Journal
CONSTRUCTION AND BUILDING MATERIALS
Volume 312, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.conbuildmat.2021.125438
Keywords
Alkali-activated mortar; Autogenous shrinkage; Calcium carbide residue; Compressive strength; Low-calcium fly ash
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Funding
- Pet-chra Pra Jom Klao Master Scholarship, King Mongkut's University of Technology Thonburi
- Thailand Research Fund (TRF) under the TRF Research Career Development [RSA6280032]
- Thailand Research and Innovation (TSRI)
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The study found that partially substituting CR in FA and activating with a higher NaOH concentration significantly improved the compressive strength of alkali-activated mortars. However, the autogenous shrinkage increased with the increased NaOH concentration.
In this study, the effects of sodium hydroxide (NaOH) concentrations, ratios of low-calcium fly ash (FA) to calcium carbide residue (CR), and adding 5% of Portland cement on compressive strength and autogenous shrinkage of alkali-activated mortar made from FA-CR mixtures were investigated and verified by examining the microstructure and morphology of alkali-activated paste. Both FA and CR were improved by grinding a finer powder. The alkali activators were a NaOH solution and a liquid sodium silicate at a constant ratio of 2:1. The results indicated that the utilization of CR partially substituted in FA and activated with a higher NaOH concentration significantly improved the compressive strength of alkali-activated mortars. The autogenous shrinkage of alkali-activated mortars increased with the increased NaOH concentration and decreased significantly when the CR partially replaced in FA. An alkali-activated mortar made from an FA-CR mixture (without cement) achieved compressive strengths up to 60.2 MPa and had an autogenous shrinkage of less than 100 x 10(-6) mm/mm. Moreover, the XRD patterns of alkali-activated pastes showed that the reaction products of C-S-H, C-A-S-H, and N-A-S-H were related to the dense structure and the Si, Al, Ca, and Na detected in SEM/EDS results.
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