Print Email Facebook Twitter Elephant skin formation on UHPC surface Title Elephant skin formation on UHPC surface: Effects of climatic condition and blast furnace slag content Author Yalçinkaya, Ç. (TU Delft Materials and Environment; Dokuz Eylul University) Copuroglu, Oguzhan (TU Delft Materials and Environment) Date 2021 Abstract Ultra-high performance concrete (UHPC), which typically contains extremely high superplasticizer amount, tends to render a special type of dense surface layer, especially under drying conditions. Even if the inner side of fresh UHPC is still in a flowable nature, the top surface of the concrete which is exposed to ambient conditions renders a dense cover called “elephant skin” in a short time after casting. In this study, the effects of climatic conditions and ground granulated blast furnace slag (GGBS) replacement on the elephant skin formation were studied. The influence of elephant skin formation on the macropore profile was assessed by micro-computed tomography scan. Observations revealed that any drying condition that does not lead to water vapor condensation on the fresh surface can trigger the formation of elephant skin within minutes after casting. Both microscopic and micro-computed tomography investigations showed that as a result of elephant skin formation, most of the air bubbles cannot escape from the fresh matrix, and locate under the skin. These air bubbles and elephant skin itself result in a multi-layered structure in UHPC body throughout the cross-section and reduce the aesthetics of the casting surface. Increasing GGBS replacement percentage significantly reduced the superplasticizer demand which is responsible for skin formation, however, did not eliminate the problem. Subject Elephant skin formationMicrostructureSlagSuperplasticizerUHPC To reference this document use: http://resolver.tudelft.nl/uuid:3a7ae99e-0cab-4947-851f-7333a4c12b49 DOI https://doi.org/10.1016/j.conbuildmat.2020.121126 Embargo date 2021-04-21 ISSN 0950-0618 Source Construction and Building Materials, 268, 1-12 Bibliographical note Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Part of collection Institutional Repository Document type journal article Rights © 2021 Ç. Yalçinkaya, Oguzhan Copuroglu Files PDF 1_s2.0_S0950061820331305_main.pdf 4.6 MB Close viewer /islandora/object/uuid:3a7ae99e-0cab-4947-851f-7333a4c12b49/datastream/OBJ/view