Experimental tests and life cycle assessment (LCA) were carried out on two strain-hardening cementitious composites (SHCC) compositions. The reference mixture (Ref) was compared to a mixture that replaced 50% of fly ash (FA) with electric arc furnace slag (EAFS) powder and incorporated a crystalline admixture. Mechanical tests performed at 28 days on specimens cured in a climate chamber (AR) and in a humid chamber (HAR) revealed a compressive strength of 27 MPa and 32 MPa for EAFS cured in AR and HAR, respectively, and a tensile strength between 3.0–3.6 MPa. LCA results attributed lower environmental impact to EAFS composition when compared to Ref in all the impact categories assessed by method IPCC 2021, focused on climate change – Global Warming Potential (GWP). The study concluded that EAFS powder is an appropriate substitute for FA.