TY - JOUR
T1 - Phosphate-activated basic oxygen furnace (BOF) slag
T2 - Understanding pH-driven hydration and strength development
AU - Schollbach, Katrin
AU - Liu, Zixing
AU - van der Laan, Sieger
AU - Chen, Wei
AU - Brouwers, H.J.H.
A2 - Tang, Yanjie
N1 - Publisher Copyright:
© 2025 The Authors
PY - 2026/1
Y1 - 2026/1
N2 - This study investigates the hydration behavior of basic oxygen furnace (BOF) slag in phosphate solutions across different pH levels, focusing on hydration kinetics, microstructure, and strength development. Acidic phosphate solutions trigger rapid dissolution via acid-base reactions, resulting in lower heat release, while alkaline phosphates promote sustained dissolution-precipitation reactions, prolonging hydration and increasing cumulative heat. The buffering effect of H2PO4−/HPO42− prolongs induction periods and inhibits hydrogarnet and layered double hydroxides (LDHs) formation. At early stages, C2S hydration is more pronounced in acidic solutions, whereas higher pH enhances late-stage hydration of C2S, brownmillerite, and wuestite, forming C-S-H, hydrogarnet, and LDHs. Despite similar porosities (11.9–13.9 %), strengths vary from 37.7 to 66.9 MPa due to a higher proportion of capillary pores and a larger average pore size at a low pH (pH at 4.2). The findings support using phosphate-rich wastewater to activate BOF slag, reducing phosphate discharge while developing low-carbon, cement-free binders.
AB - This study investigates the hydration behavior of basic oxygen furnace (BOF) slag in phosphate solutions across different pH levels, focusing on hydration kinetics, microstructure, and strength development. Acidic phosphate solutions trigger rapid dissolution via acid-base reactions, resulting in lower heat release, while alkaline phosphates promote sustained dissolution-precipitation reactions, prolonging hydration and increasing cumulative heat. The buffering effect of H2PO4−/HPO42− prolongs induction periods and inhibits hydrogarnet and layered double hydroxides (LDHs) formation. At early stages, C2S hydration is more pronounced in acidic solutions, whereas higher pH enhances late-stage hydration of C2S, brownmillerite, and wuestite, forming C-S-H, hydrogarnet, and LDHs. Despite similar porosities (11.9–13.9 %), strengths vary from 37.7 to 66.9 MPa due to a higher proportion of capillary pores and a larger average pore size at a low pH (pH at 4.2). The findings support using phosphate-rich wastewater to activate BOF slag, reducing phosphate discharge while developing low-carbon, cement-free binders.
KW - Acidic phosphate
KW - Alkaline phosphate
KW - BOF slag
KW - Hydration
KW - pH
UR - https://www.scopus.com/pages/publications/105015498039
U2 - 10.1016/j.cemconres.2025.108034
DO - 10.1016/j.cemconres.2025.108034
M3 - Article
AN - SCOPUS:105015498039
SN - 0008-8846
VL - 199
JO - Cement and Concrete Research
JF - Cement and Concrete Research
M1 - 108034
ER -