Silica Fume (SF) or microsilica is a by-product of smelting high-purity quartz, coal, wood chips, silicone, or ferrosilicon alloys. Silica fume is a common ingredient in the manufacture of high-performance concrete, which can help enhance the solidity and durability of concrete.

When silica fume is added to concrete, it does not react immediately. It’s not until the cement and water start hydrating and interacting with each other that the mix becomes active, producing certain chemical compounds, including Calcium Silicate Hydrate (CSH) and Calcium Hydroxide (CH).

Silica fumes essentially come in three types based on their density. They can either be densified (DSF), partially densified, or undensified (USF). In this article, we’ll focus on the difference between densified and undensified silica fumes.

The Difference between Densified & Undensified Silica Fume

The most notable difference between densified and undensified silica fume lies in density. The density of DSF ranges between 550 and 650 kg/m3, while the USF ranges from 250-350 kg/m3.

Densified and undensified silica fume have the same chemical characteristics but different densities. Densified silica fume is composed of agglomerates with varying sizes from 1 to 100 µm in size. Silica fume can be dispersed throughout cement with moderate ultrasonic treatment.

When densified silica fume is added to Portland cement, it offers many benefits, including improved bond strength, compression strength, corrosion resistance, and workability. Also, it minimizes porosity and permeability and is environmentally and economically viable as it saves material from landfill. Densified silica fume is used in the construction industry as well as a chemical precursor.

Unlike densified silica fume, undensified silica fume is much more active, light, and easy to reach. When added to Portland cement, undensified silica fume provides numerous benefits, including enhanced bond strength, workability, and compressive strength, and increases abrasion and corrosive resistance. This form of silica fume is widely used in construction, rubber and plastics, oil well drilling, ceramics, refractories, and coating applications.

Buy Undensified & Densified Silica Fumes from Bisley Company

Bisley Company offers a wide range of undensified and densified silica fume, including white silica fume under our brand name Extrema-Dur. Contact us today to learn more about our silica fume grades and specifications, and our sales team will help you find the perfect product for your application.

*Note, silica fume is not to be confused with fumed silica, see below for more information:
Difference Between Fumed Silica & Silica Fume