Carbonation Behaviour of Concrete Exposed to Natural and Accelerated Carbonation Conditions

Abstract

Carbonation is both one of the primary deterioration mechanisms in reinforced concrete structures and a method for sequestration of environmental CO2. Owing to rising atmospheric CO2 concentrations, understanding concrete carbonation is of increasing importance. The response of concretes can be assessed under natural carbonation (at atmospheric CO2 concentrations) or accelerated carbonation (in an environment with an artificially high concentration of CO2). This work investigates the natural and accelerated carbonation behaviour of two concretes with water/cement ratios of 0.65 and 0.7. Specimens of each mix are exposed to either natural carbonation conditions or accelerated conditions following an initial period of natural exposure. For the concretes and exposure conditions tested, results show that estimated natural carbonation coefficients derived from accelerated tests are consistently lower than those measured in natural tests. Changes in the carbonation mechanism between natural and accelerated tests as well as errors in the formulation of carbonation equations are highlighted as possible sources of this discrepancy.