# Corrosion Resistance of Fly Ash-Enhanced Cement-Based Materials in High-Chloride Gas Storage Reservoirs

## TL;DR

Fly ash improves cement durability in high-salinity gas storage by reducing chloride ingress and strengthening the material.

## Contribution

Fly ash modification is shown to synergistically reduce chloride ingress and enhance mechanical durability in high-salinity environments.

## Key findings

- PFS achieved 28.2 MPa compressive strength at 90 °C with no long-term regression.
- Chloride ingress rate in the fly ash system was reduced to 26.6% of the control group.
- Nanoscale pore refinement decreased permeability by nearly one order of magnitude.

## Abstract

What are the main findings?
PFS achieved 28.2 MPa compressive strength at 90 °C with no long-term regression.Chloride ingress rate in the fly ash system was reduced to 26.6% of the control group.Nanoscale pore refinement decreased permeability by nearly one order of magnitude.Reactive alumina promotes Friedel’s salt formation, minimizing internal chloride content.

PFS achieved 28.2 MPa compressive strength at 90 °C with no long-term regression.

Chloride ingress rate in the fly ash system was reduced to 26.6% of the control group.

Nanoscale pore refinement decreased permeability by nearly one order of magnitude.

Reactive alumina promotes Friedel’s salt formation, minimizing internal chloride content.

What are the implications of the main findings?
PFS is a superior sealing material for deep, high-salinity underground gas storage.Fly ash effectively mitigates salt corrosion risks in high-temperature wellbore environments.The study provides a theoretical basis for optimizing durability in subsurface engineering.

PFS is a superior sealing material for deep, high-salinity underground gas storage.

Fly ash effectively mitigates salt corrosion risks in high-temperature wellbore environments.

The study provides a theoretical basis for optimizing durability in subsurface engineering.

This study investigates the use of fly ash to mitigate the long-term performance degradation of Portland cement-based sealing materials in high-salinity environments, such as those found in gas storage reservoirs. We systematically evaluated the evolution of material properties under different temperatures and curing periods. Our integrated methodology combining mechanical tests, microstructural analysis, and chloride migration assessment, reveals a multi-faceted mechanism by which fly ash enhances chloride resistance. The key findings demonstrate that reactive Al2O3 in fly ash promotes the formation of Friedel’s salt, increasing chemical chloride binding and reducing the chloride ingress rate in the Portland cement–Fly ash system (PFS) to only 26.6% of that in the Portland Cement system (PCS). Concurrently, the pozzolanic reaction consumes portlandite (Ca(OH)2), forming stable C-A-S-H gel and refining the pore structure by filling interconnected channels. This nanoscale pore refinement decreased permeability by nearly an order of magnitude. After 90 days of curing in 90 °C saline solution, PFS achieved a compressive strength of 28.2 MPa and maintained an exceptionally low internal chloride content of 0.08 wt.%, demonstrating superior long-term durability. This work clarifies the synergistic mechanisms of fly ash modification and temperature effects, providing a theoretical basis for optimizing sealing materials for deep geological reservoirs and experimental support for the application of fly ash in high-temperature, high-salinity engineering environments.