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In order to explore the interactional relations of internal chloride and external chloride-binding amongst the cementitious materials, the chloride-binding capacity of mortars composed of marine sand (MS) or washed marine sand (WMS) were investigated. Results indicate that more external chloride can penetrate and diffuse more deeply into the WMS mortar than that in the MS mortar. This phenomenon suggests that the external chloride migration resistance due to WMS is lower than that caused by MS. The distribution trends of the bound chloride content in the two types of mortars are the same at different immersion times. However, a significantly decreased area of the bound chloride content exists at the border of the external penetration area (EPA) and the external unaffected area (EUA) at the immersion ages of 3 and 7 d, and then it disappears gradually with immersion time. The WMS mortar can bind more external chloride, whereas the MS mortar can bind more internal chloride, at different immersion times. The distributions of bound chloride conversion rate in the EPAs of the two types of mortars differ across immersion times. The distribution firstly decreases, and then it increases at the immersion ages of 3 and 7 d. The distribution was from increase, then decreases, and increase again at the immersion ages of 28 and 56 d. The bound chloride conversion rate in the WMS mortar is affected more greatly by external chloride penetration than that in the MS mortar. The amounts of the Friedel's salt tend to increase with prolonged immersion time. Finally, the penetration of external chloride can increase the amount of fine capillary pores smaller than 100 nm in the WMSmortar exposed for 56 d in the chloride salt solution (WMS-E) specimen. [ABSTRACT FROM AUTHOR]

The durability of recycled concrete is susceptible to degradation from both chloride salt attack and carbonation when exposed in service environment. The depth of carbonation in recycled concrete subject to chloride salt attack was studied here. This investigation assessed the effects of mineral admixture, replacement rate of recycled coarse aggregate, and quality of recycled coarse aggregate on the carbonation depth. The carbonation depth Recycled concrete was studied through accelerated simulated carbonation in the laboratory for 7d, 14d and 28d. Based on the results, the correlation analysis was conducted to investigate the relationship between depth of carbonation, mineral admixture, recycled coarse aggregate replacement rate, recycled coarse aggregate quality and the presence of chloride ions. The objective of this study was mainly to investigate the effect of internal chloride ions on the depth of carbonation of recycled concrete subjected to chloride salt attack. The study referred to previous academic research on carbonation in recycled concrete that had not been affected by chloride salts, and conducted a comparative analysis to identify the carbonation depth pattern in recycled concrete influenced by chloride salt exposure. The study discovered a negative correlation between the replacement rate of mineral admixture and recycled coarse aggregate and the carbonation resistance of concrete. Moreover, enhancing the quality of recycled coarse aggregate positively impacted the carbonation resistance of concrete. An improved model was developed that considers the effect of internal chloride salts on the carbonation depth of recycled concrete, in reference to the empirical prediction model presently available. The model demonstrated a high level of agreement with experimental outcomes, displaying an error range of between −4.32% and 8.27%. It enables an in-depth comprehension of the carbonation behavior of recycled aggregate concrete in an environment exposed to chloride salt attack. Based on the model, the service life of recycled concrete structures can be more accurately forecasted, which can provide a theoretical direction for enhancing the durability of engineering structure. • This study aims to investigate the impact of chloride salts on carbonation in recycled aggregate concrete. • The influence of recycled aggregate on carbonation of recycled aggregate concrete has been studied. • The carbonation depth of recycled concrete is reduced due to the presence of chloride ions. • An empirical prediction carbonation model of recycled aggregate concrete with embedded chloride ions has been developed. [ABSTRACT FROM AUTHOR]