Mechanical Properties of Concrete Under the Alternate Carbonation and Freezing–Thawing Actions

Three concrete mixes with different water-to-binder ratios and dosages of cement replacement materials (fly ash and slag powder) were exposed to alternate carbonation and freezing–thawing actions. The compressive strength, dynamic elastic modulus and mass of all specimens were measured and analyzed, also compared to the results obtained from the carbonation-only and freezing–thawing-only cases. Test data show that the relative compressive strength, the relative dynamic elastic modulus and the mass of concrete specimens exposed to carbonation-only cases increase with the carbonation time due to sufficient carbonation reaction, whereas they decrease with the corresponding testing time whenever they are exposed to freezing–thawing-only cases or alternate regimes. Additionally, under the same freezing–thawing numbers, the concrete specimens exposed to alternate regimes have slightly higher relative compressive strength, lower relative dynamic elastic modulus and larger mass loss than that exposed to freezing–thawing-only cases. Based on the obtained dynamic elastic modulus from the above different environmental cases, a damage mechanics fitting model of concrete considering alternate carbonation and freezing–thawing actions were established with high reliability.