Effect Of Calcined Hydrotalcite (CLDH) On The Corrosion Of Rebar By Chloride

Chloride contamination is the main reason of rebar corrosion. Therefore it is important to reduce the damage of chloride ion on the steel to improve the durability of reinforced concrete structures. In this paper, the the effect of the calcined hydrotalcite product-a kind of anion adsorption capacity of the inorganic powder (CLDH) in the presence of chloride ions in simulated pore solutions and hardened mortar block on the electrochemical corrosion behavior of steel was investigated. Meanwhile chloride ion concentration and pH value variation of the ordinary concrete pore solution and the neutralization (acid and carbonation) pore solution before and after CLDH treatment were compared. And after removal of chloride ion the CLDH structure and the rebar surface compositions were analyzed respectively by means of XRD and XPS. The effects and reasons of rebar corrosion inhibition due to chloride were surveyed and investigated systematically.Potential supervising, polarization curves and EIS results showed that after CLDH treatment in the ordinary concrete pore solution and the neutral pore solutions, the corrosion potential of rebar was significantly increased, passive range became much wider, surface impedance value increased about 5 orders of magnitude. For these several pore solutions whose initial chloride ion concentration was 0.1 mol·L-1, after the treatment with CLDH the chloride ion concentration and pH value measurement were carried out. The results revealed that the chloride ion concentrations of several pore solutions were significantly decreased by nearly 50%, while pH value increased obviously. CLDH could give an apparent reduction to the chlorine ion corrosion threshold [Cl-]/[OH-] in pore solutions, and then obviously improve the electrochemical stability of rebar.When the chloride content of hardened mortar was low (≤0.5%), CLDH could make prevent the rebar in the experiment from the corrosion. When the chloride content of hardened mortar was high (1%), the corrosion of rebar could be delayed by CLDH. After CLDH addition, the polarization resistance and charge transfer resistance increased significantly compared with the non-CLDH mortar. Results showed that CLDH could promote the stability of passive film on the rebar surface which played an important role in the rebar protection. EIS also reflected the compactability of mortar with CLDH slightly was weakened owing to CLDH.XRD tests revealed that after the treatment the microstructure of CLDH recover to the situation before calcining partly. XPS results showed that a layer of passive film with the main composition ofγ-FeOOH was observed on the rebar surface in the simulated acid treated with CLDH.