多因素作用下地下粉煤灰混凝土抗压强度灰熵分析及微观结构

通过强度试验,运用灰关联熵分析方法,以水压力、荷载、硫酸盐、氯盐与侵蚀时间作为影响因素,研究地下粉煤灰混凝土抗压强度变化情况及其关联程度,结合SEM、XRD分析了不同工况下混凝土内部结构的微观变化。结果表明:灰关联熵分析方法可以有效区分多种因素的主次关系,在选取的五种因素中,硫酸盐与混凝土强度退化灰关联熵值最大;无水压力时,Cl^-会先进入混凝土内部与水泥水化产物生成Friedel’s盐。有水压力时,水压力加速硫酸根离子侵蚀混凝土试块,Cl^-结合能力减弱并且多以自由离子形式存在于粉煤灰混凝土中;随着侵蚀时间增加,多因素作用下粉煤灰混凝土生成产物石膏越来越多,内部结构越来越稀疏,使得抗压强度下降速率大于单因素与双因素作用下粉煤灰混凝土抗压强度下降速率。

Grey Entropy Analysis and Microstructure of Compressive Strength of Underground Fly Ash Concrete under Multi-factor Action

Through strength test and grey relation entropy analysis method,taking water pressure,load,sulfate,chloride and erosion time as influencing factors,the variation of compressive strength of underground fly ash concrete and its correlation degree were studied.Microscopic changes of soil internal structure under different conditions was analyzed by SEM and XRD.The results show that the grey relational entropy analysis method can effectively distinguish the primary and secondary relationships of various factors.Among the five selected factors,the grey relational entropy of strength degradation of sulfate and underground fly ash concrete is the largest.Under anhydrous pressure,chloride ions first enter the concrete and cement hydration products to form Friedel′s salt.When there is water pressure,the water pressure accelerates sulfate ion to erode concrete blocks,and chloride ion binding ability decreases,and most of them exist in fly ash concrete in the form of free ions.With the increase of erosion time,more and more gypsum is produced in concrete of fly ash concrete under the action of multiple factors.As the structure becomes more and more sparse,the decline rate of compressive strength of fly ash concrete is greater than that of fly ash concrete under the action of two factors.