Mechanical Properties and Microstructure Characteristics of Manufactured-Sand Concrete Under Coupled Effect of Salt Erosion and Freeze-Thaw Cycles

摘要

Experimental investigations on C30, C40 and C50 manufactured-sand concrete in coupled environments of salt erosion and freeze-thaw cycles were carried out in order to obtain the deterioration law of concrete such as mass loss rate, dynamic modulus of elasticity and compressive strength, and micro-mechanism of C40 concrete by CT images. The salt erosion environment is simulated by solutions of 5 wt% Na2SO4 (S), 5 wt% NaCl (C), mixture of 5 wt% Na2SO4 and 5 wt% NaCl (C+S), and pure water (H), respectively. All the macroscopic experimental results show that salt erosion can accelerate the mass loss and strength decline of manufactured sand concrete, but it can slow down the decrease of dynamic modulus of elasticity. Different salt solutions have different effects on the deterioration of concrete performance. The results of CT test show that freeze-thaw cycle can accelerate the generation of cracks in concrete. In the C+S and C environments, the area and width of concrete cracks are larger than those in other two environments. Meanwhile, the crack width expansion rate in C environment is the fastest in all corrosive environments. In a word, sodium chloride erosion solution coupled with freeze-thaw cycles leads to the deterioration of manufactured sand concrete most severely in all the coupling effects.