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- Title
Material and Elastic Properties of Al-Tobermorite in Ancient Roman Seawater Concrete.
- Authors
Jackson, Marie D.; Moon, Juhyuk; Gotti, Emanuele; Taylor, Rae; Chae, Sejung R.; Kunz, Martin; Emwas, Abdul ‐ Hamid; Meral, Cagla; Guttmann, Peter; Levitz, Pierre; Wenk, Hans ‐ Rudolf; Monteiro, Paulo J. M.; Scherer, G.
- Abstract
The material characteristics and elastic properties of aluminum-substituted 11 Å tobermorite in the relict lime clasts of 2000-year-old Roman seawater harbor concrete are described with TG- DSC and 29 Si MAS NMR studies, along with nanoscale tomography, X-ray microdiffraction, and high-pressure X-ray diffraction synchrotron radiation applications. The crystals have aluminum substitution for silicon in tetrahedral bridging and branching sites and 11.49(3) Å interlayer (002) spacing. With prolonged heating to 350°C, the crystals exhibit normal behavior. The experimentally measured isothermal bulk modulus at zero pressure, K0, 55 ±5 GPa, is less than ab initio and molecular dynamics models for ideal tobermorite with a double-silicate chain structure. Even so, K0, is substantially higher than calcium-aluminum-silicate-hydrate binder (C-A-S-H) in slag concrete. Based on nanoscale tomographic study, the crystal clusters form a well connected solid, despite having about 52% porosity. In the pumiceous cementitious matrix, Al-tobermorite with 11.27 Å interlayer spacing is locally associated with phillipsite, similar to geologic occurrences in basaltic tephra. The ancient concretes provide a sustainable prototype for producing Al-tobermorite in high-performance concretes with natural volcanic pozzolans.
- Subjects
ELASTICITY; ALUMINUM compounds; SEAWATER; CONCRETE; NANOSTRUCTURED materials; X-ray diffraction; CALCIUM silicates
- Publication
Journal of the American Ceramic Society, 2013, Vol 96, Issue 8, p2598
- ISSN
0002-7820
- Publication type
Article
- DOI
10.1111/jace.12407