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/plasticizers: 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.
[edit] Related articles on Designing Buildings Wiki
- Admixture, additive or agent.
- Aggregate.
- Alkali-activated binder.
- Bentonite.
- Binding agent.
- Concrete.
- Concrete masonry unit CMU.
- Concrete repair mortars.
- Concrete superplasticizer.
- Graphene-reinforced concrete.
- Gravel..
- Plasticiser.
- Portland cement.
- Reinforced concrete.
- Self-compacting concrete.
- Spalling.
- The properties of concrete.
- Types of concrete.
- Ultra high performance fibre concrete.
- Waterproofing admixture.
Featured articles and news
ECA progress on Welsh Recharging Electrical Skills Charter
Working hard to make progress on the ‘asks’ of the Recharging Electrical Skills Charter at the Senedd in Wales.
A brief history from 1890s to 2020s.
CIOB and CORBON combine forces
To elevate professional standards in Nigeria’s construction industry.
Amendment to the GB Energy Bill welcomed by ECA
Move prevents nationally-owned energy company from investing in solar panels produced by modern slavery.
Gregor Harvie argues that AI is state-sanctioned theft of IP.
Heat pumps, vehicle chargers and heating appliances must be sold with smart functionality.
Experimental AI housing target help for councils
Experimental AI could help councils meet housing targets by digitising records.
New-style degrees set for reformed ARB accreditation
Following the ARB Tomorrow's Architects competency outcomes for Architects.
BSRIA Occupant Wellbeing survey BOW
Occupant satisfaction and wellbeing tool inc. physical environment, indoor facilities, functionality and accessibility.
Preserving, waterproofing and decorating buildings.
Many resources for visitors aswell as new features for members.
Using technology to empower communities
The Community data platform; capturing the DNA of a place and fostering participation, for better design.
Heat pump and wind turbine sound calculations for PDRs
MCS publish updated sound calculation standards for permitted development installations.
Homes England creates largest housing-led site in the North
Successful, 34 hectare land acquisition with the residential allocation now completed.
Scottish apprenticeship training proposals
General support although better accountability and transparency is sought.
The history of building regulations
A story of belated action in response to crisis.
Moisture, fire safety and emerging trends in living walls
How wet is your wall?
Current policy explained and newly published consultation by the UK and Welsh Governments.
British architecture 1919–39. Book review.
Conservation of listed prefabs in Moseley.
Energy industry calls for urgent reform.