Insight into Chloride Binding Mechanism of High-Volume Slag Cement by Adding Diethanol-Isopropanolamine: Improvement of Friedel's Salt Formation and Reduction of Chloride Ions in C-a-S-H

Abstract

This study investigated the chloride binding mechanism of high-volume slag cement (HVSC) with varying dosages of diethanol-isopropanolamine (DEIPA) up to 0.1 wt%. It was demonstrated that increasing DEIPA significantly enhanced chloride binding capacity, with improvements of 116.5% and 121.6% observed at 0.1 wt % of DEIPA after 7 days and 56 days, respectively. The addition of DEIPA accelerated the aluminate reaction of HVSC, facilitating the formation of Friedel’s salt (Fs), the primary chloride-binding phase. However, increasing DEIPA dosages was found to retard the silicate reaction, leading to delayed hydration onset, and decrease C-A-S-H formation. In addition, a reduction in CH content was observed with increasing DIEPA, which was attributed to inhibition by DEIPA rather than a pozzolanic reaction. Notably, the binding enhancement was lower than the increase in Fs formation at all DEIPA dosages, primarily due to (1) the reduction in C-A-S-H and (2) decreased chloride incorporation into C-A-S-H.

Keywords: High-volume slag cement (HVSC), Chloride binding, Diethanol-isopropanolamin (DEIPA), Friedel's salt