Carbonation of Steel-making Slag for CO2 Fixation and Utilization in Blended Cement
Date Issued
2014
Date
2014
Author(s)
Chen, Kuan-Wei
Abstract
This study explores the feasibility of developing sustainable construction materials via mineral carbonation of steelmaking slag, i.e., basic oxygen furnace slag (BOFS). The carbon fixation capacity of BOFS was quantified by thermo-gravimetric analysis. Various engineering properties and hydration characteristics of blended cement with 10 % of both fresh BOFS and carbonated BOFS by weight as cement replacement was investigated. The results indicate mineral carbonations accompanied by significant reduction in basicity and fixing 0.202 and 0.221 kg CO2/kg BOFS at 30 oC and 60 oC within the rotating packed bed (RPB) reactor. The reaction kinetics of carbonation experiments could be well expressed by the surface coverage model, with R2 values ranged from 0.97 to 0.98. Cement blended with 10 wt% of carbonated BOFS resulted in reduced setting times and accelerated early strength development, which was consistent with the results of hydration heat and XRD observations. The SEM observations suggest that the carbonated BOFS could serve as nuclei for the precipitation of hydration products, while also accelerating the hydration. In addition, blended cement with 10 % of carbonated BOFS improved sulfate resistance ability and drying shrinkage property compared to 10 % of fresh BOFS at ambient temperature (23oC). The mineralogical composition changes after carbonation have beneficial effects on the hydraulic property in concrete. It was thus concluded that the carbonation of steelmaking slag should be considered as a feasible and attractive process for carbon fixation and waste valorization.
Subjects
carbonation
blended cement
steelmaking slag
calcium carbonate
surface coverage model
nucleation site
SDGs
Type
thesis