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Most regulations on the manufacturing of concrete for reinforced concrete structures rest on durability models that consider the corrosion of reinforcements. Those models are based on factors such as humidity, frost, presence of chlorides, and internal characteristics of the concrete itself, like resistance, porosity, type of cement, water/cement ratio, etc. No regulations, however, adopt a purely constructive perspective when evaluating the risk of corrosion, i.e., the relative position of the reinforced concrete in buildings. The present work focuses on the relationship between the position of the damaged element and the building envelope. A total of 84 elements (columns and reinforced concrete beams) across twenty buildings were analysed in the provinces of Alicante and Murcia (Spain). The reinforcement concrete of these elements underwent carbonation-induced corrosion according to their positions in the buildings: (A) façade columns in contact with the ground; (B) interior columns in contact with the ground; (C) columns of walls in contact with the ground; (D) columns and external beams protected from rain; (E) columns and external beams exposed to rain; (F) columns and beams in air chambers under sanitary slabs; and (G), columns and interior beams. Of all types, elements (E) and (F) suffered carbonation-induced corrosion faster than the models used in the regulations, and type (G) underwent slower carbonation.

Esta investigación se ha realizado en el marco del Proyecto Europeo MASTRO “Intelligent bulk MAterials for Smart TRanspOrt industries”. Se trata de un proyecto financiado por el programa Horizonte 2020 de la Comisión Europea, con un presupuesto de 5.940.666,28 € para un consorcio de 16 participantes, liderado por Acciona y formado por: Acciona, ALKE SRL, Arkema France SA, Embraer Portugal SA, Superior Graphite Deutschland GMBH, Applynano Solutions S.L., Axia Innovation UG, BSRIA Limited, Centro di Ricerche Europeo di Tecnologie Design e Materiali, Centro Tecnologico das Industrias Textil e do Vestuario de Portugal, Centre Technique Industriel de la Plasturgie et des Composites, Diadgroup SRL, EMBRAER Portugal SA, Universidad de Alicante, Universita Degli Studi di Salerno, The University of Sheffield, PINOUT Solutions SL, Airholding S.A.. El proyecto comenzó en diciembre del año 2017 y ha finalizado recientemente, en agosto del 2021. El objetivo general de MASTRO es desarrollar materiales inteligentes para el sector del transporte basados en conceptos novedosos como metodologías de autodetección, deshielo y autocurado. ese pretende aumentar la seguridad de los consumidores, la vida útil de los componentes y su rendimiento, al tiempo que se reducen los costes de mantenimiento, la fabricación y las emisiones de gases de efecto invernadero durante su vida útil. Las funcionalidades de autorrespuesta abordados se basan en tres fenómenos físicos: la piezorresistividad (variación de la resistividad eléctrica de un material cuando se aplica una tensión mecánica), el efecto de la primera ley de Joule (la relación entre el calor generado en un conductor y el flujo de corriente eléctrica, la resistencia y el tiempo) y la disipación electrostática (para proteger un material de las descargas electrostáticas). La funcionalidad de los materiales inteligentes desarrollados se demostró en condiciones adecuadas a nivel de prototipo para los sectores aeroespacial, automovilístico y de

En este artículo se utiliza la Realidad Virtual Inmersiva (RVI) en enseñanzas técnicas tales como el Grado de Ingeniería Civil, el Grado en Fundamentos de la Arquitectura Técnica y el Máster de Ingeniería de Caminos, Canales y Puertos. Los objetivos de la investigación son: facilitar el entendimiento de los detalles constructivos, de la distribución volumétrica de espacios y del armado de elementos estructurales, algo que a veces es difícil de transmitir con las herramientas clásicas (Power Point, dibujos en pizarra, planos, etc.); aumentar la, a veces, escasa motivación del alumnado introduciendo nuevas tecnologías y facilitando su proceso enseñanza-aprendizaje; adaptar al alumnado a la rápida incorporación de la RVI en el ámbito laboral. La experiencia se llevó a cabo en cuatro asignaturas y se comprobó la mejora en la adquisición de conocimientos de los estudiantes dependiendo de la técnica utilizada: las tradicionales o la RVI. La evaluación de la consecución de los objetivos se realizó mediante cuestionarios de opinión y examinando objetivamente a los estudiantes sobre un caso en concreto analizado por una parte de ellos de la forma tradicional y por el resto mediante la RVI.

