This paper shows the effects of size, shape and volume fraction of fine aggregate on cohesion, angle of internal friction and change of cohesion with time as parameters related to the yield value of fresh mortar. The main conclusions are as follows : 1. The dispersing distance of particles - particle diameter ratio (DDDR) can be applied as a parameter for expressing the effects of size, shape and volume fraction of fine aggregate, and the relationship between DDDR and logarithm of each parameter is linear. 2. The parameters used in the model are affected by not only DDDR but also the slip between fine aggregates and cement paste.
