Table of Contents
What does silica do to concrete?
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.
What is the effect of silica fume on concrete?
Fresh concrete containing silica fume is more cohesive and less prone to segregation than concrete without silica fume. Concrete containing silica fume shows substantial reduced bleeding. Additionally, silica fume reduces bleeding by physically blocking the pores in the fresh con- crete.
Does silica increase strength?
Silica fume has been successfully used to produce very high-strength, low-permeability, and chemically resistant concrete. Addition of silica fume by itself, with other factors being constant, increases the concrete strength.
Does silica increase workability?
Silica fume is known to improve the mechanical characteristics of concrete. It is observed that the optimum dose of silica fume is 5% (by weight), when used as part replacement of OPC. The silica fume inclusion increases the workability and strength of concrete considerably.
What are the hazards of silica?
One of the most serious dangers of silica dust is silicosis, a condition that can reduce a person’s capacity to breathe. Exposure to the dust may also result in lung cancer, stomach cancer, and renal disease. It can also lead to other lung diseases, such as tuberculosis and emphysema .
How much silica fume to add to concrete?
Silica fume has been used as an addition to concrete up to 15% by weight of cement, although the normal proportion is 7 to 10% . With an addition of 15%, the potential exists for very strong, brittle concrete. It increases the water demand in a concrete mix; however, dosage rates of less than 5% will not typically require a water reducer.
Does concrete contain silica?
Concrete and masonry products, the primary materials used in road construction, contain both silica sand and rock containing silica.
How does silica fume work in concrete?
How Does Silica Fume Work in Concrete? Silica fume’s benefits are already evident in the fresh concrete state before it begins to harden. Its small particle size which is 100 times finer than ordinary portland cement complements the finess modulus of concrete and provides a ball-bearing effect, which improves thixotropic behavior, in effect modifying concrete viscosity.