Este curso 2021-22 se ha organizado y celebrado un concurso denominado City Gamers. Ha sido creado por profesorado de los departamentos de Ingeniería Civil y de Edificación y Urbanismo y ha estado orientado a estudiantes de la ESO para fomentar en ellas y ellos el interés por el urbanismo, el funcionamiento y crecimiento sostenible de nuestras ciudades, y por las disciplinas STEM en general. Como vehículo del concurso se ha empleado, por un lado, el Objetivo de Desarrollo Sostenible 11 de la Agenda 2030 y, del otro lado, el videojuego Cities: Skylines®, el cual es un simulador de creación y gestión de ciudades. Las alumnas y alumnos participantes, por equipos paritarios de hasta seis, tuvieron que desarrollar dos actividades académicas basadas en los medios anteriormente citados, a lo largo de los meses de febrero, marzo, abril y mayo. Se recabó información para poder analizar el impacto formativo del concurso en el alumnado participante, tanto al inicio como al término del concurso, mediante sendos formularios distribuidos a las y los participantes. En esta memoria se describe con mayor detalle el concurso, las herramientas empleadas y un análisis del impacto formativo logrado con esta primera edición del concurso.

Building Information Modeling (BIM) es una metodología de trabajo colaborativa que se ha venido adoptando de forma progresiva en la industria de la construcción mundial a lo largo del presente siglo. Los estudiantes de grado en Ingeniería Civil de la práctica totalidad de las universidades españolas actualmente terminan sus estudios sin conocer siquiera los aspectos fundamentales de esta metodología, crucial en su futuro laboral. Por ello, es necesario incorporarla de manera urgente a los planes de estudios de ingeniería civil, suponiendo una oportunidad excepcional para modernizar los contenidos de las asignaturas de la titulación a este tipo de metodologías de aprendizaje colaborativo basado en proyectos y herramientas TIC. Para ello, se realizaron encuestas a estudiantes y profesores de la titulación. Los resultados muestran que ambos colectivos poseen en general muy poca información y formación acerca de BIM; sin embargo, existe un amplio consenso en la necesidad de su implantación inmediata. Todo ello condujo al diseño de una estrategia a lo largo de los cuatro cursos que integran el título de grado, seleccionando aquellas asignaturas que pueden suponer un mayor impacto en su uso, y aprovechando además la oportunidad de emplear BIM como herramienta de vertebración metodológica de la titulación.

El objetivo de esta innovación docente es dar a conocer las posibilidades de las herramientas de diseño geométrico avanzado para la definición de elementos de ingeniería civil en 3D, su relación e implementación con metodologías BIM y realidad aumentada (AR), y la realización de modelos reales a escala reducida mediante impresión 3D. Estas nuevas tecnologías aportan una motivación extra al alumnado, facilitan la asimilación y comprensión de los conceptos previamente desarrollados en clase, mejoran entendimiento de las relaciones y las colisiones entre cada parte del proyecto y el aportan una nueva forma de mostrar los resultados a los clientes, así como la adquisición de las competencias del plan de estudios. Para ello se realizará una experiencia docente utilizando estas nuevas tecnologías en el Máster de Ingeniería de Caminos, Canales y Puertos. Los medios tecnológicos necesarios para que los alumnos puedan disfrutar de esta nueva metodología son: una plataforma donde alojar proyectos BIM, una aplicación para dispositivos móviles de realidad aumentada y una impresora 3D con su software asociado. La propuesta docente será evaluada mediante dos rúbricas a los alumnos y alumnas, una antes y otra después de realizar la actividad.

In this study, CNTs and graphite have been incorporated to provide electrical conductivity and self-heating capacity by Joule effect to an epoxy matrix. Additionally, both types of fillers, with different morphology, surface area and aspect ratio, were simultaneously incorporated (hybrid CNTs and graphite addition) into the same epoxy matrix to evaluate the effect of the self-heating capacity of carbon materials-based resins on de-icing and ice-prevention capacity. The self-heating capacity by Joule effect and the thermal conductivity of the differently filled epoxy resin were evaluated for heating applications at room temperature and at low temperatures for de-icing and ice-prevention applications. The results show that the higher aspect ratio of the CNTs determined the higher electrical conductivity of the epoxy resin compared to that of the epoxy resin filled with graphite, but the 2D morphology of graphite produced the higher thermal conductivity of the filled epoxy resin. The presence of graphite enhanced the thermal stability of the filled epoxy resin, helping avoid its deformation produced by the softening of the epoxy resin (the higher the thermal conductivity, the higher the heat dissipation), but did not contribute to the self-heating by Joule effect. On the other hand, the feasibility of electrically conductive epoxy resins for de-icing and ice-prevention applications by Joule effect was demonstrated.

Cement composites with hybrid conductive fillers carbon nanotubes (CNT) and graphite products (GP), have been tested as strain sensors under varying temperatures (0 °C–60 °C), and moisture conditions (0%–100% saturation degree (SD)). Cement pastes with 1% CNT and 5% GP (purified expanded graphite) presented resistivity values between 50 and 75 Ohm·cm, and their strain sensing response was observed to be independent of the loading conditions. However, the gage factor increased up to four times for higher temperatures, and was influenced by the temperature time history. Gage factors were also increased when drying the material up to a SD of 71% or with entirely dried samples.

