Assessment of Cationic Lignin as a Chloride Ion Scavenging Additive in Cement

Chloride-induced corrosion of steel reinforcement is a major factor adversely influencing the durability of reinforced concrete structures. The main objective of this preliminary study was to explore the use of waste residues generated during the bioethanol processing of sugar cane bagasse as a source of high value products, primarily lignin that can be functionalized to scavenge chloride ions in cement and therefore increase the service life of concrete structures. Lignin is next to cellulose the most abundant biopolymer on earth. Lignin coats cellulose micro-fibrils and other components in the cell wall preventing collapse and providing support to the cell walls in biomass. Being a renewable energy source, biomass is a common feedstock for biopolymers, paper and biofuel production. Being a significant portion of biomass (up to 25%), lignin left over from the production of biofuel, is often burned to generate heat for the distillation of alcoholic fuels from the fermentation liquor. With everincreasing demand of sustainable energy sources, we are exploring the recovery and modification of lignin to reduce costs of biofuel production using it as concrete admixture to scavenge chloride ions. Thus, the hypothesis of this preliminary study is that functionalized lignin (cationic lignin) can “trap” chloride ions in cement mixtures and serve as an additive to hinder the diffusion of chloride ions in concrete structures.