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- Maximum coarse aggregate’s volume fraction in self-compacting concrete for different flow restrictionsPublication . Nepomuceno, Miguel; Oliveira, Luiz Antonio Pereira de; Lopes, Sérgio Manuel Rodrigues; Franco, Rui Miguel CalaçaThe volume of coarse aggregates (Vg) in self-compacting concrete (SCC) is usually conditioned to the passing ability (PA) in an L-box test. Some mix design methods use the three bar test results in L-box for proportioning SCC. However, in real structures, gaps can differ from those of L-box. By increasing the gaps, the Vg value can be increased and, consequently, the mortar phase volume can be decreased. In this study, the model proposed by Nepomuceno et al. (2014) to quantify the Vg value was modified to allow the introduction of an additional parameter that takes account for different gaps. Four SCC mixtures with different Vg values and the same mortar phase were produced and the PA value measured in the L-box test for different sizes of gaps: R1 (34 mm), R2 (64 mm), R3 (94 mm) and R4 (no restrictions). The results showed that for less demanding gaps it is possible to increase the Vg value of SCC and comply with the PA value in L-box test (H2/H1≥0.80).
- Methodology for the mix design of self-compacting concrete using different mineral additions in binary blends of powdersPublication . Nepomuceno, Miguel; Oliveira, Luiz Antonio Pereira de; Lopes, Sérgio Manuel RodriguesInteraction between the coarse aggregates and the mortar phase of self-compacting concrete (SCC) was evaluated in a two phase program. In the first phase, 74 mortars suitable for SCC were produced, combining different volumetric ratios between powders and fine aggregates and different binary blends of powders. In the second phase, 60 concretes were produced with different volumetric ratios between the mortar phase and the coarse aggregates, and their fresh and hardened properties were evaluated. Based on this study, correlations between mix design parameters, fresh and hardened properties were obtained and a methodology was proposed for the mix design of SCC.
- Methodology for mix design of the mortar phase of self-compacting concrete using different mineral additions in binary blends of powdersPublication . Nepomuceno, Miguel; Oliveira, Luiz Antonio Pereira de; Lopes, Sérgio Manuel RodriguesThis paper details a comparative analysis of the results obtained in tests on mortars suitable for self-compacting concrete (SCC). The binary and ternary blends of powder materials used were combinations of two cements with four additions in different percentages: limestone powder, fly ash, granite filler and microsilica. The correlations between the mix design parameters of the mortar phase and the flow properties and compressive strength were evaluated. As a result of this evaluation, a simple methodology was proposed for the mix design of the mortar phase in binary blends of powder with the aim of simultaneously obtaining both adequate flow properties and the necessary compressive strength of the mortar.
- Analysis of Within-Test Variability of Non-Destructive Test Methods to Evaluate Compressive Strength of Normal Vibrated and Self-Compacting ConcretesPublication . Nepomuceno, Miguel; Lopes, Sérgio Manuel RodriguesNon-destructive tests (NDT) have been used in the last decades for the assessment of in-situ quality and integrity of concrete elements. An important step in the application of NDT methods concerns to the interpretation and validation of the test results. In general, interpretation of NDT results should involve three distinct phases leading to the development of conclusions: processing of collected data, analysis of within-test variability and quantitative evaluation of property under investigation. The analysis of within-test variability can provide valuable information, since this can be compared with that of within-test variability associated with the NDT method in use, either to provide a measure of the quality control or to detect the presence of abnormal circumstances during the in-situ application. This paper reports the analysis of the experimental results of within-test variability of NDT obtained for normal vibrated concrete and self-compacting concrete. The NDT reported includes the surface hardness test, ultrasonic pulse velocity test, penetration resistance test, pull-off test, pull-out test and maturity test. The obtained results are discussed and conclusions are presented.