The use of electric-arc furnace dust (EAFD) in civil construction is not common. In countries where this waste is collected, it is used in the recovery process of heavy metals, such as Zn, Cd, Pb, and Cr. In Brazil, these processes are still not used, because the percentages of heavy metals of commercial value are not economically feasible (e.g. zinc with only 13% of mass). Thus, more studies are necessary aimed at making EAFD a subproduct for civil construction. For this reason, the waste behavior was evaluated in Pozzolan-modified Portland cement I (MP) pastes. Setting time and hydration heat were determined, as well as mineralogical and microstructural characterization, in order to better understand the residue's effect upon cement paste's properties, both in fresh and hardened states. The results showed that EAFD slows down the Portland cement's hydration reactions. This behavior is better verified using hydration heat curves as compared to the Vicat equipment. As of the mechanical performance, it was verified that even though the EAFD retards the hydration reaction of the cement in its initial ages, in more advanced ages the trend is having significant gain of resistance in pastes containing EAFD.