再生混凝土界面过渡区纳观力学性能试验研究

对采用不同搅拌工艺的再生混凝土的宏观力学性能进行试验研究.采用纳米压痕技术和扫描电镜等设备研究了再生混凝土界面过渡区的纳观力学性能和微观结构特征.试验结果表明,采用普通搅拌工艺的新界面过渡区的弹性模量随着与老砂浆表面距离的增加而降低,但是采用二次搅拌工艺的弹性模量基本保持不变.老界面过渡区的弹性模量随着与天然骨料的距离增大而逐渐增加.采用二次搅拌工艺新的界面过渡区的微观结构较普通搅拌工艺的新界面过渡区更为致密,且孔隙率和氢氧化钙晶体含量较少.由再生混凝土的界面过渡区纳观力学性能和宏观抗压强度之间的关系,可知采用二次搅拌工艺可以改善界面过渡区的力学性能和微观结构,进而提高再生混凝土的宏观力学性能.

Experimental Study on Mechanical Properties of Interfacial Transition Zones in Recycled Aggregate Concrete

The mechanical properties of Recycled Aggregate Concrete (RAC) with different mixing approaches were comparatively investigated. Based on the experiments on the Interfacial Transition Zone (ITZ) of RAC by nanoindentation technique and scanning electron microscopy, the results indicate that, for the new ITZ with Normal Mixing Approach (NMA), the elastic modulus distribution appears to decrease significantly from the old paste matrix surface, while for the new ITZ with Two-Stage Mixing Approach (TSMA), there is no obvious trend indicating that the elastic modulus increases or decreases with the increase of distance. For the old ITZ, the elastic modulus increases as the distance increases from original aggregate surface. The TSMA can improve the microstructures of the new ITZ by reducing the volume fraction of voids and calcium hydroxide. Correlating the nanomechanical properties of ITZ and microstructure with the compressive strength of RAC, it can be concluded that TSMA can enhance the mechanical properties of RAC by improving the mechanical properties and microstructure of the new ITZ.