Large-scale micron-order 3D surface correlative chemical imaging of ancient Roman concrete

Abstract

There has been significant progress in recent years aimed at the development of new analytical techniques for investigating structure-function relationships in hierarchically ordered materials. Inspired by these technological advances and the potential for applying these approaches to the study of construction materials from antiquity, we present a new set of high throughput characterization tools for investigating ancient Roman concrete, which like many ancient construction materials, exhibits compositional heterogeneity and structural complexity across multiple length scales. The detailed characterization of ancient Roman concrete at each of these scales is important for understanding its mechanics, resilience, degradation pathways, and for making informed decisions regarding its preservation. In this multi-scale characterization investigation of ancient Roman concrete samples collected from the ancient city of Privernum (Priverno, Italy), cm-scale maps with micron-scale features were collected using multi-detector energy dispersive spectroscopy (EDS) and confocal Raman microscopy on both polished cross-sections and topographically complex fracture surfaces to extract both bulk and surface information. Raman spectroscopy was used for chemical profiling and phase characterization, and data collected using EDS was used to construct ternary diagrams to supplement our understanding of the different phases. We also present a methodology for correlating data collected using different techniques on the same sample at different orientations, which shows remarkable potential in using complementary characterization approaches in the study of heterogeneous materials with complex surface topographies.

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

“…As shown in Fig. 2F , these points (red) are distinct from the primary binding phase (yellow), which has ratios of silicon, aluminum, and calcium more closely associated with C-A-S-H binders ( 41 ). Petrographic analysis (fig.…”

“…Quantitative EDS data were plotted pixel by pixel on ternary diagrams ( Fig. 2, B and E ) to reveal the relative ratios of the three key elements of the cementitious phases—calcium, silicon, and aluminum ( 41 ).…”

Towards an understanding of the chemo-mechanical influences on kidney stone failure via the material point method

“…Furthermore, with the development of multi-detector EDS, in which two diametrically opposed detected are used to detect x-rays from the sample’s surface, it is also possible to obtain quantitative elemental information for three-dimensional surfaces. This has made it an apt choice for the study of complex composites, including Roman concrete and sea urchin teeth, particularly when combined with other complementary characterization techniques such as Raman spectroscopy [ 26 , 27 ]. The high throughput nature of EDS mapping has made it possible to combine quantitative EDS data with clustering techniques to map the distribution of chemically distinct phases throughout the mapped area of a sample [ 28 ].…”

Optical and Electronic Microscope for Minero-Petrographic and Microchemical Studies of Lime Binders of Ancient Mortars

“…The data obtained must also make it possible to obtain information on the socio-economic conditions existing at the time of manufacturing [25][26][27][28][29]. The research sector is mainly aimed at understanding the factors that have contributed to the particular durability of a mortar, with the aim of developing new types of binders and mortars [30][31][32][33][34][35][36].…”