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RISS 인기검색어
- 검색키워드
- 저자 : Van Mullem, Tim (검색결과 2 건)
- 무료
- 기관 내 무료
- 유료
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Van Mullem, Tim,Gruyaert, Elke,Debbaut, Brenda,Caspeele, Robby,De Belie, Nele Elsevier 2019 Construction & building materials Vol.203 No.-
<P><B>Abstract</B></P> <P>An important characteristic of self-healing concrete is its ability to regain liquid tightness after it has been damaged. This ability can be tested using water permeability setups. However, a lack of standardized test methods makes it difficult to compare results between different studies. Additionally, the large variation on crack widths between specimens results in a large spread of the permeability results. This, together with all other factors (e.g. internal crack geometry) contributing to the variability of permeability results, should be clearly assessed in order to develop a standardized permeability test. In this study a new active crack width control technique has been developed to significantly reduce the variation on the crack width within a series of specimens, resulting in more consistent permeability results. By analysing permeability results of specimens from test series with different nominal crack widths the factors contributing to variability could be assessed. The two main contributors are the variability on the mean crack width at the crack mouth and the variability on the internal crack geometry. The variability of the mean crack width can induce a 3 times higher variability of the permeability results. In contrast to the crack width, the internal geometry of a crack cannot be determined directly, yet it can cause a difference in permeability of more than 25% for specimens with an identical nominal surface crack width. It can be concluded that when crack widths are actively controlled, the main source of variability on permeability results is the internal geometry which cannot be controlled, regardless of the chosen cracking technique. In order to reduce the variance on the mean permeability, it is proposed to use at least six specimens per series.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Variability on permeability is dictated by crack width and internal crack geometry. </LI> <LI> Active crack control can reduce the variability on the crack width significantly. </LI> <LI> If this is done, internal crack geometry governs the variability on permeability. </LI> <LI> A minimum sample size of 6 specimens is proposed when assessing water permeability. </LI> </UL> </P>
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Ferrara, Liberato,Van Mullem, Tim,Alonso, Maria Cruz,Antonaci, Paola,Borg, Ruben Paul,Cuenca, Estefania,Jefferson, Anthony,Ng, Pui-Lam,Peled, Alva,Roig-Flores, Marta,Sanchez, Mercedes,Schroefl, Christ Elsevier 2018 Construction and Building Materials Vol.167 No.-
<P><B>Abstract</B></P> <P>Heuristically known at least since the first half of XIX century, the self-healing capacity of cement-based materials has been receiving keen attention from the civil engineering community worldwide in the last decade. As a matter of fact, stimulating and/or engineering the aforementioned functionality via tailored addition and technologies, in order to make it more reliable in an engineering perspective, has been regarded as a viable pathway to enhance the durability of reinforced concrete structures and contribute to increase their service life.</P> <P>Research activities have provided enlightening contributions to understanding the mechanisms of crack self-sealing and healing and have led to the blooming of a number of self-healing stimulating and engineering technologies, whose effectiveness has been soundly proved in the laboratory and, in a few cases, also scaled up to field applications, with ongoing performance monitoring. Nonetheless, the large variety of methodologies employed to assess the effectiveness of the developed self-healing technologies makes it necessary to provide a unified, if not standardized, framework for the validation and comparative evaluation of the same self-healing technologies as above. This is also instrumental to pave the way towards a consistent incorporation of self-healing concepts into structural design and life cycles analysis codified approaches, which can only promote the diffusion of feasible and reliable self-healing technologies into the construction market.</P> <P>In this framework the Working Group 2 of the COST Action CA 15202 “Self-healing as preventive repair of concrete structures – SARCOS” has undertaken the ambitious task reported in this paper. As a matter of fact this state of the art provides a comprehensive and critical review of the experimental methods and techniques, which have been employed to characterize and quantify the self-sealing and/or self-healing capacity of cement-based materials, as well as the effectiveness of the different self-sealing and/or self-healing engineering techniques, together with the methods for the analysis of the chemical composition and intrinsic nature of the self-healing products. The review will also address the correlation, which can be established between crack closure and the recovery of physical/mechanical properties, as measured by means of the different reviewed tests.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Review of test methods for assessing healing efficiency. </LI> <LI> Novel perspective in correlating healing to durability and mechanical recovery. </LI> <LI> Correlation between different test methods. </LI> <LI> Characterization methods of healing products. </LI> <LI> Pioneer monitored case studies are presented. </LI> </UL> </P>
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