This paper aims to study the viability of conductive cement paste and conductive concrete with the hybrid addition of carbon nanotubes (CNT) and graphite powder (GP) as a self-heating material for heating, ice formation prevention and de-icing in pavements. Different heating tests, ice-preventing tests and de-icing tests were performed with cement paste and concrete specimens. Results confirm that the conductive cement composites studied, with the addition of 1% CNT + 5% GP, exhibited heating, de-icing and ice-prevention properties, when applying constant AC/DC voltages between the two end sides of each specimen, with relatively low energy consumption. The main contribution of this work is to achieve a sufficient conductivity level for the development of the heating and de-icing function using this hybrid addition in concrete, which has not been used so far, in order to be applied in real concrete structures.

This paper proposes binary and ternary combinations of sewage sludge ash (SSA) with fly ash (FA), marble dust (MD) and rice husk ash (RHA) as partial replacements of Portland cement in concretes with a similar dosage to that used in precast blocks, with very dry consistency. Several physical-mechanical tests were carried out on concrete specimens with curing ages of 28 and 90 days: density, water absorption, capillary water absorption, ultrasonic pulse velocity and compressive strength. The combinations of residues significantly improve the properties of the cementitious systems: 30% replacement of Portland cement provides strength values similar to the reference sample, showing the synergetic effects of the combination of the mineral additions. The significance of this research relies on the combined use of the mineral additions as well as the use of them for the precast block industry. The results show synergies among the additions and even that some of them showed relevant improvements when they are used in combination, performing better than when used individually.

El mundo de la ingeniería y la arquitectura llevan años experimentando un profundo cambio tecnológico y metodológico (trabajo colaborativo). Los avances tecnológicos permiten no solo diseñar y calcular directamente en 3D, sino además, de forma económica y sencilla, visualizar los proyectos mediante realidad virtual o aumentada, lo que supone una enorme ventaja tanto a nivel técnico como comercial. La metodología BIM (Building Information Modelling) engloba todos estos aspectos tremendamente revolucionarios para la ingeniería, la arquitectura y la construcción, dando lugar a un nuevo paradigma. Sin embargo, estas prácticas no parecen haber sido implementadas en los grados y másteres universitarios encargados de dotar a los estudiantes de las capacitaciones necesarias para enfrentarse a este nuevo mundo. El trabajo aquí expuesto trata de dotar al alumnado de último curso del Máster de Ingeniería de Caminos, de algunos de estos conocimientos (metodología BIM colaborativa, software BIM y Realidad Aumentada). Finalmente, se les pidió rellenar una encuesta a partir de la cual se pudo comprobar la eficacia de las metodologías docentes eminentemente prácticas y la urgente necesidad de adaptación de los actuales programas docentes en dichas titulaciones universitarias hacia una vinculación más directa con las últimas tecnologías y avances en el mundo AEC, dadas las carencias tecnológicas en los planes de estudio actuales, y en especial hacia el entorno BIM.

Different studies in the literature indicate the effectiveness of CNTs as reinforcing materials in cement–matrix composites due to their high mechanical strength. Nevertheless, their incorporation into cement presents some difficulties due to their tendency to agglomerate, yielding a non-homogeneous dispersion in the paste mix that results in a poor cement–CNTs interaction. This makes the surface modification of the CNTs by introducing functional groups on the surface necessary. In this study, three different treatments for incorporating polar oxygen functional groups onto the surface of carbon nanotubes have been carried out, with the objective of evaluating the influence of the type and oxidation degree on the mechanical and electrical properties and in strain-sensing function of cement pastes containing CNTs. One treatment is in liquid phase (surface oxidation with HNO3/H2SO4), the second is in gas phase (O3 treatment at 25 and 160 °C), and a third is a combination of gas-phase O3 treatment plus NaOH liquid phase. The electrical conductivity of cement pastes increased with O3- and O3-NaOH-treated CNTs with respect to non-treated ones. Furthermore, the oxygen functionalization treatments clearly improve the strain sensing performance of the CNT-cement pastes, particularly in terms of the accuracy of the linear correlation between the resistance and the stress, as well as the increase in the gage factor from 28 to 65. Additionally, the incorporation of either non-functionalized or functionalized CNTs did not produce any significant modification of the mechanical properties of CNTs. Therefore, the functionalization of CNTs favours the de-agglomeration of CNTs in the cement matrix and consequently, the electrical conductivity, without affecting the mechanical behaviour.

To the author’s knowledge, this study represents the first research whose aim is to obtain a multifunctional carbon fibre high-performance concrete (MCFHPC). It will be attained through use of self-compacting concrete (SCC) and/or high-strength concrete (HSC). Multifunctionality will be achieved if low resistivity is obtained. In this study, several percentages of different types of carbon fibres (CF) were used to produce MCFHPC. Self-compacting concrete (SCC) was obtained, but conductivity was similar to control. Nevertheless, ultra-high compressive strength was obtained (higher than 100 MPa). To reduce cost, lower quantities with same dosages were fabricated as mortars with a different CF dispersion method and very low resistivity was obtained, with only 1% vol. CF. Self-sensing and heating properties were corroborated by preliminary results. Now, the efforts of this study are devoted to obtain the same MCFHPC in a standard concrete mixer with standard concrete quantities.

