Search

Copyright of Corrosion & Protection in Petrochemical Industry is the property of Corrosion & Protection in Petrochemical Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to prolong the service life of cement-based materials subjected to external chloride ion attacks, two kinds of methods, a surface treatment and chloride immobilization, were combined by fabricating a nanosilica-modified cement paste and coating it on mortar samples as a surface treatment material (HSM). The protective effect of the HSM was evaluated according to its surface hardness, and an RCM test was carried out, which indicated that the attached layer could both increase the surface hardness and decrease the chloride diffusion coefficient. Then, the chloride immobilization mechanisms were illustrated in terms of chloride blocking resistance, chemical binding and physical binding X-ray diffraction (XRD), and thermogravimetric/derivative thermogravimetric (TG/DTG) and thermodynamic modeling. The results showed that the hybrid nanomaterials that modified the cementitious surface treatment materials may effectively improve the chloride-resistant property of a matrix with content of no more than 1%. This research outcome could provide evidence that hybrid nanosilica can be applied in surface treatment technology. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research investigated the impact of substituting sand with graphite tailings (GT) on the chloride ion erosion resistance of recycled aggregate concrete (RAC). The role of GT is to significantly inhibit the penetration of chloride ions into the interior and slow down the corrosion process. However, the durability of graphite tailings recycled aggregate concrete (GTRAC) still depends on the replacement rate of recycled aggregate. At the same time, a multi-scale dynamic model of physical adsorption-chemical binding-free transport and erosion of chloride ions in GTRAC were established based on unsteady viscous fluid force and molecular dynamics. • The purpose of improve the sulfate attack performance of concrete by GT was proved. • The Proportioning design was optimized for improving the performance. • The mechanism of action of GT was discussed. • A multi-scale dynamic model was established in this paper. [ABSTRACT FROM AUTHOR]

Highlights • High cycle fatigue behaviors and chloride permeability of RC beams are investigated. • Chloride content at steel bar surface markedly increases at loading levels >0.3. • Fatigue loading level of 0.4, 0.45 combined with chloride corrosion reduce total fatigue life by at least 13%. Abstract High cycle fatigue behaviors (crack widths, deflections and fatigue life) and chloride permeability of RC beams were experimentally investigated. The experiment processes included initial fatigue loading followed by 3 months of NaCl solution wet-dry cycles without loading, and then fatigue life tests before chloride content measurement. The loading levels (ratio of the maximum fatigue loads over the ultimate static strength) and initial fatigue loading cycles are taken as parameters in this study. Results show that: (1) the fatigue behaviors of RC beams are greatly affected by the loading level and chloride corrosion, but they are rarely influenced by the initial fatigue loading cycles; (2) chloride content markedly increase when the loading levels exceed 0.3; (3) at the loading levels of 0.4 and 0.45, combined actions of initial fatigue damage and chloride corrosion cause at least 13% decrease of the total fatigue life; (4) initial fatigue loading cycles barely affect the residual fatigue life of RC beams when initial fatigue damage of RC beams are in the slow variation stage of damage development. [ABSTRACT FROM AUTHOR]

• Alkali-activated slag (AAS) mortar has better resistance to chloride ion corrosion. • Different cation types affect the D app of AAS mortar. • MIP and XRD was performed to show a decrease in porosity. • EIS was performed to show an inverse exponential relationship between R c,d and D app. This work focuses on evaluating the influence of four cationic chloride salts (NaCl, KCl, MgCl 2 and CaCl 2) on chloride ion diffusion characteristics of alkali-activated slag mortar. The chloride ion concentration profiles of alkali-activated slag mortar were tested in single cation and combined cation source solutions. The hydration products and mechanism of action were analyzed by XRD and MIP, and the chloride ion transmission characteristics of alkali-activated slag mortar were further analyzed in combination with EIS. The chloride ion apparent diffusion coefficient D app related to the chloride salt solutions with the four cation types decreases in the order of D app (KCl) > D app (NaCl) > D app (MgCl 2) > D app (CaCl 2). The combination of monovalent cations can promote the chloride ions diffusion of alkali-activated slag mortar, and the results of the combination of monovalent cations and divalent cations are different. The hydration products of slag are mainly C-S-H gels with low calcium to silicon ratio, which reacts with chloride salt to form Friedel's salt, which can fill the internal pores, optimize pore size distribution, and improve the resistance to chloride ion corrosion. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Corrosion and scaling of heat exchanger is a severe problem in oil refinery industries. In this paper, the corrosion mechanisms of tubes in the condenser at the top of the benzene tower have been investigated by elemental analyzer, optical microscopy, and scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis. It is concluded that corrosion occurred outside the tube due to a trace amount of acidic water containing chloride ion which condensed on the surface of tubes. Then the condensed acidic water led to electrochemical corrosion during heat exchanging process in the condenser at the top of the tower. Chloride ion plays a very important role in the tube corrosion. The most important point is that chloride ion could cause the depassivation of material. Moreover, chloride ion is easily absorbed onto the surface of tubes due to the negative charge. Later, the corrosion of tubes is accelerated due to ion migration if the concentration of chloride ion increases. In addition, the loose scales of corrosion product also accelerate the electrochemical corrosion since it makes the acidic aqueous solution easier to stay and concentrate on the tube surface. [ABSTRACT FROM AUTHOR]

Carbonation durability is an important subject for recycled coarse aggregate concrete (RAC) applied to structural concrete. Extensive studies were carried out on the carbonation resistance of RAC under general environmental conditions, but limited researches investigated carbonation resistance when exposed to chloride ion corrosion, which is an essential aspect for reinforced concrete materials to be adopted in real-world applications. This paper presents a study on the carbonation durability of two generations of 100% RAC with the effect of chloride ion corrosion. The quality evolution of recycled concrete coarse aggregate (RCA) with the increasing recycling cycles was analyzed, and carbonation depth, compressive strength and the porosity of RAC were measured before and after chloride ion corrosion. The results show that the effect of chloride ion corrosion negatively affected the carbonation resistance of RAC, and the negative effect was more severe with the increasing recycling cycles of RCA. Chloride ion corrosion led to a decrease in compressive strength, while an increase in carbonation depth and the porosity of RAC. The equation of concrete total porosity and carbonation depth was established, which could effectively judge the deterioration of carbonation resistance of RAC. [ABSTRACT FROM AUTHOR]