冻融与硫酸盐复合侵蚀下粉煤灰混凝土的耐久性研究

通过分析混凝土表观变化形态、抗压强度和相对动弹性模量随冻融循环次数变化的规律,讨论了不同粉煤灰掺量混凝土(0、10%、20%)与5%Na2SO4溶液耦合作用下的损伤劣化机理。借助SEM和XRD技术研究了混凝土微观结构和侵蚀产物发展演化规律,并综合热分析技术定量分析了不同粉煤灰掺量对混凝土抗冻融与硫酸盐复合侵蚀能力的影响。结果表明:在冻融试验终止时,10%、20%粉煤灰掺量混凝土强度损失率分别为60.36%、83.67%,10%粉煤灰掺量相对于20%粉煤灰掺量混凝土具有良好的抗冻性。在冻融循环100次前,混凝土试样相对动弹模量一直处于递增状态。在硫酸盐侵蚀条件下,混凝土中钙矾石含量要多于石膏。在冻融循环50次时,不同粉煤灰掺量混凝土试样中侵蚀产物含量大小排序为:20%粉煤灰>未掺粉煤灰>10%粉煤灰。

Study on the Durability of Fly Ash Concrete under the Combined Freeze-thaw and Sulfate Erosion

Based on the variation of apparent morphology, compressive strength and relative dynamic modulus of elasticity with the number of freeze-thaw cycles, the damage degradation mechanism of concrete with different fly ash content (0,10%,20%) coupled with 5% Na2SO4 solution was studied. By means of SEM and XRD technology, the development and evolution of concrete microstructure and corrosion products were observed, and the corrosion products of concrete with different fly ash content were quantitatively analyzed by comprehensive thermal analysis technology. Furthermore, the influence of fly ash content on concrete resistance to freeze-thaw and sulfate combined erosion is analyzed.The results show that at the end of freeze-thaw test, the strength loss rates of concrete with 10% and 20% fly ash are 60.36% and 83.67% respectively. The concrete with 10% fly ash has good frost resistance compared with concrete with 20% fly ash. Before 100 freeze-thaw cycles, the relative dynamic elastic modulus of concrete specimens is increasing. The content of ettringite in concrete is higher than gypsum under the condition of sulfate attack. Under the condition of 50 freeze-thaw cycles, the results of comprehensive thermal analysis show that the order of corrosion products content of concrete with different fly ash content is: 20% fly ash > without fly ash > 10% fly ash.