What is Silica Fume?
Fig.1 Chemical Composition
|Unit||Portland Cement||Slag||Flyash||Silica Fume|
|CaO||%||60 - 67||32 - 48||1 - 5||0.1 - 0.6|
|SiO2||%||17 - 25||28 - 40||40 - 55||86 - 95|
|Al2O3||%||2 - 8||10 - 22||20 - 30||0.2 - 2.2|
|Fe2O3||%||0 - 6||3 - 5||5 - 10||0.2 - 2.2|
|MgO||%||0.1 - 4.0||2 - 16||1 - 4||0.3 - 3.5|
|SO3||%||1 - 4||2 - 4||0.4 - 2.0||0.4 - 1.5|
|Na2O||%||0.1 - 1.0||0.2 - 1.2||0.1 - 2.0||0.2 - 1.8|
|K2O||%||-||-||1 - 6|
Silica Fume Application In Concrete
How Does Silica Fume Improve Concrete?
When water is added to OPC, hydration occurs forming two products, as shown below:
OPC + H2O -> CSH (Calcium silicate hydrate) + Ca(OH)2
In the presence of silica fume, the silicon dioxide from the silica fume will react with the calcium hydroxide to produce more aggregate binding CSH as follows:
Ca(OH)2 + SiO2 + H20 -> CSH
The reaction converts the calcium hydroxide into calcium silicate hydrate (which is the binder in concrete) as shown in Fig. 2. The weaker calcium hydroxide does not contribute to strength. When combined with carbon dioxide, it forms a soluble salt which will leach through the concrete causing efflorescence, a familiar architectural problem. Concrete is also more vulnerable to sulphate attack, chemical attack and adverse alkali-aggregate reactions when high amounts of calcium hydroxide is present in
The silica reacts rapidly (Fig 5) providing high early age strengths and durability. The efficiency of silica fume is 3-5 times that of OPC and consequently vastly improved concrete performance can be obtained.
Changi Water Reclamation Project (CWRP) Singapore
We are proud to be the Silica Fume Supplier to the Concrete Manufacturer for this project required to supply High Durability Concrete to meet the durability requirement.
Changi Water Reclaimation Project (CWRP) which was officially opened in August 2006 is a milestone event in the development of sanitation system in Singapore using the latest technology. The implementation of CWRP transforms the management of waste water in Singapore and provides high sanitation standards in Singapore for generations to come. Today in Singapore we consume about 300 million gallons of clean water a day. Changi Water Reclamation Plant (CWRP) provides the solution to the needs to increase water capacity with the state of art, compact and covered facilities.
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