Hot mixing: Mechanistic insights into the durability of ancient Roman concrete.

Ancient Roman concretes have survived millennia, but mechanistic insights into their durability remain an enigma. Here, we use a multiscale correlative elemental and chemical mapping approach to investigating relict lime clasts, a ubiquitous and conspicuous mineral component associated with ancient Roman mortars. Together, these analyses provide new insights into mortar preparation methodologies and provide evidence that the Romans employed hot mixing, using quicklime in conjunction with, or instead of, slaked lime, to create an environment where high surface area aggregate-scale lime clasts are retained within the mortar matrix. Inspired by these findings, we propose that these macroscopic inclusions might serve as critical sources of reactive calcium for long-term pore and crack-filling or post-pozzolanic reactivity within the cementitious constructs. The subsequent development and testing of modern lime clast-containing cementitious mixtures demonstrate their self-healing potential, thus paving the way for the development of more durable, resilient, and sustainable concrete formulations.

On the production of ancient Egyptian blue: Multi-modal characterization and micron-scale luminescence mapping.

The ancient pigment Egyptian blue has long been studied for its historical significance; however, recent work has shown that its unique visible induced luminescent property can be used both to identify the pigment and to inspire new materials with this characteristic. In this study, a multi-modal characterization approach is used to explore variations in ancient production of Egyptian blue from shabti statuettes found in the village of Deir el-Medina in Egypt (Luxor, West Bank) dating back to the New Kingdom (18th-20th Dynasties; about 1550-1077 BCE). Using quantitative SEM-EDS analysis, we identify two possible production groups of the Egyptian blue and demonstrate the presence of multiple phases within samples using cluster analysis and ternary diagram representations. Using both macro-scale non-invasive (X-rays fluorescence and multi-spectral imaging) and micro-sampling (SEM-EDS and Raman confocal microspectroscopy) techniques, we correlate photoluminescence and chemical composition of the ancient samples. We introduce Raman spectroscopic imaging as a means to capture simultaneously visible-induced luminesce and crystal structure and utilize it to identify two classes of luminescing and non-luminescing silicate phases in the pigment that may be connected to production technologies. The results presented here provide a new framework through which Egyptian blue can be studied and inform the design of new materials based on its luminescent property.

Blowpipes and their metalworking applications: New evidence from Mayapán, Yucatán, Mexico.

This study presents evidence of two tuyères, or blowpipe tips, used in metalworking at the Postclassic period city of Mayapán. Blowpipe technology has long been hypothesized to be the production technique for introducing oxygen to furnaces during the metal casting process on the basis of ethnohistorical depictions of the process in ancient Mesoamerica. To our knowledge, the tuyères recovered at Mayapán are the first archaeologically documented tuyères for pre-Hispanic Mesoamerica. The dimensions, internal perforation, vitrification, and presence of copper prills within the ceramic fabric, suggest that they were used in pyrotechnological production, likely metalworking, and is consistent with previous evidence for small-scale metalworking at Mayapán. Blowpipe use in metallurgical production is a logical extension of a much longer tradition of blowgun use in hunting, which was likely already present in Mesoamerica by the time metal was introduced to West Mexico from South America. Furthermore, the dimensions of the Mayapán tuyères are consistent with the internal diameter of ethnohistorically-documented blowguns from Jacaltenango in the southwest Maya region. We conducted replication experiments that suggest that when combined with wooden blowpipes, the Mayapán tuyères would have been ideal for small-scale, furnace-based metallurgy, of the type identified at Mayapán from Postclassic period contexts.