Influence of agricultural residue ash on early cement hydration and chemical admixtures adsorption

• Agricultural residue ash (ARA) samples were prepared with high surface areas.
• ARAs showed similar pozzolanicity to silica fume.
• Internal surface area of ARAs did not affect cement early hydration.
• ARAs reduced influence of retarders in cement paste due to their high surface areas.
• ARAs adsorbed a high amount of air entraining agent in cementitious systems.

This study investigated impacts of internal surface area of wheat straw ash (WSA) and rice straw ash (RSA) on cement early hydration as well as on chemical admixture adsorption in cementitious systems. Results were compared to those of silica fume. Hydration kinetics and mortar strength experiments showed RSA and WSA to have similar reactivity to silica fume. High surface areas of WSA and RSA did not increase early hydration as compared to silica fume. However, high surface areas of WSA and RSA dramatically increased their adsorption capacity of air entraining agents and retarders compared to silica fume.