Influence of bleeding on properties and microstructure of fresh and hydrated Portland cement paste

The influence of bleeding on slump flow and solid phase distribution of fresh Portland cement paste, as well as the hydration product distribution, splitting behavior, and porosity of the hydrated cement paste were investigated. It is manifested that bleeding results in heterogeneous distribution of solid phases in fresh cement paste, clinker particle is descended due to gravity and the suspension made of liquid and gypsum particle is impelled to ascend. This results in the abundance of gypsum particle and ettringite crystals in the upper part of fresh and hydrated cement paste respectively. Meanwhile, bleeding can impair mechanical property and anti-penetration ability of the hydrated cement paste. (c) 2016 Elsevier Ltd. All rights reserved.