粉煤灰对水泥土力学性能的影响

以粉煤灰掺量、比表面积、养护方式及硫酸盐质量分数为影响因素,研究掺入粉煤灰后水泥土抗压强度和抗硫酸侵蚀性的变化规律,利用扫描电镜观察粉煤灰水泥土的微观结构。结果表明,在水泥掺量20%的条件下,随粉煤灰掺量增加,水泥土各龄期抗压强度增大,但增大幅度逐渐减小。龄期7 d时,粉煤灰比表面积增大对水泥土抗压强度有显著影响,龄期28 d和60 d时,粉煤灰比表面积增大对水泥土抗压强度影响不显著。水中养护对水泥土前中期的抗压强度有促进作用,对后期强度有一定的抑制作用。在硫酸盐侵蚀条件下,随着粉煤灰掺量的增加,抗压强度逐渐增大,强度损失率逐渐下降,粉煤灰掺量为10%,水泥土在3%Na2SO4和5%Na2SO4溶液中强度损失率分别为24%、35%,相较不掺粉煤灰的水泥土抗压强度损失率降低42.1%、28.2%。微观结构显示,粉煤灰能够改善水泥土内部结构,增加结构致密性。

Effects of Fly Ash on Mechanical Properties of Soil-Cement

The changes of compressive strength and sulphate resistance of soil-cement after incorporation of fly ash were studied by taking fly ash content,specific surface area,curing method and sulfate concentration as influncing factors.The microstructure of cement soil mixed with fly ash was observed by SEM.The results show that the compressive strength of cement soil increases with the increase of fly ash content when the cement content is 20%,but the increase rate gradually decreases.At 7 d,the specific surface area of fly ash had a significant impact on the compressive strength of cement soil,while at 28 d and 60 d,the specific surface area of fly ash had no significant effect on the compressive strength of soil cement.The early and medium-term compressive strength of cement soil was improved by water conservation,but it had inhibition effect on late compressive strength.Under the condition of sulfate corrosion,with the increase of fly ash content,the compressive strength gradually increased,strength loss rate gradually decreased,in 3%Na2SO4 and 5%Na2SO4 solution,with fly ash content of 10%,cement-soil strength loss rate were 24%and 35%respectively,compared with 0%fly ash,the compressive strength of cement-treated soil loss rate decreased by 42.1%and 28.2%.The microstructure shows that fly ash can improve the internal structure of soil-cement and increase the compactness of the structure.