Formation factor of fresh cementitious pastes

Formation factor of fresh cementitious pastes was investigated experimentally as a function of time from initial mixing and mixture design properties such as supplementary cementitious material (SCM) replacement level, water-to-binder ratio (w/cm), and superplasticizer dosage. SCM types included fly ash, slag and silica fume. A total of 54 paste mixtures were studied. The formation factor of each fresh paste was determined at the 30th, 60th, and 90th minutes from initial mixing. It was shown that the formation factors of fresh cementitious pastes were strongly correlated with porosity, tortuosity and w/cm. Slag and fly ash considerably decreased tortuosity of the pastes, whereas silica fume did not have a significant effect. Superplasticizer addition increased tortuosity through a better distribution of the solid particles. A model representing the formation factor of the tested fresh cementitious pastes was provided. Similar models can be used to determine the initial setting time of cement-based materials and quality control of fresh mixtures in precast and ready-mix concrete plants.