The addition of a carbon material, such as carbon nanotubes (CNTs) or graphite powder (GP)as conductive ingredients transforms the resulting mixture into a conductive material. This yields the possibility of using the new material for other functions different to the structural one, so that it can be considered a multifunctional material, such as the sensing and heating function. Increasing CNTs or/and GP content decreases the resistivity. Once the percolation threshold is reached it makes no sense to increase % because the resistivity is not anymore significantly changed. Then strain-sensing and heating functions can be can be carried in these conductive cement based materials.

En esta red se ha tratado de adecuar la asignatura obligatoria de primer curso del grado de ingeniería civil denominada “Ingeniería y Empresa”, mediante la implantación de un sistema basado en proyectos y en la participación activa y continua de los alumnos. El objetivo fundamental de la red es crear las bases para la futura implantación en esta asignatura de una metodología basada en ambos principios, para lo que fue necesario adaptar parte del temario. Tras los procesos de investigación, análisis de resultados y autocrítica, se recogen en esta memoria los principales resultados obtenidos. De acuerdo con las notas obtenidas por los alumnos el resultado numérico ha sido satisfactorio. No obstante, queda mucho camino por recorrer para obtener resultados cualitativos (fundamentalmente ampliando esta experiencia en los próximos cursos) así como para adaptar y mejorar esta metodología para alcanzar cotas suficientes de eficiencia, siempre adecuándose a las exigencias del EEES. Algunas de las dificultades encontradas han sido el elevado número de alumnos en las prácticas de ordenador que hacían imposible un trato y control individualizados frente a la tremenda disparidad de conocimientos previos entre los alumnos, escenario que se ha corregido para este curso con la creación de un nuevo grupo.

The electrical resistivity of carbon fiber reinforced cement composites (CFRCC) has been widely studied for the functional applications of these composites. CFRCC with enhanced electrical properties can be used as strain or damage sensor, heating or deicing material, or anode in different electrochemical techniques, like chloride extraction or cathodic protection. In this work, carbon fiber reinforced cement mortars have been prepared using a conductive aggregate produced from the valorization of Electric Arc Furnace slag (EAF slag). Cement based mortars containing EAF slag aggregates revealed lower resistivity; hence, the carbon fiber percolation threshold decreased. Additionally, the strain sensing capacity of those composites with conductive aggregates was also enhanced, indicating similar sensitivity and lower dispersion than equivalent mortars containing limestone aggregates. The best linear regressions between the electrical and mechanical measures were achieved for EAF slag cement mortar containing 1.29 vol% of oxidized carbon fibers.

La adición de fibras de carbono en materiales cementicios permite, además de mejorar sus prestaciones mecánicas, su utilización en otras funciones no estructurales, p. ej., sensor de deformaciones. Al incluir adiciones crecientes de fibras en pastas de escoria de alto horno activada alcalinamente se consiguió mejorar su resistencia a compresión y flexión, reducir su retracción por secado, y relacionar su resistividad con la deformación sufrida por el material en ciclos de compresión. Sin embargo, para optimizar la percepción de su deformación es necesario modificar las condiciones de saturación del material, al no funcionar correctamente estando saturado., The addition of carbon fibres is used in cement composite materials with a twofold objective: enhancement of their mechanical performance, and functionalisation of the composite, e.g. as strain sensor. Alkali-activated blast furnace slag pastes were reinforced with carbon fibres, which increased bending and compressive strengths, controlled drying shrinkage, and their resistivity could be related to strains during cyclic compression tests. However, in order to optimise this strain self-sensing property, changes in water saturation of samples are necessary, because fully saturated samples did not work properly as a strain sensor.

Stainless steel is a corrosion resistant metal that has now wide record of good performance in several aggressive media, in spite of which is not fully immune to different types of attack. In present work is presented the performance of 304 stainless steel as forming part of the tubes of a tank that has been operating from 1964 for Liquefied Natural Gas storage. The stainless steel tubes are part of a pipeline connecting the Liquefied Natural Gas tanks TK-1200A/B at the Barcelona plant. The pipeline had been continuously operating for more than 40 years, with cooling cycles from ambient temperature down to cryogenic temperatures. The paper shows that the working conditions and the marine environment did not embrittle or modify the properties of the tubes.

