硫酸盐渍土地区粉煤灰混凝土力学性能试验研究

Experimental research on mechanical properties of fly ash concrete in sulfate saline soil area

【目的】探究硫酸盐渍土地区粉煤灰掺量对混凝土抗压强度的影响,为实际的工程建设提供参考。【方法】在试验场地埋置4组(粉煤灰掺量分别为0%、10%、15%和20%)共48块尺寸为150 mm×150 mm×150 mm的标准立方体混凝土试块,定期测量其抗压强度,并用扫描电镜分析其微观结构。【结果】在侵蚀早期不同配合比混凝土试块的抗压强度出现一定幅度的增长;但随着侵蚀时间的增加,抗压强度开始逐渐下降,结合正交试验分析认为粉煤灰的最佳掺量为10%;在侵蚀后期渗入混凝土内部的SO_(4)^(2-)与水化产物结合生成的钙矾石晶体逐渐增多,钙矾石吸水膨胀并导致微裂缝进一步扩展,影响了结构的整体密实度。使用MATLAB中的General Model Gauss函数对侵蚀早期混凝土抗压强度的试验数据进行拟合,拟合效果较好。【结论】对于硫酸盐渍土地区粉煤灰混凝土耐久性的研究,需采用多种试验方法对混凝土力学性能的变化过程进行分析;加强数值仿真手段与试验结果的结合可以对混凝土抗压强度进行更好的预测。

[Purposes]The paper aims to explore the influence of fly ash content on concrete compressive strength in sulfate saline soil area to provide some reference for practical engineering construction.[Methods]Four groups of 48 standard cubic concrete test blocks with side length of 150 mm were embedded in the test site,whose fly ash contents were 0%,10%,15%and 20%,respectively.The compressive strength was measured regularly and the microstructure was analyzed through scanning electron microscope.[Findings]The compressive strength of concrete test blocks with different mix proportion increases to a certain extent at the early stage of erosion.With the increase of erosion time,the compressive strength begins to decrease gradually.Combined with orthogonal test analysis,it is considered that the best content of fly ash is 10%.The ettringite crystals formed by the combination of SO_(4)^(2-) penetrated into the concrete and hydration products gradually increase at the later stage of erosion,and the ettringite absorbs water and expands,resulting in the expansion of micro cracks and affecting the overall compactness of the structure.The General Model Gauss function in MATLAB was used to fit the test data of early concrete compressive strength.The results show that the fitting effect is good.[Conclusions]For the research on the durability of fly ash concrete in sulfate saline soil area,a variety of test methods should be used to analyze the changes of mechanical properties of concrete,and the combination of numerical simulation and test results should be strengthened to make a better prediction of the compressive strength of concrete.