Durability advances for reinforced concrete structures in chloride environments

Yu Jiang

This thesis starts from a review of recent technological advances that can prevent or mitigate the risk of chloride-induced rebar corrosion in concrete and enhance the durability of reinforced concrete structures in chloride environments. These include corrosion inhibiting admixtures, self-healing concrete, concrete made from waste materials, concrete surface treatments, rebar coatings, migrating corrosion inhibitors and electrochemical corrosion rehabilitation methods. Based on the knowledge from literature review, two objectives were designed and investigated in this thesis. The first objective was developing an advanced nano-modified concrete sealer with enhanced performance. The second objective was evaluating four types of corrosion inhibiting admixtures extracted from plats, for their application in reinforced concrete. These objectives were explored through laboratory investigations, as detailed below. Transport properties of cement mortar samples treated by graphene oxide (GO) modified concrete sealers were tested. Two ways of GO modification were implemented on a commercial concrete sealer, and both improved the sealer's performance. In addition, water contact angle and porosity of the treated mortar samples were tested. A strong linear relationship between the water absorption rate and the surface free energy was established. Also, a linear relationship between the gas permeability coefficient and the porosity of treated mortar was found. The results suggest that the GO modified sealers have the potential to improve the durability of concrete. Multifunctional corrosion inhibiting admixtures for cement mortar under a chloride environment were evaluated. Four types of "green" admixtures were tested, which were a mixture of liquid chemicals extracted from waste peony leaves, Kentucky blue-grass, waste sugar-beet leaves, and dandelion. The results reveal that all of them had side effect on the compressive strength but could improve other properties of the mortar samples. In addition, the resistance to chloride-induced rebar corrosion in the mortars were evaluated using open circuit potential, electrochemical impedance spectroscopy, and linear polarization resistance measurements. These admixtures provided promising corrosion inhibition performance under investigated condition. The results suggest that these green chemicals from the patented zero-waste process have the potential to be served as multifunction corrosion inhibiting admixtures for concrete, with side benefits in water reducing and set retarding.

Durability advances for reinforced concrete structures in chloride environments

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