1. Durability of Concrete §4.5 Durability of Concrete Definition Importance of Durability Anti-permeability Freezing Resistance Carbonation /Neutralization Alkali-aggregate Reaction Steps to Improve Durability

2. Carbonation /Neutralization Fig.4.5.7 Sketch Map of Carbonation Carbonation refers to CH in concrete reacted with CO 2 in air. It causes the neutralization of concrete, and decreases the protection of concrete to steel bar.

3. Fig.4.5.8 Instrument in Carbonation Test

4.  Types of cement (quicker carbonation with mineral admixture)  W/C  Time of carbonation  Humidity  Concentration of CO 2  Admixture Major Factors Influencing Carbonation

5.  Reducing concrete’s alkalinity  Lessening the protection to reinforcement  Improving concrete shrinkage  Leading to minor crack Influence on concrete performance

6.  Improving compressive strength (taking resilience method into consideration)  Filling the pore with CaCO 3, producing water after carbonation, favoring cement hydrate Influence on concrete performance

7. In short, the disadvantage of carbonation overweighs the advantage, so the speed of carbonation should be slowed down.In short, the disadvantage of carbonation overweighs the advantage, so the speed of carbonation should be slowed down.