Influence of demolished concrete blocks on mechanical properties of recycled blend concrete

Recycled blend concrete (RBC) is a concrete mix made of fresh concrete (FC) and coarsely-crushed demolished concrete blocks (DCBs) larger than the conventional recycled aggregates. Structural members made of RBC have been used in engineering structures for several years, indicating that RBC is a practicable method for recycling demolished concrete (DC). To use RBC for structural applications, the mechanical properties of RBC are essential for the analysis and design of structural members. However, there are no design codes or specifications for the mechanical property requirements of RBC. Mechanical property data of RBC are scarce in the literature. Hence, this paper reports the results of an experimental investigation on the mechanical properties of RBC and establishes the relationship of the mechanical properties of RBC with the strength and replacement ratio of DCBs. Compressive, tensile and flexural tests on the specimens made of RBC with various strengths and replacement ratios of DCBs were carried out. The formulas for the compressive, tensile and flexural strengths, modulus of elasticity, and non-dimensional stress-strain relation of RBC have been formulated to account for the effects of the strength and the replacement ratio of DCBs. The microstructure of the interface zones between DCBs and FC and failure mechanisms were also investigated.