为研究经历荷载历史后的混凝土在荷载历史与环境因素联合作用下的损伤演化规律,对105个尺寸为100 mm×100 mm×300 mm的棱柱体试块施加轴压荷载历史并进行硫酸钠溶液单独侵蚀、硫酸钠溶液与干湿循环联合侵蚀,以试验测得的相对动弹性模量、轴心抗压强度作为损伤评价指标来研究混凝土的损伤特性和机理.试验结果表明:无论经历荷载历史与否,混凝土在硫酸钠溶液作用下力学性能早期均有所提高.在双因素联合作用下,干湿循环和荷载历史都加快了混凝土内部损伤和强度劣化,干湿循环加速损伤作用更加明显.在三因素联合作用下,混凝土损伤劣化速度和程度与硫酸钠溶液浓度成正比,但并非随着历史荷载的应力水平呈现单调变化,在25%应力水平的荷载历史下影响最大.
In order to investigate the laws of damage evolution of concrete under the interaction between loading history and various external environmental conditions, 105 concrete specimens with size of 100 mm × 100 mm × 300 mm are exposed to sodium sulfate solution attack and wet-dry cycles after experiencing loading history.Dynamic elastic modulus and axial compressive strength are measured in the tests as damage evaluation.Experimental results show that the mechanical properties of concrete under the effect of sodium sulfate solution attack are improved in the early stage no matter there are loading history or not.Wet-dry cycles and loading history can both accelerate the internal damage and the strength degradation of concrete subjected to sulfate attack, and wet-dry cycles play a main role in the damage process of concrete.Under the combined effect of the three factors, the damage degree and strength degradation speed of concrete are in proportion to the concentrations of sulfate solution, which are not a monotonic change along with the stress levels of loading history.Significant effects of loading history on the deterioration of concrete under combined actions of sodium sulfate solution attack, dry-wett cycles and 25% stress level of loading history are observed.