Study on Mineral Compositions of Direct Carbonated Steel Slag by QXRD, TG, FTIR, and XPS

Xue Wang,Siqi Zhang,Keqing Li,Wen Ni,Jiajie Li

doi:10.3390/en14154489

Abstract

Steel slag CO2 sequestration helps mitigate global warming and decrease the stockpile of steel slag (SS). Through orthogonal design tests and single-factor tests, this paper evaluated the effects of the water/solid mass ratio (w/s), gypsum ratio (G/SS), molding pressure, and curing duration on uniaxial compressive strength (UCS) and CO2 uptake of the compacts. The results indicated that high w/s enhanced both strength and CO2 capture ability. The proper addition of gypsum helps promote UCS increase and CO2 uptake of steel slag. In addition, increasing the molding pressure can significantly improve UCS without reducing CO2 uptake. The optimum conditions in the study were a w/s of 0.20, G/SS of 1/16, and molding pressure of 27 MPa, under which conditions 1 d UCS and CO2 uptake were 55.30 MPa and 12.36%, respectively. Microanalyses showed that gypsum activates mainly mayenite in steel slag. An increase in water addition also increased the hydration and carbonation products greatly, and the strengthened molding pressure had a significant densification effect on micro-pore structures. The study gives guidance in the application of steel slag in CO2 capture and manufacturing green construction material.

Highlights

Carbon dioxide emissions contribute to global warming in ways that cannot be ignored
A paste mixer was used to mix and and stir stir the the steel steel slag slag powder, powder, gypsum, gypsum, and and water water for for 2 min after they were weighed according to the experimental proportion (Table 2)
Phases and single-factor tests, this paper evaluated the effects of the water/solid mass ratio (w/s), and the ratio monocarboaluminate hadpressure an Al 2ponbinding of around

Summary

Introduction

Carbon dioxide emissions contribute to global warming in ways that cannot be ignored. Feasible carbon capture and storage (CCS) technologies mainly include geological, ocean, biological, and mineral sequestration [1], among which mineral sequestration is considered the safest method. It sequesters carbon dioxide from emission sources, such as steel companies and power stations, with Ca- or Mg-bearing minerals to form thermodynamically stable carbonates [2,3,4]. Industrial solid wastes, including blast-furnace slag [5], coal fly ash [6,7], and steel slag [8,9,10,11,12,13,14], were chosen to be suitable CCS feedstock because of their low cost, high carbon reactivity, and wide availability. Using steel slag to capture CO2 is one of the most feasible ways of dealing with steel slag and CO2 emission at a low cost

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