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

Water

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 Water Supply

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

Reclaiming Water from Concrete Production

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

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

Design and Control of Concrete Mixtures

?