Percorrer por autor "Saldanha, Rui"
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- INFLUENCE OF CONCRETE DENSITY AND STRENGTH ON THE BOND STRENGTH OF COMPOSITE MEMBERSPublication . Saldanha, Rui; Santos, Pedro; Júlio, EduardoThe present paper addresses the influence of both material density and strength in the adhesion between concrete layers cast at different ages. A Normal Oensity Concrete (NOC), a LightWeight Aggregate Concrete (LWAC) and an Ultra High Durability Concrete (UHDC) were considered. The latter is characterized by presenting enhanced durability properties. Nevertheless, the production of the UHDC presents both economical and environmental disadvantages. In order to minimize the impact of its use and, simultaneously, take advantage of its properties, it is proposed to use it only in the cover layer of structural members, being the bulk produced in ordinary concrete. An experimental study was conducted to characterize the adhesion between UHDC/NOC and UHDC/LWAC by means of the Modified Slant Shear Test (M-SST). This new bond test was developed by the authors to always ensure adhesive failures in composite specimens. Two different surface conditions were selected for the interface: i) smooth surface, as-cast against steel formwork; and ii) surface obtained by casting against a plastic wavy formwork. Experimental results are discussed and conclusions are drawn.
- A modified slant shear test designed to enforce adhesive failurePublication . Saldanha, Rui; Júlio, Eduardo; Dias-da-Costa, Daniel; Santos, PedroPresently, there are several tests available to evaluate the adhesion between concrete layers cast at different times. Among these, the Slant Shear Test (SST) has a wide spread use, mainly for being sensitive to the roughness of the interface surface, one of the most influencing parameters in this scope, but also because of the simplicity of the experimental setup. However, the major drawback of this test is the fact of being often obtained cohesive (monolithic) failures, therefore providing a lower bound of the interface strength, which is related with the concrete compressive strength. To definitely solve this issue, i.e., to enforce adhesive (interface debonding) failures in all situations, the 'Modified Slant Shear Test' (M-SST) was herein designed and developed. Both numerical and experimental tests have been conducted to validate this new method. All relevant conclusions are presented. In summary, it can be stated that the M-SST always enforces adhesive failure, therefore allowing to accurately assessing the adhesion of concrete-to-concrete interfaces.