超细粉煤灰对桥梁混凝土单轴压缩损伤特征的影响分析

Study on Influence of Fly Ash Substitution Rate on Uniaxial Compression Damage Characteristics of Bridge Concrete

为了研究粉煤灰取代率对桥梁混凝土损伤特征的影响,对取代率分别为0、5%、10%和15%的4组混凝土进行了单轴压缩试验,采用声发射(AE)技术混凝土损伤特征进行动态分析。根据桥梁混凝土受压损伤时所释放的声发射信号,定量探讨了材料的损伤程度,并以声发射指标为基础建立了损伤演化曲线。结果表明:混凝土单轴压缩的应力-应变曲线可分为弹性变形、塑性损伤、屈服破坏和残余变形4个变形阶段;随着粉煤灰含量增大,混凝土的塑性特征明显增强,取代率为10%时强度最大;声发射计数的结果可以作为结构损伤的量化表征指标,不含粉煤灰的混凝土声发射信号活跃期集中在塑性损伤阶段,而粉煤灰改性混凝土的声发射活跃期集中在破坏阶段;粉煤灰的改性作用提高了混凝土的变形性能,且对损伤的发展有一定抑制效果;以声发射指标为基础建立的损伤系数与混凝土结构损伤程度的吻合度较好,可为混凝土力学行为的理论研究与工程应用提供可靠的依据。

In order to study the effect of fly ash substitution rate on the damage characteristics of bridge concrete,uniaxial compression tests were carried out on four groups of concrete with substitution rates of 0,5%,10%and 15%,respectively.The acoustic emission(AE)technique was used to analyze the dynamic damage characteristics of the specimens.According to the acoustic emission signal released by the concrete under compression,the damage degree of the material is quantitatively discussed,and the damage evolution curve is established based on the acousticemission index.The results show that the stress-strain curve of concrete under uniaxial compression can be divided into four deformation stages:elastic deformation,plastic damage,yield failure and residual deformation.With the increase of fly ash content,the plasticity of the test specimen is obviously enhanced,and the strength of the test specimen with the substitution rate of 10%is the highest.The results of acoustic emission count can be used as a quantitative indicator of structural damage.The active period of acoustic emission signal of concrete without fly ash is concentrated in the plastic damage stage,while that of concrete modified with fly ash is concentrated in the failure stage.The modification of fly ash improves the deformation property of samples and inhibit the development of damage to a certain extent.The damage coefficient based on acoustic emission index is in good agreement with the structure damage degree,which can provide a reliable basis for theoretical research and engineering application of concrete mechanical behavior.