Concrete, a primary building material, typically sourced from quarrying and excavation alters natural landscapes. Growing construction results in depletion of natural aggregates, leading to environmental harm. Thus, substituting these materials with waste or environmentally friendly alternatives becomes imperative. This article presents an experimental investigation on the mechanical behaviour of high volume GGBFS concrete with additions to coal cinder as coarse and fine aggregate. The coarse and fine cinder are substituted with natural aggregates at varying percentage levels of 0, 25, 50, 75, and 100% by weight of the aggregate for a systematic examination of the properties of cinder-based slag cement concrete. The following characteristics of the concrete were determined, i.e.: density, flexural tensile strength, compressive strength, stress–strain behaviour, modulus of elasticity and sorptivity. The results obtained suggest that the use of coarse cinder led to a strength increase, while the addition of fine cinder had an adverse effect on concrete strength. Incorporating coarse cinder demonstrated enhancements in mechanical properties, resistance to cracking, and durability; however, it significantly affected the workability of the concrete. Additionally, the inclusion of cinder has proven to enhance strength and reduce the density of concrete, resulting in a lower dead load and consequently enabling the construction of smaller-sized structural elements.