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 workability

Filler

 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)