Autogenous and drying shrinkage of mortars based on Portland and calcium sulfoaluminate cements
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ORIGINAL ARTICLE
Autogenous and drying shrinkage of mortars based on Portland and calcium sulfoaluminate cements Davide Sirtoli
. Mateusz Wyrzykowski . Paolo Riva . Pietro Lura
Received: 8 May 2020 / Accepted: 21 September 2020 Ó The Author(s) 2020
Abstract Calcium sulfoaluminate (CSA) cement can be used as an alternative binder in concrete, partially or fully replacing ordinary Portland cement. While CSA cement considerably accelerates the mechanical properties development, the rapid evolution of the microstructure together with the high water demand cause rapid and large volume changes at early ages. As volume changes may lead to early-age cracking, measures to reduce them may be required In this paper, autogenous and drying shrinkage are studied in mortars prepared with Portland cement, CSA cement or a 50/50 blend as binder. Very fast selfdesiccation and high autogenous shrinkage of the CSA-based mortar were observed compared to the mortar made with Portland cement. On the other hand,
Electronic supplementary material The online version of this article (https://doi.org/10.1617/s11527-020-01561-1) contains supplementary material, which is available to authorized users. D. Sirtoli (&) P. Riva Department of Engineering, University of Bergamo, Viale Marconi 5, 24044 Dalmine, Italy e-mail: [email protected] D. Sirtoli M. Wyrzykowski P. Lura Empa, Swiss Federal Laboratories for Materials Science and Technology, Du¨bendorf, Switzerland P. Lura Institute for Building Materials, ETH Zurich, Zurich, Switzerland
the early-age volume changes can be limited if a blend of the two cements is used. The blended system revealed a bi-modal trend in the evolution of selfdesiccation and autogenous shrinkage, in which the initial fast self-desiccation and shrinkage enter the dormant phase after the first couple of days and again start after about 28 days. Keywords CSA OPC/CSA blends Early age Volume changes
1 Introduction With a yearly production of 4 billion tons [1], ordinary Portland cement (OPC) is essential for the construction industry but it also represents an ecological issue due to the high energy consumption and large amounts of CO2 emitted during its production [2, 3]. Partial solutions to alleviate this problem are the use of supplementary cementitious materials blended with OPC [4] and the use of alternative fuels in cement kilns [5]. As about 60% of the CO2 emissions in Portland cement production come from the calcination of limestone, another more radical alternative is to modify the cement chemistry, in particular towards cements that are to a lesser degree based on CaO [3]. Calcium sulfoaluminate cement (CSA) emits less CO2 compared to OPC thanks to both the use of raw
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materials containing less limestone and the lower temperature of clinkerization [6]. The key-component of this material is ye’elimite, a calcium sulfoaluminate mineral (C4 A3 S); other phases are belite (C2S), ferrite (C4AF), mayenite (C12A7) and anhydrite [7].
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