The alkali-activated materials (AAM) are considered to be an alternative cementless binder to reduce the carbon footprint. In the hydration of binders, the alkali activators are essential and provide a high pH environment, which makes the hydration process faster. Desired alkali activators (molarity solution) can be prepared by mixing the sodium silicate and sodium hydroxide pellets in water under normal atmospheric pressure. In this study, natural pozzolans such as pumice and calcined clay are used as a replacement for the cement. In this paper, two types of natural pozzolan based alkali-activated concrete are tried to develop as a substitute cementitious material. The first one contains 40% pumice, 40% calcined clay, 15% limestone 5% gypsum, which is the 100% replacement of cement (i.e., lime pumice calcined clay concrete). The second one contains 50% cement of OPC 53 grade, 15% pumice, 15% calcined clay, 15% limestone, and 5% gypsum, which is the 50% replacement of cement (i.e., lime pumice calcined clay cement concrete). The influences of different molality of SH on the compressive strength and microstructural behavior of the two developed mixes are evaluated and reported.