Material and Elastic Properties ofAl‐Tobermorite in Ancient Roman Seawater Concrete

Abstract

The material characteristics and elastic properties of aluminumsubstituted 11 A tobermorite in the relict lime clasts of 2000year-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) A interlayer (002) spacing. With prolonged heating to 350°C, the crystals exhibit normal behavior. The experimentally measured isothermal bulk modulus at zero pressure, K 0 , 55 ±5 GPa, is less than ab initio and molecular dynamics models for ideal tobermorite with a double-silicate chain structure. Even so, K 0 , 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 A 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.

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

“…The intial pozzolanic reactivity of the ash constituents-glassy alkali-rich groundmass scoriae and clay and zeolite surface textures-with portlandite was replaced by authigenic hydration processes in the presence of moisture permeating the concrete fabric that produced further crystalline cementitious reinforcements over the long-term history of the monument. Authigenic cementitious processes also occur in seawater concretes of Roman maritime harbor structures that use pulvis, pumiceous ash from the Gulf of Naples (de Architectura 2.7.2-3; 2.6.1-4) (14), but these are dominated by an Altobermorite and zeolite mineral assemblage (57).…”

Recent studies of cements and concretes by synchrotron radiation crystallographic and cognate methods

“…Finally, soft X-ray nanotomography has also been employed for characterizing 2000-year-old Roman seawater concrete. [101] The data analysis showed clusters of Al-tobermorite crystals displaying both platy and elongated 1-2 µm crystals typical of geological 11 Å-tobermorite . 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 24 M.A.G.…”

“…[99] A similar study for jennite, measured up to 6 GPa, yielded a bulk modulus of 64 GPa. [100] The isothermal bulk modulus of aluminium-substituted 11Å-tobermorite from relict lime clasts of 2000-year-old Roman seawater harbour concrete was also measured, yielding K o = 55 GPa [101]. Other works reported the bulk modulus for selected samples of interest in cement chemistry like stratlingite: K o = 23 GPa, hemicarboaluminate: K o = 15 GPa, monocarboaluminate: K o = 54 GPa and hydrogarnet: K o = 70 GPa.…”

Kinetics of intercalation of fluorescent probes in magnesium–aluminium layered double hydroxide within a multiscale reaction–diffusion framework

“…The 27 Al isotropic chemical shifts are used to differentiate between the tetrahedral Al (tetra) and the octahedral Al (octa) coordination, where the range of Al (tetra) is 90-100 ppm and that of Al (octa) is 0-20 ppm [25,26]. In this study, the 27 Furthermore, the solid-state fluorescence lifetime of RhB in all the extracted MgAlA LDHs exhibits a double exponential decay, indicating the coexistence of two different populations of RhB.…”