Shrinkage characteristics of alkali-activated fly ash/slag paste and mortar at early ages |
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| Affiliation: | 1. Hubei Key Laboratory of Roadway Bridge and Structural Engineering, Wuhan University of Technology, Wuhan 430070, China;2. State Key Laboratory of Silicate Materials for Architecture, Wuhan University of Technology, Wuhan 430070, China;3. Department of Civil Engineering, Logistical Engineering University, Chongqing 401311, China;1. Institute for Multidisciplinary Research, University of Belgrade, Kneza Viseslava 1, 11000 Belgrade, Serbia;2. Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11000 Belgrade, Serbia;1. Department of the Built Environment, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands;2. State Key Lab of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, PR China |
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| Abstract: | The purpose of this study is to investigate the shrinkage characteristics of alkali-activated fly ash/slag (henceforth simply AFS) and the factors affecting it. A series of tests were conducted to determine the chemical shrinkage, autogenous shrinkage and drying shrinkage. The microstructures and reaction products were also characterized through XRD and SEM/EDS analyses. An increase in the slag content from 10% to 30% resulted in a denser matrix and showed a higher Ca/Si ratio of C–N–A–S–H in the microstructure. Higher sodium silicate and slag contents in a mixture caused more chemical, autogenous, and drying shrinkage, but led to a higher compressive strength. From the test results, it can be concluded that the autogenous shrinkage of AFS mortar occurs mainly due to self-desiccation in hardened state rather than volume contraction by chemical shrinkage in fresh state. The AFS paste showed higher drying shrinkage than ordinary Portland cement (OPC), which may be caused by the higher mesopore volume of the AFS paste compared to that of OPC paste. |
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| Keywords: | Shrinkage Microstructure Reaction products Alkali-activated fly ash/slag Compressive strength Porosity |
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