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Menendez E.,IETCC CSIC | de Frutos Y.J.,Complutense University of Madrid
Boletin de la Sociedad Espanola de Ceramica y Vidrio | Year: 2012

In this paper, we study how to generate and accelerate, expansive phenomena within cementitious composites, considering elements of addiction using both fly ash and slag. We present results of monitoring of these processes from the beginning and characterize chemical, microstructural, and crystallographic by X-ray diffraction, backscattering electron microscopy, X-ray dispersive energy and mercury porosimetry. These data are supplemented with values of mechanical behavior of materials to determine their functionality. As a result of these studies, we propose a model for the generation and progression of microcracks for each alteration processes studied.

Torrens-Martin D.,Polytechnic University of Catalonia | Fernandez-Carrasco L.,Polytechnic University of Catalonia | Blanco-Varela M.T.,IETcc CSIC
Journal of Thermal Analysis and Calorimetry | Year: 2013

Different binders of Portland cement, calcium aluminate cement and calcium sulphate (PC/CAC/CS) have been investigated to determinate the influence the CAC and CS amount in the reactions mechanism. Several mixtures were studied, ratios of 100, 85/15 and 75/25 of PC/CAC with 0, 3 and 5 % of CS. Conduction calorimetric technique was used to follow the hydration during 100 h. The XRD and FTIR techniques were used as support in the analysis of the hydration products. The results have shown that the studied ternary systems form an extra amount of ettringite, and changes in the reactions mechanism with respect to a PC. The reactions mechanism depends on the CAC and CS amount present in the different binders. © Akadémiai Kiadó, Budapest, Hungary 2013.

Martinez De Mingo S.,Madrid | Gutierrez Jimenez J.P.,IETcc CSIC | Garcia Alonso M.D.,Technical University of Madrid
Engineering for Progress, Nature and People | Year: 2014

Nowadays there is an increasing need of reusing/recycling existing means. This also occurs in construction field where numerous ageing buildings and infrastructures need to be upgraded. Externally bonded FRP (fiber reinforced polymer) laminates has been proven a useful technique for structural strengthening not only for reinforced concrete structures but for others like masonry ones. An ultimate limit state method to design and check unreinforced masonry sections with externally bonded FRP strengthening subject to bending and compression has been developed.Different design formulations are proposed with the aim of covering all flexural failure modes. The work focuses on determinate a "bond reduction factor" to assess the value of FRP design strain. This factor must prevent intermediate FRP debonding failure. The proposed factor is obtained by means of an extensive bending test database. The method has also been checked with the help of this database.

Nevshupa R.,IETCC CSIC | Conte M.,IK4 Tekniker | Van Rijn C.,Noon Energy S.L.
Measurement Science and Technology | Year: 2013

The measurement uncertainty and linearity of a bundle fibre-optic displacement sensor were studied on a wide range of displacements using experimental and simulation approaches. The theoretical He-Cuomo distribution functions of light intensity yielded the simulated modulation characteristic that best fitted the experimental data in the range of dimensionless distances to the target surface from 0 to 50 but diverged beyond. The coefficient of variation of the output signal of the sensor varied non-monotonically with the distance to the target surface. This variation is suggested to stem from small randomly distributed imperfections on the mirror surface. © 2013 IOP Publishing Ltd.

Nevshupa R.A.,IETCC CSIC | Conte M.,IK4 Tekniker | Igartua A.,IK4 Tekniker | Roman E.,CSIC - Institute of Materials Science | De Segovia J.L.,CSIC - Institute of Materials Science
Tribology International | Year: 2015

The main difficulty in designing of an ultrahigh vacuum (UHV) tribometer combined with tribophysical and tribochemical characterization techniques is to find the critical compromise between the scientific requirements and technical or technological limitations from different subsystems and components. The principal conflicts, their possible solutions and the recommended tribometer configurations are analyzed. The developed methodological principles were applied for designing and construction of two UHV experimental tribological systems: TriDes-2 and Ca3UHV. The advances in the design and development of the vacuum system as well as the UHV force sensor and sample holder are presented and discussed. © 2015 Elsevier Ltd. All rights reserved.

