A review of sample preparation and its influence on pH determination in concrete samples

If we are to monitor the chemical processes in cementitious materials, then pH assays in the pore solutions of cement pastes, mortars, and concretes are of key importance. However, there is no standard method that regulates the sample-preparation method for pH determination. The state-of-the-art of different methods for pH determination in cementitious materials is presented in this paper and the influence of sample preparation in each case. Moreover, an experimental campaign compares three different techniques for pH determination. Its results contribute to establishing a basic criterion to help researchers select the most suitable method, depending on the purpose of the research. A simple tool is described for selecting the easiest and the most economic pH determination method, depending on the objective; especially for researchers and those with limited experience in this field.Peer ReviewedPostprint (published version

Integrated value model for sustainable assessment of school centers construction

Hundreds of new school centers were built in Catalonia between 2000 and 2009. It was a governmental decision in order to solve an endemic lack of centers that in the early 2000s had worsen. Masonry and poured on site reinforced concrete structures were used to build most of these schools as it had been done previously. The novelty was the use of interesting off site construction processes such as prefabricated concrete, steel and wood technologies. These school edifices and their building processes were analyzed in the author’s thesis in 2009. Later in 2011 the author analyzed the lyfe cycle process of the construction of these centers. In this paper the authors assess the sustainability of these schools using a dynamic evaluation tool optimized for this case study. This tool has been defined using the Integrated Value Model for Sustainable Assessment (Modelo Integrado de Valor para una Evaluación Sostenible - MIVES).Postprint (published version

Decision-making through sustainability

From immemorial time, dams have contributed significantly for the progress of civilizations. For this reason, nowadays, there is a vast engineering heritage. Over the years, these infrastructures can present some ordinary maintenance issues associated with their normal operation or with ageing processes. Normally, these problems do not represent an important risk for the structure, but they have to be attended. To do it, owners of dams have to finance many ordinary interventions. As it is impossible to carry out all of them at the same time, managers have to make a decision and select the most “important” ones. However, it is not easy because interventions usually have very different natures (for example: repair a bottom outlet, change gates, seal a crack...) and they cannot use a classical risk analysis for these type of interventions. The authors, who are aware this problem, present, in this paper, a multi-criteria decision-making system to prioritize these interventions with the aim of providing engineers a useful tool, with which they can prioritize the interventions from the most important to the least. To do it, the authors have used MIVES. This tool defines the Prioritization Index for the Management of Hydraulic Structures (PIMHS), which assesses, in two phases, the contribution to sustainability of each intervention. The first phase measures the damage of the dam, and the second measures the social, environmental and economic impacts. At the end of the paper, a case of study is presented where some interventions are evaluated with PIMHS.Postprint (published version

La responsabilidad de entender y el deber de hacerse entender: el texto reglamentario como diálogo entre normadores y normados

En el ámbito de los textos de ingeniería civil existen diferentes géneros, con sus correspondientes características. Uno de esos tipos es el que se centra en la reglamentación técnica. ..

Infrastructure, innovation and industry as solutions for breaking inequality vicious cycles

Currently, poverty and inequality are crucial social issues around the world. They demand objective evaluations with the purpose of defining policies and prioritizing actions. Most of the times the most important problem lies on the fact that individuals under poverty circumstances or belonging to vulnerable collectives cannot escape these conditions by themselves and need external assistance or interventions. Another added difficulty is that both poverty and inequality can be studied from different angles and require a multidimensional approach whose definition is not straightforward. There exists a vicious cycle defined by a collection of determinants or events that lead to a phenomenon in which various disadvantages work circularly so that it is impossible for individuals or households to break the cycle. In this context, setting the background in which these vicious cycles arise can be helpful in order to conduct in-depth studies as a first step to establishing possible solutions. Even though many researchers have proposed alternative schemes for the poverty’s vicious circle, none has been introduced for inequality. In this contribution, a meaningful and integrated cycle is defined for inequality at two different levels: first of all, at an individual level; secondly, at a collective level in which a certain group is made vulnerable. This cycle includes similar parameter as those comprised in the poverty cycle such as income, access to education and access to healthcare. However, it additionally places emphasis on other aspects such as participation in politics and access to leadership positions. Besides, a conceptual and analytical framework is built, whose objective is to describe ways in which infrastructure, innovation and industry can help interrupt the continuation of the cycle. This model integrates a collection of different measures that is to be potentially helpful for policy makers. Additionally, the frame accounts for not only the fight of current existing cycles, but also of future generations ones, hence considering sustainability dimensions.Postprint (published version

