复合盐冻融循环后PE-ECC拉伸性能及劣化机理研究

Study on tensile properties and deterioration mechanism of PE-ECC under coupling attack of freeze-thaw cycle and sulfate-chloride

为研究聚乙烯纤维水泥基复合材料(PE-ECC)复合盐冻后的拉伸性能,设置了纯水和复合盐侵蚀(5%Na2SO4+3.5%NaCl)两种冻融环境,分别进行了0,50,100,150,200次冻融循环后的轴向拉伸试验。试验结果表明:两种冻融环境下试件的损伤程度均随着冻融次数的增加而增大;相同冻融次数下,复合盐冻条件下试件表面剥蚀程度更严重,变形性能更低,但极限应变均能保持在2%以上。在此基础上,通过XRD、SEM、EDS能谱分析、核磁共振等技术研究复合盐冻后PE-ECC拉伸性能劣化的微观机理。结果表明,复合盐侵蚀产生的膨胀性水化产物如水镁石、石膏、钙矾石等大量堆积,使孔隙和微裂缝开展,与孔中水结冰共同作用,加剧了内部结构的损伤。

In order to study the tensile properties of polyethylene fiber engineered cementitious composites(PE-ECC)under coupling attack of freeze-thaw cycle and sulfate-chloride,two kinds of environments,pure water and sulfate-chloridesolution(5%Na2SO4+3.5%NaCl),were set up,and the axial tensile tests were carried out after 0,50,100,150,and 200 freeze-thaw cycles,respectively.The test results showed that the damage degree of the specimens in both environments increased with the freeze-thaw cycles,but the degree of surface spalling was more serious and the deformation performance was lower in the sulfate-chloride environment under the same freeze-thaw cycles,but the ultimate strains could all achieve above 2%.On this basis,the micro-mechanism of deterioration of PE-ECC tensile property was investigated by XRD,SEM,EDS energy spectrum analysis,NMR and other techniques.The results show that swelling hydration products such as brucite,gypsum and ettringite produced by sulfate-chloride erosion cause pores and micro-cracks to develop,which work together with the freezing of water in the pores,aggravates the damage of the internal structure.