders good or lucky?
Cecilia Pace, a materials scientist at the University of Sheffield (UK), believes that some of these ancient makers may have been lucky. In the old days, they could put just about anything into the mix, as long as it was cheap and readily available for the project. Over time, the remaining structures are the result of the right combinations, like a process of “natural selection”.
In contrast, Thirumalini Selvaraj, a professor at India’s Vellore Institute of Technology, believes that “strange” ingredients were deliberately added. According to Selvaraj’s research, in humid regions of India, builders used local herbs to help structures resist moisture.
Or along the coast, ancient builders said… Palm sugar may help limit the harmful effects of sea salt. In areas at high risk of earthquakes, they used a type of “floating brick” made from rice husks.
“They know the area, soil conditions and climate to make the right ingredients,” Selvaraj said.