The pull-out method for the on-site estimation of the elastic modulus of concrete

The paper describes a new experimental mechanical method for the on-site evaluation of the elastic modulus of concrete. It is based on a modification of the well-known pull-out test, which is currently used for the estimation of concrete strength. The method consists in pulling out a metal insert embedded in the concrete mass and measuring the force–displacement curve consequent to the extraction. Three displacement transducers were used in order to correctly detect the displacement of the insert. Moreover, an adequate number of loading–unloading cycles was performed in order to stabilize the system and eliminate possible phenomena of mutual sliding between the mechanical parts of the apparatus and between the insert and the concrete mass. By performing a certain number of pull-out tests the stiffness value of the system is obtained. The material deformability is then estimated through an appropriate correlation curve between pull-out stiffness and elastic modulus, which has been worked out on the basis of finite element simulations and experimental results. The proposed method offers interesting possibilities of application for the characterization of existing structures at affordable costs.