India is the second-largest producer of rice, where we get plenty of rice husk, most of which gets wasted. Converting them to ash and utilizing it as an efficient construction material brings in research opportunities for minimizing the use of cement with high embodied energy. Rice Husk Ash (RHA) is known for its excellent silica content, cost-efficient, and non-toxic qualities as a construction material. This experimental analysis aims at improving the setting time properties of cement paste with partial replacement of cement with RHA (10, 20, and 30%) mainly to bring out RHA as an admixture in improving the basic properties of cement and as a replacement material in an eco-friendly way. The hardened cement paste was studied for mineralogical characterization to know the internal chemical reactions. SEM analysis to see the hydration occurred, amorphous gel formation, and the presence of Ettringites. The thermal transitions of the composite was identified by DSC–TGA. The study results encourage organic admixtures and cement replacement to minimize the carbon footprint. Organic admixtures and cement replacements cultivate the use of eco-friendly supplements in improving the lesser embodied energy constructions for a sustainable, pollution-free future.