Journal
CONSTRUCTION AND BUILDING MATERIALS
Volume 272, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.conbuildmat.2020.121812
Keywords
Historical mortars; Roman mortars; Pozzolanic materials; Durability; Permeability; Ductility
Categories
Funding
- NSF CAREER Award [EAR1451345]
- School of Earth, Energy, and Environmental Sciences at Stanford University
- Roy W. Carlson Chair
- NSF [CMMI-1532224]
- NSF as part of the National Nanotechnology Coordinated Infrastructure [ECCS-1542452]
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The study on Roman marine concrete reveals its long-term physicochemical resilience and durability. Through stress-strain measurements, structural microscopy, and chemical spectroscopy, it was found that the low permeability of RMC is related to its microstructure dominated by mortar and the presence of sulfur-rich fibrous minerals in a crossbred matrix. This fine interweaving of sulfur-rich fibers enhances aggregate bonding and contributes to the durability of Roman concrete.
Roman-era concrete is the iconic embodiment of long-term physicochemical resilience. We investigated the basis of this behavior across scales of observations by coupling time-lapse (4-D) tomographic imaging of macroscopic mechanical stressing with structural microscopy and chemical spectroscopy on Roman marine concrete (RMC) from ancient harbors in Italy and Israel. Stress-strain measurements revealed that RMC creeps and exhibits a ductile deformation mode. The low permeability of concrete samples was linked to mortar-dominated microstructures showing no debonding with the aggregates. Structural and chemical imaging shows the presence of well-developed sulfur-rich, fibrous minerals that are intertwined and embedded in a crossbred matrix having the chemical traits of both a calcium-alumi num-silicate-hydrate and a polymerized alkali-alumino-silicate. This latter likely reflects the ultra-alkaline volcanic nature of the primary source materials. We hypothesize that the fine interweave of sulfur-rich fibers within this crossbred matrix enhances aggregate bonding, which altogether contributes to the durability of RMC. (C) 2020 Elsevier Ltd. All rights reserved.
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