PSI - Issue 17

Ana Isabel Marques et al. / Procedia Structural Integrity 17 (2019) 1002–1009 Ana Isabel Marques / Structural Integrity Procedia 00 (2019) 000–000

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The σ c and dynamic E tests were performed on three specimens for each set of test parameters. Each of these test parameters set had to use new specimens, since the σ c test is a destructive testing methodology. The static E tests were performed on six mortar specimens for each test parameters set. Since these specimens didn't have to undergo a destructive testing methodology, they were used for every age tested.

3. Description of the proposed experimental methodology

The experimental methodology to determine static E values (SME) for coating mortars presented in this paper aims to solve some of the major issues found by other researchers that have worked with mortar or concrete specimens (Cikrle et al., 2005; Popovics et al., 2008; Rosell et al., 2012). This experimental methodology aims to improve the reliability of the collected data and solve issues related to internal defects and overall geometry of the specimen. This experimental methodology corresponds to a cyclic compression test, based on the standard ISO 6784 (1982) for static E tests on concrete specimens. After several iterations on the test methodology, most of the reported problems were solved through the application of the following measures: • Development of a measuring device equipped with two displacement transducers (transducer L1 and transducer L2), which integrate a larger specimen length than other solutions like strain gages, to obtain more reliable strain data (Fig. 1, left); • Development and application of a specific clamping solution that allows proper use of the measuring device, without damaging the specimen or the device, while obtaining reliable data. This solution makes use of pressure screws, applied on the specimen against reinforced areas (Fig. 1, right). These local surface reinforcements are made with two component polyester putty; • Establishment of adequate criteria to gauge specimen quality regarding geometric and volumetric defects, intrinsic to the molding process with coating mortars. These defects, apart from having the potential to negatively influence the obtainable static E value, can also generate specimen flexion during the compressive loading cycle. This is caused by off centered compressive loads applied on the specimen due to a lack of parallelism between both loading surfaces; • Application of a revised experimental testing methodology, based on the previous concepts. This experimental methodology is briefly described in the following page.

Fig. 1. (left) Measuring device, including the two displacement transducers (L1 and L2); (right) clamping solution used.

The final version of the measuring device is made of two aluminium rings that are clamped to the test specimen by eight sharp pointed pressure screws (Fig. 2), against the previously mentioned reinforced areas. The rings are attached to two precisely spaced sections of the specimen (45 ± 0.5 mm), by two spacing bars, to allow for proper strain calculations. This configuration allows the two displacement transducers to measure the displacement applied