| The influence of external factors such as stress,aggressive ions,splash-erosion,tidal action,and the variation of temperature and humidity has caused the degradation of cement-based materials under ocean and salt lake environments.Because of this,materials were deprived of service properties,leading to relatively shorter severce life compared to the life expectancy.The internal factors,such as composition,structure and the addition of supplementary cementious materials,also affects the degradation of materials subject to external factors.On this basis,the durability of cement based materials under different service environment has been a hot topic of engineering and academic.In this paper,the degradation process of concrete and motar under the coupling function of flexural loading,drying-wetting cycles and salt solution were studied by simulating the similar environment in the tidal and splash zone.In addition,the microstructure damage evolution of cement-based materials were discussed,which provided a theoretical basis for the durability life prediction of concrete under complex conditions.In this paper,the degradation process of motar and concrete exposed composite solution under flexural loading and drying-wetting cycles was researched by testing the relative dynamic modulus of elasticity in the different age.The results indicated that damage process of motar and concrete exposed to composite solutions consists of initial damage stage,improving performance stage and deterioration stage.Accelerating the frequency of drying-wetting cycle and increasing stress ratio and concentration of sulfate speeds up the damage process in motar.What’s more,the time of improving performance stage is shortened and the deterioration stage appears early.Increasing concentration of chloride and long-term immersion retard the damage.Decreasing the water-binder ratio and the appearance of supplementary cementious material(fly ash and slag)improve the durability of motar.Besides,the change of micro-structure,the corrosion productions and the variation of motar morphology were evaluated by X-CT,MIP,XRD and ESEM.The results showed that the damage of motar micro-structure,content of corrosion production and the corrosion degree in tensile region were more serious than that in compressive region.With the accelerating of drying-wetting cycle frequency and the increasing of stress ratio and concentration of sulfate,the porosity and harmful pore increase signally.However,increasing concentration of chloride retard the damage for micro-structure.The porosity of motar under long-term immersion was below that of pristine motar due to the corrosion production filling.Low water-binder ratio and the appearance of mineral admixture improve the micro-structure,which enhance the durability of mo tars subject to aggressive solution. |
