Effect of NaOH content on hydration, mineralogy, porosity and strength in alkali/sulfate-activated binders from ground granulated blast furnace slag and phosphogypsum

By Katrijn Gijbels, Y. Pontikes, P. Samyn, S. Schreurs, W. Schroeyers. 2020

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Abstract This study investigates the effect of NaOH content on alkali/sulfate-activated binders from 90 wt% ground granulated blast furnace slag (GGBFS) and 10 wt% phosphogypsum (PG). Alkali activators were prepared with a NaOH molarity ranging from 0 M to 4 M. The hydration was monitored using in-situ X-ray diffraction (XRD) and isothermal calorimetry. The hydration product assemblage was investigated using XRD, thermogravimetric analysis (TGA), Fourier-transformed infrared (FTIR) spectroscopy, nitrogen adsorption/desorption and compressive strength tests. A molarity of 0 M NaOH gave rise to the highest porosity and highest strength, although setting occurred only after 7 days. From a molarity of 2 M NaOH and higher, ettringite disappeared and got replaced by a monosulfate phase (i.e., NaCa4Al2O6(SO4)1.5.15H2O) and amorphous aluminum-hydroxide. This study shows the potential of using GGBFS and PG for the development of novel by-product based cementitious binders.

Subfields: Civil and Structural Engineering, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/2595e8912eb350b3352c95c3e77888d78bc87d11