Comparación de métodos para determinar el frente de carbonatación en estructuras en concreto reforzado, caso de estudio hospital universitario de Neiva.

Abstract

Carbonation of concrete is one of the most relevant deterioration mechanisms in reinforced concrete structures due to its direct impact on pH reduction and steel depassivation. Traditionally, carbonation depth has been assessed using phenolphthalein; however, recent studies have highlighted its limitations in accurately representing the actual extent of the phenomenon, particularly in detecting partially carbonated zones. In this context, this study aims to compare the reliability, applicability, and applicability of different pH indicators for determining the carbonation front in in-service concrete structures. The research was conducted through an in-situ comparative experimental approach, evaluating four indicators (phenolphthalein, thymol blue, alizarin, and indigo carmine) on structural columns of the Hospital Universitario de Neiva. Controlled grooves were executed to expose fresh concrete surfaces, and carbonation depths were measured for each indicator. The analysis focused on variability, consistency, and visual interpretability under real inspection conditions. The results show significant differences among indicators, with average carbonation depths of 40.1 mm for thymol blue, 62.6 mm for phenolphthalein, 70.7 mm for alizarin, and 85.4 mm for indigo carmine. These findings confirm the existence of an alkalinity gradient within concrete and the presence of a partially carbonated zone, whose extent depends on the pH response range of each indicator. It is concluded that the carbonation front should not be interpreted as a single boundary but rather as a transition zone, and that relying solely on phenolphthalein may lead to underestimation of carbonation depth. Therefore, a comparative approach incorporating alternative indicators is recommended to improve diagnostic accuracy in existing structures.