146 research outputs found

    Rammed Earth Construction: A Proposal for a Statistical Quality Control in the Execution Process

    Get PDF
    Unlike other common contemporary construction materials such as concrete, mortars, or fired clay bricks, which are widely supported by international standards and regulations, building with rammed earth is barely regulated. Furthermore, its quality control is usually problematic, which regularly encourages the rejection of this technique. In the literature, many authors have suggested ways to safely build a rammed earth wall, but only a few of them have delved into its quality control before and during the construction process. This paper introduces a preliminary methodology and establishes unified criteria, based in a statistical analysis, for both the production and the quality control of this constructive technique in cases dealing with both samples and walls

    The use of non-destructive testing to evaluate the compressive strength 1 of a lime-stabilised rammed-earth wall: Rebound index and ultrasonic pulse velocity

    Get PDF
    The non-standardization of rammed earth construction involves the quality control of such a technique to be so troublesome that it is generally avoided. As a possible approach to improve the mentioned quality control, this paper deals with a series of univariate and multivariate statistical analyses concerning the correlation between a pair of non-destructive testings (rebound index and ultrasonic pulse velocity)and the compressive strength of a specific composition of rammed earth. Both non-linear (univariate)and linear (multivariate) regression models are established so that the variability of the compressive strength is accurately explained by means of both kind of non-destructive testings

    Considerations on the physical and mechanical properties of lime-stabilized rammed earth walls and their evaluation by ultrasonic pulse velocity testing

    Get PDF
    This study examines the influence of moulding moisture content on the compressive strength, dry density and porosity of a rammed earth wall, using ultrasound as a complementary technique. Non-parametric and multivariate statistical techniques were applied to analyse the behaviour of variables with a sufficiently large population. The statistical analysis demonstrated that excessive or insufficient moulding moisture content directly determines the physical-mechanical properties of such walls. Ultrasound was confirmed as a valid technique for assessing the quality of a wall, since its response, albeit with certain limitations, was consistent with physical-mechanical properties

    Durability of API class b cement pastes exposed to aqueous solutions containing chloride, sulphate and magnesium ions

    Get PDF
    Este trabajo se basa en el estudio de la durabilidad de un cemento API clase B, utilizado en pozos petrolíferos someros, frente a la agresividad de las aguas de formación a las que puede estar expuesto. Su eficacia frente a la exposición a los iones más importantes –SO4 =, Mg+2 y Cl-– se relaciona con su capacidad de asimilar la acción agresiva de cada agente perjudicial, así como de las reacciones químicas que sufra por la reactividad de alguno de sus compuestos. La metodología aplicada supone la preparación de probetas de este cemento y su inmersión en disoluciones neutras, conteniendo los referidos iones a distintas concentraciones, para evaluar el desarrollo de las reacciones existentes en su seno. A tal fin se realizaron análisis de las disoluciones y estudios de DRX durante más de un año para conocer su evolución mineralógica. El objetivo del trabajo ha sido determinar los efectos resultantes de los ataques conjuntos de los citados iones al referido cemento; así como la observación de las variaciones de las concentraciones de calcio en diferentes disoluciones acuosas de Na2SO4, MgCl2 y NaCl en contacto con pastas de cemento API clase B.This paper discusses a durability study conducted on API class B cement, the type used in shallow oil wells, when exposed to aggressive formation water. Its resistance to the major ions, namely –SO4 =, Mg+2 and Cl-–, is related both to its capacity to assimilate the aggressive action of each harmful agent and to the changes in the chemical reactivity of some of its components. The methodology used consisted in preparing and immersing cement specimens in neutral solutions containing variable concentrations of these ions to monitor the chemical reactions taking place. These solutions were analyzed and XRD studies were conducted for over a year to identify mineralogical variations. The purposes of the study were to determine the effects of joint ionic attack on this kind of cement and to monitor the variations in the calcium concentration in the aqueous solutions of Na2SO4, MgCl2 and NaCl in contact with API class B cement pastes

    Learning networks at university context. E-Learning for "Materiales de Construcción" and "Historia de la Construcción" Subjects at Escuela Universitaria de Arquitectura Técnica de la Universidad de Sevilla

