Carbonation of steel slag at low CO2 concentrations: Novel biochar cold-bonded steel slag artificial aggregates

Jun Liu; Canrong Zeng; Zhenlin Li; Guang Liu; Weizhuo Zhang; Guangming Xie; Feng Xing

doi:10.1016/j.scitotenv.2023.166065

Carbonation of steel slag at low CO₂ concentrations: Novel biochar cold-bonded steel slag artificial aggregates

Sci Total Environ. 2023 Dec 1:902:166065. doi: 10.1016/j.scitotenv.2023.166065. Epub 2023 Aug 4.

Authors

Jun Liu¹, Canrong Zeng², Zhenlin Li³, Guang Liu², Weizhuo Zhang², Guangming Xie², Feng Xing¹

Affiliations

¹ College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, PR China; Guangdong Provincial Key Laboratory of Durability for Marine Civil Engineering, Shenzhen University, Shenzhen 518060, PR China.
² College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, PR China.
³ College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, PR China. Electronic address: lizhenlin2020@email.szu.edu.cn.

PMID: 37544445
DOI: 10.1016/j.scitotenv.2023.166065

Abstract

Carbonation technology resolves the volume expansion of steel slag by combining CO₂ with f-CaO, but the previous stringent carbonation conditions (99%vol) significantly limit the application prospect of steel slag. To achieve the carbonation of steel slag at lower CO₂ concentrations, a novel cold-bonded artificial aggregates (CASSAs) based on steel slag and biochar is produced in this paper. The carbon capture capacities of CASSAs with different biochar contents (5 wt%, 10 wt%, and 15 wt%) are investigated in a low-CO₂ concentration environment (10.79 % vol) and natural environment using the porosity and CO₂ adsorption capacity of biochar. The changes in the performance of CASSAs before and after carbonation are investigated at different curing ages (7 d and 28 d). The results reveal that biochar increases the pores of the CASSAs. At 7 d, B15 achieves complete carbonation at low concentrations and can uptake 6.5 wt% of CO₂. CO₂ adsorption capacity by biochar in the natural environment facilitates the diffusion of CO₂ in CASSAs. Regarding mechanical properties, the addition of biochar makes B15 at 7 d half as strong as B0, but B15 exhibits long-term strength development. B15 at 7 d has a strength of 8.49 MPa after carbonation, which is almost the same as B0. In addition, B15 achieves a net CO₂ emission of -39.9 kg/ton. This study combines biochar with CASSAs to provide a potential method to carbonate steel slag at low CO₂ concentrations. A new methodology was also used to quantitatively assess the ability of biochar CASSAs to solidify CO₂ under low concentration conditions and natural environments from a macroscopic perspective. Biochar CASSAs have great potential to realize resource utilization and carbon capture from steel slag.

Keywords: Biochar; Carbon capture; Cold-bonded artificial aggregates; Low CO(2) concentration carbonation; Porosity; Steel slag.