Recycled cement paste (RCP) is a kind of CaO-rich recourse, which is separated and recycled from
waste concrete. Due to its chemical composition, RCP could partially replace lime as a flux and be
loaded into electric arc furnace (EAF) steelmaking process. Rapid RCP assimilation and liquid slag
formation have significant effects on EAF steelmaking process. In this study, the dissolution
behaviours of RCP and lime at temperatures of 1400°C to 1500°C were investigated using static
dissolution experiment. The dissolution rate, interfacial microstructure, as well as dissolution
mechanisms were discussed. It was found that the dissolution rate of RCP was much higher than
that of lime. RCP could be completely dissolved into slag in 60 secs at 1500°C. The dissolution rate
of lime was in range of 3.910-4 g/(cm2ꞏs) to 2.610-3 g/(cm2ꞏs), while that for RCP was in range of
1.510-3 g/(cm2ꞏs) to 4.910-3 g/(cm2ꞏs). As for lime dissolution, a dense layer of dicalcium silicate
(C2S) generated at the dissolution interface, and the diffusion of Ca2+ in C2S layer was the limited
step for lime dissolution. Some of calcium ferrite could be observed at the interface between lime
and C2S layer. As for the RCP dissolution, there is no obvious product layer of C2S formed at the
dissolution interface, Fe2+ continuously diffused into RCP layer during the dissolution, and small
amount of FeOꞏMgO solid solution generated and gathered at the dissolution interface. The
dissolution rate of RCP in EAF slag was quite higher than that of lime, partially add RCP as flux in
EAF could accelerate the slag formation process.