Superplasticizers (SP) are chemical admixtures that represent a significant innovation in the concrete industry due to their positive effects on workability and mechanical properties. The influence of SP on hybrid concrete with steel slag (SS) replacing coarse aggregates (up to 100%) and waste glass (WG) replacing cement (up to 30%) by weight remains ambiguous. The research gap addresses the motivation of this paper to thoroughly analyze the SP’s performance within a hybrid system. Such research objectives strongly support global efforts toward sustainability and environmental preservation. The properties of the developed concrete upon SP inclusion can be precisely monitored by fitting the independent factors (SS, WG, and w/b) to the target responses. The mathematical models were developed using Minitab 21 software. For fresh concrete, w/b was the most influential factor in determining the SP/b dosages needed to keep the slump within the range of 185 mm ± 25 mm. Meanwhile, SS and WG counteracted each other, reducing their impact on workability. However, the responses measured included the compressive strength at 28 and 91 days of water curing, as well as splitting tensile strength and thermal conductivity after 91 days of curing. In all cases, SP enhanced the desired properties of concrete. With the addition of 1.2% SP (by weight of binder i.e. cement and WG) the compressive strength increased from 40 MPa to over 80 MPa. The thermal conductivity rose by 0.1 W/m·K with an SP dosage of 0.1%. The mechanical and thermal properties of concrete responded linearly to SP dosages.
