The primary reason why steel rebars can withstand the alkali-silica reaction in concrete is because of the passive film that forms on their surface and the alkaline environment of the concrete.
When steel rebars are embedded in concrete, they develop a passive film on their surface. This film serves as a protective layer that prevents direct contact between the steel and the aggressive alkali-silica reactive aggregates that are present in the concrete. The formation of this passive film is a result of the high pH of the alkaline environment created by the cement in the concrete, which usually has a pH level of 12-13. This high pH aids in the creation of an oxide layer on the surface of the steel rebar, effectively shielding it from the reactive elements in the aggregates.
Moreover, the alkaline environment of the concrete plays a crucial role in maintaining the passivity of the steel rebars. The alkalinity of the concrete enables the passive film to remain stable and intact, providing a continuous barrier against the alkali-silica reaction. As long as the pH of the concrete remains high, the steel rebars will continue to resist the reaction.
It is important to note that the thickness and quality of the passive film on the steel rebars are vital in guaranteeing their resistance to the alkali-silica reaction. Any factors that can compromise the integrity of this film, such as carbonation or chloride contamination, can increase the risk of the reaction occurring.
In conclusion, the resistance of steel rebars to the alkali-silica reaction in concrete is primarily due to the presence of a passive film on their surface, which is formed by the alkaline environment of the concrete. This film functions as a protective barrier, preventing direct contact between the steel and the reactive aggregates and minimizing the likelihood of the reaction occurring.
Steel rebars resist alkali-silica reaction in concrete primarily due to their passive film and the alkaline environment of the concrete.
When steel rebars are embedded in concrete, they form a passive film on their surface. This film acts as a protective layer that prevents direct contact between the steel and the aggressive alkali-silica reactive aggregates present in the concrete. This passive film is formed due to the high pH of the alkaline environment created by the cement in the concrete, which typically ranges between pH 12-13. This high pH helps in creating a protective oxide layer on the surface of the steel rebar, preventing it from coming into contact with the reactive elements in the aggregates.
Furthermore, the alkaline environment of the concrete helps in maintaining the passivity of the steel rebars. The alkalinity of the concrete allows the passive film to remain stable and intact, providing a continuous barrier against the alkali-silica reaction. As long as the pH of the concrete remains high, the steel rebars will continue to resist the reaction.
It is worth noting that the thickness and quality of the passive film on the steel rebars are crucial in ensuring their resistance to alkali-silica reaction. Any factors that can compromise the integrity of this film, such as carbonation or chloride contamination, may increase the risk of the reaction occurring.
In summary, steel rebars resist alkali-silica reaction in concrete due to the presence of a passive film on their surface, which is formed by the alkaline environment of the concrete. This film acts as a protective barrier, preventing the steel from coming into direct contact with the reactive aggregates and thus, mitigating the likelihood of the reaction occurring.
Steel rebars resist alkali-silica reaction in concrete by serving as a barrier that prevents direct contact between the alkalis present in the concrete and the reactive silica aggregates. The protective oxide layer formed on the surface of the rebars acts as a physical and chemical barrier, preventing the alkalis from penetrating and reacting with the aggregates. Additionally, the high pH environment created by the concrete also helps in passivating the steel rebars, further enhancing their resistance to alkali-silica reaction.
