- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 12 Apr 2018
Admixtures in concrete
An admixture is a substance which can be added to concrete to achieve or modify its properties. Admixtures are added to the concrete, in addition to cement, water and aggregate, typically immediately before or during the mixing process.
Admixtures can be used to reduce the cost of building with concrete, or to ensure certain required properties or quality of the cured concrete. If problems arise with the concrete during the construction process, admixtures can be used as an emergency measure to try and prevent failure. In addition, some of the main functions of using admixtures include:
- Water-reducing: Can reduce the water content needed to reach a required slump by 5-10%.
- Retarding: Slow the setting rate of concrete, keeping it workable and are often used to counteract the accelerating effect of hot weather.
- Accelerating: Increase the rate of early-strength development and reduce the time required for curing.
- Superplasticizers: Can reduce water content by 12-30% to make a highly fluid but workable form of concrete known as flowing concrete.
- Corrosion-inhibiting: Used to slow the corrosion of reinforcing steel in the concrete. Often used in marine structures, bridges and others that will be exposed to chloride in high quantities.
- Air-entraining: Small bubbles of air formed uniformly through the concrete mix to increase cohesion and resistance to freeze-thaw degradation.
- Improving the curing of the concrete.
- Providing waterproofing properties.
- To improve hardness.
- Providing colour.
- Offsetting or reducing a chemical reaction.
- Aeration to reduce the weight.
- Offsetting or reducing shrinkage.
- Dispersing cement particles when mixed with water.
- Alkali-silica reactivity reduction.
Admixtures are usually provided in a liquid form. Some admixtures, such as pigments, pumping aids and expansive agents, are typically added manually from pre-measured containers as the amount used is very small.
 Related articles on Designing Buildings Wiki
- Admixture, additive or agent.
- Alkali-activated binder.
- Binding agent.
- Concrete repair mortars.
- Concrete superplasticizer.
- Portland cement.
- Reinforced concrete.
- Self-compacting concrete.
- The properties of concrete.
- Types of concrete.
- Waterproofing admixture.
Featured articles and news
This CIOB article explores the concept of value in building design and construction.
BREEAM and Measurabl announce integration to improve the financial performance of commercial real estate.
Rogers Stirk Harbour + Partners' release new images of soon-to-open 3WTC tower in New York.
A document can be called a bond or a guarantee. Does the name matter and what is the difference between them?
New briefing note is launched focusing on increasing knowledge of housing that promotes health and wellbeing.
Arbitration is a private, contractual form of dispute resolution used in the construction industry.
The European Parliament has approved a revised Energy Performance of Buildings directive.
One in six MPs supports the ring-fencing of retentions as proposed in the 'Aldous Bill'.
A stakeholder is anyone who has an interest in the process or outcome of a construction project.
BRE launches online self-assessment tool for ethical labour sourcing.
Tower refurbishment failed to meet safety standards on several counts, according to leaked report.