Polycarboxylate superplasticizer as strengthening additive in carbonated artificial steel slag aggregate

This article presents an investigation on the application of polycarboxylate superplasticizer (PCE) to improve the mechanical properties of carbonated artificial steel slag aggregate (CSSA). It is observed that dispersion effect of PCE on steel slag particles significantly improves the degree of compaction of CSSA before carbonation and the PCE molecules slows down the evaporation of water leading to the higher residue water–solid ratio (w/s) of CSSA after carbonation, which are beneficial for the improvement of CO2 uptake and mechanical properties of CSSA. Moreover, the cross-linked PCE molecules by calcium ions from steel slag hinders the early carbonation reaction of steel slag which is conducive to the CO2 diffusion from outside to inside of CSSA thus results in a more homogenous structure of CSSA. Additionally, reconstituted PCE molecules promotes the leaching of calcium ions leading to an increase of CO2 uptake of CSSA at the long-term (24 h) duration of carbonation. At optimum of 1% PCE, the compressive strength of CSSA reaches a maximum value of 164 MPa, which is 141% higher than that of CSSA without PCE.