Cement composites with nano-additions have been vastly studied for their functional applications, such as strain and damage sensing. The capacity of a carbon nanofiber (CNF) cement paste has already been tested. However, this study is focused on the use of CNF cement composites as sensors in regular concrete samples. Different measuring techniques and humidity conditions of CNF samples were tested to optimize the strain and damage sensing of this material. In the strain sensing tests (for compressive stresses up to 10 MPa), the response depends on the maximum stress applied. The material was more sensitive at higher loads. Furthermore, the actual load time history did not influence the electrical response, and similar curves were obtained for different test configurations. On the other hand, damage sensing tests proved the capability of CNF cement composites to measure the strain level of concrete samples, even for loads close to the material’s strength. Some problems were detected in the strain transmission between sensor and concrete specimens, which will require specific calibration of each sensor one attached to the structure.

Los materiales multifuncionales, también denominados materiales activos o materiales inteligentes, poseen atributos más allá de la primordial resistencia y rigidez, que típicamente conduce la ciencia y la ingeniería en los materiales para sistemas estructurales. Así, los materiales estructurales pueden ser rediseñados para tener integración eléctrica, magnética, óptica, térmica y posiblemente otras funcionalidades, que trabajan en sinergia para proporcionar ventajas más allá de la suma de las capacidades individuales, y con las cuales es posible desarrollar un sinfín de aplicaciones, que van desde las militares hasta las más convencionales en la vida diaria. Este tipo de materiales son capaces de responder de modo reversible y controlable ante diferentes estímulos físicos o químicos externos, modificando alguna de sus propiedades. En las últimas décadas se han presentado a la comunidad científica un número significativo de estudios sobre distintas matrices con adición de fibras de carbono, polvo de grafito o fibras de acero, como elemento conductor. Por otra parte, más recientemente la nanotecnología ha experimentado tremendos avances en muy distintos ámbitos científicos. Dentro de este campo destacan especialmente los nanotubos de carbono (NTC) y las fibras y nanofibras de carbono (NFC) por sus apreciables cualidades mecánicas, térmicas y eléctricas. Sin embargo, a pesar de la gran cantidad de avances en muy diversos materiales compuestos y aplicaciones prácticas –componentes electrónicos, sensores, matrices poliméricas, metálicas o cerámicas, etc. —se ha prestado escasa atención al potencial uso de aquellos en matrices cementicias. Es más, la mayoría de estos trabajos se han centrado más en la utilización de NTC que en la de NFC. Muchos métodos y técnicas que han sido investigadas para la eliminación del hielo en carreteras causan enormes pérdidas en vidas humanas, infraestructuras y materiales. Los métodos mecánicos de eliminación de la nieve son los más usados

La función de calefacción que poseen los materiales cementantes conductores presenta un importante campo de aplicación en las infraestructuras de transporte. La adición de fibras de carbono (FC) en bajas cantidades al hormigón mejora sustancialmente su conductividad eléctrica, lo que puede ser aprovechado para acometer actuaciones de prevención y curación de heladas en pavimentos de carreteras y aeropuertos, frente a otros métodos más agresivos o de mayor coste económico.

This paper aims to study the feasibility of highly conductive carbon fiber reinforced concrete (CFRC) as a self-heating material for ice formation prevention and curing in pavements. Tests were carried out in lab ambient conditions at different fixed voltages and then introduced in a freezer at −15 °C. The specimens inside the freezer were exposed to different fixed voltages when reaching +5 °C for prevention of icing and when reaching the temperature inside the freezer, i.e., −15 °C, for curing of icing. Results show that this concrete could act as a heating element in pavements with risk of ice formation, consuming a reasonable amount of energy for both anti-icing (prevention) and deicing (curing), which could turn into an environmentally friendly and cost-effective deicing method.

Alkaline activation has become a useful procedure to obtain high strength cement composites without Portland cement. Different industrial byproducts can be activated using this technique, e.g. blast furnace slag, fly ash or metakaolin. Thus a new generation of more sustainable composites is being developed. However, the main disadvantage of these composites is their high drying shrinkage strain. Among the different approaches to address this problem, shrinkage reducing admixtures are the most used, but the addition of fibers can be useful for this purpose. In this work, alkali activated slag (AAS) pastes have been reinforced with carbon fibers (CF). The effect of the concentration of alkaline activator (Na2O% and silica modulus) and the fiber aspect ratio (using different length fibers with the same diameter) on the mechanical properties has been assessed. Mechanical characterization comprised bending and compressive strength tests, ultrasonic pulse velocity and density measurements, and drying shrinkage tests, in which CF were capable of improving the mechanical strengths of AAS pastes while controlling the specimens strain due to shrinkage. CF additions increased bending strength up to five times, and increases up to 20% in compressive strength were observed. Furthermore, CF can be a convenient addition to control the drying shrinkage of AAS composites. Even in adverse conditions, such us 50% RH, where unreinforced specimens actually broke, CF could guarantee the stability of the specimen.

