Review of basics and new opportunities for the chemical realkalization of carbonated concrete including the application of alkali-activated materials

Corrosion of steel in steel-reinforced concrete is one of the main factors limiting the durability of existing reinforced concrete components. Based on the corrosive circumstance, there are different methods of prevention and repair which can be applied to the concrete. In case of carbonation-initiated corrosion, the chemical realkalization is one of the standard measures to counteract the alteration processes in the concrete which lead to corrosion of the reinforcement. This review paper summarizes the current state of research on carbonated concrete chemical realkalization with regard to the various materials that have been investigated over time for their applicability to this repair measure. This review summarizes current research results in the field of carbonated concrete and the proven pozzolanic reactivity of the carbonation products in contact with portlandite which suggests an inhibitory effect on chemical realkalization, although the influence of this has not yet been investigated. Further, there are initial approaches that deviate from the application of a classic Portland cement as a repair material, but their applicability in practice must be questioned. The use of alternative binders and the associated different composition of the pore solution and the varying alkalinity of these binders, such as composite cements with a high substitution rate or alkaline-activated binders, have not yet been brought into connection with repair processes such as chemical realkalization, although the chemical composition of the binders is of the greatest importance for a successful application of the repair measure.