粉煤灰和再生粗骨料掺量对再生混凝土性能的影响研究

Research on the Influence of Amount of Fly Ash and Recycled Coarse Aggregate to the Performance of Recycled Concrete

摘要: 研究了两种再生粗骨料取代率(80%和100%)，三种粉煤灰掺量(0%，15%和30%)对再生混凝土抗压强度和抗冻性能的影响，测试了其抗压强度和质量损失率，并且通过XRD对其微观结构进行了试验分析。试验结果表明：1) 再生混凝土的抗压强度随粉煤灰掺量的增加呈现出先增后减的趋势，粉煤灰掺量为15%，再生粗骨料取代率为80%时，试件的28天抗压强度最高；2) 75次冻融循环后，所有试件的质量损失率均小于5%，粉煤灰掺量和再生粗骨料取代率为15%和100%时，试件质量损失率最低；3) 再生粗骨料的增多会导致再生混凝土内部结构缺陷的增多，而适量的粉煤灰可以有效改善这些缺陷。

Abstract: The effects of two kinds of recycled coarse aggregate replacement rates (80% and 100%) and three fly ash additions (0%, 15% and 30%) on the compressive strength and frost resistance to recycled concrete were researched and tested its compressive strength and mass loss rate. Simultaneously, the microstructure of the recycled concrete was tested by XRD. The results indicated that: 1) The compressive strength of recycled concrete showed a trend of increasing first and then decreasing with the raise of fly ash amount. When the fly ash content was 15% and the recycled coarse aggregate replacement rate was 80%, the 28-day compressive strength of specimens highest. 2) After 75 freeze-thaw cycles, the mass loss rate of all specimens was less than 5%. When the fly ash amount and the recycled coarse aggregate substitution rate were 15% and 100%, the mass loss rate of specimens was the lowest. 3) The increase in recycled coarse aggregate resulted in a raise in the internal structural defects of recycled concrete, and an appropriate amount of fly ash can effectively improve these defects.