NANOMECHANICAL PROPERTIES OF INTERFACIAL TRANSITION ZONES IN RECYCLED AGGREGATE CONCRETE

摘要

Interfacial Transition Zone(ITZ)is an important phase that influences the mechanical properties of Recycled Aggregate Concrete(RAC).The nanomechanical properties and microstructures characterization of new ITZ and old ITZ in RAC were investigated by Atomic Force Microscopy(AFM)and nanoindentation.Based on the nanoindentation study,it is indicated that the thicknesses of old and new ITZs are in the range 40～50 and in the range 55～65,respectively.It is also found that the average indentation modulus of old ITZ is 70％～80％of that of old paste matrix,while the average indentation modulus of new ITZ is 80％～90％of that of new paste matrix.Additionally,the influences of mix proportion,aggregate types and hydration age on the properties of ITZs in RAC are discussed in this study.With the increase of hydration age,the new ITZ thickness appears to be reduced and the nanomechanical properties at new ITZ tends to became higher because of the development of hydrates with the age.