The influence of casting position and disturbance induced by reinforcement on the structural concrete strength

It is well known that control specimens used to assess the concrete strength of new structures have different casting and curing conditions than those of actual structures. Notably, after pouring of the concrete and before its hardening, a number of phenomena such as concrete bleeding and plastic settlement occur, influencing the in-situ strength with respect to that of small and homogeneous control specimens (cubes or cylinders). In addition, the development of these phenomena and their structural implications are influenced by the presence of reinforcing bars, disturbing the settlement and bleeding of fresh concrete. In this paper, these aspects, with particular emphasis on the effective structural strength, are investigated by means of a testing program performed with refined measurement techniques such as tomography and Digital Image Correlation. On that basis, consistent design rules are derived to correct the strength of control specimens in order to calculate the resistance of a structural concrete member.