The influence of curing and surface preparation on the adhesion of protective coatings on concrete

摘要

In cases where concrete has to be repaired or protected due to exposure to anudaggressive environment, a protective coating is often used. The guidelinesudreferenced on the subject of repairs and coatings of concrete require the substrateudmust be clean, dry and free from loose material but no mention is made of audpreferred method of surface preparation.udThis research report presents details of an investigation in which concrete wasudsubjected to different curing regimes in order to induce different qualities of surfaceudconcrete. The different surface qualities were prepared using four alternative surfaceudpreparation methods prior to coating. After an initial investigation, five differentudcoatings were chosen in order to cover a broad spectrum of coatings available to theudconstruction industry.udOnce the applied coatings had cured they were tested using a pull-off testing deviceudto determine the adhesion properties. The mode of failure was determined by visualudexamination. In addition, surface characteristics were determined using an opticaludmicroscope and the water sorptivity test.udResults indicate that preparing the surface before application of coatings doesudimprove adhesion. The preparation that was easiest to carry out, and which alsoudgave the best adhesion results, was the wire brushing technique. Considering theudpracticality for site application, the mechanical method would be most appropriate.udFrom the findings, aliphatic coating exhibited the best adhesion properties, whileudepoxy resin and cementitious-based materials also gave satisfactory results.udB T Benn 7231599 iiiudElastomeric coating with lower adhesion strengths at early ages may be suited toudsurfaces that are expected to crack, as the elastic nature of the material will bridgeudthe gap. Masonry paint, which was only used for comparative purpose did notudperform as well as expected and had the lowest bond strengths. Where the removaludof defective concrete is likely to result in a rough surface the cementitious materialudmay be preferable.