Understanding the effect of vitamin B3, B6 and C as a corrosion inhibitor on the ordinary Portland cement hydration: Experiments and DFT study

The existence of vitamins nicotinic acid (B3), pyridoxine (B6) and ascorbic acid (C) affects cement hydration when utilized as a new corrosion inhibitor. The mechanism of the effect of vitamin molecules on ordinary Portland cement hydration is still unclear at the atomic level. In this work, the microstructures of hydration products are found to be changed by vitamin inhibitors, which is the main reason for their impact on cement workability and mechanical performances. The pre-induction period was delayed in various degrees by vitamin inhibitors. The paste with vitamin C shows no induction and acceleration period in the tests. DFT calculations show that vitamin molecules dissociated in the adsorption process. The dissociated H atom occupied the ionic O site of the C3S (tricalcium silicate) surface, preventing the dissociation of water. This phenomenon may be one reason for the hydration postponement of cement with vitamin type inhibitors at the atomic level. The charge density difference and the independent gradient model analysis also confirmed the chemical and physical in-teractions between vitamin molecules and the C3S surface. The findings in this research may broaden the applicability of these new environment-friendly corrosion inhibitors.