Andrade C.,IETCC CSIC | D'Andrea R.,IECA
2nd International Conference on Sustainable Construction Materials and Technologies | Year: 2010

Current codes have requirements for the durability design of concrete based on compressive strength and provisions related to cement content and water - cement ratio. However, such requirements do not take into account important parameters related to the behaviour of concrete against to aggressive attack. The electrical resistivity of the hardened concrete is related to connectivity of pores network under saturated condition. This paper proposes a methodology of design based on the Archie law, which is originated from the concept of diffusion and provides properties such as electrical resistivity, porosity, and tortuosity, for estimating the ideal mix of concrete (maximum water cement, the minimum content of cement and cement type) for a specific environmental class and service life. It also considers the chemical reaction of chloride and carbonation with the phases of cement, so called factor of reaction (r) which depends on the type of cement and indicates the delay on the agressive penetration.

Mahrova M.,Tribology Unit | Conte M.,Anton Paar | Conte M.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Roman E.,CSIC - Institute of Materials Science | Nevshupa R.,IETCC CSIC
Journal of Physical Chemistry C | Year: 2014

Processes of mechanochemical degradation of imidazolium bis((trifluoromethyl)sulfonyl)imide ionic liquids with alkyl and monomethoxypoly(ethylene glycol) (mPEG) side groups were studied using the novel technique of mechanically stimulated gas emission spectroscopy. Mechanical stimulus caused degradation of both the anionic and cationic moieties. For the latter, the degradation was concentrated on the alkyl and ether chains rather than on the imidazole. For the anionic moiety, various degradation steps associated with the emission of CHxFy volatile products followed by SO2 and SO3 emission were identified. Simulation of frictional heat dissipation revealed that tribochemical reactivity was induced by the mechanical energy supply rather than the temperature increase. Thermal degradation of the same ionic liquids studied using thermogravimetric analysis and Fourier transform infrared spectroscopy was concentrated mainly on the cationic moiety. Thermal stability significantly depended on the side chains. The decomposition of mPEG-functionalized ionic liquids was a two-step process, where the lower temperature step corresponded to mPEG decomposition. © 2014 American Chemical Society.

Tanner P.,IETcc CSIC | Lara C.,IETcc CSIC | Prieto M.,IETcc CSIC
Engineering for Progress, Nature and People | Year: 2014

The assessment of an existing structure to determine its suitability for present and future use entails different sorts of problems than encountered when designing new structures. The differences revolve essentially around the nature of the information available. In existing structures, deteriorated or otherwise, the accuracy of the models used for such assessments can usually be improved by acquiring more data. The Spanish Technical Building Code defines a procedure for the evaluation of existing structures that includes the same verification format as normally applied for designing new structures, but in which the representative values for the variables and the partial factors may be modified on the basis of updated information. Tools intended for such modifications, developed for the safety assessment of existing sound and deteriorated concrete structures, are applied to the structural assessment of the main dome over La Laguna cathedral, Tenerife, Spain.

Tanner P.,IETcc CSIC | Hingorani R.,IETcc CSIC
Safety, Failures and Robustness of Large Structures | Year: 2013

Explicit risk analysis, a powerful structural safety decision-making tool, was applied to investigate the collapse of a movable scaffolding system (MSS) during construction of the River Verde Viaduct at Almuñécar, Spain in 2005, in which six workers lost their lives. Systematic qualitative risk analysis was conducted to identify the MSS structural safety hazards that may have theoretically caused the collapse. Based on exhaustive experimental and theoretical studies, these hazards were classified by their relevance to the accident. Logical combinations of the hazards were subsequently established to ascertain possible failure scenarios. This was followed by quantitative risk analysis, in which probabilistic methods were deployed to corroborate the likelihood of occurrence of the scenarios envisaged. Without such methods, no credible conclusions could have been drawn.

Uniform and/or burst triboluminescence (TL) modes were observed during sliding of a diamond pin along a soda-lime disc in an Ar atmosphere in the pressure range between 105 and 10-2 Pa. Various combinations of these modes in different pressure regions produced four behaviour patterns of TL: chaotic weak bursts, periodic strong bursts, chaotic bursts with uniform TL and only uniform TL. The surface electrostatic potential was measured simultaneously with TL in order to evaluate the rates of charge build-up and recombination. Optimal conditions for charge recombination through the gas discharge were in the pressure range 0.17-4 kPa. The configuration of the electric field was simulated using a finite element model and the experimental data. The electric field was dominated by the concentrated positive charge on a tiny surface area of the pin, while the influence of a negative charge spread over a larger area on the disc was negligible. It was concluded that, in contrast to the prevalent belief, the electric discharge producing TL around the contact zone was a positive corona rather than bipolar. Using the Townsend approach, a model of the corona TL offering a plausible explanation for the experimentally observed TL features and behaviour was proposed. © 2013 IOP Publishing Ltd.

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