Up to now, glass capsules, which cannot resist the mixing process of concrete, have been mostly used in lab-scale proof-of-concept to encapsulate polymeric agents in selfhealing concrete. This study presents the design of polymeric capsules which are able to resist the concrete mixing process and which can break when cracks appear. Three different polymers with a low glass transition temperature T g have been extruded: Poly(lactic acid) (PLA) (T g = 59 °C), Polystyrene (PS) (Tg = 102 °C) and Poly(methyl methacrylate/n-butyl methacrylate) (P(MMA/n-BMA)) (Tg = 59 °C). After heating the capsules prior to mixing with other components of the mix, to shift from a brittle state to a rubbery state, their survival ratio considerably increased. Moreover, a part of the capsules, which previously survived the concrete mixing process, broke with crack appearance. Although some optimization is still necessary concerning functional life of encapsulated adhesives, this seems to be a promising route.

This paper presents an ultrasonic method, based on the nonlinear acoustic mixing of coda waves with lower-frequency swept pump waves, for providing an efficient global detection of small cracks in cementitious materials. By simultaneously comparing, forboth uncracked and cracked mortars, the ultrasonic velocity variations and decorrelation coefficients between the unperturbed and perturbed signals with pump amplitude, this method makes it possible to accurately detect cracks with widths of around 20 μm in correlation with velocity variations of approximately 0.01%. The potential influence of certain material parameters such as microscopic damage is also discussed

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In this work the non-destructive monitoring of the self-healing progress of cracked mortars is presented through the use of three combined methods: nonlinear Coda Wave Interferometry, 3D microscopy and X-ray computed microtomography (CT). The aim of the acoustic method is to compare, at various healing stages, both the ultrasonic velocity variations and decorrelation coefficients between a reference coda signal and a signal perturbed by a high level lower-frequency elastic wave. The decrease in the relativevariation of the extracted nonlinearities demonstrates its ability to accurately monitor global crack filling.3D microscopy also reveals this capability. Measurement results of these two techniques agree for the influence of age at cracking on healing potential. In reducing the voxel size to 12 l m, X-ray CT images confirm the creation of localized bridges between crack faces and provide information on their location

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Coupling statistical indentation and microscopy to evaluate micromechanical properties of materials: application to viscoelastic behavior of irradiated mortars

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Anthropogenic greenhouse gas emissions need to be cut to limit climate change. Thus, universities, in the same way as citizens and companies, are starting to raise awareness about this issue and to take action to reduce their carbon footprint. Centrale Nantes, a French “Grande école”, initiated a low carbon transition with the calculation of the 2018 carbon footprint of the university. This report presents an individual carbon footprint estimator developed within the scope of the university, based on the new open-source French national simulator called “Nos Gestes Climat” proposed by ABC (Association Bilan Carbone (Association for the implementation of Carbon footprint assessment)) and ADEME (French Environment and Energy Management Agency). Development context and important features of the national version are described. Then, to meet university user’s expectations, feedback from a panel of testers has been collected in order to guide the declination development and promote good practices ensuring user engagement. The transparency of the data model, the accurate explanations, the variety of actions have been found to be key success factors for the development and the adoption of such a simulator. Results also suggested that users are keen to involve themselves in the university initiative to reach carbon neutrality.

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