Monitoring the carbonation front progress in a cementitious composite having its pore structure analyzed through μ-CT imaging

ABSTRACT

The carbonation process is one of the factors that cause a reduction in the hydrogenionic potential (pH) in cementitious composites, which can lead to a depassivation of the reinforcement structures, thus furnishing conditions for a corrosion process to begin. In this paper, the research sought to monitor the progress of the carbonation front according to European standard EN 14630, concurrently with the measurement of pH variation on the cementitious composite surface. Cylindrical mortar specimens with size of (2 x 4) cm were placed in a carbonation chamber with controlled conditions, keeping up the humidity at 65%, temperature at 28 °C and the CO₂ concentration of 5%. The void structure of the matrix was evaluated by X-ray microtomography technique (μ-CT). The pH reading enabled the monitoring of the carbonation front progress in function of loss of alkalinity, even before the procedure laid down in standard EN 14630. The images obtained through µ-CT did not enable the visualization of the densification of the material found in the outermost layer of the specimen.

Keywords:
mortar; carbonation; pH; Xray microtomography.