We often look with wonder at the buildings of the past, wondering sometimes with a paternalistic air, how it was possible that the ancients built those buildings. And the truth is that these structures still keep some secrets. The last to be revealed is the mortar used by the ancient Mayas.
A long-lasting mix. A team of researchers from the University of Granada has managed to unravel the recipe that the Mayans used to create lime mortars and stuccos with which they fixed the rest of the materials in their constructions. The compound was not only based on inorganic materials but also took advantage of compounds such as those that give the shells of mollusks their characteristic hardness.
The mixtures they used contained a cement of calcite crystals (CaCO3). According to the researchers, these crystals contain biomaterial-like nano- and mesostructural (ie, on scales between the atomic and micrometer) characteristics, including calcite, that make bivalve shells so strong.
“Until now, it was not known what was the secret by which the monuments built by the ancient Mayan builders, in many cases, currently present an excellent state of conservation, despite having been exposed for more than a thousand years to a very aggressive tropical climate” explained Carlos Rodríguez Navarro, one of the authors of the study, in a press release.
More than 1,000 years standing. The researchers analyzed in their work the archaeological site of Copán, located in western Honduras. What are now well-preserved ruins was once one of the most important Mayan cities of the Mesoamerican classic period. The city was built between the 4th and 9th centuries, rediscovered by the Spanish conquerors in the 16th century and excavated as early as the 19th century.
The researchers tried to verify if the construction techniques present in the cultures of the area today could be linked to pre-Columbian architectural uses, so they began to investigate the possible parallels.
These contemporary techniques include the use of organic compounds in lime mortars as a hardening compound. And it is that organic calcites, as in the case of mollusk shells, show higher levels of hardness than inorganic ones.
Thanks to technical advances. For their analysis, the researchers turned to high-resolution analyzes such as transmission electron microscopy (TEM) and high-resolution X-ray diffraction through synchrotron radiation, the authors explain. They thus managed to verify the similarities between ancestral and modern techniques.
“To do this, we prepared replicas of lime mortars dosed with extracts rich in polysaccharides from the bark of common trees in the Mayan area, such as the chukum (Havardia albicans) and the jiote (Bursera simaruba),” explained Rodríguez Navarro. “Our analytical results demonstrate that the replicas have characteristics similar to those of ancient Maya mortars and stuccos that contain organic compounds.”
Details of the research have recently been published in an article in the journal Science Advances.
Biomimetismo ancestral. The human being has always tried to imitate the techniques and tricks that we observe in our environment for their own benefit. Yet it is only now that we have given this imitation a name: biomimicry.
The use of organic materials to create more resistant structures is an archaic example of something that we can see today, from the shape of some airplanes to the sonar of submarines. Understanding how to benefit from the tricks created from millions of years of evolution can help us in many of our projects as humanity.
As the researchers involved in this latest discovery point out, this one is no exception. One day, materials based on these discoveries could be used in a variety of fields, from heritage preservation to the construction of new, more sustainable buildings.
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Imagen | Hans Birger Nilsen
