低强度再生混凝土微观形态与力学性能的相关性研究

Research on Correlation Between Microstructure and Mechanical Properties of Low Strength Recycled Concrete

建筑垃圾来源复杂,为提高再生混凝土的资源利用,并满足基本工程应用要求,在仅考虑再生骨料密度、吸水和含水率、压碎指标的条件下,采用再生粗骨料混凝土配合比设计法配置低强度再生混凝土,结合切片法和SEM扫描电镜对再生混凝土的孔隙结构变化与微观形貌进行观察,分析水胶比、减水剂、粉煤灰对低强度再生混凝土内部结构的影响,发现当水胶比降低时,再生混凝土内部结构的密实度提升,絮状C-S-H之间更为密实,多害孔的比例降低,抗压和劈裂强度提高;当减水剂掺量提升时,钙钒石(AFt)的含量增加,内部结构更为致密;粉煤灰对再生混凝土的抗压和劈裂强度呈负面影响,降低C-S-H与再生骨料之间的粘结性,内部孔隙率变大,坍落度升高,可降低经济成本。

In order to improve the resource utilization of recycled concrete and meet the requirements of basic engineering applications,under the condition of only considering the density,water absorption and moisture content and crushing index of recycled aggregate,the design method of recycled coarse aggregate concrete mix ratio is used to configure low-strength recycled concrete.Combined with slicing method and SEM scanning electron microscopy,the pore structure changes and micromorphology of recycled concrete are observed,and the effects of water-to-adhesive ratio,water reducing agent and fly ash on the internal structure of low-strength recycled concrete are analyzed.It is found that when the water-to-adhesive ratio decreases,the compactness of the internal structure of recycled concrete is improved,the density between flocculent C-S-H is higher,the proportion of harmful pores is reduced,and the compressive and splitting strength is improved.When the content of water reducing agent increases,the content of calcium vanadium(AFt)increases,and the internal structure is more dense.Fly ash has a negative impact on the compressive resistance and splitting strength of recycled concrete,reduces the adhesion between C-S-H and recycled aggregate,increases the internal porosity and the slump,which can reduce the economic cost.