Cement is one of the most valuable building materials in the construction industry; however, its production is a high-energy process that emits CO2 directly from burning fossil fuels and indirectly via the chemical processes. Cement production relies on non-renewable resources but as these resources become scarcer, the sustainability of cement production is being demeaned. To find an alternative solution, plenty of research is going on to investigate reducing cement consumption through technological advancement to enhance the efficiency of cement concrete and structures. Addressing both solution techniques this paper presents the properties of concrete made of two different grades, cast in two separate layers the top layer being a normal concrete of M20 made of Portland slag cement (PSC) and the bottom layer with M30 made of Portland pozzolana cement (PPC). Further, from the bottom layer of concrete, PPC was replaced 40–70% with ground granulated blast furnace slag (GGBFS) 33–63% at a 10% gap with 7% lime. To analyze the mechanical properties the compressive, tensile, and flexural strength tests were conducted at 7, 14, 28, 56, 91, and 182 days. The results showed that the combination of M20 and M30 grades executed better results than the individual results of its parent layers. On replacement of PPC up to 50% by 43% GGBFS and 7% lime, the 28-, 56-, 91-, and 182-day results increased when compared to the results constituent layers. The results indicated an enhancement of the efficiency of structural concrete when cast layers.