Non-destructive lab-scale monitoring of carbonation propagation in cementitious systems using the measurement of intrinsic electrical property

Abstract

Monitoring carbonation in concrete is crucial for assessing the long-term durability of structures, particularly as sustainability efforts increasingly incorporate supplementary cementitious materials (SCMs) to reduce clinker content. While beneficial, SCMs alter the pore structure and pore solution chemistry, necessitating advanced methods to evaluate carbonation progression. Traditional techniques, such as splitting specimens and using pH indicators like phenolphthalein to detect changes in alkalinity, are destructive and primarily designed for ordinary Portland cement (OPC), limiting their effectiveness for SCM-incorporated systems. This paper presents the development of a novel lab-scale carbonation monitoring method based on conductivity measurements in the cementitious matrix. The proposed method examines how carbonation impacts the electrical conductivity of concrete, enabling in-situ monitoring of carbonation propagation in mortar specimens using mini-sensors embedded within the material. These mini-sensors consist of 10 sets of stainless steel 4-point Winner electrodes, spaced 2.54 mm apart, ensuring accurate conductivity measurements. By strategically placing these mini-sensors within the cementitious matrix, real-time measurements can be carried out, allowing for continuous monitoring of carbonation progression. The method provides new insights into how carbonation impacts the electrical properties of concrete, revealing dynamic changes such as a distinct peaking behavior in conductivity at the reactive carbonation front. This feature enables identification of partial carbonation front, which traditional colorimetric methods cannot detect. The results validate the method's effectiveness for OPC system and indicate its applicability when SCMs are incorporated.