Bond behavior of self consolidating concrete

The new generation of innovative projects has led to the use of greater amounts of reinforcement and the development of concrete with specific characteristics. It is necessary to use a material that ensures the uniformity of the cross section, as well as the adherence of the existing reinforcement, and due to this, the self-consolidating concrete becomes an technique alternative has great potential to achieve these properties. The aim of this paper is to analyze the bond behavior of self-consolidating concrete that was obtained by means of the Beam Test performed within a large experimental campaign of characterization. Four types of SCC were studied with two strength levels (40 MPa and 60MPa) and two different types of granular skeletons, using two specimens at each age (3, 7, and 28 days). All specimens were tested with a corrugated steel bar 10 mm in diameter. The results show that the adhesion tension independently of resistance presents a rapidly evolving at 7 days reached 95% of the total adhesion by 28 days.Postprint (published version

Modelo de obtención de distribuciones de temperaturas y de tensiones longitudinales autoequilibradas en puentes de hormigón

El interCs por la problemática de los efectos tCrmicos en las estructuras de hormigón y, en particular, en los puentes de hormigón ha ido aumentando notablemente en los últimos años. En este artículo se presenta un modelo de obtención de distribuciones de temperaturas y de tensiones longitudinales autoequilibradas en puentes de hormigón basado en un esquema bidimensional en diferencias finitas correspondiente al método explícito de resolución de ecuaciones diferenciales en derivadas parciales. Los resultados obtenidos mediante la aplicación del presente modelo se comparan con resultados experimentales y analfticos obtenidos por otros autores apreciándose una gran bondad en el ajuste. El programa numirico desarrollado se muestra como una útil herramienta de cara a su aplicación al análisis y diseño de puentes de hormigón -puentes losa, puentes cajón y puentes de vigas- frente a los efectos térmicos ambientales.During the last years, the interest in the study of thermal effects on concrete bridges has increased considerably. In this paper, an analytical model based on two-dimensional finite difference method is described to determine the time-dependent temperature distributions antl the self-equilibrated longitudinal stresses distributions within the cross section of concrete bridges. The results derived from the present method are compared with experimental and analytical results obtained by other authors, exhibiting a general good agreement. The numerical program developed has shown to be an useful tool for the analysis and design of concrete bridges in front of environmental thermal effects.Peer Reviewe

Distribution of fibers in SFRC segments for tunnel linings

This paper presents research results regarding the distribution of steel fibers in concrete used to build precast tunnel segments for Line 9 of the Barcelona Metro. The fiber distribution was studied using the actual fiber contents obtained by means of crushed cores drilled from different points of three full-scale tunnel lining segments. A statistical analysis determined that the fiber content in the ends of segments tends to be greater than in the central zone. The way of transporting, pouring and compacting concrete influences the fiber content and the fiber distribution across the thickness of the segment. In addition, cores with a diameter of 150 mm were found to have a lower scatter in the fiber content than smaller diameter specimens. Finally, based on probabilistic approaches, a minimum of 11 cores is proposed to control the fiber content in FRC segments.Peer ReviewedPostprint (author's final draft

Sustainability based-approach to determine the concrete type and reinforcement configuration of TBM tunnels linings. Case study: Extension line to Barcelona Airport T1

Fibre-reinforced concrete (FRC) is a suitable alternative to the traditional reinforced concrete used in the manufacture of precast segments used to line tunnels excavated with a tunnel boring machine (TBM). Moreover, its use as a structural material has been approved by several national codes and by the current fib Model Code (2010). The use of FRC in segmental linings confers several technical and economic advantages, evidenced by the fact that structural fibres have been used to partially or entirely replace reinforcing bars in many TBM tunnels built over the past 20 years or currently under construction. FRC could also have been used in other tunnels, which are currently in the planning stage or under construction. However, despite its technical suitability and approval in current codes, the use of FRC was not possible in some cases. The impediment has sometimes been an incomplete understanding of the structural behaviour of the material, but a more general motive has been that comparisons of materials have taken into account only direct material costs and have not considered indirect costs or social and environmental factors. The aim of the present research is to develop a method for analysing the sustainability of different concrete and reinforcement configurations for segmental linings of TBM tunnels using the MIVES method (a multi-criteria decision making approach for assessing sustainability). This MCDM method allows minimising subjectivity in decision making while integrating economic, environmental and social factors. The model has been used to assess the sustainability of different alternatives proposed for manufacturing the segmental tunnel lining for the extension of the rail line of Ferrocarrils de la Generalitat de Catalunya (FGC) to Terminal 1 of El Prat Airport in Barcelona.Peer ReviewedPostprint (author's final draft