Releases of bound chlorides from chloride-admixed plain and blended cement pastes subjected to sulfate attacks

Xu, Jinxia; Zhang, Changkuan; Jiang, Linhua; Tang, Li; Gao, Guofu; Xu, Y.

doi:10.1016/j.conbuildmat.2013.03.068

Cited by 58 publications

(11 citation statements)

References 15 publications

(16 reference statements)

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“…At low Na 2 SO 4 concentrations (≤ 5 wt%), Cl − and SO 4 2 − gradually migrated into the concrete; however, SO 4 2 − preferentially reacted with C-S-H, CH, or Friedel’s salt to form Aft, and Friedel’s salt was effectively corroded away by Na 2 SO 4 . A portion of the Cl − was also released to form free Cl − [ 56 , 57 , 58 ], causing the Cl − concentration in the pores to increase. At the same time, corrosion products filled the concrete pores, cracks, and ITZ, which changed the pore distribution in these samples, specifically, this caused the transition from large pores to middle and small pores, thereby hindering Cl − migration.…”

Section: Discussionmentioning

confidence: 99%

Study on Concrete Deterioration in Different NaCl-Na2SO4 Solutions and the Mechanism of Cl− Diffusion

Zhang

Feng

et al. 2021

Materials

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The diffusion of sulfate (SO42−) and chloride (Cl−) ions from rivers, salt lakes and saline soil into reinforced concrete is one of the main factors that contributes to the corrosion of steel reinforcing bars, thus reducing their mechanical properties. This work experimentally investigated the corrosion process involving various concentrations of NaCl-Na2SO4 leading to the coupled erosion of concrete. The appearance, weight, and mechanical properties of the concrete were measured throughout the erosion process, and the Cl− and SO42− contents in concrete were determined using Cl− rapid testing and spectrophotometry, respectively. Scanning electron microscopy, energy spectrometry, X-ray diffractometry, and mercury porosimetry were also employed to analyze microstructural changes and complex mineral combinations in these samples. The results showed that with higher Na2SO4 concentration and longer exposure time, the mass, compressive strength, and relative dynamic elastic modulus gradually increased and large pores gradually transitioned to medium and small pores. When the Na2SO4 mass fraction in the salt solution was ≥10 wt%, there was a downward trend in the mechanical properties after exposure for a certain period of time. The Cl− diffusion rate was thus related to Na2SO4 concentration. When the Na2SO4 mass fraction in solution was ≤5 wt% and exposure time short, SO42− and cement hydration/corrosion products hindered Cl− migration. In a concentrated Na2SO4 environment (≥10 wt%), the Cl− diffusion rate was accelerated in the later stages of exposure. These experiments further revealed that the Cl− migration rate was higher than that of SO42−.

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Section: Discussionmentioning

confidence: 99%

Study on Concrete Deterioration in Different NaCl-Na2SO4 Solutions and the Mechanism of Cl− Diffusion

Zhang

Feng

et al. 2021

Materials

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“…In the case of reinforced concrete structures, the decrease in alkalinity of the concrete pore solution also decreases the stability of the reinforcement passivation film, thus increasing the risk of reinforcement corrosion. It is well known that the molar ratio of free chlorides to hydroxide ions (Cl − /OH − ) can be used to assess the corrosion potential of reinforcing steel in a chloride-containing environment [ 24 ]. In this context, it is clear that the blending of fibre has an effect on the variation in both chloride and hydroxide contents during erosion.…”

Section: Resultsmentioning

confidence: 99%

“…In addition, the damage pattern and damage mechanism of concrete cannot be considered by a simple superposition of a single erosion factor when both chloride and sulphate are present in the external environment. This is because chloride and sulphate interact and influence each other in a complex manner during the erosion process [ 24 , 25 , 26 , 27 , 28 ]. However, most of the current studies only considered a single chloride environment and neglected the coupling effect of sulphate attack and drying–wetting cycles, which does not correspond to the complexity of the actual marine environment.…”

Section: Introductionmentioning

confidence: 99%

Chloride Diffusion Property of Hybrid Basalt–Polypropylene Fibre-Reinforced Concrete in a Chloride–Sulphate Composite Environment under Drying–Wetting Cycles

