High pressure study of low compressibility tetracalcium aluminum carbonate hydrates 3CaO·Al2O3·CaCO3·11H2O

Synchrotron X-ray diffraction data was collected from a sample of monocarboaluminate 3CaO·Al2O3·CaCO3·11H2O from ambient pressure to 4.3 GPa. The refined crystal structure at ambient pressure is triclinic with parameters a = 5.77(2) Å, b = 8.47(5) Å, c = 9.93(4) Å, α = 64.6(2)°, β = 82.8(3)°, γ = 81.4(4)°, and space group of P1 or Pimage. 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.