engleski

Carbonation induced corrosion of steel in mortar based on low pH binders

With an increase of awareness of society and industry on the environmental footprints, there is an increasing need in innovative materials, usually secondary resources and by-products, utilised as partial or full substitution of ordinary Portland cement. Most of these materials have beneficial particle size distribution and/or chemical composition, leading to concrete with lower permeability and higher electrical resistivity. At the same time, their different chemistry leads to changes in pH values of pore solution and in concrete microstructure, which could consequently lead to the changes in corrosion properties of reinforcing steel, especially when concrete is exposed to long-term carbonation process. The aim of this paper is to research the difference in corrosion behaviour of steel in carbonated mortar based on different types of alternative binders. In the paper results on three mortar mixes are presented, all having different type of binder – reference mix with ordinary Portland cement, mix with high volume of fly ash and silica fume and mix with blast furnace slag cement with the addition of nanosilica. Mixes of binders were taken from the literature, in which they are studied as an alternative to the classical Portland cement, mainly due to their lower ecological footprint and beneficial properties. After curing reinforced mortar samples were carbonated at 3% CO2 to ensure representativeness with natural carbonation. During early ages and after carbonation changes of corrosion potential, corrosion rate and electrical impedance parameters are monitored. Corrosion behaviour was connected to the changes in microstructure of these different types of mortar during carbonation.

low pH binders; fly ash; nanosilica; metakaolin; lime; EIS

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