## 1 Introduction
MK is also increasingly recognised and appropriate for engineering applications because of its enhanced durability qualities, which include its resistance to acid attacks and reduction of the effects of efflorescence and alkali-silica reactions (ASR) [15]. Ground granulated corex slag (GGCS) is a molten slag residue obtained from iron steel production through the smelling reduction (corex) process by the ArcelorMittal steel plant in South Africa. This approach is environmentally friendly, unlike the traditional methods involving metallurgical coke and blast furnaces, yielding ground granulated blast furnace slag (GGBS) [16]. The addition of GGCS to MK in the development of a one-part geopolymer binder/concrete is poised to make up for the lack of calcium in MK. The addition of GGCS introduces a binding phase, increases early strength development of the matrix, and allows an ambient curing method. Using efficient alkali reagents at the optimum proportion is a solution to obtaining sustainable geopolymer concrete. The most used alkali reagents are Na\({}_{2}\)SiO\({}_{3}\) and NaOH; however, the exploration of alternative reagents was necessitated by the intensive energy demand of 850-1088 \({}^{\circ}\)C in the production of Na\({}_{2}\)SiO\({}_{3}\) from the direct fusion of sand and Na\({}_{2}\)CO\({}_{3}\) and the generation of CO\({}_{2}\) emissions [7; 17; 18]. Hence, incorporating Ca(OH)\({}_{2}\) reduces dependence on energy-intensive reagents. Ca(OH)\({}_{2}\) has been used as an admixture, which improved the compressive strength of geopolymer binder and led to the early precipitation of calcium silicate hydrate (C-S-H) polymeric gel and enhanced its early age strength development [19; 20]. As a result, the presence of Ca(OH)\({}_{2}\) encouraged the synthesis of certain products that gave the matrix its stiffness. The use of Ca(OH)\({}_{2}\) further increases the calcium content in the geopolymer mixture. It enhances the compatibility of the mixture with the use of admixtures such as superplasticiser and retarder, similar to the conventional PC. Hence, Na\({}_{2}\)SiO\({}_{3}\).5H\({}_{2}\)O, NaOH and Ca(OH)\({}_{2}\) were used in this study. However, according to [PERSON] et al. [21], the degree of cement hydration can be indicated by the amount of calcium hydroxide (CH) and ettringite (AFt), which are common hydration products in cement. The incorporation of calcium-rich precursors in a one-part geopolymer binder leads to the early formation of calcium-containing hydrate, thereby increasing the setting time of the matrix [22]. Priorresearch has shown that trisodium phosphate is a useful retarding agent in two-part alkali-activated binder (AAB) systems and Portland cement paste [21; 23; 24]. However, its impact on one-part geopolymer binder or concrete is sparse [17]. In addition, sustainability in the industry is a major challenge due to the excessive consumption of natural resources and the contribution to global waste generation [25; 26]. Hence, turning consumable wastes such as waste plastic (RESIN8) and glass into fine grain-size aggregates is beneficial for economical concrete and reduces the environmental pollution caused by these wastes. RESIN8 is a type of recycled waste plastic that encompasses all seven (7) types of plastic. The Centre for Regenerative Design and Collaboration (CRDC) processing operation of RESIN8 involves the collection of these waste plastics from industrial and environmental waste streams, shredding, and subjecting them to melting temperatures ranging from 190 \({}^{\circ}\)C to 200 \({}^{\circ}\)C for low-density polymers and 230 \({}^{\circ}\)C for high-density plastics. The melted plastic is then batched, pre-conditioned to eliminate odours, further melted during the heat extrusion stage, and cooled in water. After drying, the waste plastic is granulated to achieve the desired particle size. According to estimates by [PERSON] et al. [27], global plastic production between 1950 and 2015 reached 8800 Mt.