20,21 Therefore, it is necessary to selectively and promptly remove deleterious anions as soon as they penetrate the concrete structure to maintain durability and life span. 19 This deteriorates the life-span of the concrete structures by providing easy penetration paths for other corrosion species.ĭeterioration in performance or structural damage of reinforced concrete structures not only adversely affects safety, but also causes enormous losses to society and the national economy over a long period of time. When the concrete is neutralized and water and air infiltrate, the corrosion of steel and the volume expands, causing cracks in the concrete cover, resulting in loss of the strength and durability of the structure ( eqn (3)). This lowers pH and causes general internal volume expansion in the concentrate. 16–18 Carbonation occurs by CO 3 2− anions, which originate from carbon dioxide, diffusing into the concrete matrix from the air, reacting with calcium hydroxide to form calcium carbonate. 15 SO 4 2− anion attack occurs by diverse forms drawing on chemical sources, including seawater, acid rain, or combustion gas from industry, leading to destruction of the original properties of concreate ( eqn (2)). 13,14 It can penetrate into concrete in diverse forms drawing on the chemical sources of SO 4 2− anions from the environment, which also promotes corrosion of steel rebar in concrete. 11,12 In this case, the Cl − anion can easily penetrate concrete structures through capillary adsorption, hydrostatic pressure, or diffusion, accelerating steel rebar corrosion ( eqn (1)). Penetration of Cl − anions to reinforced concrete is significantly detrimental, especially for structures near marine environments exposed to high concentrations of salts. 8 Corrosion is generally initiated by electrochemical flow of electrons and ions. Three major anions from different sources are particularly harmful: chloride (Cl −), sulfate (SO 4 2−), and carbonate (CO 3 2−) anions. 4–6 Nevertheless, corrosion of steel rebar can be readily initiated when passivity is compromised by damage 7 or when the bond between concrete and steel rebar is destroyed by anionic species. 2,3 In general, concrete structures present good durability to corrosion because the structure of concrete presents high alkalinity in the pores of the surrounding concrete, forming a protective, passive layer on the surface of the steel rebar. 1 However, it is always exposed to corrosion, leading to deterioration in concrete structures, which determines their durability and life span, particularly in natural environments. Introduction Building in concrete structures with steel rebar was a remarkable innovation in the construction industry because it adds strength to concrete, providing durability and allowing more specialized designs. The novel adsorption mechanisms of these CaFe-LDHs-induced crystals and corresponding corrosion protection properties are elucidated drawing on synergy of memory effects and chemical reactions. Furthermore, the steel rebar exposed to an aqueous solution containing the three anionic sources shows a fast corrosion rate (1876.56 × 10 −3 mm per year), which can be remarkably inhibited showing 98.83% of corrosion inhibition efficiency when it is surrounded by those CaFe-LDHs. The synthesized CaFe-LDHs with phase transfer show notable improvement of removal capacity ( Q max) toward Cl − and SO 4 2− over 3.4 times and over 5.69 times, respectably, then those of previous literatures. It is applied for the removal of Cl −, SO 4 2−, and CO 3 2− anions as well as corrosion inhibition on steel rebar in aqueous solutions. Here, we synthesize CaFe-layered double hydroxide (CaFe-LDHs) by a simple one-step co-precipitation technique and structural modulation by calcination process. Efficient removal of these deleterious anions at the early stage of penetration is crucial to enhance the lifespan and durability of concrete structures. The three anionic species chloride (Cl −), sulfate (SO 4 2−), and carbonate (CO 3 2−), are typical chemical factors that environmentally accelerate failure of concrete structures with steel rebar through long-term exposure.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |