A review of the mechanisms of set-retardation in portland cement pastes containing organic admixtures

Abstract Various mechanisms have been proposed to explain how organic admixtures affect the hydration of cement clinker compounds. These are reviewed and discussed critically. Complex formation between the organic compounds and aluminate or silicate ions may enhance the initial reactivity of the anhydrous compounds. Set-retardation may be primarily due to retarding of the hydration of tricalcium silicate through the adsorption of organic admixtures onto calcium hydroxide nuclei. Adsorption onto the initial hydration products of tricalcium aluminate can also retard further hydration.