Adding fly ash microsphere to improve packing density, flowability and strength of cement paste

Fly ash microsphere (FAM) is a superfine fly ash. Being finer than cement, it can fill into the voids between cement grains. To study the effects of adding FAM, cement paste samples with FAM contents ranging from 0 to 60% and different water contents were made for packing density, flowability and strength measurements. The results showed that the addition of up to 40% FAM would significantly increase the packing density of the cementitious materials. With the voids partially filled by FAM and the same volume of water in the voids released, the addition of FAM could increase the water film thickness of the cement paste. Consequently, the addition of FAM could increase flowability at same strength, increase strength at same flowability, or increase both strength and flowability. Hence, FAM is an effective cementitious filler for improving the performance of cement paste and concrete.

The addition of fly ash microsphere (FAM) can increase the packing density and reduce the voids ratio of the cementitious materials as shown in the following figure. Hence, it is an effective cementitious filler for improving the performance of cement paste and concrete.Figure optionsDownload as PowerPoint slideHighlights
► Fly ash cenosphere can fill into the voids of cement to increase packing density.
► Its effects on rheology were evaluated in terms of the water film thickness.
► It would enhance the flowability and strength of cement paste.