Moisture and ion mobilization and stratification in post-tensioned (PT) grout during hydration

Permeh, Samanbar; Lau, Kingsley; Tansel, Berrin

doi:10.1016/j.cscm.2021.e00644

Cited by 4 publications

(2 citation statements)

References 30 publications

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“…The most electronegative potentials and greatest corrosion rates of steel developed in specimens from the INT tee header coincident with the highest sulfate ion concentrations. Although not as sharply parced here with testing of Grout A and B, MIT specimens in other research [14,15] have shown similar discrimination for susceptible grout materials. The results imply that the simple INT test setup can be useful to identify grout segregation robustness.…”

Section: Risk Assessment Based On the Sulfate Limitmentioning

confidence: 43%

“…The corrosion was not associated with bleed water or void formation and chloride ion concentrations were not significantly elevated in those cases. Some of these cases were associated with physically and chemically deficient segregated grout characterized as moisture-rich and low cement content material with high concentrations of sulfate and alkali ions [15][16][17]. The accumulation of sulfate ions were apparently manifested by the grout segregation process that occurred soon after grout placement due to the ionic mobility of the sulfate ion that originated from the original grout material [16].…”

Section: Introductionmentioning

confidence: 99%

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Assessment of Post-Tensioned Grout Durability by Accelerated Robustness and Corrosion Testing

Permeh,

Lau

2023

Construction Materials

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The corrosion of steel in post-tensioned tendons has been associated with deficient grout materials containing high free sulfate ion concentrations. In a Florida bridge in 2011, tendon corrosion failures occurred for a prepackaged thixotropic grout that had developed material segregation. However, the available grout and corrosion testing prescribed in material specifications, such as grout bleed water testing, was not able to identify the propensity or modality for the grout deficiencies and the associated steel corrosion that was observed in the field. It was of interest to identify corrosion testing methods that could prescribe grout resistance to segregation-related deficiencies that can form by aberrations in construction. The objectives of the work presented here included (1) characterizing the development of physical and chemical grout deficiencies due to excess mix water and water volume displacement, (2) developing small scale test methodologies that identify deficient grout, and (3) developing test methodologies to identify steel corrosion in deficient grout. The inverted-tee test (INT) and a modified incline-tube (MIT) test were assessed and both were shown to be useful to identify the robustness of grout materials to adverse mixing conditions (such as overwatering and pre-hydration) by parameters such as sulfate content, moisture content, electrical resistance, and steel corrosion behavior. It was shown that the different grout products have widely different propensities for segregation and accumulation of sulfate ions but adverse grout mixing practices promoted the development of grout deficiencies, including the accumulation of sulfate ions. Corrosion potentials of steel < −300 mVCSE developed in the deficient grout with higher sulfate concentrations. Likewise, the corrosion current density showed generally high values of >0.1 μA/cm2 in the deficient grouts. The values produced from the test program here were consistent with historical data from earlier research that indicated corrosion conditions of steel in deficient grout with >0.7 mg/g sulfate, further verifying the adverse effects of elevated sulfate ion concentrations in the segregated grout.

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Section: Risk Assessment Based On the Sulfate Limitmentioning

confidence: 43%

Section: Introductionmentioning

confidence: 99%

Assessment of Post-Tensioned Grout Durability by Accelerated Robustness and Corrosion Testing

Permeh,

Lau

2023

Construction Materials

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Measurement of sulfate ion concentration in segregated post-tension grout

Permeh,

Lau,

Simmons

2024

CEMENT

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The influence of nano-SiO₂ emulsion on sulfate resistance of cement-based grouts

Li,

Yuan,

Cheng

et al. 2024

Materials Science-Poland

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Sulfate attack is one of the most significant durability issues for cement-based grouts, which are widely used to repair concrete structures in sulfate-rich environments. The purpose of this study was to investigate the impact of nano-SiO2 emulsion on the sulfate resistance of cement-based grouts. The durability of the mixes was evaluated on the basis of weight loss and compressive strength. X-ray diffraction (XRD) and scanning electron microscopy (SEM) of hardened grout matrix were used to analyze the hydration products and microstructure of the hardened grout matrix. The results indicate that the hydration degree of nano-SiO2-modified samples is higher than that of the control sample. The compressive strength from highest to lowest was 16 NSE, 10 NSE, NSP, and the control sample. The XRD and SEM results suggest that the deterioration of properties may be attributed to the formation and growth of ettringite (AFt) crystals, which may result in crack generation and extension and in the corrosion of gypsum, leading to exfoliation. The addition of nano-SiO2 to cement-based grouts through a preprepared emulsion, which facilitates dispersion within the cement matrix, has the potential to reduce AFt and gypsum contents, enhance microstructure density, decrease the migration channels of SO 4 2 − \[\text{SO}_{4}^{2-}\] , and ultimately improve the resistance to sulfate attack. This work will provide a novel route to enhance the sulfate resistance of cement-based grouts, which may be serviced in a sulfate-rich environment.

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Moisture and ion mobilization and stratification in post-tensioned (PT) grout during hydration

Cited by 4 publications

References 30 publications

Assessment of Post-Tensioned Grout Durability by Accelerated Robustness and Corrosion Testing

Assessment of Post-Tensioned Grout Durability by Accelerated Robustness and Corrosion Testing

Measurement of sulfate ion concentration in segregated post-tension grout

The influence of nano-SiO₂ emulsion on sulfate resistance of cement-based grouts

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Moisture and ion mobilization and stratification in post-tensioned (PT) grout during hydration

Cited by 4 publications

References 30 publications

Assessment of Post-Tensioned Grout Durability by Accelerated Robustness and Corrosion Testing

Assessment of Post-Tensioned Grout Durability by Accelerated Robustness and Corrosion Testing

Measurement of sulfate ion concentration in segregated post-tension grout

The influence of nano-SiO2 emulsion on sulfate resistance of cement-based grouts

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Product

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The influence of nano-SiO₂ emulsion on sulfate resistance of cement-based grouts