Existence of Dividing Strength in Concrete Containing Recycled Coarse Aggregate

Concrete is a composite material consisting of mortar and coarse aggregates. The use of recycled aggregates in concrete is increasing gradually. Recycled coarse aggregates are highly porous and often contain microcracks and weak interfacial transition zone (ITZ). Therefore, the recycled aggregates are weaker than natural coarse aggregate and their modulus of elasticity (E) is expected to be lower than that of natural coarse aggregate. This paper examines and presents the existence of dividing strength in concrete containing recycled coarse aggregate. In this study 192 concrete cylinders (100 phi x200mm) and 192 mortar cubes (50x50x50mm) were cast and tested at 28days for compressive strengths of natural aggregate concretes (NAC) and recycled aggregate concretes (RAC). In the case of NAC, the linear relationship between the compressive strength of concrete and that of mortar is observed. However, in the case of RAC, a distinct two-stage relationship between concrete strength and mortar strength is observed indicating the existence of the dividing strength of recycled aggregate concrete. This paper emphasizes that more research needs to be conducted in the existence of dividing strength as the properties of recycled coarse aggregates very quite substantially depending on the contents.