Predicting the Impact of Water Transport on Carbonation-Induced Corrosion in Variably Saturated Reinforced Concrete

Keskeiset käsitteet

A new theoretical and computational framework is presented that accounts for the interplay between water transport, concrete carbonation, and corrosion in cracked and uncracked reinforced concrete.

Tiivistelmä

The study presents a new coupled model for predicting water transport, carbonation, and corrosion in concrete. The model accounts for the impact of cracks on water and carbon dioxide transport, the link between water saturation and corrosion current density, and the complex interplay between carbonation and water content.
The key highlights and insights from the study are:

The model can accurately simulate the wetting and drying of concrete, including the enhancement of water transport through cracks. It is validated against experimental data on water transport in uncracked and cracked concrete.

The model captures the impact of water saturation on carbonation, including the interplay between the opposite trends of saturation-dependent neutralization reaction rate and saturation-dependent carbon dioxide diffusivity. An optimal water saturation point is identified for an intermediate value of humidity.

Cyclic wetting and drying leads to significant acceleration in the evolution of the carbonation front. Even short intense wetting periods can substantially accelerate the carbonation process.

The corrosion current density changes significantly with varying concrete saturation, dropping to 56% of its maximum value for a concrete specimen with boundary water saturation periodically varying between 40 and 80%.

The presence of surface cracks significantly shortens the time to corrosion initiation, with a 30% reduction observed in the investigated case study.

The model can be further extended to account for growing cracks, sorption hysteresis, chloride-induced corrosion, different wetting cycles, and the role of oxygen saturation.

Tilastot

The maximum corrosion current density is 3.7 µA/cm2.
The critical porosity level is 0.185.
The concrete porosity of fully carbonated concrete is 0.11.
The initial porosity of uncarbonated concrete is 0.16.

Lainaukset

"Carbonation results from the penetration of atmospheric carbon dioxide (CO2) into concrete, leading to a series of chemical reactions involving the transformation of calcium hydroxide into calcium carbonate, which causes acidification of the basic concrete pore solution [1–3]."
"Concrete water saturation and microstructure play a dominant role in the carbonation process [1, 6, 12]."
"Developing models capable of resolving the interplay between cracks, carbonation, water content and corrosion is critical to deliver service life predictions; yet this is an area that remains to be explored."

Tärkeimmät oivallukset

Predicting the impact of water transport on carbonation-induced corrosion in variably saturated reinforced concrete

by E. K... klo arxiv.org 05-07-2024

https://arxiv.org/pdf/2405.02611.pdf

Syvällisempiä Kysymyksiä

How could the model be extended to account for the impact of different types of wetting cycles on carbonation and corrosion?

To account for the impact of different types of wetting cycles on carbonation and corrosion, the model could be extended in several ways:

Incorporating Variable Wetting Patterns: The model could be modified to simulate different wetting patterns, such as intermittent wetting and drying cycles, continuous wetting, or periodic wetting events. By adjusting the boundary conditions to reflect these different scenarios, the model can capture how varying moisture levels affect carbonation and corrosion rates over time.

Including Sorption Hysteresis Effects: Sorption hysteresis, where the water content in concrete does not follow the same path during drying and wetting, can significantly impact carbonation and corrosion processes. By incorporating sorption hysteresis effects into the model, it can better simulate the complex interactions between moisture content, carbonation, and corrosion under different wetting cycles.

Integrating Oxygen Saturation Effects: Oxygen availability plays a crucial role in the corrosion process. By including the impact of oxygen saturation levels in the model, especially under different wetting conditions, the model can provide a more comprehensive understanding of how varying oxygen levels influence carbonation-induced corrosion in concrete structures.

Considering Crack Propagation: As wetting and drying cycles can influence crack propagation and development, incorporating a mechanism to simulate crack growth under different moisture conditions can enhance the model's ability to predict the evolution of carbonation and corrosion in cracked concrete.

How could the insights gained from this study be leveraged to develop new concrete mix designs or surface treatments that are more resilient to carbonation-induced corrosion in structures subjected to variable moisture conditions?

The insights gained from this study can be leveraged to develop more resilient concrete mix designs and surface treatments by:

Optimizing Cementitious Materials: Understanding the impact of water saturation on carbonation and corrosion can guide the selection of cementitious materials with improved durability characteristics. By choosing materials with enhanced resistance to carbonation and corrosion under variable moisture conditions, the longevity of concrete structures can be improved.

Incorporating Supplementary Cementitious Materials: Utilizing supplementary cementitious materials like fly ash, slag, or silica fume can help reduce the permeability of concrete and enhance its resistance to carbonation. By incorporating these materials in concrete mix designs based on the insights from the study, structures can be better protected against carbonation-induced corrosion.

Implementing Surface Treatments: Surface treatments such as coatings, sealants, or corrosion inhibitors can be tailored to mitigate the effects of carbonation and corrosion in structures exposed to variable moisture conditions. Insights from the study can inform the development of surface treatments that provide an additional layer of protection against deterioration.

Designing Proper Drainage Systems: Proper drainage systems can help manage moisture levels around concrete structures, reducing the risk of carbonation and corrosion. Insights from the study can guide the design of effective drainage systems to control water ingress and minimize the impact of variable moisture conditions on concrete durability.