Centre of Materials and Building Technologies

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Publications

Estudo do desempenho de misturas betuminosas com incorporação de fibras celulósicas

Publication . Afonso, Márcia Isabel Lopes; Maia, Maria; Almeida, Marisa S. Dinis; Martinho, Fernando; Fael, Cristina Maria Sena

As administrações de estradas em todo o mundo têm tomado consciência da importância do estudo das misturas betuminosas a aplicar nas camadas superficiais dos pavimentos rodoviários, face à necessidade de aumentar a durabilidade e o desempenho mecânico e funcional dos pavimentos. O principal objetivo deste estudo é avaliar o comportamento de quatro tipos de misturas, duas misturas drenantes e duas misturas densas. Foi, ainda, avaliada a influência da incorporação de fibras celulósicas aditivadas, com vista a melhorar a adesividade entre os agregados e o ligante. As fibras, de dois tipos distintos, irão contribuir para evitar a perda de ligante por escorrência, aumentar a afinidade entre agregado e betume e aumentar a resistência à deformação permanente.

2019-11Conference object

Open access

Neutral Axis Depth versus Ductility and Plastic Rotation Capacity on Bending in Lightweight-Aggregate Concrete Beams

Publication . Bernardo, Luís; Nepomuceno, Miguel; Pinto, Hugo

This article presents an experimental study on the evolution of the neutral axis depth at failure in the critical section with the flexural ductility and plastic rotation capacity of reinforced concrete (RC) lightweight-aggregate concrete (LWAC) beams. For this, the results of a previous experimental program involving RC LWAC beams tested in flexure until failure are used. The variable studies were the concrete compressive strength (between 22.0 and 60.4 MPa and dry density between 1651 and 1953 kg/m3) and the longitudinal tensile reinforcement ratio (between 0.13% and 2.69%). The flexural ductility and the plastic rotation capacity of the RC LWAC beams are characterized by a ductility index and a plastic trend parameter, respectively. The influence of the variable studies, as well as the relation of the flexural ductility and plastic rotation capacity with the values for the neutral axis depth at failure are analyzed and discussed. Some conclusions are drawn which can be useful for the design of RC LWAC beams for flexure. In particular, it is shown that the practical rule of limiting the neutral axis depth at failure to ensure ductile behavior, as used in normal-weight aggregate concrete beams, is also valid for RC LWAC beams.

2019Journal article

Open access

Evaluation of Self-Compacting Concrete Strength with Non-Destructive Tests for Concrete Structures

Publication . Nepomuceno, Miguel; Bernardo, Luís

Self-compacting concrete (SCC) shows to have some specificities when compared to normal vibrated concrete (NVC), namely higher cement paste dosage and smaller volume of coarse aggregates. In addition, the maximum size of coarse aggregates is also reduced in SCC to prevent blocking effect. Such specificities are likely to affect the results of non-destructive tests when compared to those obtained in NVC with similar compressive strength and materials. This study evaluates the applicability of some non-destructive tests to estimate the compressive strength of SCC. Selected tests included the ultrasonic pulse velocity test (PUNDIT), the surface hardness test (Schmidt rebound hammer type N), the pull-out test (Lok-test), and the concrete maturity test (COMA-meter). Seven sets of SCC specimens were produced in the laboratory from a single mixture and subjected to standard curing. The tests were applied at different ages, namely: 1, 2, 3, 7, 14, 28, and 94 days. The concrete compressive strength ranged from 45 MPa (at 24 h) to 97 MPa (at 94 days). Correlations were established between the non-destructive test results and the concrete compressive strength. A test variability analysis was performed and the 95% confidence limits for the obtained correlations were computed. The obtained results for SCC showed good correlations between the concrete compressive strength and the non-destructive tests results, although some differences exist when compared to the correlations obtained for NVC.

2019Journal article

Open access