Investigation of the High Temperature Properties of Lightweight Foamed Concrete under Incremental Amplitude Cyclic Triaxial Compression

Foamed concrete (FC) is used extensively in construction, road bases, and tunneling engineer-ing for its light weight, thermal insulation, energy absorption, and deformation capacity. Therefore, its cyclic loads bearing capability after high temperature treatment warrants further investigation. To evaluate the fatigue resistance of high temperature treated FC, incremental amplitude triaxial cyclic compression tests were carried out after four temperature treatments (25 degrees C, 100 degrees C, 200 degrees C, 300 degrees C) under different confining pressures (0 MPa, 0.3 MPa, 0.5 MPa, 0.8 MPa). Based on the stress-strain curve and fracture mode, the peak stress, residual stress, elastic modulus, and brittleness index were analyzed. The damage evolution of FC was ana-lyzed based on hysteretic energy and the failure mechanism was elucidated from the perspec-tive of energy dissipation. In addition, the applicability of the crushable-foam yielding criterion to FC was verified and the strength prediction model of FC was proposed. The results indicate that the fracture pattern of FC is significantly influenced by confining pressure and that the stress-strain curve exhibits strain hardening under high confining pressures. The mechanical parameters of FC are negatively correlated with temperature and positively correlated with confining pressure. The damage evolution consists of three stages and the damage grows slowly in the initial compaction stage. The high confining pressure can restrain the crack de-velopment and enhance the elastic strain energy storage efficiency. The crushable-foam yield criterion has good applicability to FC and thermal damage remarkably declines the hydrostatic yield strength of FC.