ON SITE EVALUATION OF THE ELASTIC MODULUS OF CONCRETE

A new experimental method for the on site determination of the elastic modulus of concrete is described. It is based on the pull-out test, which is commonly used for the estimate of concrete strength. The method consists in pulling out a metal insert embedded in the concrete mass and measuring the pulling force and the subsequent displacement of its point of application. In order to correctly detect the displacement and process the experimental data, it is needed to solve some technical problems such as:- the control of the hole verticality: it is ensured by the use of three displacement transducers;- the elimination of all phenomena of mutual sliding between the mechanical parts of the apparatus and between the insert and the concrete mass: it is achieved by performing an adequate number of loading-unloading cycles. The stiffness value of the system is calculated through pull-out tests. The material deformability is then estimated through an appropriate correlation curve between stiffness and elastic modulus which has been worked out on the basis of finite elements simulations and experimental results. The proposed method offers interesting possibilities of application for the characterization of existing structures at affordable costs.