Effect of Deoxyribonucleic Acid on the Chloride Diffusion Behavior of Cement Mortar

Abstract

Corrosion of reinforcement bar caused by chloride ions diffusion is a crucial durability problem for concrete structures. Deoxyribonucleic acid (DNA) is a new type of corrosion inhibitor. Previous research has concentrated primarily on the influence of DNA on the corrosion of reinforcement bar caused by chloride salts in simulated concrete pore solution and cement-based materials, with scant attention to the chloride diffusion behavior of cement-based materials with DNA. In this work, the chloride diffusion behavior of cement-based materials with DNA was studied using chloride binding isotherm, chloride rapid migration (RCM), and natural diffusion tests. The composition, content, and morphology of the hydration products and pore structure were monitored using X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) tests. The results show that DNA can improve the chloride-binding capacity and enhance the chloride diffusion resistance in cement-based materials. The lowest chloride migration coefficient and chloride diffusion coefficient were found in cement mortar with 4% by weight DNA, which were 45.58% and 42.36% lower than those of the reference group, respectively. DNA can stimulate the cement hydration reaction to produce more C-S-H gels and can increase the Ca/Si ratio of C-S-H. This is conducive to physical chloride adsorption. DNA can be combined with calcium ions to form insoluble aggregates that can fill the pore structure of mortar. Mortar with 4% by weight DNA maintained the lowest porosity, which effectively enhanced the chloride diffusion resistance.