# Effects of Steel Slag and Ethylenediaminetetraacetic Acid (EDTA) on Enhancing the CO2 Sequestration Performance of Gangue-Based Cemented Backfill Materials

## TL;DR

Adding steel slag and EDTA improves cement backfill strength and CO2 capture, but only at optimal amounts.

## Contribution

A novel approach using steel slag and EDTA to enhance CO2 sequestration and mechanical properties of cemented backfill materials.

## Key findings

- Optimal performance occurs at 10% steel slag and 0.5 g/L EDTA.
- EDTA chelates Ca²⁺/Mg²⁺, enhancing ion release and carbonation.
- Excessive steel slag or EDTA reduces hydration products and performance.

## Abstract

What are the main findings?
Proper steel slag and EDTA improved cemented paste backfill strength and CO2 uptake.Strength and CO2 uptake rose then fell with slag/EDTA, optimum at 10% slag, 0.5 g/L EDTA.EDTA chelates Ca2+/Mg2+ in steel slag, enhancing ion release and catalyzing carbonation.CO2 sequestration consumes hydration products, reducing compressive strength of backfill.

Proper steel slag and EDTA improved cemented paste backfill strength and CO2 uptake.

Strength and CO2 uptake rose then fell with slag/EDTA, optimum at 10% slag, 0.5 g/L EDTA.

EDTA chelates Ca2+/Mg2+ in steel slag, enhancing ion release and catalyzing carbonation.

CO2 sequestration consumes hydration products, reducing compressive strength of backfill.

What are the implications of the main findings?
Synergistic steel slag and EDTA optimize backfill by balancing strength and CO2 uptake.The results provide a feasible pathway for the co-utilization of coal-based wastes and steel slag.This approach advances green mining and high-value steel slag use.

Synergistic steel slag and EDTA optimize backfill by balancing strength and CO2 uptake.

The results provide a feasible pathway for the co-utilization of coal-based wastes and steel slag.

This approach advances green mining and high-value steel slag use.

To enhance the support capacity of cemented paste backfill (CPB) in goaf areas and its ability to sequester CO2, steel slag and ethylenediaminetetraacetic acid (EDTA) were incorporated into gangue-based cemented backfill materials. A stress–carbonation-coupled reaction system was employed to carbonate the CPB, and the effects of steel slag and EDTA on compressive strength, CO2 uptake, and microstructure were studied. The findings indicate that steel slag remarkably enhanced the performance of the CPB, with both strength and CO2 uptake initially increasing before declining as steel slag content increased. The optimum performance was achieved at a steel slag content of 10%. The incorporation of EDTA further enhanced the compressive strength and CO2 uptake, with the best results at 0.5 g/L. Microstructural analyses demonstrated that steel slag increased the availability of Ca2+ and Mg2+ in the cement paste system, while EDTA accelerated their leaching, promoted hydration products, and catalyzed carbonation via chelation. However, excessive steel slag or EDTA reduced hydration products and deteriorated material performance. This work may provide a reference for enhancing the properties of CPB and promoting the efficient utilization of coal-based solid wastes.