This study deals with a comparison of the environmental performance of one-way slabs utilizing steel fibrereinforced limestone calcined clay cement (LC3) concrete with the control case of Ordinary Portland cement concrete. The experimental program constituted compressive and residual strength testing of concrete mixes and beams reinforced with traditional longitudinal steel reinforcement as opposed to steel fibres. The code-compliant design of the one-way slabs confirmed that, by adding steel fibres, 45% replacement of longitudinal steel reinforcement could be achieved. The cradle-to-gate life cycle analysis proved that the use of LC3 as a binder and integration of steel fibres lowers the environmental impact of one-way slabs by 10% despite the slight increase in the concrete cover of the steel fibre-reinforced concrete slabs for carbonation resistance purposes. Several scenario analyses were carried out to confirm that the savings could reach 40% depending on concrete mix design optimization and the potential use of recycled fibres.