This research studies the self-heating produced by the application of an electric current to conductive cement pastes with carbonaceous materials. The main parameters studied were: type and percentage of carbonaceous materials, effect of moisture, electrical resistance, power consumption, maximum temperature reached and its evolution and ice melting kinetics are the main parameters studied. A mathematical model is also proposed, which predicts that the degree of heating is adjustable with the applied voltage. Finally, the results have been applied to ensure that cementitious materials studied are feasible to control ice layers in transportation infrastructures.

Se plantea la combinación binaria y ternaria de cenizas de lodo de depuradora (CLD) con ceniza volante, polvo de mármol y ceniza de cáscara de arroz, como sustitución parcial o como adición respecto al cemento Portland en hormigones, con una dosificación similar a la utilizada en la prefabricación de bloques (consistencia muy seca). Se llevaron a cabo ensayos físico-mecánicos sobre probetas de mortero y hormigón con edades de curado de 28 y 90 días: densidad, absorción y resistencia a compresión. Se comprueba que la sustitución de cemento por CLD supone una disminución de la densidad y de la resistencia respecto a la muestra patrón, sin embargo, las combinaciones con otros residuos mejoran notablemente las características de los materiales cementantes. La adición de CLD proporcionó densidades y resistencias similares a la muestra de control y reduce significativamente la absorción de agua., This paper proposes binary and ternary combinations of sewage sludge ash (SSA) with fly ash, marble dust and rice hull ash, as partial replacement or addition relative to Portland cement in concretes with a similar dosage to that used in the manufacture of precast blocks, with very dry consistency given its manufacturing process in plant. Several physical-mechanical tests were carried out on concrete and mortar specimens with curing ages of 28 and 90 days: density, water absorption and compressive strength. It is proved that replacing cement by SSA involves a decrease in density and compressive strength compared to the reference sample, however, the combinations of residues significantly improve the characteristics of the cementitious materials. The addition of SSA provided densities and resistances similar to the control sample and significantly reduces the water absorption.

Binary and ternary combinations of sewage sludge ash (SSA) with marble dust (MD), fly ash (FA) and rice husk ash (RHA) as replacement in Portland cement pastes, were assessed. Several tests were carried out at different curing ages: thermogravimetry, density, water absorption, ultrasonic pulse velocity and mechanical strengths. Pozzolanic effects of the mineral admixtures, densities similar to control sample and improved absorptions when combining waste materials were identified. In general, the compressive strength reaches or exceeds the cement strength class, and blending SSA, FA and RHA (30% cement replacement) increase of strength by 9%, compared to the control sample, was achieved.

The viability of carbon nanofiber (CNF) composites in cement matrices as a self-heating material is reported in this paper. This functional application would allow the use of CNF cement composites as a heating element in buildings, or for deicing pavements of civil engineering transport infrastructures, such as highways or airport runways. Cement pastes with the addition of different CNF dosages (from 0 to 5% by cement mass) have been prepared. Afterwards, tests were run at different fixed voltages (50, 100 and 150V), and the temperature of the specimens was registered. Also the possibility of using a casting method like shotcrete, instead of just pouring the fresh mix into the mild (with no system’s efficiency loss expected) was studied. Temperatures up to 138 °C were registered during shotcrete-5% CNF cement paste tests (showing initial 10 °C/min heating rates). However a minimum voltage was required in order to achieve a proper system functioning., En este artículo se estudia la viabilidad del uso de matrices cementicias con adición de nanofibras de carbono (NFC) como elementos calefactores. Esto permitiría aumentar la temperatura de estancias en edificación o el deshielo de pavimentos en obras civiles. Se han fabricado pastas de cemento con distintas dosificaciones de NFC (0, 1, 2 y 5% respecto masa del cemento) y sometidas al paso de corriente continua a distintos potenciales fijos (50, 100 y 150 V), mientras se controlaba la temperatura en distintos puntos. Se ha estudiado la viabilidad de utilizar la proyección de la pasta fresca como método de puesta en obra, sin perjudicar la eficiencia del sistema. Se consiguieron temperaturas de hasta 138 °C (con velocidades iniciales de 10 °C/min) para pasta proyectada con 5% NFC. Además se ha detectado la necesidad de un potencial mínimo para que la densidad de corriente resultante sea suficiente para producir el efecto esperado.

In the present paper, changes in mechanical properties of Portland cement-based mortars due to the addition of carbon nanotubes (CNT) and corrosion of embedded steel rebars in CNT cement pastes are reported. Bending strength, compression strength, porosity and density of mortars were determined and related to the CNT dosages. CNT cement paste specimens were exposed to carbonation and chloride attacks, and results on steel corrosion rate tests were related to CNT dosages. The increase in CNT content implies no significant variations of mechanical properties but higher steel corrosion intensities were observed.

