Silica Based Concrete Additives
Silica Based Concrete Additives: How They Work And How To Use
Silica Based Concrete Additives | Image Resource : microsilica-fume.com
Concrete additives are as important as concrete itself. In fact, without additives concrete is useless in most large construction projects. These additives enhance some attributes of concrete in keeping with their applications in various construction projects having special requirements. They can help engineers achieve desired workability even with low water cement ratio, and also enhance setting time required for long distance transportation.
Concrete additives and their importance
It is important for a civil site engineer to know about the types of additives and their properties for better selection and application in concrete works. Concrete additives are defined as materials, aggregates, hydraulic cement, pozzolans, slag and fibers which reinforce concrete. So you have both mineral Silica based concrete additives and chemical additives. They are used in concrete or mortar immediately before mixing or during mixing so that it can modify various properties of concrete either in the plastic stage or in the hardened state.
Additives For Concrete And How They Modify Different Attributes
Additives are mixed with mortar in order to modify various attributes of concrete. This includes -
- Increasing workability of concrete without increasing its water content
- Keeping the workability of concrete unchanged even when less water is used.
- Retarding initial setting time.
- Reducing settlement or prevent it altogether.
- Reducing or prevent bleeding of concrete.
- Reducing segregation.
- Improving pump-ability of concrete.
- Reducing slump.
- Retarding heat evaluation in early hardening.
- Accelerating the rate of development of strength in the initial period.
- Increasing the compressive and tensile strength of concrete
- Increasing resistance to conditions owing to exposure.
- Reducing permeability and therefore enhancing protection against chlorides.
- Controlling expansion arising out of reaction of certain constituents with alkaline materials.
- Increasing concrete bond for reinforcement of steel.
- Increasing bond between new and existing concrete.
- Improving abrasion resistance and impact resistance.
- Inhibit corrosion of underlying metal.
- Producing coloured mortar or concrete
When to use concrete additives
Civil engineers need to use concrete additives -
When concrete properties cannot be modified by changing the composition of basic ingredients.
To get desired effect at less cost.
When it is not possible to improve a poor concrete mixture.
However, Additives For Concrete are never a substitute for best practices of concrete. Moreover, the dose of additives must be determined carefully.
How to Use silica based concrete additives
Using silica based concrete additives is not a casual job. It must be planned carefully and executed methodically. The civil engineer needs to -
- Check specifications for the given project
- Use correct additives. If the purpose is to reduce permeability of concrete against chlorides and other harmful gases, the engineer needs to use silica based concrete additives.
- Do not use additives from a container which is not marked properly
- Keep the container closed so that there is no accidental contamination.
- Decide the correct proportion and then add. Even a bit extra additive may modify the property in different ways than desired.
- Using a dispenser is a good practice
- Wash the container thoroughly after mixing
- The best practice is to add the additives for concrete to the water before mixing
- Dose of additive recommended by manufacturer is normally adequate
- Get some trial mixes in order to determine the most effective proportion.