超临界CO 2条件下混凝土界面过渡区微结构特征演变规律研究

Study on the Evolution of Microstructural Characteristics of Concrete Interfacial Transition Zone Under Supercritical CO 2 Conditions

为研究粉煤灰混凝土在超临界碳化前后界面过渡区(interfacial transition zone,ITZ)微结构的演变规律,采用扫描电镜对碳化前后ITZ附近的微观形貌进行了分析,同时构建了ITZ和水泥砂浆的孔隙率与压痕模量的关系模型.通过纳米压痕试验测得ITZ和水泥砂浆的压痕模量,并通过压汞试验测得水泥砂浆的孔隙率,推导出了ITZ的孔隙率.研究结果表明:经过超临界碳化处理后,粉煤灰混凝土界面过渡区变得更加密实.此外,超临界碳化前ITZ孔隙率范围为20%~35%,碳化后ITZ孔隙率范围为10%~26%,相比前者减少了25%~50%.

The purpose of this study was to investigate the evolution of the microstructure of the interfacial transition zone(ITZ)in fly ash concrete before and after supercritical carbonation.Scanning electron microscopy was used to analyze the microstructure near the ITZ before and after carbonation.A relationship model between the porosity and indentation modulus of the ITZ and cement mortar was constructed.The porosity of the ITZ was derived from the indentation modulus of the ITZ and cement mortar obtained by nanoscale indentation testing and the porosity of the cement mortar obtained by mercury intrusion porosimetry.The results show that the ITZ of fly ash concrete becomes denser after supercritical carbonation treatment.In addition,the porosity range of the ITZ before carbonation is 20%to 35%,while after carbonation,it is 10%to 26%.Compared with before carbonation,the porosity of the ITZ after carbonation decreases by 25%to 50%.