不同品质粉煤灰混凝土的微观力学性能研究

Effect of Different Grades of Fly Ash on Micromechanical Properties of Concrete

系统研究了Ⅰ级粉煤灰、Ⅲ级粉煤灰和等外粉煤灰对混凝土抗压强度和自收缩的影响,并采用纳米划痕仪重点分析了不同品质粉煤灰混凝土的微观力学性能。结果表明:Ⅲ级粉煤灰和等外粉煤灰均明显降低混凝土的早期和后期抗压强度,且随着掺量的增加而下降,而Ⅰ级粉煤灰能明显提高混凝土的后期强度,且随着掺量的增加而增加。Ⅰ级粉煤灰、Ⅲ级粉煤灰和等外粉煤灰均能明显降低混凝土的自收缩,且等外粉煤灰降低效果最好。在微观力学性能方面,Ⅰ级粉煤灰与水泥基体界面区结构显著优于Ⅲ级粉煤灰和等外粉煤灰,且界面区微观力学性能明显高于Ⅲ级粉煤灰和等外粉煤灰。

The effect of grade Ⅰ, grade Ⅲ and offgrade fly ash on comperssive strength and autogenous shrinkage of concrete was systematically investigated. Meanwhile,the micromechanical properties of fly ash concrete were analyzed by nano-scratch technique. The results showed that the additions of grade Ⅲ and offgrade fly ash decreased the compressive strength of concrete obviously, and the comperessive strengths decreased with increasing the amounts of fly ash. However, the addition of grade I fly ash increased the later strength of concrete, and the later strengths increased more with increasing the amounts of fly ash. The additions of grade Ⅰ, grade Ⅲ and offgrade fly ash decreased the autogenous shrinkage of concrete, and the effect of offgrade fly ash was the best one. In addition, the interface zone between grade Ⅰ fly ash and cement matrix was denser than those of concretes containing grade Ⅲ fly ash or offgrade fly ash, and the micromechanical properties of the interface were also much higher than those of concretes containing grade Ⅲ fly ash or offgrade fly ash.