White Microsilica



ID: 309

White Microsilica is now back in stock in 20Kgs bags.  This is a different type of Microsilica than we have carried before and the mixing directions are slightly different.  Check the advice sheet that comes with your product.

Microsilica is a concrete additive that results in a high-density and stronger concrete.  Especially suited to polishing for concrete worktops and floors.
HOW MICROSILICA WORKS IN CONCRETE:  Microsilica in concrete contributes to strength and durability two ways: As a pozzolan, microsilica provides a more uniform distribution and a greater volume of hydration products.  As a filler, microsilica decreases the average size of pores in the cement paste.  Dosages of microsilica used in concrete have typically been in the range of 5 to 10 percent by weight of cement, but percentages as high as 40 have been reported.  Used as an admixture, microsilica can improve the properties of both fresh and hardened concrete.  Used as a partial replacement for cement, microsilica can substitute for energy-consuming cement without sacrifice of quality.
Microsilica is a mineral composed of ultrafine, amorphous glassy spheres of silicon dioxide (SiO2). Microsilica powder is composed of ultra fine solid spherical particles of amorphous silica each approximately 100 times smaller than a cement grain.  In a typical mix, with a 10% dosage of microsilica (measured against cement weight), there will be between 50,000 and 100,000 microsilica particles for every grain of cement.
The ultrafine spheres fill the gaps between the cement grains, filling the voids in the fresh concrete. The particles act like ball bearings and, while making the concrete much more cohesive, actually give more mobility to the mix by allowing the concrete to flow more easily.  Finishing is improved while at the same time reducing or eliminating bleed water.
Microsilica is a pozzolan.  This means that it will react with the calcium hydroxide given off by the cement and water.  Due to the very fine size of the microsilica particles, the crystalline structure formed by this reaction is also very fine and fills the void spaces within the concrete – this densifies the whole concrete structure, resulting in increased strength (20 - 50%) and significant reductions in permeability.
What does this mean in simple terms?  Due to the increased density of the concrete the quality of a polished finish is improved dramatically and the concrete is more stain and water resistant.  Recommended dosage is between 5 & 10% when measured against powdered cement weight (between 1.25 and 2.5Kgs of Microsilica for every 25Kg bag of powdered cement).
PLEASE NOTE:  It is VERY important to use a high-range, water reducing plasticiser such as Cemcraft's PXR-Max with Microsilica.  Adding Microsilica to concrete will result in a very thick mixture, if you simply add water to achieve better flow you just shoot yourself in the foot by cancelling out any of the advantages (strength, density) of using the Microsilica in the first place.
While this form is called 'White Microsilica' it is not a true 'snow-white' colour.  It is, in fact a very, very light grey.  We carry this form as it has the least impact on most colours of pigmented concrete.


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