    Get PDF
    Due to the requirements of the Treaty of Lisbon, of the different EU regulations and communications to achieve the main human and economic progress area in the world, it is necessary to make changes in the formative process of its main figures. In this sense, the European Higher Education Area is an opportunity for the redefinition of structures, teaching methods and roles of all of those implicated in Higher Education processes. The use of digital platforms in the ordinary Higher Education formative processes makes us wonder about the quality of the formative proposals we offer to our students. This work deals with the study of the usefulness of ICT tools to develop innovative methodologies for “Materiales de Construcción” and “Historia de la Construcción ” subjects at Escuela Universitaria de Arquitectura Técnica de la Universidad de Sevilla; accordingly, it implies a transformation process of responsible lecturers in matters such as: professional training, updating methodologies, etc.; towards University studen

    An argument for using alizarine yellow R and indigo carmine to determine in situ the degree of alkalinity in reinforced concrete

    Get PDF
    The commonest way of determining the passivation of steel in reinforced concrete is to spray a pH indicator onto the surface of a reinforced concrete specimen. To do so, the traditional indicator used has been phenolphthalein in ethanol, which shifts from colourless to purple in the pH range of 8.5–10.0. If the concrete encasing the rebar turns purple, it indicates it is passivated; that is, it has a film of iron oxide impermeable to oxygen that protects it from oxidation. However, the reduction in the pH of the concrete due to carbonation (between 11.4 and 8.5) indicates, despite the reddish-purple colour, the disappearance of the passive layer of the steel. Consequently, we propose a novel in situ technique for determining with a high degree of reliability, the passive state (pH over 11.7) and the active state (pH under 11.4) using two reactants: alizarine yellow R and indigo carmine

    Integración de los sistemas urbanos de drenaje sostenible como acción de rehabilitación hidrológica en barrios

    Get PDF
    The design of urban systems that allow the introduction of techniques for the recycling and drainage of rainwater represents a new aspect for the development of urban planning with sustainability criteria, since its main objectives include: the optimisation of the use of water as a resource in cities, the minimisation of the impacts on the natural cycle of water, and the protection of the ecosystem upon which it depends. Our proposal is based on the so-called water-sensitive urban rehabilitation’, and involves planning a management system that can be applied to the rehabilitation of neighbourhoods or urban units, built on a new design of urban elements. In the present paper, a model of analysis is proposed of the urban area of intervention in order to be able to perform the water diagnosis and to develop the water rehabilitation plan. This data forms the basis for the selection of systems that enable the characterisation of rainwater collected in the urban unit under study: that coming from the roofs of buildings and from roads and open urban spaces. With this information, we can choose those sustainable urban drainage systems (SUDS) that are the most appropriate for the urban area studied, in order to enable a housing project to be carried out that allows the rehabilitation of water in the neighbourhood or in the urban area with sustainability criteria. It should be emphasised that, when choosing an urban unit or neighbourhood as a basis for our proposal, apart from providing a more detailed analysis of sustainability criteria for the accomplishment of the project, it allows us to suggest actions that strengthen the assimilation of social and cultural elements of the neighbourhood. In this respect, we conclude the communication with the development of a project of water rehabilitation for an area selected in the neighbourhood of Los Bermejales, Seville, as an experimental model.El diseño de sistemas urbanos que permitan introducir técnicas de recuperación y drenaje de las aguas pluviales, representa un nuevo camino en el desarrollo de la planificación urbana con criterios sostenibles, ya que sus principales objetivos son: optimizar en las ciudades el uso del agua como recurso, minimizar los impactos sobre el ciclo natural del agua y proteger los ecosistemas que de él dependen. Nuestra propuesta de actuación se sustenta en lo que viene denominándose “rehabilitación hidrológica urbana sostenible”, planteando un modelo de actuación que puede ser aplicado a la rehabilitación de barrios o unidades urbanas, a partir de un nuevo diseño de los elementos urbanos. En la presente comunicación proponemos un modelo de análisis de la zona urbana de intervención, para poder realizar el diagnóstico hidrológico y elaborar el plan de rehabilitación hidrológica. Estos datos serán la base para seleccionar los sistemas que nos van a permitir caracterizar el agua de lluvia que se recogerá en la unidad urbana de estudio: tanto la procedente de las cubiertas de los edificios como la de los viales y espacios libres urbanos. Con esta información podremos seleccionar los Sistemas Urbanos de Drenaje Sostenible (SUDS) más apropiados al área urbana de estudio a fin de poder realizar un proyecto de urbanización que permitirá la rehabilitación hidrológica del barrio o el área urbana con criterios sostenibles. Cabe destacar que al elegir una unidad urbana o barrio como base para nuestra propuesta de actuación, además de facilitarnos el análisis de los criterios sostenibles con mayor detalle para la concreción del proyecto, va a permitirnos proponer acciones que potencien la integración de los elementos sociales y de identidad cultural del barrio. En este aspecto, concluimos la comunicación con la realización de un proyecto de rehabilitación hidrológica para un área seleccionada en el Barrio de los Bermejales de Sevilla, como paradigma piloto

