Utilization of sea sands and coral aggregate for concrete in ocean construction is increasingly attracting the attention all over the world. However, the potential risk of steel corrosion resulting from chloride in these raw materials was one of the most concerned problems. To take this risk into account, chloride transporting to the surface of steel should be hindered. The formation of Friedel’s salt in hydration process is widely accepted as an effective manner for this hindrance. In this study, an attempt to hasten the formation of Friedel’s salt by adding triisopropanolamine (TIPA) was done in the cement-fly ash system, with intention to chemical bind chloride, and the chloride-binding capacity at 60 d age was examined. The results show that TIPA can enhance the chloride-binding capacity of cement-fly ash paste at 60 d age, and the reason is that the formation of Friedel’s salt can be accelerated with addition of TIPA. The mechanism behind is revealed as follows: on the one hand, the accelerated cement hydration provides more amount of calcium hydroxide to induce the pozzolanic reaction of fly ash, which can hasten the dissolution of aluminum into liquid phase; on the other hand, TIPA can directly hasten the dissolution of aluminum in fly ash, offering more amounts of aluminum in liquid phase. In this case, the aluminum/sulfate (Al/S) ratio was obviously increased, benefiting the formation of Friedel’s salt in hydration products. Such results would expect to provide useful experience to promote the chloride-binding capacity of cement-fly ash system.
P.Y. Guo,Q.H. Wu,X.J. Wang,M.X. Wei,Y. Shao,Z.G. Liu
Due to the combined effects of high-density electric fields, water vapor, and residues, adjacent solder joints are prone to electrochemical migration. This study investigates the electrochemical reaction processes and mechanisms of Sn and Sn-58Bi in methanesulfonic acid(MSA), sulfosalicylic acid(SSA), diethanolamine(DEA), triethanolamine(TEA), and triisopropanolamine (TIPA) flux solutions. The results show that under natural corrosion conditions Sn-58Bi exhibits better electrochemical corrosion resistance than Sn. Under dynamic potential conditions, reaction rates of Sn-58Bi exceed that of Sn due to the dissolution of Bi. The dissolution threshold for Bi occurs at approximately 0.15 V in the TEA solution, 0.37 V in the TIPA solution, and 1 V in the DEA solution. Sn-58Bi in the MSA and SSA solutions primarily undergoes Sn dissolution, whereas in the DEA, TEA, and TIPA solutions, Bi dissolution is the dominant process. Under a constant voltage of 1 V vs.SCE , the dissolution current of Sn is lower than that of Sn-58Bi. Sn-58Bi in the TIPA solution shows instability in the passivation film. Under a constant voltage of 5 V vs.SCE , the stable current values for both solders are similar.
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