Composition of Corroded Reinforcing Steel Surface in Solutions Simulating the Electrolytic Environments in the Micropores of Concrete in the Propagation Period

Abstract

In the present work, the composition of a corroded reinforcing steel surface is studied at different pH values (related to different degrees of development in the corroding zones of the corrosion process) in solutions simulating chloride-contaminated environments. The media considered consist of saturated calcium hydroxide solutions, progressively neutralized with FeCl2 or by adding 0.5 M NaCl to the solution. The results found in present work confirm higher levels of acidity in the solutions with higher concentrations of Fe2+.In the present work, emphasis is given to the composition of the oxides in solutions that simulate the conditions that exist inside of a localized corrosion pit as a consequence of the reaction of chloride on reinforcing steel. The oxides were studied using Raman and XPS techniques; the results obtained with both techniques are mutually coherent. Thus, in the passive state, the oxides found are those reported previously by other authors, while in the corroding state, the present results are more comprehensive because the conditions tested studied a variety of pore solution composition with several pH values; we tried to reproduce these values inside the pits in conditions of heavy corrosion (very acidic). The oxides found are those typically produced during iron dissolution and seem not the best route to study the corrosion process of steel in concrete; the electrochemical tests better characterize the corrosion stage.

Variation of Corrosion Rate, Vcorr, during the Carbonation-Induced Corrosion Propagation Period in Reinforced Concrete Elements

“…In most cases, cracks do not appear until the advanced stages of corrosion due to the assumed bond between steel and concrete. The majority of oxidation products occupy a volume between two and six times the initial volume of the steel [ 44 , 45 ], depending on the type of generated oxide: FeO, magnetite Fe 3 O 4 , maghemite γ-Fe 2 O 3 , and hematite α-Fe 2 O 3 can occupy approximately twice the volume of the initial Fe; lepidocrocite γ-FeOOH and iron hydroxides Fe(OH) 2 and Fe(OH) 3 , four times the initial volume; and hydrated iron hydroxide Fe(OH) 3 + 3H 2 O, six times the initial volume [ 46 , 47 ]. However, the larger volume of oxidation products can diffuse or flow through the network of pores, capillaries, and potential microcracks in the concrete, resulting in a smaller effective expansion on the concrete cover than what the initial steel actually experiences [ 48 , 49 , 50 , 51 , 52 ].…”

Experimental Study on the Flexural Properties of Concrete Beams Reinforced with Hybrid Steel/Fiber-Belt-Bars

“…Reinforcement corrosion is an important factor affecting the durability of reinforced concrete structures, and this poses a great threat to the safety of reinforced concrete (RC) structures [ 1 , 2 , 3 ]. Particularly, the corrosion in prestressed concrete bridge-beams provokes significant prestress losses, which induces cracking and excessive deflections during service conditions [ 4 , 5 ].…”