Using laser-induced breakdown spectroscopy for the study of chloride diffusion in mortar and concrete

Abstract

In this work, the applicability of Laser-Induced Breakdown Spectroscopy (LIBS) for the analysis of chloride diffusion in mortar and concrete has been studied. The high resolution of this technique allows it to obtain a mapping of the chloride ions distribution in these materials upon being exposed to salted environments, thus providing an image of how chlorides diffuse inside them. The technique has been applied to mortar samples submerged in a salt-saturated solution for 3, 9, and 30 months. It has been demonstrated that the penetration profiles fit reasonably well Fick’s second law in a modified version. The apparent diffusion coefficients for these samples were obtained (D3months = (5.94 ± 0.05) × 10− 13 m2/s; D9months = (3.6 ± 0.6) × 10− 13 m2/s; D30months =(2.1 ± 0.8) × 10− 13 m2/s). These results are in the range of the values found in other similar studies. The study of the evolution of these parameters over time revealed an age-factor α = 0.449 ± 0.006. Finally, LIBS was also applied to a concrete sample submitted to a long-period (60 months) immersion in the salt-saturated solution, giving similar good results (D60months = (1.81 ± 0.03) × 10− 13 m2/s), which demonstrates its suitability for the study of chloride diffusion in this type of material.