Bleeding characteristics of high consistency heavyweight concrete mixtures

Bleeding, a type of static segregation derives from density difference of concrete ingredients in fresh state. Due to having this difference higher than normal weight counterparts, heavyweight concrete is more susceptible to bleeding, thus, this type of concrete is commonly produced in low slump values. In order to give a response to advances and demands in concrete technology, heavyweight concrete mixtures with high slump values were designed at various mixture characteristics, and their bleeding characteristics were researched in the study. For this purpose, totally, thirty-five concrete mixtures with ≥150 mm slump values were produced by using common cement replacement materials (silica fume and fly ash), viscosity modifier, and various water/binder ratios at two binder dosages. The mixtures showed excessive bleeding capacities ranged from 0 to 11.7% and bleeding rates ranged from 0 to 5.1 kg/m2/h. Silica fume was found as the most effective admixture for reducing or elimination of the bleeding. Bleeding time generally shorten at high binder content and at high water/binder ratio. It was observed that the bleeding adversely affects the hardened characteristics of heavyweight concrete mixtures.