氯盐干湿循环下风积沙混凝土微观结构演变

The microstructure evolution of aeolian sand concrete under dry-wet cycles of chlorine salt solution

为探究干湿循环作用下风积沙混凝土内部微观结构的演变规律,试验采用河砂质量的0、25%、50%、75%及100%的风积沙替代河砂制备混凝土,在NaCl质量分数为3.5%的溶液中进行干湿循环试验。利用扫描电镜、核磁共振等技术对氯盐干湿循环作用下风积沙混凝土(aeolian sand concrete, ASC)的微观结构及氯离子侵蚀机理进行分析。结果表明:随风积沙质量分数增大,ASC内部自由氯离子质量分数先减小后增大;随侵蚀深度的增加,自由氯离子质量分数逐渐减小;氯盐干湿循环使ASC内部产生了大量盐结晶,结晶压力造成ASC内部孔结构劣化,核磁共振T2图谱不断右移,其中采用河砂质量的100%的风积沙替代河砂的混凝土(A100)在氯盐干湿循环过程中损伤最严重。

In order to investigate the evolution of the internal microstructure of aeolian sand concrete under the action of dry-wet cycling,Tests were conducted using 0,25%,50%,75%and 100%of the mass of river sand in place of river sand for concrete preparation,and the dry-wet cycling test was carried out in a solution with a NaCl mass fraction of 3.5%.Scanning electron microscope,nuclear magnetic resonance and other techniques were used to analyze the microstructure and chloride erosion mechanism of ASC under the dry and wet cycles of chloride salt.The results showed that the mass fraction of free chloride ions inside the AsC decreased and then increased with the increase of the mass fraction of aeolian sand concrete,and the mass fraction of free chloride ions gradually decreased with the increase of the erosion depth.The dry and wet cycles of chloride salts produced a large amount of salt crystals inside the AsC,and the crystals pressure caused the deterioration of the internal pore structure of the ASC,and the nuclear magnetic resonance T,pattern was constantly shifted to the right,in which Aio0 was most seriously damaged during the chlorine salt dry-wet cycling process.