基于正交试验粉煤灰细骨料混凝土抗压强度研究

Study on compressive strength of fly ash instead of fine aggregate concrete based on orthogonal test

为研究粉煤灰替代率、水胶比、养护环境对粉煤灰等体积替代细骨料混凝土抗压强度的影响,取前期、中期、后期即7、28、90d三个龄期作为研究对象,进行了三因素三水平正交试验。通过极差分析确定了各因素以及各因素中各水平对抗压强度的影响程度,其中7 d时抗压强度最大的因素水平为粉煤灰替代率15%,水胶比0.5,绝湿养护。28、90 d时为粉煤灰替代率35%,水胶比0.5,绝湿养护。即最优试验方案确定为粉煤灰替代率35%,水胶比0.5,绝湿养护。同时设置未掺入的对照组,结果表明:90 d时,有粉煤灰掺入较未掺粉煤灰组强度提高16.34%,说明粉煤灰细骨料混凝土强度性能优于普通混凝土。通过SEM电镜观察微观结构可印证结论的正确性,同时可知粉煤灰发挥微集料效应及火山灰效应使混凝土内部结合更加致密从使强度提高。

In order to study the effects of replacement ratio of fly ash,water-binder ratio,and maintenance environment on the compressive strength of fine aggregate concrete replaced by fly ash,the three ages of 7,28 and 90 d in the early,middle and later stages were taken as the research object.The three-factor three-level orthogonal test was conducted.The degree of influence of each factor and each factor on the compressive strength was determined by range analysis.The factor with the highest compressive strength at 7 days was the fly ash replacement rate of 15%,the water-to-plastic ratio of 0.5,and the maintenance of humidity.At the age of 28 and 90 days,the replacement rate of fly ash was 35%,the ratio of water to cement was 0.5,and the water-curing ratio was maintained.That is,the optimal test program was determined as,fly ash replacement rate 35%,water-to-plastic ratio 0.5,and humidity conservation.At the same time,the unincorporated control group was set up.The results showed that the strength of fly ash mixed with fly ash was increased by 16.34%at 90 days,indicating that the strength performance of fly ash fine aggregate concrete is better than that of ordinary concrete.The correctness of the conclusions can be confirmed by the SEM observation of the microstructure,and it can be seen that the fly ash exerts the micro-aggregate effect and the volcanic ash effect to make the internal bonding of the concrete more compact and increase the strength.