An accelerated carbonation procedure for studies on concrete

Abstract

Carbonation of the concrete leading to reduced alkalinity around the steel is one of the main reasons for the corrosion of reinforced concrete. Studies of carbonation-induced corrosion and of rehabilitation methods, such as electrochemical re-alkalization, require the convenient preparation of realistically large specimens of carbonated concrete in a sufficiently short time. This paper describes a rapid method of preparing carbonated concrete by exposing concrete, which has been dried to an internal relative humidity of 60%, to a pure atmosphere of carbon dioxide gas at 15 bar pressure (1500 kPa). The pressure chamber used can accommodate specimens up to 150 mm diameter or 100 × 100 mm section and such specimens can be fully carbonated in 2 weeks, much more quickly than by other methods. Carbonation increases the electrical resistivity and strength of the concrete and reduces the water absorption. Optical and electron microscopical investigations on the carbonated concrete confirm that the microstructure is no different from that produced in concrete by carbonation under natural exposure. The accelerated carbonation method can be used for development work on materials and repair methods and has been used by the authors in preparing carbonated concrete specimens for re-alkalization tests.

Modification of Composition and Microstructure of Portland Cement Pastes as a Result of Natural and Supercritical Carbonation Procedures

“…1,2 A well-known phenomenon associated with cement-based materials placed in natural environmental locations is the carbonation that occurs naturally over numerous years owing to the reaction with atmospheric CO 2 . 3 In the case of steel reinforced concrete, this is one of the major causes of concrete structure deterioration over time, because the reduction of the pH in the cement paste pore solution due to carbonation enables the corrosion of steel. 4 On the other hand, concrete carbonation allows the use of other nonexpensive reinforcement products, such as glass, plastics, vegetal fibers, and so forth.…”

The Useful Life of Reinforced Concrete Structures with Reinforcement Corrosion Due to Carbonation in Non-Aggressive and Normal Exposures in the Spanish Mediterranean

“…Some researchers suggest that with a high concentration of CO 2 , the porosity of artificially carbonated concrete is greater than that obtained by natural exposure. However, this is controversial, as other studies have shown that even with 100% CO 2 overpressure, the same microstructure occurs as in natural carbonation [47]. All the buildings studied are located in natural and/or urban environments in areas with little traffic and adequately ventilated; only three of the buildings had basements for parking or vehicle traffic, but in all cases, they were well ventilated and with minimal occupancy.…”

Carbonation-induced corrosion minimization in steel reinforced concrete structures

“…It was found that 100% of CO2 under increased pressure produce the same microstructure as natural carbonation (Al-Kadhimi et al, 1996). Some codes have estimated carbonation induced corrosion initiation as shown in Table 1.…”