Benefits of Low Modulus of Elasticity and of Fibre Reinforcement of Cement Based Mortars as Thin Bonded Overlay Materials

Abstract

The paper, associating experiment and simulation approaches, deals with the debonding propagation between a thin bonded cement-based overlay and a substrate simulating a repair of old concrete structure. The material used for the overlay is a fibre reinforced and rubberised mortar. In the experimental investigations, three point static bending tests were carried out on composite specimens. The effects of shrinkage of the overlay, restrained by the substrate, and the role of fibre reinforcement are thus involved. Direct tensile tests on notched specimens were firstly conducted to obtain the tensile strength and the residual normal stress-crack opening relationship. The debonding opening-residual normal tensile stress relationship was investigated by static tensile tests. The propagation of the debonding interface was monitored using a video-microscope with an enlargement of 175x. On the basis of the parameters identified and quantified, the above mentioned static tests were modelled by the finite element method using CAST3M code developed in France by CEA (Commission for Atomic Energy). The model predictions showed good agreement with the experimental results. The shrinkage effect on the durability of the composite specimens was clarified. The results also proved the important role of fibre-reinforcement in restraining the crack opening by transferring stresses through the crack.