PCC Admixtures

Admixtures are the ingredients in PCC other than aggregate, portland cement and water.  Typically, an admixture is added to alter a specific PCC property such as workability, setting time, strength or durability.

 
Type Desired Effect Material
Accelerators
  • Accelerate setting and early strength development
  • Calcium chloride, triethanolamine, sodium thiocyanate, calcium formate, calcium nitrite, calcium nitrate
Air detrainers
  • Decrease air content
  • Tributyl phosphate, dibutyl phthalate, octyl alcohol, water-insoluble esters of carbonic and boic acid, silicones
Air-entraining
  • Improve durability in environments of freeze-thaw, deicers, sulfate and alkali reactivity
  • Improve workability
  • Salts of wood resins, lignin, petroleum acids, proteinaceous material or sulfonated hydrocarbons
  • Some synthetic detergents
  • Fatty and resinous acids and their salts
  • Alyklbenzene sulfonates
Alkali-reactivity reducers
  • Reduce alkali-reactivity expansion
  • Pozzolans, blast-furnace slag, salts of lithium and barium, air-entraining agents
Bonding
  • Increase bond strength
  • Rubber, polyvinyl chloride, polyvinyl acetate, acrylics, butadienestyrene copolymers
Corrosion inhibitors
  • Reduce steel corrosion activity in a chloride environment
  • Calcium nitrite, sodium nitrite, sodium benzoate, certain phosphates or flurosilicates, fluroaluminates
Damp proofing
  • Retard moisture penetration into dry PCC
  • Soaps of calcium or ammonium stearate or oleate
  • Butyl stearate
  • Petroleum products
Cementitious Minerals
  • Hydraulic properties
  • Partial cement replacement
  • Ground granulated blast-furnace slag
  • Natural cement
  • Hydraulic hydrated lime
Natural pozzolans
  • Pozzolonic activity
  • Improve workability, plasticity, sulfate resistance
  • Reduce alkali reactivity, permeability, heat of hydration
  • Partial cement replacement
  • Filler
  • Diatomaceous earth, opaline cherts, clays, shales, volcanic tuffs, pumicites
  • Fly ash (classes C and F)
  • Silica fume
Inert minerals
  • Improve workabilityFiller
  • Marble, dolomite, quartz, granite
Permeability reducers
  • Reduce permeability
  • Silica fume, fly ash, ground slag, natural pozzolans, water reducers, latex
Pumping aids
  • Improve pumpability
  • Organic and synthetic polymers
  • Organic flocculents
  • Organic emulsions of paraffin, coal tar, asphalt, acrylics
  • Bentonite and pyrogenic silicas
  • Natural pozzolans
  • Fly ash
  • Hydrated lime
Retarders
  • Retard setting time
  • Lignin, borax, sugars, tartaric acid and salts
Superplasticizers
(high-range water reducers)
  • Reduce water-cement ratio by a minimum of 12%
  • Increase workability at low water-cement ratios
  • Sulfonated melamine formaldehyde condensates
  • Sulfonated naphthalene formaldehyde condensates
  • Lignosulfonates
Water reducer
  • Reduce water demand by a minimum of 5%
  • Lignosulfonates
  • Hydroxylated carboxylic acids
  • Carbohydrates
Workability agents
  • Improve workability
  • Air-entraining admixtures
  • Cementitious materials, natural pozzolans and inert minerals (except silica fume)

 

 

 

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