Effect of freeze-thaw cycles on the stress-strain curves of unconfined and confined concrete

An experimental research was performed on the complete compressive stress-strain relationship for unconfined and confined concrete after exposure to freeze-thaw cycles. For the unconfined concrete, tests were carried out on three series of prisms specimens (100 mm x 100 mm x 300 mm) with water/cement ratio of 0.60, 0.54 and 0.48 respectively. While for confined concrete, two series of tied columns (150 mm x 150 mm x 450 mm prisms) with confinement index of 0.317 and 0.145 were prepared. Analytical models for the stress-strain relationship of frozen-thawed unconfined and confined concrete were empirically developed respectively. Through the regression analysis, formulations for the main parameters were established, including the compressive strength, peak strain and elastic modulus. Compared with the available experimental data, the proposed models were shown to be applicable to concrete after different numbers of freeze-thaw cycles.