Concrete admixtures are used to improve the behavior of concrete under a variety of conditions and are of two main types: chemical and mineral.
Chemical admixtures reduce the cost of construction, modify properties of hardened concrete, ensure quality of concrete during mixing/transporting/placing/curing, and overcome certain emergencies during concrete operations.
Chemical admixtures are used to improve the quality of concrete during mixing, transporting, placement and curing. They fall into the following categories:
• Air entrainers
• water reducers
• set retarders
• set accelerators
• super plasticizers
• specialty admixtures: which include corrosion inhibitors, shrinkage control, alkali-silica reactivity inhibitors, and coloring
Concrete Admixtures – ASTM Categories
ASTM C494 specifies the requirements for seven chemical admixture types. They are:
• Type A: Water-reducing admixtures
• Type B: Retarding admixtures
• Type C: Accelerating admixtures
• Type D: Water-reducing and retarding admixtures
• Type E: Water-reducing and accelerating admixtures
• Type F: Water-reducing, high range admixtures
• Type G: Water-reducing, high range, and retarding admixtures
Admixtures are used for one purpose: to improve some characteristics of the concrete. This section will include admixtures that can be used to provide the following results:
• Protect Against Freeze Thaw Cycles Improve Durability
• Water Reduction in the Mix
• Mid-Range water reducers
• High-Range water reducers superplasticizers
• High Strength Concrete
• Corrosion Protection
• Set Acceleration
• Strength Enhancement
• Set Retardation
• Crack Control (shrinkage reduction)
• Flowability
• Finish Enhancement
• Fly Ash- Making Concrete Stronger, More Durable, and Easier to Work With
• Silica Fume: Early Strength and Reduced Permeability
• Produce a fluid backfill, which flows easily and is self leveling