Miguel Costa Santos Nepomuceno

Parameters for Self-compacting Concrete Mortar Phase

This paper reports on an experimental study that was conducted on 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 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.

Flexural ductility of lightweight-aggregate concrete beams

AbstractThis paper describes an experimental study on the flexural ductility of lightweight-aggregate concrete beams including concretes with compressive strengths between 22.0 and 60.4 MPa and dry densities between 1651 and 1953kg/m3. Nineteen simply supported beams were tested until failure. Two symmetrical concentrated loads were applied at approximately one third of the span. Ductility was studied by defining ductility indexes. The main variables are the concrete compressive strength and the longitudinal tensile reinforcement ratio. It is shown that the parameter with higher influence on ductility is the longitudinal tensile reinforcement ratio. The test results are also compared with the requirements from some codes of practice. It is shown that ACI Code requirements give more guaranties as far as ductility is concerned, when compared with European codes.

Use of refurbished shipping containers for the construction of housing buildings: details for the structural project

AbstractConstruction using refurbished shipping containers is a recent building system, with already many successful examples around the world. This system presents a huge potential in the field of sustainable construction provided by the recycling of used containers. This paper aims to contribute to a better knowledge of this construction system in what concerns to the structural project. The general constitution of two maritime shipping containers is presented as well as some aspects of their structural behavior. For this purpose, numerical analyses were performed using a finite elements analysis program. Normative aspects for the structural project are also presented. This paper also presents the analysis of a case study with the use of refurbished shipping containers to build a single-family house. The evaluation of the strength of the refurbished shipping containers to building actions is carried out. It is shown that such evaluation is not easy because some mechanical parameters of noncommercial ste...

Critérios para definição da composição de betões leves autocompactáveis com agregados de argila expandida

RESUMO Este artigo resume um estudo experimental que teve como objetivo definir parâmetros para a composição de betões leves autocompactáveis (BAL), incorporando agregados grossos de argila expandida e agregados finos de areia natural. Partindo da metodologia proposta por Nepomuceno et al. para os betões autocompactáveis de densidade normal (BAC), investigaram-se as alterações necessárias para produzir os BAL. Avaliou-se a curva granulométrica de referência dos agregados grossos leves e as propriedades do escoamento das argamassas adequadas à produção dos BAL. Avaliou-se a segregação estática e investigou-se a relação entre os parâmetros da mistura, a trabalhabilidade, a resistência à compressão e a massa volúmica seca. Concluiu-se que a absorção dos agregados leves constitui um aspeto relevante e que a curva de referência dos agregados grossos, bem como as propriedades reológicas das argamassas propostas por Nepomuceno et al. para os BAC, são adequadas à obtenção de BAL. Concluiu-se que a composição terá de resultar do equilíbrio entre a resistência à compressão e a massa volúmica seca pretendidas, uma vez que a resistência à compressão depende da razão água/cimento e do volume de agregados leves e este último afeta a massa volúmica seca.

Analysis of Within-Test Variability of Non-Destructive Test Methods to Evaluate Compressive Strength of Normal Vibrated and Self-Compacting Concretes

Non-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.

Plastic rotation capacity of lightweight-aggregate concrete beams

This article describes a study on the plastic behaviour of lightweight-aggregate concrete beams. The experimental results of nineteen simply supported beams previously tested by the authors were used in this study. The experimental plastic rotation capacity of the tested beams was characterized by a parameter called Plastic Trend Parameter (PTP). The main variables studied were the concrete compressive strength and the longitudinal tensile reinforcement ratio. It was found that plastic rotation capacity slightly increases as the concrete compressive strength increases. An appropriate range for the longitudinal tensile reinforcement ratio to ensure plastic rotation capacity is proposed. The results of this study were also compared with the requirements from some codes of practice. From this analysis, it was shown that ACI Code requirements give more guaranties as far as plastic rotation capacity is concerned, when compared with European codes. First published online: 28 Jan 2016