Microstructure of Recycled Aggregate Concrete

Abstract

The microstructural characterization of concrete prepared with RCA is described in this chapter. The interfacial transition zone (ITZ) between the aggregate and the cement mortar matrix is the most important interface in concrete. Particularly, this is very important in RAC, as the recycled aggregate concrete has more interfaces than normal concrete, i.e., the interfacial transition zone between the original aggregate and the adhered mortar (old ITZ), and another interface between the adhered mortar and new mortar matrix (new ITZ) in recycled aggregate concrete. Therefore, the characteristics of ITZ of RAC in terms of hydration compounds, anhydrous cement, porosity examined by using SEM are discussed in this chapter. A detailed procedure of specimen preparation for scanning electron microscope (SEM) examination is also discussed. Further, the influence of these parameters on the strength of concrete is elaborated. ITZ characteristics were also examined by using Vickers microhardness and a relationship between compressive strength and ITZ microhardness was established. Furthermore, it discussed the influence of the binder, quality, and quantity of adhered mortar, strength of source concrete from which the RCA derived on interfacial transition zone of RAC.