Material and elastic properties of Al-tobermorite in ancient roman seawater concrete
AuthorsJackson, Marie D.
Emwas, Abdul-Hamid M.
Levitz, Pierre E.
Wenk, Hans Rudolf
Monteiro, Paulo José Meleragno
KAUST DepartmentImaging and Characterization Core Lab
Advanced Nanofabrication, Imaging and Characterization Core Lab
MetadataShow full item record
AbstractThe 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 29Si 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. © 2013 The American Ceramic Society.
SponsorsThis research was supported by Award No. KUS-l1-004021, from King Abdullah University of Science and Technology (KAUST). Data were acquired at beamlines 12.2.2 and 12.3.2 at the Advanced Light Source at the Lawrence Berkeley Laboratories, supported by the Director of the Office of Science, Department of Energy, under Contract No. DE-AC02-05CH11231, and the Advanced Nanofabrication Imaging and Characterization Laboratories at King Abdullah University of Science and Technology. We thank CTG Italcementi researchers and staff, especially B. Zanga, in Bergamo, Italy; G. Vola at Cimprogetti S.p.A., Dalmine, Italy; S. Clark at the 12.2.2 beamline; and N. Tamura at the 12.3.2 beamline; and the ROMACONS drilling program: J. P. Oleson, C. Brandon, R. Hohlfelder. T. Teague, D. Hernandez, C. Hargis, I. A. Delaney, and B. Black provided research support. We thank J. G. Moore, M. Sintubin, G. Sposito, P.-A. Itty, and J. Kirz for critical discussions, and three anonymous reviewers whose comments improved the manuscript.