Design and Control of Concrete Mixtures
Mixing Water for ConcreteDesign and Control of Concrete MixturesCHAPTER 7
Design and Control of Concrete Mixtures
Overview
• Sources of Mixing Water• Effects of Impurities in Mixing Water on
Concrete Properties• Organic Impurities• Interaction with Admixtures
Design and Control of Concrete Mixtures
ASTM C1602ASTM C1602 includes provisions for:• Potable water• Non-potable water• Water recovered from concrete production
operations• Combined water
Design and Control of Concrete Mixtures
ASTM C1602Performance Requirements for Questionable Mixing Water Sources
Design and Control of Concrete Mixtures
ASTM C1602Optional Chemical Limits for Combined Mixing Water
Design and Control of Concrete Mixtures
Sources of Mixing Water
• Municipal water supply• Municipal reclaimed water supply• Site-sourced water• Water from concrete operations• Other sources
Design and Control of Concrete Mixtures
Municipal Water SupplyTypical Analyses of City Water Supplies and Seawater
Design and Control of Concrete Mixtures
Municipal Reclaimed Water
• Treated wastewater• Used for nonpotable applications
Design and Control of Concrete Mixtures
Site-Sourced Water
• Paving projects, remote sites• Wells, ponds, rivers• May contain silt and organic impurities
Design and Control of Concrete Mixtures
Recycled WaterEffect of Recycled Water on Concrete Properties*
Design and Control of Concrete Mixtures
Seawater
• Useable in plain, unreinforced concrete• Use sulfate-resistant cement for marine
applications• May aggravate ASR• May cause efflorescence and dampness
Design and Control of Concrete Mixtures
Effects of Impurities
• Alkali carbonate and bicarbonate• Chloride• Sulfate• Miscellaneous inorganic salts• Acid and alkaline waters• Industrial wastewater• Silt or suspended particles• Organic impurities
Design and Control of Concrete Mixtures
Alkali Carbonate and Bicarbonate
• Sodium carbonate – rapid setting• Bicarbonates – accelerate or retard setting• Threshold for testing – 1000 ppm• May aggravate AAR
Design and Control of Concrete Mixtures
Chloride
• ACI 318 Limits:– Prestressed concrete - 0.06%– Reinforced concrete exposed to chloride in service
- 0.15%– Reinforced concrete that will be dry or protected
from moisture in service - 1.00%– Other reinforced concrete construction - 0.30%
Design and Control of Concrete Mixtures
Sulfate
• May aggravate sulfate attack• ASTM C1602 limits sulfate to 3000 ppm
Design and Control of Concrete Mixtures
Other Common Salts
• Carbonates of calcium and magnesium- not very soluble in water and seldom found in sufficient concentration
• Bicarbonates of calcium and magnesium- present in some municipal waters
• Magnesium sulfate and magnesium chloride- present in high concentrations without harmful effects on concrete strength
Design and Control of Concrete Mixtures
Iron Salts
• Acid mine waters - may contain rather large quantities• Iron Salts - concentrations up to 40,000 ppm do not
usually affect concrete adversely
Design and Control of Concrete Mixtures
Miscellaneous Inorganic Salts
• Manganese, tin, zinc, copper, lead – strength reduction, setting time fluctuation
• Sodium iodate, phosphate, arsenate, borate – retard setting
• Tolerated up to 500 ppm• Sodium sulfide – 100 ppm can be detrimental
Design and Control of Concrete Mixtures
Acid and Alkaline Waters
• Acceptance based on concentration• Acids may cause handling problems• High concentrations of alkaline waters may
reduce strength• Alkaline waters may aggravate AAR
Design and Control of Concrete Mixtures
Industrial Wastewater
• Most sources < 4000 ppm• Strength reduction usually 10%-15%• Certain industries produce undesirable
impurities• Best to test if solids > 100 ppm
Design and Control of Concrete Mixtures
Silt or Suspended Particles
• Suspended clay or fine rock < 2000 ppm• Cement fines < 50,000 ppm
Design and Control of Concrete Mixtures
Organic Impurities
• Sanitary sewage– Little effect with diluted sewage
• Sugar– Retarder in small doses, accelerator in large doses
• Oils– Decreased strength, affects air
• Algae– Decreased strength
Design and Control of Concrete Mixtures
Interaction with Admixtures
• Impurities affect admixture chemistry• Hard water may cause increased need for air-
entraining admixture• Trial mixtures should include chemical
admixtures
Design and Control of Concrete Mixtures
Summary
• Standards• Sources• Effects of Impurities• Interactions with Admixtures