How does silica fume work in concrete?
3.1 How Silica Fume Works Researchers generally agree that silica fume reacts with portland cement concrete in two ways: by altering the hydration reaction, and by the “microfiller effect.” When water is added to portland cement, hydration occurs, form- ing two primary products.
Is silica fume used in concrete?
9 – Use of silica fume in concrete It reacts readily with the calcium hydroxide, which is produced during Portland cement hydration. Silica addition refines pore structure and produces concrete of improved mechanical strength.
What is silica fume PDF?
Silica fume concrete is composed of cement, silica fume, fine aggregate, coarse aggregate, and water. Fresh and hardened properties of silica fume concrete is superior to conventional concrete. For instance, it has higher compressive and flexural strength.
Does silica fume make concrete stronger?
Addition of silica fume by itself, with other factors being constant, increases the concrete strength. Incorporation of silica fume into a mixture with HRWR also enables the use of a lower water-to-cementitious-materials ratio than may have been possible otherwise.
How does silica fume affect workability?
The silica fume inclusion decreases the workability and increases the strength of concrete considerably.
Why does silica fume increase strength?
Silica fine is 100 times finer than the cement particles. Hence, the use of silica fume results a denser concrete matrix which impacts the strength parameters positively. Due to high pozzolanacity, reactivity and fine particles of Silica fume, It improves all hardened properties of concrete.
What is silica fume?
Silica fume is a by-product from the production of elemental silicon or alloys containing silicon in electric arc furnaces. At a temperature of approximately 2000°C the reduction of high-purity quartz to silicon produces silicon dioxide vapor, which oxidizes and condenses at low temperatures to produce silica fume.
What is silica fume and its properties?
Silica fume is a by product resulting from the reduction of high – purity quartz with coal or coke and wood chips in an electric arc furnace during the production of silicon metal or silicon alloys. Silica fume is known to improve the mechanical characteristics of concrete.
What is the advantage of using silica fume?
Condensed silica fume has a very low permeability to chloride and water intrusion. Silica fume increases the durability of concrete. It also improves abrasion resistance. Silica fume decreases the bleeding and segregation thereby allowing a better efficient finishing process to the concrete.
Why do we use silica fume?
Silica fume, a by-product of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. It may be added directly to concrete as an individual ingredient or in a blend of portland cement and silica fume.
What is silica fumed?
What is the source of silica fume?
Production. Silica fume is a byproduct in the carbothermic reduction of high-purity quartz with carbonaceous materials like coal, coke, wood-chips, in electric arc furnaces in the production of silicon and ferrosilicon alloys.
Is silica fume hazardous?
HAZARD SUMMARY * Silica, Amorphous (Fume) can affect you when breathed in. * Silica, Amorphous (Fume) can irritate the eyes on contact. Repeated exposure can damage the eyes. * High exposure to Silica, Amorphous (Fume) can cause a flu-like illness with headache, fever, chills, aches, chest tightness and cough.
Is silica fume expensive?
A disadvantage to utilizing silica fume in cement is the cost. Condensed silica fume costs from $400-$1,000/ton, which is significantly higher than portland cement ($90/ton).
What is the difference between silica fume and fumed silica?
Fumed silica and silica fumed are two different terms for two substance. They are both silica dioxide. On some occasions people confused with them. They have different derivations, technical characteristics, and applications, then the price is different.
How do you clean fumed silica?
Wash thoroughly with plenty of water. Any unavoidable deposit of dust must be regularly removed. Use only in well ventilated areas.
Why is silica used in cement?
Silica fume is an excellent admixture for concrete as it leads to better engineering properties. It will reduce thermal cracking caused by the heat of cement hydration, improve durability to attack by sulphate and acidic waters, and increase strength.