High pressure study of low compressibility tetracalcium aluminum carbonate hydrates 3CaO center dot Al2O3 center dot CaCO3 center dot 11H(2)O

Abstract

Synchrotron X-ray diffraction data was collected from a sample of monocarboaluminate 3CaO center dot Al2O3 center dot CaCO3 center dot 11H(2)O from ambient pressure to 4.3 GPa. The refined crystal structure at ambient pressure is triclinic with parameters a=5.77(2) angstrom, b=8.47(5) angstrom, c=9.93(4) angstrom, alpha=64.6(2)degrees, beta=82.8(3)degrees, gamma=81.4(4)degrees, and space group of P1 or P (1) over bar. It showed some degree of perfectly reversible pressure-induced dehydration with a non-hygroscopic pressure-transmitting medium. However the dehydration effect does not critically affect a bulk modulus due to its strong framework. The isothermal bulk modulus of monocarboaluminate was found to be 53(5) GPa and 54(4)GPa with 3rd order and 2nd order Birch-Murnaghan Equation of state, respectively. That value is higher than for any other reported AFm or AFt phase. The pressure-volume behavior of the monocarboaluminate was compared with that of previous studied hemicarboaluminate.