Question:

I am a producer of calcium aluminate cement.

In the past two years, we used corundum castables and high alumina bauxite castables to test the cement setting time. It was found that after adding certain silica fume (such as 3%), the same cement was added with silica fume, and the setting time was longer.

What effect does silica fume have on the setting time of cement?

Answer:

Mr. Tsui: It is related to the pH value of silicon micropowder. The acidified silica fume has a retarding effect, and the alkaline one has a procoagulant effect.

The lower grade of silica fume will have an effect on the setting time of the cement because of the high impurity content.

I hope to help you.

Mr. Chu: In refractory materials, silica fume (silica micropowder) is a binder.

Among low-cement refractories, silica fume is the main cementitious material and has the effect of improving the rheological properties of the castable.

In the application of Portland cement mortar or concrete, silica fume is an auxiliary cementing material, also known as mineral admixture, which can improve the strength, impermeability and corrosion resistance of concrete and mortar.