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Ch. Hellmich, R. Lackner, H.A. Mang:
"Thermochemomechanical Material Model for Shotcrete";
in: "Numerical simulation in tunneling", G. Beer (ed.); Springer, Wien, 2003, ISBN: 3-211-00515-3, 61 - 81.

Employing a thermodynamic framework, thermochemomechanical couplings for shotcrete are treated in this chapter. A material model based on multi-surface thermochemoplasticity is presented. It accounts for
hydration kinetics, chemomechanical couplings related to strength growth, stiffness properties, and to autogeneous shrinkage in early-age shotcrete. Creep is modelled by means of two mechanisms: stress-induced water movement in the capillary pores of shotcrete, and a relaxation mechanism in the nanopores of the cement gel. The underlying material functions are intrinsic, i.e., independent of field and boundary conditions. They are determined from standard material tests. As for the numerical treatment of the constitutive equations of the material model, an extended form of the return mapping algorithm is presented.
Microcracking is considered by means of a Drucker-Prager failure surface for the compressive load regime and by means of Rankine surfaces for tensile brittle failure.

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