    Lime-crusted rammed earth: materials study

    Get PDF
    This study analyses the durability of rammed-earth wall construction techniques. The analysis focuses on three medieval masonry types from the Castle of Villavieja (Castellón, Spain) using two variations of lime-reinforced rammed earth in its walls: lime-crusted rammed earth and brick-reinforced rammed earth. Materials analysis reveals the good properties of the materials used in the outer wall facing despite its age. It also clearly shows how deterioration depends more on the construction technique (construction of the wall with a base, cornice, facings, core; on-site installation, bonds, etc.) than on the material itself. These two types of lime-reinforced rammed earth (lime-crusted rammed earth and brick-reinforced rammed earth) are the most common kinds of fortified architecture in the Iberian Peninsula as well as in northern Africa and the Middle East. The case presented herein is therefore highly relevant as it advances our knowledge of the behaviour of the materials comprising these walls and lays the foundations for suitable future conservation works of a vast array of architectural heritage

    Geochemical study of products associated with spontaneous oxidation of coal in the Cerro Pelado Formation, Venezuela

    Get PDF
    The aim of this research work is a geochemical, mineralogical, and textural characterization of spontaneously smouldered coal-derived products in northwestern Venezuela (Cerro Pelado Formation, some 10 km from Pedregal city). Several solid samples were collected from this formation, six of unweathering coal, an other six of resulting unmelted rocks forming on a surface coal bed, and the last four of mineralizations found accumulating around gas vents. The fresh coal and the unmelted material were analysed by scanning electron microscopy, X-ray diffraction, and proximate techniques. Products such as magnetite and chabazite-K were identified in the alteration rocks. Likewise, both materials were also studied in order to determine the mobilization of 17 elements into the environment; such elements were analysed through inductively coupled plasma atomic emission spectroscopy on extracts obtained by a sequential extraction method: each sample was firstly extracted with MilliQ water and then the resultant residue was washed. This and the subsequently resulting residues are extracted according to the mentioned procedure by using, respectively, ammonium acetate, chlorhydric acid, peroxide and chlorhydric acid, nitric acid and fluorhydric acid, and nitric acid. The studied elements are classified as highly mobile (Na, Ni, ...), nearly immobile (Ti, P) and partially mobile (Mg, Fe, K,...). In regards to mineralizations around fumaroles associated with smoldering coal seams, Fourier-transform infrared spectroscopy and X-ray diffraction analyses have revealed the presence of salammoniac, mascagnite and other solid combustion compounds formed by reaction of gas emitted from coal oxidation, in addition to previously non-reported sulfur-rich by-products associated with gas fissures, particularly ammonium thiosulfate, a phase first obtained only synthetically in the laboratory. Another objective of the research was to collect and analyse gases escaping from surficial vents. Relatively high concentrations of several aromatic compounds were detected in the gas collected at the studied coal outcrop, as well as aliphatic hydrocarbons including ethane, propane, butanes, among others. High contents of carbon monoxide, methane and carbon dioxide were also measured for gas samples

    Los morteros del Convento de Santa Paula (Sevilla)

    Get PDF
    El estudio de los materiales constitutivos de una obra o edificación, además de ser una de las etapas que permite la recopilación de información en el análisis de su situación, debe tener una gran influencia en la posterior toma de decisiones sobre las actuaciones que se van a realizar sobre ella. En esta ocasión, dentro del proyecto de intervención de la Miras del Convento de Santa Paula (Se- villa), se ha llevado a cabo la caracterización de los morteros mediante el análisis de su composición y dosificación, porosidad, adherencia, y mediante la utilización de la lupa binocular. Los resultados obtenidos muestran en general el empleo de morteros con elevados contenidos en cal y abundante presencia de fibras de origen vegetal. Esta información ha sido de utilidad para la elaboración de los morteros de reposición de los revestimientos con mayor deterior
    corecore