Binary and ternary combinations of sewage sludge ash (SSA) with marble dust (MD), fly ash (FA) and rice husk ash (RHA) as replacement in Portland cement pastes, were assessed. Several tests were carried out at different curing ages: thermogravimetry, density, water absorption, ultrasonic pulse velocity and mechanical strengths. Pozzolanic effects of the mineral admixtures, densities similar to control sample and improved absorptions when combining waste materials were identified. In general, the compressive strength reaches or exceeds the cement strength class, and blending SSA, FA and RHA (30% cement replacement) increase of strength by 9%, compared to the control sample, was achieved.

[EN] This paper is focused on the assessment of sewage sludge ash added on precast concrete blocks, therefore, based on a matrix of Portland cement with particular characteristics (dry consistency). A pilot experience was performed, by manufacturing commercial concrete blocks at an industrial local plant, using mixes in which sand replacements of 5, 10 and 15% by sewage sludge ash, being the results compared with reference concrete block (without sand replacement). The tests applied are prescriptive for marketing as European regulations (CE marking), which will also let to test the physical and mechanical properties of concrete. The results are promising: these wastes could be commercialized, because the improvement of the characteristics of the concrete blocks such as compressive strength, and consequently to reduce a large volume of a material typically used as a raw material and by means of the valorization instead of sending to landfill, [ES] El presente artículo se centra en la valorización de las cenizas de lodo de depuradora adicionadas en bloques de hormigón prefabricados, por tanto, en una matriz a base de cemento Portland con características particulares (consistencia seca). Se realiza una experiencia piloto mediante la fabricación de bloques en una planta industrial local, utilizando mezclas con porcentajes de sustitución de árido fino del 5, 10 y 15% por cenizas de lodo de depuradora, cuyos resultados se compararán con bloques de referencia (sin adición). Los ensayos aplicados son los preceptivos para su comercialización según normativa europea (marcado CE), lo que permitirá igualmente comprobar las características físicas y mecánicas de los hormigones. Los resultados obtenidos son prometedores: la utilización de este residuo permitiría su comercialización, mejora características de los bloques como la resistencia a compresión, y permitiría reducir un gran volumen de material utilizado habitualmente como materia prima y consumir un residuo destinado a vertedero.

The electrical resistivity of carbon fiber reinforced cement composites (CFRCCs) has been widely studied, because of their utility as multifunctional materials. The percolation phenomenon has also been reported and modeled when the electrical behavior of those materials had to be characterized. Amongst the multiple applications of multifunctional cement composites the ability of a CFRCC to act as a strain sensor is attractive. This paper provides experimental data relating self-sensing function and percolation threshold, and studying the effect of fiber aspect ratio on both phenomena. Higher fiber slenderness permitted percolation at lower carbon fiber addition, affected mechanical properties and improved strain-sensing sensitivity of CFRCC, which was also improved if percolation had not been achieved.

En la aplicación de la técnica de extracción electroquímica de cloruros (EEC), tradicionalmente se ha venido empleando como ánodo externo una malla de Ti-RuO2. En este artículo se aportan los resultados de investigaciones basadas en la utilización de ánodos formados por pasta de cemento conductora con adición de nanofibras de carbono (NFC) y su aplicación en EEC. Las experiencias se desarrollaron en probetas de hormigón contaminado previamente con cloruro. Las eficiencias alcanzadas se compararon con las obtenidas empleando un ánodo tradicional (Ti-RuO2), así como pastas de cemento con adición de otros materiales carbonosos. Los resultados muestran la viabilidad en la utilización de la pasta de cemento conductora con NFC como ánodo en la aplicación en EEC en hormigón, encontrándose eficiencias similares a las obtenidas con la tradicional malla de Ti-RuO2 pero teniendo la ventaja añadida sobre esta de que es posible adaptarla a geometrías estructurales complejas al ser aplicada en forma de pasta., In the application of the electrochemical chloride extraction (ECE) technique, traditionally, the Ti-RuO2 wire netting has been used as the external anode. This article provides the results of the research based on the use of conductive cement paste with addition of carbon nanofibers (CNF) as anodes and its application in ECE. The tests were developed in concrete specimens previously contaminated with chloride. The efficiencies achieved were compared with those obtained using a traditional anode (Ti-RuO2) and cement pastes with the addition of other carbonaceous materials. The results show the feasibility of using conductive cement paste with CNF as the anode in the electrochemical extraction of chlorides in concrete, finding similar efficiencies to those obtained with traditional Ti-RuO2 wire netting but with the added advantage that it can be adapted to complex structural geometries as it can be applied as a paste.

Both strain and damage sensing properties on carbon nanofiber cement composites (CNFCC) are reported in the present paper. Strain sensing tests were first made on the material’s elastic range. The applied loading levels have been previously calculated from mechanical strength tests. The effect of several variables on the strain-sensing function was studied, e.g. cement pastes curing age, current density, loading rate or maximum stress applied. All these parameters were discussed using the gage factor as reference. After this first set of elastic experiments, the same specimens were gradually loaded until material’s failure. At the same time both strain and resistivity were measured. The former was controlled using strain gages, and the latter using a multimeter on a four probe setup. The aim of these tests was to prove the sensitivity of these CNF composites to sense their own damage, i.e. check the possibility of fabricating structural damage sensors with CNFCC’s. All samples with different CNF dosages showed good strain-sensing capacities for curing periods of 28 days. Furthermore, a 2%CNF reinforced cement paste has been sensitive to its own structural damage.

