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- Parameters for Self-compacting Concrete Mortar PhasePublication . Nepomuceno, Miguel; Oliveira, Luiz Antonio Pereira deThis paper reports an experimental study on the mortar phase for self-compacting concrete. A series of mortars were produced with similar flow properties, measured by spread and v-funnel tests, adequate to produce self-compacting concrete. The water content and the modified carboxylic superplasticizer dosage were determined experimentally for each mortar. Different percentages of cement replacement materials were used in binary blends, each one combining one of the two types of cement with one of the three mineral additions selected: limestone powder, granite filler and fly ash. Each of the binary blends of powders was combined in five different proportions in volume with the fine aggregate (Vp/Vs). Mortars were tested for compressive strength at 28 days age and this value was related to the water/cement ratio, the percentage of replacement materials, and Vp/Vs parameter. The analysis revealed the possibility of establishing adequate mortar parameters to obtain simultaneously the self-compactability and the required compressive strength of self-compacting concrete.
- 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).
- Mix design of structural lightweight self-compacting concrete incorporating coarse lightweight expanded clay aggregatesPublication . Nepomuceno, Miguel; Oliveira, Luiz Antonio Pereira de; Pereira, Sandrine de FreitasThis paper reports an experimental study that aimed to define the parameters for the mix design of structural lightweight self-compacting concrete (LWSCC) incorporating coarse lightweight expanded clay aggregates and natural sand. The starting point was the methodology proposed by Nepomuceno et al. (2014) for normal density self-compacting concrete (SCC). The necessary modifications were evaluated and new correlations obtained to support the definition of the mix design parameters. It was concluded that the coarse aggregates reference curve, as well as the mortar phase flow properties proposed by Nepomuceno et al. (2012) for the SCC, are adequate to produce LWSCC. Correlations to quantify the volume of coarse lightweight aggregates (Vg) are presented. It was shown that Vg depends on the mortar phase proportions, concrete workability properties, concrete compressive strength and concrete oven-dry density. The analysis of dynamic and static segregation shows a satisfatory performance with a uniform distribution of lightweight aggregates.
- 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.
- Evaluation of Self-Compacting Concrete Strength with Non-Destructive Tests for Concrete StructuresPublication . Nepomuceno, Miguel; Bernardo, LuísSelf-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.
- An eco-friendly self-compacting concrete with recycled coarse aggregatesPublication . Oliveira, Luiz Antonio Pereira de; Nepomuceno, Miguel; Rangel, Mauro Edson CarrasqueiroThe potential uses of coarse recycled aggregates in the composition of SCC increases the ecological value and partly solve the issues of waste disposal sites generated by construction and demolition of structures. Thus, this paper present an experimental study of SCC properties where the normal coarse aggregates were replaced by different percentages of recycled aggregates, i.e., 0% (SCC), 10% (SCCR10), 20% (SCCR20), 30% (SCCR30) and 40% (SCCR40). The results from fresh concrete (rheological properties and self-compactability) as the hardened concrete properties (compressive strength, density and dynamic modulus of elasticity), show only minor discrepancies. From the standpoint of mechanical behaviour, the results confirm the viability to incorporate coarse recycled aggregates in the SCC demonstrating the conservative character of the currently recommended limits.
- Permeability properties of self-compacting concrete with coarse recycled aggregatesPublication . Oliveira, Luiz Antonio Pereira de; Nepomuceno, Miguel; Gomes, João Castro; Vila, Maria de Fátima CarmoThis article addresses to the issue of durability related properties of self-compacting concrete (SCC) with the use of coarse recycled aggregates obtained from demolition of concrete structures. The objective was to verify the influence of recycled aggregates on SCC permeability properties. For this purpose four different types of concrete mixes were produced, one of them used as reference with natural coarse aggregates and the others prepared with 20%, 40% and 100% of recycled coarse aggregates. The properties related to the durability of SCC, as air and water permeability and capillary absorption were determined on concrete specimens with and without preconditioning. The results from fresh and hardened concrete properties lead to the conclusion that it is viable to replace natural coarse aggregates by recycled coarse aggregates since the present research does not show any detrimental to the SCC permeability properties.
- Experimental evaluation of the potential use of waste recycled concrete fine aggregates to produce self-compacting concretePublication . Pinto, Hugo; Nepomuceno, Miguel; Bernardo, Luís; Oliveira, Luiz Pereira deThe current concern with sustainability in the construction sector has led to the adoption of processes to minimise the impact on the environment. The use of recycled concrete aggregates in self-compacting concrete (SCC), as an alternative to natural aggregates, seems to be a solution with great potential. However, it is common knowledge that the use of recycled aggregates in the production of SCC instead of natural aggregates may causes changes in some of its properties, both in the fresh and hardened state, and that the magnitude of those changes will depend on the percentages of incorporation and the nature of recycled aggregates. When using the mix design methodology proposed by Nepomuceno et al, SCC is assumed to be consisted basically of two phases, namely, the liquid phase (mortar phase) and the solid phase (coarse aggregates), being the main SCC properties controlled by the mortar phase. In this perspective, this research work reports the results obtained when testing mortars with flow properties appropriate to produce SCC, when binary and ternary blends of powder materials were used and natural fine aggregates were partially replaced by recycled concrete fine aggregates. The experimental program carried out involved, in a first stage, the production and testing of 11 binary mortar mixtures suitable for the production of SCC, with replacement percentages of natural fine aggregate by recycled concrete fine aggregate varying from 0% (reference mixture) to 50%, in 5% increments. Subsequently, 6 ternary mortar mixtures were produced and tested for the same purpose, with replacement percentages of natural fine aggregate by recycled concrete fine aggregate varying from 0% (reference mixture) to 50%, in 10% increments. Binary mortars included Portland cement type I 42.5R and limestone powder, while ternary mortars included Portland cement type I 42.5R, limestone powder and fly ash. In both cases, the dosages of superplasticizer and mixing water were determined experimentally to obtain the required fresh properties suitable to produce SCC. The results indicate that the 28 days age compressive strength and density of the mortars decrease with the increase in the percentage of incorporation of recycled concrete fine aggregates, regardless of whether they are mortars with binary or ternary blends of powders. In binary mixtures, the mixing water dosage increases with the percentage of incorporation of recycled aggregates, while in ternary mixtures the opposite occurs, at least up to a percentage of 40% of incorporation of recycled aggregates. The superplasticizer dosages, necessary to obtain the appropriate flow properties, were always higher in the ternary mixtures compared to the binary mixtures, even comparing only the reference mixtures. It can be concluded that mortars with the incorporation of recycled concrete fine aggregates constitute a viable material with potential for use in the construction industry, provided that the necessary adjustments to its performance are considered, thus contributing to the sustainability of construction.