Abstract
In this paper, the types, formation time, structural morphology, and influence of steel corrosion products in seawater and sea-sand concrete were studied, and the intermediate and final products of steel corrosion under different conditions were determined. The corrosion products of steel in these concrete specimens under two curing methods were studied separately by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Due to the presence of a large amount of chloride ions in the concrete, the rust layer on the surface of a steel bar contained many intermediates, such as lepidocrocite (γ–FeOOH) and aka-ganeite (β–FeOOH). Under wet/dry cycles, with the addition and loss of moisture in concrete, various corrosion products were also dynamically converted into each other. In the specimens immersed in seawater for a long time, the intermediates of corrosion were lepidocrocite (γ–FeOOH) and aka-ganeite (β–FeOOH), which were substituted for oxygen as the new depolarizers of cathode reduction reaction, and consumed themselves to ensure smooth corrosion.
Highlights
With the continuous development of marine resources in China, the construction of islands is an unavoidable topic
Researchers have extensively studied the corrosion of steel bars in concrete caused by chloride ions, but most of the studies are focused on the corrosion rate of steel bars and the degradation of the structural properties of reinforced concrete [7,8,9,10,11,12]
It can be seen from the two graphs that the corrosion products of carbon steel were a mixture of wustite (FeO), aka-ganeite two graphs that the corrosion products of carbon steel were a mixture of wustite (FeO), aka-ganeite (β–FeOOH), lepidocrocite (γ–FeOOH), goethite (α–FeOOH), magnetite (Fe3 O4 ), maghemite (γ–Fe2 O3 ), (β–FeOOH), lepidocrocite (γ–FeOOH), goethite (α–FeOOH), magnetite ( Fe3 O4 ), maghemite and hematite (α–Fe2 O3 )
Summary
With the continuous development of marine resources in China, the construction of islands is an unavoidable topic. Considering the cost of transportation and time, it is of great practical significance to use sea stones and sea-sand on reefs as concrete aggregates for materials in island engineering projects. Due to the large amount of chloride adhering to the aggregate surface of seawater and sea-sand concrete, the steel reinforcement in concrete is the first to be affected by corrosion [1,2,3,4,5,6]. Researchers have extensively studied the corrosion of steel bars in concrete caused by chloride ions, but most of the studies are focused on the corrosion rate of steel bars and the degradation of the structural properties of reinforced concrete [7,8,9,10,11,12]. Researchers have investigated the formation mechanism of various corrosion components of climate steel bars in atmospheric environment [17,18,19,20,21]
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