In this research, strain-sensing and damage-sensing functional properties of cement composites have been studied on a conventional reinforced concrete (RC) beam. Carbon nanofiber (CNFCC) and fiber (CFCC) cement composites were used as sensors on a 4 m long RC beam. Different casting conditions (in situ or attached), service location (under tension or compression) and electrical contacts (embedded or superficial) were compared. Both CNFCC and CFCC were suitable as strain sensors in reversible (elastic) sensing condition testing. CNFCC showed higher sensitivities (gage factor up to 191.8), while CFCC only reached gage factors values of 178.9 (tension) or 49.5 (compression). Furthermore, damage-sensing tests were run, increasing the applied load progressively up to the RC beam failure. In these conditions, CNFCC sensors were also strain sensitive, but no damage sensing mechanism was detected for the strain levels achieved during the tests. Hence, these cement composites could act as strain sensors, even for severe damaged structures near to their collapse.

In recent years, several researchers have shown the good performance of alkali activated slag cement and concretes. Besides their good mechanical properties and durability, this type of cement is a good alternative to Portland cements if sustainability is considered. Moreover, multifunctional cement composites have been developed in the last decades for their functional applications (self-sensing, EMI shielding, self-heating, etc.). In this study, the strain and damage sensing possible application of carbon fiber reinforced alkali activated slag pastes has been evaluated. Cement pastes with 0, 0.29 and 0.58 vol % carbon fiber addition were prepared. Both carbon fiber dosages showed sensing properties. For strain sensing, function gage factors of up to 661 were calculated for compressive cycles. Furthermore, all composites with carbon fibers suffered a sudden increase in their resistivity when internal damages began, prior to any external signal of damage. Hence, this material may be suitable as strain or damage sensor.

El presente artículo se centra en la valorización de las cenizas de lodo de depuradora adicionadas en bloques de hormigón prefabricados, por tanto, en una matriz a base de cemento Portland con características particulares (consistencia seca). Se realiza una experiencia piloto mediante la fabricación de bloques en una planta industrial local, utilizando mezclas con porcentajes de sustitución de árido fino del 5, 10 y 15% por cenizas de lodo de depuradora, cuyos resultados se compararán con bloques de referencia (sin adición). Los ensayos aplicados son los preceptivos para su comercialización según normativa europea (marcado CE), lo que permitirá igualmente comprobar las características físicas y mecánicas de los hormigones. Los resultados obtenidos son prometedores: la utilización de este residuo permitiría su comercialización, mejora características de los bloques como la resistencia a compresión, y permitiría reducir un gran volumen de material utilizado habitualmente como materia prima y consumir un residuo destinado a vertedero., This paper is focused on the assessment of sewage sludge ash added on precast concrete blocks, therefore, based on a matrix of Portland cement with particular characteristics (dry consistency). A pilot experience was performed, by manufacturing commercial concrete blocks at an industrial local plant, using mixes in which sand replacements of 5, 10 and 15% by sewage sludge ash, being the results compared with reference concrete block (without sand replacement). The tests applied are prescriptive for marketing as European regulations (CE marking), which will also let to test the physical and mechanical properties of concrete. The results are promising: these wastes could be commercialized, because the improvement of the characteristics of the concrete blocks such as compressive strength, and consequently to reduce a large volume of a material typically used as a raw material and by means of the valorization instead of sending to landfill.

En este artículo se han estudiado los cambios en las propiedades mecánicas de los morteros de cemento Portland debido a la adición de nanofibras de carbono (NFC). Se han determinado las resistencias a flexotracción y a compresión de los morteros en relación a la cantidad de NFC añadidas a la mezcla, al tiempo de curado y a la porosidad y densidad de los mismos. Además se han investigado los niveles de corrosión de barras de acero embebidas en pastas de cemento con NFC expuestos al ataque por carbonatación y por ingreso de cloruros. El aumento en el porcentaje de NFC añadido se traduce en un aumento la intensidad de corrosión registrada y una mejora de las propiedades mecánicas., This paper reports on recent work that is directed at studying the changes in the mechanical properties of Portland cement based mortars due to the addition of carbon nanofiber (CNF). Both flexural and compression strength has been determined and related to the CNF addition to the mix, to the curing time and to the porosity and density of the matrix. Also, corrosion of embedded steel rebars in CNF cement pastes exposed to carbonation and chloride attacks has been investigated. The increase in CNF addition implies higher corrosion intensity and higher levels of mechanical properties.