Masanori KOIKE

Effect of Double Mixing Process on Fluidity of Fresh Mortar

Supervisor: Kyuichi MARUYAMA


The mixing process of concrete is one of the influential factors on the quality of hardened concrete. The double mixing process is considered very effective to mix fresh concrete uniformly with a given amount of water. The objective of the study is to clarify how the double mixing process influences the fluidity of fresh mortar.

The double mixing process implies pouring water at two different stages in the mixing process. Since the total amount of mixing water is kept constant, the ratio of water amount at the first stage to that at the second stage may be a key for mixing effectiveness. In the experimental test mortal flow was measured at several intervals with respect to the ratio from 0.03 to 0.30.

In the case of a water cement ratio of around 0.30, the mortal flow just after mixing becomes larger with a smaller ratio of water at the first stage. However, the flow loss of mortar with elapse of time is larger for the case of larger initial flow.