Phase changes under efflorescence in alkali activated materials with mixed activators

Srinivasamurthy, Lakshmikanth and Chevali, Venkata S. ORCID: https://orcid.org/0000-0002-5648-0344 and Zhang, Zuhua and Wang, Hao (2021) Phase changes under efflorescence in alkali activated materials with mixed activators. Construction and Building Materials, 283:122678. pp. 1-13.


Abstract

Efflorescence in alkali-activated materials is a strong function of precursor and activator composition, which dictates their engineering properties and durability. In this study, the efflorescence of naturally cured NaOH/Na2SiO3 alkali-activated fly ash and alkali-activated fly ash-slag blended binder mixes was assessed with alkali concentration of 9 wt% Na2O, and 10 to 30 wt% of slag, and compared with binder mixes with 9 wt% Na2O, and 10 to 30 wt% of slag along with 2 wt% Na2CO3. The effects of efflorescence were assessed using visual and leaching inspections, and the compressive and split tensile strengths were determined post activation. Atomic absorption spectrometry was used to quantify free alkalis in the leachate, and X-ray diffraction, and Fourier transform infrared spectroscopy, magic-angle-spinning nuclear magnetic resonance and thermo-gravimetric analysis were performed to analyse the phase changes in binder pastes after efflorescence. The increased slag content facilitated the formation of C-A-S-H gel and enhanced both chemical and mechanical properties of binder pastes. Furthermore, the inclusion of slag content also led to the reduction of the open porosity and efflorescence formation. Subsequent exposure of binder specimens to efflorescence conditions aided the formation of carbonate products, degradation of N-A-S-H and N-(C)-A-S-H gel, and a decrease in split tensile strength in the binder paste specimens.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Date Deposited: 10 Mar 2021 23:20
Last Modified: 10 Mar 2021 23:20
Uncontrolled Keywords: Alkali-activated materials; Durability; Efflorescence; Fly ash; Leaching; Nuclear magnetic resonance; Slag
Fields of Research (2008): 09 Engineering > 0905 Civil Engineering > 090503 Construction Materials
09 Engineering > 0912 Materials Engineering > 091202 Composite and Hybrid Materials
Fields of Research (2020): 40 ENGINEERING > 4016 Materials engineering > 401602 Composite and hybrid materials
40 ENGINEERING > 4005 Civil engineering > 400505 Construction materials
Socio-Economic Objectives (2020): 12 CONSTRUCTION > 1203 Construction materials performance and processes > 120301 Cement and concrete materials
24 MANUFACTURING > 2403 Ceramics, glass and industrial mineral products > 240301 Cement products and concrete materials
Funding Details:
Identification Number or DOI: https://doi.org/10.1016/j.conbuildmat.2021.122678
URI: http://eprints.usq.edu.au/id/eprint/41538

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