To the Problems of Anchoring Adhesives in High Performance Concrete

摘要

The paper deals with selected problems of special use of bonded anchors.It is focused closely on the limits of some epoxy and vinyl ester resins for use as anchoring adhesive in high strength concrete.If the anchor is loaded by tension force in such conditions,the adhesive maybe the weakest material in the anchoring system.Therefore,it is necessary to study and describe which parameter is mostly influencing the final resistance of the anchor.The first part of the contribution discusses the design approaches used in codes for the bond failure type.The influence of concrete and adhesive performance is closely described in related references.In the main part of the analysis,experiments with epoxy and vinyl ester adhesives suitable for anchoring in high strength concrete are presented.The analysis is closely focused on bond strength experiments using the steel specimens.The effect of concrete influence is excluded in this case.Several mixtures of high performance epoxy resin and vinyl ester resin are presented.Some tests of resin filled by milled limestone and milled recycled FRP reinforcement are also included.The problem of the testing epoxy adhesive strength itself is also one of the aims of the analysis.The thickness of the adhesive layer is very small in such applications,therefore,it is quite complicated to find appropriate test configuration and also the shape of test specimen.Results of experiments in concrete specimens have shown that the shear strength of the adhesive is the crucial parameter under such conditions.Therefore,the new steel specimen,which is effective for the testing of this shear strength,was designed.The design of this specimen is presented in this paper.The results of this analysis show that the limiting value of the shear strength of such adhesives is close to 30 MPa.In addition,some problems of adhesive shrinkage during the hardening time appeared in tests and they are presented in load-deformation diagrams.The progress and configuration of the experiments as well as the results are described in this paper.