Yong

Niu

2021

Materials

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The effect of fibre reinforcement on the chloride diffusion property of concrete is controversial, and the coupling effect of sulphate erosion and drying–wetting cycles in marine environments has been neglected in previous studies. In this study, the chloride diffusion property of hybrid basalt–polypropylene fibre-reinforced concrete subjected to a combined chloride–sulphate solution under drying–wetting cycles was investigated. The effects of basalt fibre (BF), polypropylene fibre (PF), and hybrid BP–PF on the chloride diffusion property were analysed. The results indicate that the presence of sulphate inhibits the diffusion of chloride at the early stage of erosion. However, at the late stage of erosion, sulphate does not only accelerate the diffusion of chloride by causing cracking of the concrete matrix but also leads to a decrease in the alkalinity of the pore solution, which further increases the risk of corrosion of the reinforcing steel. An appropriate amount of fibre can improve the chloride attack resistance of concrete at the early stage. With the increase in erosion time, the fibre effectively prevents the formation and development of sulphate erosion microcracks, thus reducing the adverse effects of sulphate on the resistance of concrete to chloride attack. The effects of sulphate and fibre on the chloride diffusion property were also elucidated in terms of changes in corrosion products, theoretical porosity, and the fibre-matrix interface transition zone.

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“…The reinforced concrete structures exposed to marine environment subjected to both chloride-induced corrosion and sulphate attack. Several studies (Batis et al, 2004;Jarrah et al, 1995;Saillio et al, 2016;Xu et al, 2013) have reported that the presence of sulphate promotes the chloride-induced corrosion to greater extent. The similar conclusions are also reported by Liu et al (2016), with electrochemical studies conducted on the steel specimen subjected to sodium chloride and/or sodium sulphate ions in saturated Ca(OH) 2 solution.…”

Section: Introductionmentioning

confidence: 99%

Corrosion performance of steel reinforcement in concrete admixed with magnesium chloride and sulphate

Babu

Kondraivendhan

2020

ACMM

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Purpose Besides with a large amount of Na+ and Cl− ions in seawater, the presence of Mg+2 and SO4−2 ions builds more complex corrosion mechanism. This paper aims to investigate the corrosion of embedded reinforcement in concrete with the environment of both Cl− and SO4−2 anions associated Mg+2 cation. Design/methodology/approach The concrete specimens were prepared by using ordinary Portland cement (OPC), and OPC blended with metakaolin (MK) for water to cementitious material ratio (w/cm) 0.48 and 0.51. The concrete mixes were contaminated with the addition of MgCl2 alone and combined MgCl2 and MgSO4 in mix water. Reinforcement corrosion was evaluated by half-cell potential and corrosion current densities (Icorr) at regular intervals. Moreover, the influence of cementitious material type, salt type and w/cm ratio on electrical resistivity of concrete was also investigated. The statistical models were developed for electrical resistivity as a function of calcium to aluminium content ratio, compressive strength, w/cm ratio and age of concrete. Findings Although the corrosion initiation time increases in the concomitant presence of MgSO4 and MgCl2 as internal source compared to MgCl2, Icorr values are higher in both OPC and MK blended concrete. However, electrical resistivity decreased with addition of MgSO4. MK blended concrete performed better with increased resistivity, corrosion initiation time and decreased Icorr values. Originality/value This study reports statistical distributions for scattered Icorr of rebar in different concrete mixtures. Stepwise regression models were developed for resistivity by considering the interactions among different variables, which would help to estimate the resistivity through basic information.

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Releases of bound chlorides from chloride-admixed plain and blended cement pastes subjected to sulfate attacks

Cited by 58 publications

References 15 publications

Study on Concrete Deterioration in Different NaCl-Na2SO4 Solutions and the Mechanism of Cl− Diffusion

Study on Concrete Deterioration in Different NaCl-Na2SO4 Solutions and the Mechanism of Cl− Diffusion

Chloride Diffusion Property of Hybrid Basalt–Polypropylene Fibre-Reinforced Concrete in a Chloride–Sulphate Composite Environment under Drying–Wetting Cycles

Corrosion performance of steel reinforcement in concrete admixed with magnesium chloride and sulphate

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