Effect of triisopropanolamine on chloride binding of cement paste with ground-granulated blast furnace slag

Chloride was one of important factors resulting in steel bar corrosion in reinforced concrete when using sea resources. In this paper, an attempt to promote the chloride binding capacity of the cement-ground-granulated blast furnace slag (GGBS) system was made by adding triisopropanolamine (TIPA). The paste was prepared by 70 wt% cement and 30 wt% GGBS, sodium chloride, TIPA (0.03%, 0.06% and 0.10%, by weight of binder) and water. The paste was cured for 7 d and 60 d, and the chloride binding ratio (CBR) were measured. The hydration heat and compressive strength were examined, then the hydrates and pore structure of the hardened paste were also analyzed; and the effect of TIPA on aluminum and ferric dissolution of GGBS was also studied. The results showed that TIPA could promote CBR at both 7 d and 60 d. The reason was ascribed to three aspects: (1) TIPA facilitate the formation of FS, which contribute to chemical binding; (2) TIPA promoted the formation of C-S(A)-H gel, which would increase the physical binding; (3) TIPA refined the pore structure and increased fractal dimension, which could enhance the migration resistance. Furthermore, TIPA promoted cement hydration and pozzolanic reaction of GGBS by facilitated the dissolution of aluminum and ferric in GGBS. Additionally, the formation of Friedel's salt was promoted due to the transformation of ettringite to AFm-like phase promoted by TIPA. Such results suggested a new way to improve chloride binding capacity of cementitious materials by adding alkanolamine.