Study on carbonation of low strength concrete made of brick aggregate

Abstract

In urban and industrial settings, one of the most prevalent durability challenges faced by reinforced concrete (RC) structures is the corrosion of steel reinforcement due to carbonation. While numerous studies have explored the characteristics of stone aggregate concrete concerning carbonation-induced corrosion of reinforcement, there is limited research on concrete made with brick aggregates. As a result, an investigation into the impact of carbonation on pre-existing reinforced concrete structures utilizing brick aggregates has been undertaken, and its findings have been compared with existing research. Within this study, a total of 84 concrete core samples, with diameters measuring 67 mm and 50 mm, were extracted from selected structural components of four pre-existing reinforced concrete structures utilizing brick aggregates, which ranged in age from 17 to 73 years. The collection of core samples and their testing procedures adhered to the relevant ASTM methods. Furthermore, carbonation depths were assessed in accordance with BS standards using phenolphthalein solution. Additionally, 24 concrete dust samples were gathered from the same locations to establish correlations with the core sample results. The experimental outcomes revealed a direct relationship between carbonation depth and concrete age, indicating that carbonation depth increases with concrete age. This study also demonstrated that the rate of carbonation is influenced by the concrete's grade, with an inverse relationship between them. Therefore, it is crucial to consider carbonation in scenarios involving low-strength concrete, particularly those with compressive strengths below 25 MPa, when the concrete is exposed to harsh environmental conditions and inadequate concrete cover. Consequently, when constructing new structures, employing relatively high-strength concrete is advisable to ensure extended service life by mitigating the effects of carbonation.