Strength and Microstructure Characteristics of Metakaolin-Based Geopolymer Mortars with High Water-to-Binder Ratios

Lander Frederickx, Thi Nhan Nguyen and Quoc Tri Phung
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Lander Frederickx: Belgian Nuclear Research Centre (SCK CEN), Institute for Environment, Health and Safety, Boeretang 200, 2400 Mol, Belgium
Thi Nhan Nguyen: Belgian Nuclear Research Centre (SCK CEN), Institute for Environment, Health and Safety, Boeretang 200, 2400 Mol, Belgium
Quoc Tri Phung: Belgian Nuclear Research Centre (SCK CEN), Institute for Environment, Health and Safety, Boeretang 200, 2400 Mol, Belgium

Sustainability, 2022, vol. 14, issue 6, 1-14

Abstract: Geopolymers and other alkali-activated materials were investigated in detail as alternatives to ordinary Portland cement because of their reduced CO 2 emissions, high (radionuclide) binding capacities, and low permeabilities. The last two properties make them potential materials for the immobilization of several types of chemical waste. In this context, the direct immobilization of liquid waste streams would be a useful application. This study aimed to develop geopolymers with high water-to-binder ratios, but with good mechanical strengths, while elucidating the parameters that dictate the strengths. Three potential metakaolin geopolymer recipes were cast and cured for 28 days, after which their strengths, mineralogy, and microstructures were determined. The results show that it is possible to attain acceptable mechanical strengths at water-to-binder ratios that vary from 0.75 to 0.95, which is a significant increase from the ratio of 0.55 that is commonly used in the literature. It was found that the most important parameter that governs the mechanical strength is the dilution of the activating solution, which is represented by the H 2 O/Na 2 O ratio, while the microstructure was found to benefit from a high SiO 2 /Al 2 O 3 ratio.

Keywords: geopolymer; metakaolin; mortar; microstructure; mineralogy (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2022
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