Unveiling the secret of ancient Maya masons: Biomimetic lime plasters with plant extracts

Abstract

Ancient Maya produced some of the most durable lime plasters on Earth, yet how this was achieved remains a secret. Here, we show that ancient Maya plasters from Copan (Honduras) include organics and have a calcite cement with meso-to-nanostructural features matching those of calcite biominerals (e.g., shells). To test the hypothesis that the organics could play a similar toughening role as (bio)macromolecules in calcium carbonate biominerals, we prepared plaster replicas adding polysaccharide-rich bark extracts from Copan’s local trees following an ancient Maya building tradition. We show that the replicas display similar features as the organics-containing ancient Maya plasters and demonstrate that, as in biominerals, in both cases, their calcite cement includes inter- and intracrystalline organics that impart a marked plastic behavior and enhanced toughness while increasing weathering resistance. Apparently, the lime technology developed by ancient Maya, and likely other ancient civilizations that used natural organic additives to prepare lime plasters, fortuitously exploited a biomimetic route for improving carbonate binders performance.

From Nanoparticles to Gels: A Breakthrough in Art Conservation Science

“… 135 Inspiration in designing novel sustainable materials with enhanced properties can also come from ancient civilizations and cultures, where nanomaterials and interfacial phenomena were exploited based on empirical knowledge. Examples include archeological or paleontological materials that survived to recent times, 136 or the enhanced properties of Maya plasters (that mixed biomacromolecules in calcium carbonate biominerals) 137 and Roman cement. 138 With today’s awareness and scientific understanding of colloidal and interfacial processes, the time thus is ripe for a new, sustainable breakthrough in the preservation of works of art.…”

Exploring the Potential of Nonclassical Crystallization Pathways to Advance Cementitious Materials

“…Rodriguez-Navarro et al have shown that, most likely without knowing, the Mayas masons used a biomimetic strategy to produce superior binders involving the incorporation of organics in between and inside the calcite crystals (Figure ). This gave the mortar a plastic behavior and a higher toughness while increasing its resistance to weathering processes . This biomimetic approach is really promising for improving the properties of CASC.…”

“…In addition to exerting polymorphic control, the occlusion of organics within the carbonated products could be exploited to create biomimetic organic–inorganic hybrid structures, which exhibit superior mechanical performance compared to pure calcium carbonate phases (see Section ). Interestingly, this phenomenon has been observed in the lime-based mortars of Copán (Honduras), relics of ancient Mayan craftsmanship, which stand out as some of the most durable lime plasters on the planet . There is evidence that Maya masons used plant extracts rich in polysaccharide, that could be the key behind the incredible durability of their lime-based materials.…”

“…Interestingly, this phenomenon has been observed in the lime-based mortars of Copán (Honduras), relics of ancient Mayan craftsmanship, which stand out as some of the most durable lime plasters on the planet. 305 There is evidence that Maya masons used plant extracts rich in polysaccharide, 306 that could be the key behind the incredible durability of their lime-based materials. Rodriguez-Navarro et al have shown that, most likely without knowing, the Mayas masons used a biomimetic strategy to produce superior binders involving the incorporation of organics in between and inside the calcite crystals ( Figure 41 ).…”

Short-Term Effect of Biopolymer-Based Coatings on Surface Hardness and Color of Limestone Exposed to Tropical Outdoor Conditions

“…Biopolymers extracted from cactus plants, rice (amylopectin), and tree bark are considered "traditional natural materials", and their use has transcended generations through oral information and local practice, which has allowed for their biotechnological application in the field of conservation and restoration [5][6][7]. Recently, Rodriguez-Navarro and coworkers [8], using a multidisciplinary approach, elegantly demonstrated that polysaccharide-rich bark extracts from Mayan trees contributed to the production of a calcite cement with meso-to-nanostructural features, matching those of calcite biominerals (e.g., shells). These authors proved the hypothesis that organics (biopolymers) could play a similar toughening role as (bio)macromolecules in calcium carbonate biominerals.…”