AbstractThe requirements of early strength gain in concrete are indispensable in various structural applications such as precast industry, underwater construction, construction at low temperatures, shotcrete concrete, and so on. Generally, to accelerate the strength gain process in concrete under such applications, conventional hardening accelerators are used, which often suffer from different limitations, such as lowering of ultimate strength and durability properties. Calcium silicate hydrate (C-S-H) seed-based accelerators have the potential to overcome the limitations associated with conventional accelerators. Therefore, they are gradually becoming popular. In this research work, a novel ion-exchange process-based method has been developed and validated for the synthesis of a C-S-H-based accelerator, which successfully eliminated the limitations associated with commercially available hardening accelerators. The synthesis process used inexpensive resources such as agricultural waste to produce a C-S-H seed suspension that is almost free from harmful chemical impurities. Different characterization studies were performed to determine the structural, morphological, and chemical properties of the synthesized C-S-H seed. The heat of hydration and compressive strength studies proved that the material is effective in achieving early strength gains in concrete. The presence of synthesized C-S-H seeds in concrete effectively accelerated the strength gain process by approximately 40% during the initial hours of setting. Therefore, the developed hardening accelerator, when incorporated in concrete, has the potential to reduce the formwork removal time, resulting in the acceleration of the production cycle of precast elements.