Parametric Study for the Creation of the Interface between Concrete and Repair Products

An analysis as large as possible presents factors acting when a repair system comes into contact with a concrete support. The appetency of the first one for the second is defined from the properties of the support and the new layer – essentially in its liquid phase – as well as from the environmental conditions. These properties are cited or explained for each material: roughness, porosity, superficial cohesion and interstitial water into concrete, nature and concentration of the binder, rigidity modulus, capillary succion for repair systems. The thermodynamic properties of the materials as well as transport mechanisms – diffusion, capillary succion – at the interface and roughness of the concrete support are particularly developed. A sequential flow sheet related to the parameters influencing the creation of the interface is proposed

Adaptation of the pull-off test for the evaluation of the superficial cohesion of concrete substrates in repair works: analysis of the test parameters

Concrete repair works involve most of the time the removal of the damaged or contaminated surface layer. It is necessary to assess the effect of that operation (tool, procedure, etc) upon the integrity of the residual concrete substrate, prior to the placement of the repair material, since it can affect significantly the adhesion of the repair system. This paper summarizes the findings of a study intended to develop a simple test method for that purpose. After a thorough review of the related scientific documentation, it has been decided to adapt the so-called pull-off test, which is commonly used to determine the bond strength of repair products. An experimental program has been conducted to evaluate the influence of various test parameters on the measured cohesion of a reference concrete surface: transfer plate thickness and diameter, core drilling depth, speed of loading, adhesive type and thickness, and number of tests. A multivaried statistical analysis of the test results clearly shows that the plate diameter and core depth are the most significant parameters, presumably with threshold values, and that there exists a synergetic effect between them. Also, a minimum number of tests can be defined based on the standard deviation and required level of confidence of the results. Overall, the test method shows good potential for a sound quantitative evaluation of a concrete surface mechanical integrity prior to repair, provided that the test parameters are selected properly